MDF, or Medium-Density Fiberboard, is a popular composite wood product that can be used for various projects, including exterior trim, decorative moldings, cabinetry, and even outdoor furniture. However, it is not suitable for outdoor use due to its susceptibility to moisture damage. The best paint-grade trim for interior items is finger-jointed pine, poplar, or medium-density fiberboard (MDF). MDF can only be used outside when it has undergone a waterproofing treatment and is somewhat protected from the elements directly.
PVC (polyvinyl chloride) is the best material for exterior trim board due to its durability, low maintenance requirements, and resistance to moisture, insects, and rot. PVC trim boards are also easy to install. MDF garden furniture should not be used outside in humid and wet conditions.
MDF trim and moulding are specifically designed to resist warping, bowing, swelling, cracking, and splitting, making it an excellent choice for long-term installation. One of the best ways to use MDF is for trim—baseboards, crown moulding, wainscoting, and board and batten. Traditional trim can be costly when combined with other materials.
Exterior grade MDF is versatile in its applications, including exterior trim, decorative moldings, cabinetry, and even outdoor furniture. However, there is no real exterior rated MDF, and some MDF products are rated for exterior use. Moisture-resistant MDF can be used outdoors if properly sealed, and Extira is a product manufactured for exterior use.
MDF dents easily and any exposure to moisture makes it puff up and stain. It should only be used in rentals where you’re careful. MDO is what sign painters use and is specifically made for exterior use. Regardless of the method used, MDF is moisture-resistant, not water-resistant, nor waterproof, and is still prone to swelling.
📹 MDF VS. PLYWOOD (Which Is Better?? Pros + Cons!!)
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What are the disadvantages of MDF trim?
MDF is less eco-friendly than solid natural wood and has durability issues in high-traffic areas. However, it is often used for baseboard trim and casings, with popular wood materials like oak, maple, pine, and poplar. Poplar and finger-jointed pine are popular for trim work due to their durability, cost, and paintability. Using wood for trim allows for more creative finishing options, such as painting or staining, to match your design vision. For a more high-end or custom look, exotic woods like teak or ipe can be chosen. Understanding the pros and cons of MDF can help you evaluate its suitability for your project needs.
Where should you not use MDF trim?
MDF mouldings are unstainable and cannot be stained, making their appearance unappealing. They are vulnerable to chipping due to their soft material, making them susceptible to water damage. In areas like bathrooms, where water may come into contact, MDF mouldings may not be the best option. While they can be used in bathrooms, other moulding options may have better longevity. Understanding the pros and cons of MDF mouldings can help determine which type is best for your home or application. In general, MDF mouldings may suit your application if.
Can MDF be used for exterior trim?
Medium-density fiberboard (MDF) is a composite wood product that is primarily used for indoor use due to its moisture sensitivity. However, with proper precautions, it can be used for outdoor applications to some extent. MDF is prone to swelling and warping when exposed to moisture, making it unsuitable for direct exposure to rain, snow, or extreme humidity. To make MDF more resistant to outdoor conditions, sealing all sides and edges with an exterior-grade sealer or paint is crucial.
This creates a barrier that prevents moisture from penetrating the surface, reducing the risk of swelling and warping. Applying multiple coats of an exterior-grade paint or primer also enhances the material’s moisture resistance.
How well does MDF hold up outside?
MDF boards are water-resistant to a certain extent, but can become weathered over time, making them more susceptible to moisture. However, there are products available that are more resistant to moisture and fire, both exterior and interior grade. The furniture sector has seen constant innovation in recent years, with new construction methods and timber possibilities emerging due to growing concerns about sustainability and building carbon footprint. This blog will provide an overview of MDF boards, a relatively new entrant in the wood panel industry, and answer any questions you may have about them.
Can you seal MDF for outdoors?
To make MDF moisture-resistant, you can use high-quality wood sealant, varnish, stain, or moisture-resistant paint. Avoid using waterborne polyurethane as it may not bind readily to the MDF’s surface. To waterproof MDF, apply a latex primer or a primer designed specifically for MDF, using a 3/8-inch paint roller and a paintbrush to reach into areas not otherwise reached. Let the primer dry for six hours. Apply a sealant or water-resistant paint, using a 3/8-inch roller, and paint the corners and edges, taking about four hours to dry.
Can MDF be installed outside?
Moisture-resistant (MR) MDF is a type of MDF that can withstand high humidity areas and is suitable for interior applications where moisture is a concern. It is easy to sand and mill, and can withstand most adhesives, veneers, and paints. It is ideal for kitchens, bathrooms, boilers, and laundry rooms. MR MDF is more expensive than standard MDF but is worth the investment due to its moisture-resistant feature.
To make MDF moisture-resistant, you can add a high-quality wood sealant, varnish, stain, or moisture-resistant paint to your project. However, avoid using waterborne polyurethane, as it may not bind readily to the MDF’s surface. Both methods are essential for ensuring the longevity and durability of your project.
Can MDF go outdoors?
Due to its durability and susceptibility to moisture, MDF is not an optimal choice for outdoor applications. However, certain variants exhibit enhanced resistance to moisture, offering a potential solution for specific outdoor applications.
What is MDF not good for?
MDF, like particle board, has several disadvantages, including its ability to absorb water and liquids, making it difficult to hold screws, being heavy, and not able to be stained. It also contains VOCs, making it difficult to work with and causing unpleasant staining. Plywood, an engineered wood product, is made by pressing and binding wood veneer sheets into one solid piece. It comes in different thicknesses and grades, with lower grades used in house construction, while higher grades, such as stain and cabinet grade, are more attractive and smoother. Careful handling of these materials is essential to avoid inhalation of VOCs.
What is the biggest drawback of using MDF?
Medium-density fiberboard (MDF) is a material with a relatively weaker nature than wood. It has a shorter lifespan and is susceptible to cracking or splitting under extreme stress. The material absorbs water at a faster rate than wood and contains volatile organic compounds (VOCs), which have the potential to cause respiratory and ocular irritation. Wood laminate is susceptible to staining from condensation and may exhibit delamination after a relatively short period of time, typically within the first few months.
When should you not use MDF?
MDF is a popular choice for many companies due to its ability to dispose of waste and its ability to hold nails or screws well. However, it is not well-suited for use in homes due to its lack of face grain, moisture resistance, and presence of urea-formaldehyde, a suspected carcinogen. Workers exposed to MDF manufacturing have high rates of lung and nose cancer, which can be dangerous for both homeowners and carpenters. Additionally, MDF is not made to last, as it easily chips on impact, especially on sharp edges and corners.
To avoid these issues, it is recommended to consider using renewable wood products like Poplar, a smooth, tight-grain hardwood known for its durability and utility in various applications. Poplar is used for frames, crates, upholstered furniture frames, trim, and baseboards, making it a more sustainable and eco-friendly option.
Is MDF OK in the rain?
Standard MDF, composed of wood fibers and resin adhesive, exhibits resistance to moisture but lacks complete waterproofing properties. The absorption of water and subsequent swelling render the material useless. Notwithstanding these limitations, the material is suitable for indoor use, such as in cabinets and shelves, in areas with low moisture or humidity. Short-term exposure to water or prolonged water exposure can result in damage to MDF, rendering it suitable for indoor use.
📹 I was wrong about MDF…
I torture tested MDF vs. Plywood to see how they would hold up to water, weight and fire! The results were unexpected. What to …
I watched this and the previous article at cheap desk with a painted MDF top. When it gets a tiny scratch, any amount of water (condensation on glasses, spilled drinks, or even from sweat in the summer) causes it to swell and create bumps. There’s no fixing it. Stumpy Nubs had a tip to use CA glue to re-seal the mdf, so it won’t get worse in those locations, but the desk has pock marks all over it now.
we used the physical properties of MDF to save our basement in case of flooding. Two tracks of U-shaped aluminium on both sides of a critical doorway, just slightly wider than the thickness of the MDF-Board. A bead of silicone to seal the entrance. If water entered the basement the MDF expanded and closed the gap in the u profile stopping the water to intrude any further.
I made shelves a long time ago with MDF and they warped so hard it was more a roller coaster than a shelf even though there was very little weight put on to them (the vertical boards held pretty well which is interesting). I also made another shelve around the same time I made the MDF ones but this one was made from plywood and it is still standing strong even after putting a huge old heavy tv on it for years.
Kinda wish you’d have tested to failure on dry vs wet plywood & mdf, like that last test. Also it’s probably worth mentioning in the swell tests, that that massive amount of swelling will do things like rip screws through MDF. Even if your shelf doesn’t outright fail, it’ll weaken and loosen considerably after even limited moisture exposure – not because the board itself is substantially compromised, but because the swelling and shrinking process is so extreme that it shakes the whole structure up.
Brad, I hate to break it to you, but those ARE NOT bags of concrete, but rather concrete mix. 😁 Unlike the plywoods, the types of binders used in MDF produce VOCs that significantly contribute to “sick home syndrome”… and I hate the weight of MDF… moving full sheets of 3/4” gets old really quickly.
Two thoughts: One, I’ve noticed that both MDF and particle board fail slowly when they have a constant load on them. Shelves that seem fine with a certain weight when built will gradually bow and eventually break over the course of years. I suspect it has to do with changing humidity, but that’s just a guess. Second, what is the water resistance rating of the glue in that plywood? I think most ply now uses water-resistant glue, but I know that if you soaked a piece of older standard plywood overnight you would just have a stack of veneer flitches when it dried out. MDF has its uses, but I wouldn’t use it for anything that is load-bearing or that has a high probability of getting wet. These tests pretty much reinforce my opinions formed over several decades of using the stuff.
Great article! As far as moisture resistance goes….30 years ago I had Formica counter tops made. The counter top guy told me to paint the underside of the back splash with oil base kilz or oil base primer before he installed it. He said this would keep the particle board from swelling up if the silicon caulk seal should fail. I also paint the underside of the front (especially near a sink). I have had great success with both applications. I would also paint the side of the particle board on the side of the cut out for a sink. I would paint any wood product for this kind of application. (I was a professional painter. I would understand if people are saying, they paint everything.)
Brad—always appreciate these kinds of educational articles; am wondering if you could do an educational article on LEDs 101? I know you’ve done a couple articles (which I’ve watched) on putting LEDs in your work but feeling like I can’t find a soup to nuts article from design to installation on LEDs in woodwork and think you’d be great at teaching something like that. Thanks for any consideration you give this idea.
Hi. Regarding the plywood I think the radiata pine as not a very good sample. As a plywood manufacturer we should test it in 72h in water in order to meet the international standards to ship it abroad. (72 hours and it cant unglue and need to have fibers after the shearing test). We do it in Ellitti and Taeda pine, and those are weaker than the radiata one.
Brad, firstly, thank you for your effort. But I’m an engineer so let’s really nerd out here and have some fun with this. There is a very specific thing at the @6:13 portion of the article that you are missing. Not only are you loading the platform with 300lbs, you are doing so across the span of the platform. From a statics standpoint, the study of forces on non-moving objects, this is an example of loading the lever arms close to the point of rotation. If you were to put the same load but focus it directly at the center of the platform, there would be a larger moment-arm on the lever arm, this being the side wood support for the platform. This test shows the ability of a platform to support a load statically applied evenly across its surface area, with minimal acceleration of the load. The same load focused at the midpoint of the shelf would have likely resulted in failure of the platform. I believe that the same load applied more rapidly with some induced acceleration acting in the same plane as the deflection of the platform would have also likely resulted in failure. Was that nerdy enough? Thanks for the awesome article man. Cheers.
Great tests, data, and presentation! Easy subscribe Would be interesting to see how different woods fare in more realistic conditions – say a room with high humidity over the course of a few months. The wicking action I think helps the plywood dry faster, but that wouldnt necessarily be so relevant if the air itself was moist. Would be a hard test to do though, something so subtle over a long time vs something more extreme over a short time. Maybe a decent humid air test setup could be constructed within a plastic box with a little fan inside and then stuck in the garage for a few months It’s a relevant point that warped wood can be stronger than flat wood, if you utilize the curvature to help distribute the force like you did in the shelf deformation test. Whereas I cant think of any situation where wettened mdf would ever get better The slowmo breaking looked like a cartoon with how much faster the wood floor broke out vs how long it took the concrete to start falling lol
Fantastic testing, Brad! Really well done! 😃 My problem with MDF is that it’s REALLY humid here where I live… So, if I buy MDF and there are scraps left… They turn into mud in about 6 months. 😬 BUT… There’s the waterproof MDF (which I forgot the name)… And I still need to try it! Anyway, stay safe there with your family! 🖖😊
The only thing I see that could be questionable when you place the weight on the shelf. You’ve got it dispersed across the two sides more than in the middle. I would be curious if you stacked one row of concrete directly in the middle vertically how much it would hold that would be a better representation of the strength
All my life I had (and still have) furniture made out of MDF/MDP because it’s cheaper, and my experience is : 1- The most common dammage is caused by screws and things placed in the side. 2 – As all MDF furniture sold on common stores are laminated, water in the face does nothing to it, but if the water goes to the corner, it will expand and ruin it (most times you can still use the furniture, but it will be ugly as hell). 3 – As MDF is used in cheaper furniture, I feel that the money saving in the structure of the furniture is always more limiting than the material. For example, I had a bookcase plank that fell of due to the weight of the books, but the plank itself only got damaged where the support pins were placed. There were only 2 pins on each side, and no screws. If they also had some screws or at least 2 more pins, it would have lived to this day.
As I look at this, there are 908 comments, so I’m not going to go through all of these to see if this has been noticed, but: 3:14: in the immersion test, it’s clear that the “map pop” plywood strips are crosscut in the surface plies, while the “rad” plywood strips are cup parallel with the grain in the outer veneers. That’s going to make a big difference in how far up the water is going to be drawn in the plies. Because of that, you really can’t make a direct comparison between the susceptibility of the two kinds of ply to absorb water.
Interesting and informative article. I work on cabinets (mostly refinishing existing cabinets) and I have the same experience with MDF shelves that I’m reading in the comments about warping over time. I’ve seen it on both ply and MDF but is certainly more pronounced in MDF. If we don’t end up replacing the shelves for whatever reason, I just flip them over.
I’d love to have seen the edged MDF tested until breaking. For a follow up consider mdf versus moisture resistant (mr) mdf AND acetylated mdf (e.g. Trycoya). The latter has the wood fibres chemically modified before bonding making them hydrophobic. It is claimed to be suitable for structural work outdoors. Very expensive but, if it’s as good as claimed, you might get a free sample from the manufacturer. Would be really interesting to see if the considerable extra expense is worth considering for e.g. making perfectly smooth external doors and trim.
Interesting information. Thanks for spending the time doing it. But after building cabinets for 50 years. There is no comparison in the quality and strength of the cabinet between MDF and plywood. The plywood is going to be much lighter and much stronger because all of the joints are far stronger with plywood.
Another great article. In the UK we have different grades of MDF big box is worst ( crumbly edge ), normal MDF and MR MDF ( moisture resistance ). Edit after a little research Medite ( better quality MDF maker ) also do a Flame retardant MDF, no added formaldehyde MDF, Exterior MDF, Breathable MDF, Lightweight MR MDF, Industrial (High density) MDF .
The only thing I would say is that by widening your gap that the mdf had to span you built in a flaw to your test because no matter the material, the wider the gap with weight centered on it, the more deflection and lower load capacity it will have. Wish you’d kept the gap the same width as when you were testing to 600 lbs. at that width you might have actually gotten to 1000 lbs. Also, did you consider testing plywood with a hard wood edge banding? That’s the most common method is hobbyists use. Love your content and the conversation.
💢 I live in Belgium/Europe. I have access to several MDF manufacturers and can tell there is a 1 to 10 difference form one board to another. In low cost DIY shops you find boards you can tear open with your nails and bare hands. Next you find boards like the one you seem to have in your article. Then there are green boards that can withstand water in reasonable conditions, you can for example build floors or bathroom structures with it. And next you have HDF that is very hard and even need to predrill to avoind snapping te screws. Size of fibers, ratio of glue, compression and additives are 4 variables of the MDF equation.
That new MDF snap-dance is gonna be a big hit at the club! 😀 What really got me was the sealed MDF still swelling like crazy. In the past I’ve used SMD Sunflash fiberglass resin to seal MDF, but after seeing this, I’m changing my materials list for a couple sheltered outdoor projects to avoid MDF entirely. Thank you!
Home depot lumber/building materials/hardware department supervisor here… I have many, many questions. But, I’ll just start with I would be interested to see the results if pressure treated plywood was added to the scenario. We store out PT plywood outside a lot of the time, and when I tell u I have zero faith in its ability to survive all weather conditions, I mean it. Those bunks come in and if they have been sitting outside more than a week or so, half of the sheets are unusable. Bowed and bent in every direction. I don’t get it. Ain’t it supposed to be able to handle rain? Lol… it’s “all weather” but a little bit of rain will completely destroy it. Makes zero sense to me. Also, I was very surprised by the outcome of the MDF. We are taught to tell people MDF can NEVER get wet. I have changed what I tell customers and how it train people based off your articles. Thank you for that .👍💪💪
I was trying to break a piece of MDF in half by leaning on it a while back (I wanted to take it to the tip, and it was too big to fit in the car). I didn’t realise that, as your article shows, it fails abruptly with absolutely no warning. I suddenly found myself leaning with no support. Not a mistake I’ll make again.
Hey, from first-hand experience I can tell you if your tests fail it is 100% your own fault. I say this because my son had a dresser thing you know where you put clothing, socks underwear etc… anyway we gave him a fish tank and a goldfish and set it up, sometime later the top of the dresser had swelled and was not even smooth or leave or sealed anymore, it looked bad so I went out got a new sheet put it back on top after it was painted and it happened again, I guess I should have tried maybe that weird laminated thing or just used plywood 🙂 Good luck.
I have a 55 gallon tank resting on a half inch MDF cabinet, I don’t trust it but it’s probably pusing 800lbs of tank/water/stone with no noticeable deflection. E: Ahem, I believe the proper term they used was “marine grade particle board” or something along those lines. Maybe something to look into if you want to give it another whack.
Water? There IS a water resistant MDS version – about two bucks more per sheet. MDF dust is much worse. To survive in wet areas unless it needs to be well painted/sealed. You’ve heard of veneers and paint, right? It also depends what you are making. MDF is MUCH flatter than most timbers WITHOUT sanding it or needing a thicknesser. For Loudspeakers, MDF trounces timber – Game, Set, Match – better resonance distribution. Timber resonates. Great if you’re making a stringed instrument – the exact opposite of what’s needed for speakers.
When I build cabinets (years ago) for a sink or any use where wood would be exposed to water, I use Marine Grade CDX plywood. That stuff never rots, It’s been a long time since I have built cabinets, can who still buy Marine Grade CDX with same formula we had years ago?? With CDX plywood, you could place it in the ground for years before it would start to deteriorate. It was expensive but if you ever discovered you had a long term leak under the sink the only damage would be is the paint had bubbled. I have done umpteen complete tear outs due to MDF and God help you if you had a trailer house with MDF.
Ok, so I sell ready mix concrete. Saying cement isn’t wrong in this aspect lol. Those bags contain Portland cement powder, gravel, sand, and some powdered admixtures probably. Once you ad water, it’s concrete. Would a bowl of flour, sugar, and other dry ingredients be cake? I don’t think so until you add your liquid. Not even batter until then. All this to say, you weren’t wrong lol
You still missed the mark a bit. A wet towel isn’t enough. You need to get the mdf soaked like it was with the dye – maybe even for a week. Mdf will disintegrate after prolonged water exposure, such a hidden plumbing leak. You can poke holes in it with your finger when it breaks down. It turns to sawdust.
During Christmas week of 1984, my wife, 9 yr old son and I went to my mother’s house 100 miles south for a week. Temps dropped to about 22 degrees Fahrenheit, enough to freeze the water pipes in my mobile home. It was a 1969 model, built with 3/4″ MDF flooring. The water covered the kitchen, living room, and hallway floors, all carpeted. We tore up the carpets and replaced them, and over the next 6 months, the floors started sagging between joists. I had to pull up the new carpeting, and replace the flooring. I used 3/4″ CDX plywood (I think about $8.00/sheet at the time) and it’s still there, having had pet water spills and another 2-day flood sit on it. I’d probably have had to replace MDF at least twice more.
Anyone that has worked with these products absolutely knows their limitations. ANY glued wood, whether it be plywood or MDF or Oriented Strand Board, will ALL suffer significant water damage if exposed to it. It also fails dramatically right when LEAST expected, like say on a bright sunny day when temp hit the high 90’s while you are relaxing in your pool side Chaise having a few pina colada’s to stave off the heat………when suddenly the expanded hot roof damaged OSB or plywood collapses right into your Dream Home. Yea, that actually happened to me. The BEST Roofing plywood is a special type of structural plywood called Marine Grade Plywood. It is not cheap for a reason. IT IS THE BEST. OSB takes longer to get wet than plywood but also takes longer to dry out. When used as a roof sheathing, this tendency to hold moisture means it can degrade faster than plywood when exposed to chronic leaks. (Think Asphalt Shingle roofs folks) MDF is mostly used as a cabinetry material or wood trim material. Just pay the price for quality and stop the Cheap crap unless you are trying to flip a house. Then of course go cheap, by the time it fails you will be long gone with the DOUGH. IF you are buying a HOUSE make Damn Sure you hire a professional inspection service to evaluate ALL the structural elements, plumbing and electrical or you will be paying thru the nose later.
Built custom cabinetry, shelving and whatnot for 30+ years and have never heard any tradesman call it “edge banding”. ‘Finished edge’, ‘nosing’, ‘front edge’, ‘trim boards’, ‘front supports’… probably a bunch more names for it. We always use ‘edge banding’ if it’s just a veneer over the edge of the shelf material.
The thing that’s hardest to test, but that I’ve observed in the real world is how in humid environments over time the ambient moisture tends to soak into MDF and make it sponge up, and weaken then fall apart. Which is why when I was looking at vanities for my bathroom remodel, I looked specifically for wood construction and immediately nixed any that had any mention of MDF
Interesting of the many US ‘woodworkers’ I watch I have never seen anyone use MRMDF (Moisture Resistant MDF) it has a green core and takes a screw fixing better that plain MDF (with a pilot hole) it also paints better both on the face and the edges + it makes less dust when cutting I don’t use MDF at all now on MRMDF (yes it costs a bit more) they also make a fully moisture resistant MDF, but I have never used it but there is a article by a guy named Robin Clevett on youtube where he left it in a tank of water for a month, he used it on the exterior of a building for soffit & Facias!!! I’m in the UK, do you have the other ones out there?
Watched the last article and this one and found them both pretty interesting but I had a couple of random thoughts/notes I wanted to share. The line for the radiata pine on the chart at about 6:52 I think suggests some kind of non-elastic deformation above 400lbs. Maybe that was the eye-bolts getting bent/pulled out? or maybe one of the layers developed a crack? There’s also just not that many data points so it could be just one of the measurements being flawed in some way. The bow going up making the board stronger makes sense geometrically: that’s the design of the hoover dam. Something that might be interesting w/ the boards left standing in the water is weighing them to see just how much water they’ve absorbed giving us some more things we could graph (though I’m not sure just how actually useful those points would be for comparison purposes they might be fun to see). The way the three materials fail will likely be different and somewhat interesting. In the case of the mdf it’s probably relatively tame when it fails and will likely break horizontally with relatively straight edges whereas I think the plywoods due to the grain structures will be a bit more spectacular w/ more jagged edges to the breaks and will probably be a bit more likely to fling chunks out. That’s my guess anyway so it’d be cool to see it put to the test. Also, if you’re gonna be intentionally breaking these boards you might want to consider some safety squints.
The MDF will sag much worse than plywood over time. Even a tall beam-like section will. Just look at older MDF / particleboard furniture or shelves. I’m not saying a plywood or solid wood shelf won’t sag but they won’t be as bad or as quick as MDF! I’ve seen shelves fail to stay on the pins because the sag took up too much length and the whole unit was garbage. The real problem with getting MDF wet isn’t getting it damp once; it’s the third time that will turn it into powder. Even OSB does this. The water makes it weaken more quickly with cycles of wet / dry. To the point where any rational person would be wary of using it for any kind of critical or load bearing use where water could ever be a factor.
you talk a lot about the different types of wood in the ply, but if you care about wet behavior what’s more important is the glue. There are a lot of different plywood ratings, interior, non-structural, structural, structural exterior, marine bonded, and BS1088. These ratings refer to both the quality of veneers, whether they promise to not have internal voids or not, and the quality of the glue. Exterior uses a wateproof glue, and also marine ply uses high quality veneers with no voids. BS1088 has been actually certified waterproof, but marine bonded just uses waterproof glue but is not actually certified. I’ve read a recommendation to test a particular brand of ply for boat building, you can do a boil test. boil the plywood, then let it dry out again, and if doesn’t delaminate, it’s good enough to build a boat. (but you’d still seal it with epoxy etc)
MDF is a junk product for off the shelf use. MDF only has strength vertically not horizontally. MDF was designed for trim and other visual only products as it is cheaper to manufacturer in longer lengths. It is essentially a cardboard product that is compressed with glue to create a moldable product. Real wood and plywood has the ability to soak and then dry overtime. That is why houses from the 1950s and earlier didn’t rot with no water, moisture, or vapor barriers. If you leave the plywood to air dry rather than using a fan it would go back to the original size as it normalized.
MDF is for cheap projects. Wanna save money and replace things every few years then use mdf. If you live in a humid climate I wouldn’t even build a speaker box out of MDF. Let’s see- scientifically ply wood is multiple sheets of wood glued in layers with specific grain alterations and MDF is saw dust that’s been glued and pressed to resemble a board. MDF is literally HIGH FIBER CARDBOARD.
I don’t think I ever seen a article by this guy (Though my memory sucks).. So I didn’t see what prompted this update.. and.. I have a MILLION ideas here.. some of which is.. Why is he stating the obvious”.. also.. I have a billion OTHER thoughts… f.ex. There ARE specific TYPES of ply-wood intended for different uses.. F.ex. there is plywood LITERALLY created to be used while making a boat.. yes.. to be the hull (though then you usually cover it in specific two-component plastic paint), but also possibly to be the bottom of the boat, OR to be used as the board you throw out onto a bridge to leave your boat.. THOSE suckers would be VERY fun to be seen to be put to the test. .. Some thing he mentions (like the strength of an MDF shelf with a hardwood-so-and-so.. ).. are things that.. I already knew, BUT I kind of think he failed at adding context.. I mean.. IF you have a shelf.. and then a different shelf.. and you want to compare them?.. fair enough.. a good experiment is a good experiment.. BUT..i f you chose to add an EXTRA thing to that first shelf?.. why not do so with the second too?… ALSO.. why not try to do the SAME thing.. but NOT use hardwood?.. I mean.. I went to technological secondary school (kind of the most impressive secondary school in Sweden, but.. also not so impressive compared to.. I dunno.. A university class?.. or.. actual real life experience?.. ).. either way; What I wanted to get to was the heavy math I did (it WAS the class of choice IF you wanted to become a civil engineer.
Like fake karate, you spread the weight two bags wide. All you did was test the cleats. If you applied pressure of weight just in the center say with a single two by four with the weight applied only over the two by four and not spread out then the test is more valid. Karate board breaking is a fraud!
Whats the point of testing MDF against Plywood in terms of waterresistens or strength? You use MDF mainly as a door or sometines your sides at your cabinet but at least together with a waterproof finish on it! Why should the MDF itself get that wet or endured by heavy cement? If we talk about well made furniture it is way more imprortant what you can do with the material and if there are any emissions in your childs room!
Hello Two bags of concrete side by side is not the same loading as one bag on top of the other….so you are not comparing like for like with respects to the applied loads. The bending moment on a beam with a uniformly distributed load is half of that compared to the same beam with the distributed load all applied at the mid point. Interesting experiment none the less.
The reason the MDF snapped was because the space between the supports in the second test was wider apart which made the middle weaker. Its the same idea that if you take a 2 ft 4×4 and support it at 45 degrees and do the same with a 4 ft piece you would be able to drive a vehicle up the 2 ft but it would snap the 4 ft.
It truly is apples and oranges. Any neophyte with a years experience knows that water makes MDF swell. Over time materials do change (in the beginning plywood was considered cheap garbage for exterior sheathing, then waterproof glues were invented). Use the correct product for the project in order to yield the best results. Want a perfectly flat table top, apply solid wood veneers to both sides of MDF or HDD with either veneer or solid wood edging. I use solid hard woods, veneers, exterior plywood, interior plywood, Baltic Birch, MDF, etc. Simply depends what I’m making. I would NEVER use MDF to make shelving or place it in a bathroom. I have mostly always worked in the very high end, however, it truly doesn’t matter, using the correct materials for the project is always best. And yes, use OSB for beams for it’s superior shear strength.
Why are people so worried about getting MDF wet? What on earth are people using it for that you are constantly risking getting it wet? Are people making boats out of it? I can’t think of a single time where I have used MDF in a situation where it would ever get directly wet. If you are worried, put 3-4 coats of poly over it, just like you would with anything you wanted to protect from occasional spills.
An interesting thing, I removed MDF baseboards in a flooded basement, 6″ deep, severely soaked, and it remained fully, dimensionally stable. It was so flexible I could almost bend a 5 foot radius without snapping it, but it didn’t swell one bit. The only reason we threw it in the dumpster is because of mold. Else, we could have let it dry and reinstall it. I think it’s a different MDF than sheet goods, because I’ve seen them double in thickness when soaked. I like the t-shurt.
Good article as always. I enjoyed the various tests you performed and have no complaints. I do wonder how well a “MR/moisture resistant” mdf such as Medite MR or a pressure treated plywood would have faired. I know we don’t usually use pressure treated plywood much as woodworkers but I do use MR style mdf on occasion. I am a fan but I’m not THAT heavy! 😊 Ron
These look like a combo of fun, curiosity, and hard work to make. Thanks! For future one’s regarding water exposure: 1) Seeing Marine Plywood in comparison would be interesting to see if/when it’s worth using 2) What easy and fast to apply finishes (and how much) return adequate water protection. Eg how far Water based Poly or Lacquer go vs expoxy. Is soray can sufficient.
I built a boat and a 17 foot sea kayak out of top quality marine plywood, the kayak in 4mm and the dinghy in 6mm for the hull. I got lots of offcuts and used some on my chicken coup. It wasn’t treated with epoxy or paint, nothing and it’s been exposed now for over 3 years to soaking wet winters and over 100F summer temps and that ply has faded but the ply’s are all still glued tightly together and nothing has swelled up. If that was similar thickness MDF it would be destroyed in one year easily, especially in the wet winter months. I also built a basic gate for the coup and used the ply for the corners to give it some structural integrity, those little triangular corner pieces are also still in great condition
I have a genuine question – Is there a GOOD reason why the glue used in plywood and MDF production is NOT waterproof ? Is it “expense ? and 2. Is there a GOOD reason NOT to completely urethane-seal a board intended for an application of the sort we’re seeing here (shelves, etc. ) to PREVENT water incursion – especially over TIME ? I’ve EVEN gotten some FANTASTIC EXTENDED-USE out of Urethane-sealed boards of VARIOUS base materials by using Spray APPLIANCE Epoxy paint of VARIOUS colors or EVEN as a compatible under-color BASE for Conventional Paint Finishing. Yeah “Primer” is less “expensive”, and I’m a HUGE Primer fan – especially SPRAY Primer …, but 3. Is there a GOOD reason NOT to seal the Board Material before putting it into service ? Shoot – I even hit drilled holes and similar cuts, with a matching-color shot of Spray Appliance Epoxy so that I’ve protected my work as far as is reasonable . I’m GUESSING my fix for the water-based glues holding both Construction-grade (!!) and Finish-Grade plywood, as WELL as MDF would have fared pretty well in the absorbsion tests, but I really AM curious about the 3 questions I started here with . If ANYONE can offer input re: ANY reason besides PRODUCTION EXPENSE, it would be welcome ! Thanks ! Chuck .
1 bag of cement on the shelf for 3 days outside would show Massive difference you tested instant deformation not over time. If you leave a sheet of 6 x 4 1″ mdf leaning against a wall outside with daily rain it will bow in the middle and be ruined by it’s own weight after a week. Plywood is fine a week in the rain. I ruined a 100 hour carpentry piece to learn that. Why not sprinkler, why not outside?
The comments you received on your last article were from dumb people (like the one you highlighted at the beginning of this article). Every material has its application and if there’s material failure, it’s the fault of the builder/maker for not knowing which material to use for which application. I’ve built cabinets and shelving units with 1/4 MDF (yes, 1/4) that I can guarantee will outperform most of the plywood crap I see people build. But you know what I wouldn’t build out of MDF? A boat.
Engineered wood products can hold up incredibly well if they’re well-supported. I have a desk that’s almost 30 years old with a 1/2″ chipboard (low density) top that hasn’t warped at all. It’s 60″ wide, 32-ish” deep (not sure off the top of my head), and has supported hundreds of pounds for much of its life – I’ve stood on it next to multiple CRT monitors! But it’s supported by a pair of 20″-wide, full-depth cabinets, to which it’s clamped down. Those are attached to each other with an old-fashioned modesty panel.
After MDF has been wet, it’s no longer structurally sound, but I still use it for forms, templates, and router carving projects. I glue a few layers together and use the router to make dishes and trays, then cover with epoxy or polyurethane and paint. If it’s so far gone that it’s flaky and brittle, it makes some pretty hot fires, once it completely dries again.
I’m a bespoke furniture builder in Brazil. Here almost 100% of woodwokers use MDF foi furnitures and everything works perfectly. Sure, MDF has its owns limitations, but is a great material. Pretty reliable, has some great textures and colors, no need to caulk and paint (here we use mostly melaline covered MDF, unless you want a Lacca finnish). Plywood it’s most expensive here and need more work to get the same visual result. Great article though.
Can you borrow me some of your knowledge?I wanted to make a 1.8m (about 6 feet) long computer table without the vertical plank that usually those tables have. What thickness of MDF i can use to do that without much warping? I dont have much things in my table, just screen, mouse and keyboard. But ireally didn’t wanted the support plank under. Awesome article by the way, keep up the good work!
Did you put a coat of total boat on the cut ends of all of those pieces too? Doesn’t look like it. Total boat, if applied properly, should have been completely waterproof. I beg to differ with “do not mix flame with wood”. There is an ancient Japanese technique for making wood not only insect proof, but also water resistant. Shou Sugi Ban (or Yakisugi). Pronounced “shoe-shugee bahn”. It’s been used since at least the 1700’s. This is a technique as you just did, charring the wood to black with a scale-like surface. Brush off the loose ash, and seal. It’s still being used to this day, even on house boats … and it’s become a very expensive product that’s used not only for furniture, but for siding. If it’s burned, applied and sealed properly, It resists rot, insect infestation, and water (even salt water, which is how they can use it on house boat exteriors). Next time you char wood “just for fun”, check how waterproof IT is 😉 I mean, how do trees that are hundreds of years old survive a wildfire … as long as it doesn’t kill the roots?
Your final weight test wasn’t comparable because the span was a lot more, in your shorter span I think you would have gone further, but I understand your goal was not a linear test but to break it! Like the MYTHBUSTERS,” if it doesn’t blow up with the mythical amount of explosives, use 1000 times as much!
Thank you for this article – very informative. I really liked how scientific the experiments were presented and would like if you went a bit further. When you put the flame to the wood, it reminded me of the Japanese method of preserving wood posts that go into the ground by charring to create a thin carbon layer that resists water absorbing which prevents rot. I am willing to bet folding money that you could come up with an experiment to show or debunk this. Thanks again.
From my personal files It’s a conspiracy for 2 popular items 1. MDF, every instance I installed MDF has failed, sooner or later they all do. 2. Super Glue, I will glide across plastic and ceramic sometimes it seems what I put it on becomes alive and just will not stick where I need it. BUT let a molecule of that stuff touch your skin and Ka-POW your stuck.
As a residential contractor, I’ve replaced under-sink plumbing in dozens of sinks, possibly hundreds, I don’t really keep track. Cabinets made of of MDF, if the leak has been around for a while, say multiple weeks or even months, I’ve put my hand through them. However, I’ve replaced under-sink plumbing in kitchens with plywood floors that had leaks that may have been there for years and the floors were just fine once they dry out. MDF is fine for construction that you know will always be dry, say a bedroom dresser or in-wall desk. But if there is ever any chance of moisture, say kitchen cabinets or bathroom vanities, you better go with plywood. When I frame houses, I won’t even use OSB on the floors because I’ve seen what happens if it gets wet and it’s inevitable that the floor of a house will eventually be wet. Just like MDF, OSB has it’s place, but it’s not a replacement for plywood.
these temporary wetting tests are a poor representation of the long-term viability of these materials. Come back with a 1 year test of leaving these outdoors to the mercy of your local weather in all seasons and you’ll be able to see which materials were designed to fail. This is called “accelerated aging”, and it’s the actual scientific way to test these things.
Your plywood shelf has the grain running the weak direction with stress transmitted perpendicular to face grain. Grain direction makes a big difference on plywood for deflection & bending failure. Radiata pine doesn’t usually carry an APA stamp but an APA certified touch-sanded, 7-ply, 23/32″ panel will have a moment of inertia (governing deflection) almost 6X larger when with the face grain running the length of the shelf and an effective section modulus (governing bending failure) almost 2x large with the face grain running the length of the shelf. MDF is homogeneous with an effectively random cellulose grain so it will perform about the same in any orientation.
Sooooo… When they say “plywood”… Can they be more specific? I mean, I’m not sure completely on names, but I know I’ve worked with different types. One is primarily wood chunks glued together in sheets subsequently glued together. Another is sheets of wood strips glued together crossing the grain. Then there’s one that’s got thick sheets of veneer around what’s kind of like a particle-board core….
Example … Ikea Billy bookcases vs a basement mini flood. About 1/2 inch of water came into our old basement and the solid wood Billy recovered after the wood dried out, the fancier MDF version ultimately deteriorated to the point of uselessness. Water was pulled into the end grains and solid wood survived much better than the MDF. From experience plywood also fails when the end grain faces submergence if the plywood isn’t sealed.
Not only is material strength important but geometry plays a far greater role. That’s why aluminum structures can be so strong. Due to geometry. ie. diameter of tube or square stock, I or H beams, trusses, and triangles, and combo of all of them. You changed the geometry dramatically by adding the hardwood edge.
Why did you test MDF with hardwood edge banding, but not plywood with hardwood edge banding? You have a straggler variable there. Also, I live in Florida and just the moisture in the air is enough for MDF to slowly expand over time. MDF, sadly, is completely useless in florida unless you have lab-like humidity control.
I made some book shelves 20 years ago from (I think) 3/4 inch plywood, perhaps 4ft wide and 1 ft deep (made from leftover scraps from another project). They have a distinct bow/sag in the fronts today. I did support them with a datto plate on the rear, but the fronts have sagged over time. If I were to do this again I’d support the front with ‘something’ and maybe use 1 inch instead (books are heavy when you have a hundred of them), perhaps a piece of solid trim on the front would have helped. Or design it in such a way that the shelves can be removed and flipped over to reverse any deflection. MDF is good for a lot of stuff, but just like plywood or solid it has unique weaknesses. MDF is really forgiving when painted and won’t develop surface cracks over time (read: good for small desks or tables, with supported tops). If you want something that will be strong you would be well served to design your project with vertical support as a key feature rather than letting the wood handle it (compression vs tension). If it might get wet (or you have high humidity), either seal it very well, or consider plywood or even solid. Can’t really beat solid though, ‘it just works’.
We might point out that plywood comes with different types of glue. The kind you tested is the weakest. It’s for always-dry areas only. When most people think of plywood’s wet performance they are thinking of exterior-type glues, as are used in all exposure-1-rated panels for sheathing, subfloors, underlayments, and any areas which might get a little wet. They can last a year outdoors in the rain without major loss of performance. Your towel test for MDF I’m sorry was not real world. Think of nice custom cabinets where you use it as a sink cabinet bottom. I’ve seen many, many particle board (& some MDF) which just melt under that very slow drip that often happens over months & years. Plywood lasts exponentially longer under those real-world types of long-term drip exposure.
You should try real plywood like baltic birch plywood with waterproof glue, with 1mm layer thickness, that one is simply indestructible (I had one big chunk on balcony, open rain, sun, snow, frost… after 2 years like that it got just black fungus/mold on the bottom… no visible deformation or layer separation)
Not all MDF is created equal, same with plywood. They are 2 very different materials and knowing when it’s better to use one over the other is important. MDF does have some advantages. It’s easy to work with, uniform, and usually in stock when plywood isn’t. It’s ability to dampen sound is much better than plywood which is why subwoofer boxes are made of it. It’s major disadvantage is how it loses stability over time. Anyone that’s owned a shelf made from MDF will tell you it doesn’t take long to sag. It doesn’t stand up to abuse like plywood can. Move a piece of MDF furniture and it starts to wobble. For structural purposes plywood is better in every way. The sheathing and subfloor of our homes is plywood for a reason. I don’t understand why people try to argue otherwise. Don’t worry, I know what you’re thinking, just add more support. Tell us how needing extra reinforcement for one material than another makes it a better material.
If I can get away with it, I will always choose plywood over MDF just for weight purposes. As for water damage, I am in agreement with what you showed. Plywood will change its shape more but tends to still be structurally sound. MDF absorbs a lot more water and the damage gets worse as time passes. Its really up to the glue, while with plywood its more up to the fibers. I used to handle large amounts of plywood, Melamine, MDF, and some other composite woods. The melamine and MDF were by far the heaviest. And the particle boards showed a lot more damage from water, and seemed to have bigger problems with mold once they got wet. Plywood and pine still got moldy, but mostly just surface stuff that could be lightly sanded away. MDF and melamine absorb and trap so much water and it seemed like thr mold would dig in much deeper.
Sadly, the people who poured the walkway along our garage (done before I was around) brought it right up to the MDF siding. When I went to paint, some of the nails were out a good quarter of an inch. To give the MDF an edge, I used the plastic 3/4″ quarter round and siliconed the heck out of it against the garage and concrete (none on the paint, so paining was not compromised). Crossing my fingers.
Sorry about this nonMDF related rant: why would you call a bag of powder concrete ? Concrete is a mix of cement, water, gravel or stone, and other additives depending on use case. Concrete mixers dont mix a powder for no reason, they mix the mouldable liquid so it doesn’t start hardening 🙂 Then concrete gets poured into the mould, hardens and you get concrete base, walls, pillars, etc. Again, sorry, but that’s English 🙂
This test is unfair. Standard MDF does absorb water but for interior applications that’s fine. You can get exterior MDF that performs very well. As for creep/sag, if you want to use it in a load bearing application like shelving, the surfaces are veneered to form a stressed skin panel. All this data is freely available and MDF manufacture is remarkably consistent. Plywood is a different story. Few manufacturers have good quality control. Cheap stuff has core gaps, pleats and adhesive with so much extender. I have even encountered urea adhesive with brown dye in it to look like phenolic. About the only reliable plywood is Finnish birch, where the quality control is so good that you can treat it as an engineering material with guaranteed strength properties.
MDF is not meant for construction purposes or usage in humid environments. However I used Medite Tricoya to build my isolated garage doors. It’s immensely stable and water resistant like teak, even without paint it holds itself. This type of MDF is also not meant for construction purposes but but it’s close to ideal for outdoor usage. Keep in mind you have to use the right glue, look at the specifications from the manufacturer. Standard white wood glue is unsuitable.
Yes, but what brand/ type/ specific composition of MDF? There are many different versions of MDF. I am more interested in seeing a comparison of 5 different types of MDf that represent the spectrum of MDF products. Also, people who anecdotally say “MDF is bad” need to identify the composition of the MDF product that failed before they draw any meaningful conclusion.
this is why you can’t build with MDF in Michigan, or any other swampy or formerly swampy areas. There’s too much humidity in the air any time it’s not freezing. The MDF will just soak it up overtime and swell. If it has any plastic veneer, expect the seams to start popping in 3 years, even if it’s kept inside and dry.
Mdf is not meant to be soaked. I don’t understand the point of this test. They make a product called armorite wich us basically exterior grade MDF. I work at a high end cabinet shop and we make out door kitchens out of exterior grade MDF or Armorite and we haven’t had any problems. MDF is not meant to get wet it’s indoor use only. This test is silly.
Most likely real world dampness test of sheetstock is a sink cabinet. Either angle stop develops a leak or the faucet gets one. Slow constant water source which destroys the fixed shelf. And this article is obviously indoor cabinet focused. Talk about sheetstock for applications in an unheated garage and you learn that plywood has the X grade which MDF does not. And zero credit for shear strength. MDF wins for thickness consistency from the manufacturer and surface finish and economy….
I’ve been doing cabinets for over 25 years. Sink cabinets with an MDF bottom will turn into a bowl after a long slow leak. Plywood might get moldy, but it will still be flat. MDF shelves are a no-no, unless they are 16 inches or less wide, as they will sag tremendously over time. Just getting rain on the ends of melamine shelves causes them to blister as they suck up the moisture. A true sign of cheap cabinets is particle board.
This was cool and funny. I’ve never made a shelf or a bookcase out of either plywood or mdf, though. They both sag a lot. How about a test with solid lumber? Wide glueups are easy, and if you want easier, you can buy solid wood shelf board, already planed to width and thickness at most big box home stores. For rough work, you can just use 2x12s side by side.
I’m not a carpenter or woodworker of any sort couldn’t tell you the difference between any type of wood. However I find MDF just so unappealing, it offends all my senses, feels bad, looks cheap, smells bad when cutting it… I’m sure there are very good uses for it but as someone that knows nothing I could see why other people don’t like it. Isn’t that what cheap put together yourself furniture is made of? If so humidity kills it, leave it in a humid place and gravity will do the rest.
It blows my mind that they make mass market cabinets that go under sinks out of particle board… It always gets water on it, bubbles up, gets gross, and gets even weaker…. I’ve had to cut out and replace them in both houses I’ve owned. This time I went with thick plywood and about 1/8th inch white plastic sheet on top…
You would not have done well at a job I had when I was younger – lol! 😉 I had to test the strength of concrete with different admixtures. I’d have to make small concrete tubes with various amounts/types of strengtheners then put them in a vise-like machine. It would slowly add pressure to the tube until finally it exploded. Of course I had to stand fairly close to watch the dial to see the point of failure. Hated that job. 🙂
A GREAT test would be, testing which of the three failed at the pins, and how they failed, in standard shelves, because of being overloaded. Common particle board (as opposed to MDF) is a recipe for disaster, at the pin areas. To solve or greatly reduce that problem, one could add stiffners under the ends, to spread the load across the entire ends.
Climate plays a huge role here, I grew up in coastal Florida where MDF and particle board furniture just does not hold up, swells and crumbles from humidity alone, if it gets wet with actual liquid water it will never dry, its now trash. plywood lasts a while but eventually de-laminates also, you even have to be careful even with solid wood, pressure treated wood may make it 5-10 years in ground contact, untreated wood will not make 1 year in contact with the ground or moisture. I moved to the high desert west for a while and I was shocked at the difference, unprotected bare wood buildings stand for over 100 years or longer, particle board and MDF furniture are rock solid for decades indoors. people treat wood differently there also, you regularly see wood in contact with he ground as a regular course of construction which just looks wrong to me.