MDF, or medium-density fiberboard, is a popular material for interior and exterior construction projects due to its incredible resistance to moisture and weather conditions. However, it should not be used outside due to its poor resistance to moisture and weather conditions. To waterproof MDF, select a sealer or primer approved for use with MDF.
MDF boards are water-resistant to a certain level, but they can get weathered after prolonged exposure, making them more vulnerable to moisture. There are products on the market that are more resistant to moisture and even fire (exterior grade and interior grade). Moisture-resistant MDF can be used outdoors if properly sealed, and there is also an MDF product called Extira manufactured for exterior use.
MDF is inherently prone to swelling and warping when exposed to moisture, making it unsuitable for direct exposure to rain, snow, or extreme humidity. Protecting MDF for outdoor use involves waterproofing it to avoid moisture penetration. There are two approaches to “waterproofing” MDF so it can withstand moisture in high humidity areas: use ure Resistant (MR) MDF or make it water-resistant.
Exterior-grade MDF can withstand harsh weather conditions, including rain, moisture, and UV rays, without warping, cracking, or expanding. Prime and paint are the best ways to seal and protect MDF. MDF is made of wood fiber bound together by resin adhesive, making it moisture resistant but not waterproof. Water-resistant MDF, also known as MDF Exterior, is suitable for use in damp areas, both indoors and outdoors.
📹 MDF for use outside
This is a short follow up of the how to paint mdf and how to mitre large boards featuring extreme tricoya mdf great for all weathers.
Is MDF or plywood better outdoors?
Outdoor furniture, particularly in the rainy UK, requires a material that can withstand the weather. Plywood is a better choice due to its water resistance, making it less likely to expand or warp due to moisture. Moisture-resistant MDF boards, like Medite Moisture Resistant MDF, are now available for outdoor use. For bench or treehouse construction, plywood or moisture-resistant MDF can be suitable.
If painting furniture after construction, MDF is an ideal choice due to its grain-free, smooth surface. Sanding the cut edges and using an oil-based primer are recommended for best results. However, preparing the surface for paint may compromise the natural look of the plywood’s veneered surface.
What are the weaknesses of MDF?
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.
How to protect MDF outdoors?
To make MDF water-resistant, use a high-quality wood varnish, sealant, or stain like Barrettine treatment, available in various colors, to make the timber look attractive and provide waterproof protection. For all-year protection, consider Sikkens products, which offer protection from all elements, including sunlight. Applying a few coats of the sealant is a simple process, suitable for kitchens, bathrooms, or exterior doors, saving time, money, and repair costs in the long run.
What is the durability of MDF board?
MDF is a durable material suitable for high-humidity environments, making it ideal for use along the coastline of eastern, southern, and western India. It is also termite-resistant, as termites thrive in hot weather and are more dangerous in cold weather. MDF is bonded under high pressure using thermosetting resins, making it resistant to damage from these pests. This makes it an ideal choice for protecting your space.
What is exterior MDF called?
EXTIRA is a No Added Urea Formaldehyde MDF precision engineered, high resin, high temperature cured all hardwood fiber composite used for various millwork applications where high moisture causes other wood composite substrates to fail. It is suitable for exterior molding patterns, window components, door components, exterior signs, column facings, cabinet components, core materials, gable vents and louvers, counter tops, star risers, stair skirting, and flat trim.
EXTIRA is a great substitute for Redwood and Cedar, with interior and exterior molding patterns available in all 16′ lengths. Its uniform density and excellent machinability make it versatile for use in moisture-prone areas and flexible for almost anywhere machine wood is needed.
Is MDF suitable for exterior use?
Medium-density fiberboard (MDF) is a composite wood product 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, several steps can be taken, such as using moisture-resistant or exterior-grade options.
What is the disadvantage of using MDF?
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.
How weatherproof is MDF?
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.
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.
Is MDF more waterproof than plywood?
For outdoor furniture in the rainy UK, plywood is a suitable material due to its water resistance. Unlike MDF, plywood is less likely to expand or warp due to moisture. Moisture-resistant exterior grade MDF boards, like Medite Moisture Resistant MDF, are now available at Cworkshop. These boards can be used for building new benches or treehouses in gardens, making plywood or moisture-resistant MDF suitable for outdoor furniture construction.
Does MDF rot when wet?
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.
📹 This stuff changed my mind about MDF projects
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Thank you for recommending this board! I read up about it while researching different boards and got really excited about it 🙂 Have you got any experience with magnesium-oxide boards? I would love to see you do a article on them sometime. I find the trouble with new products is the availability and price. Takes time before they become main stream enough so you can get them at your local builder supply. I live far north in Norway btw 😉
Haha you have to explain yourself to the experts here on YouTube, the ones who don’t article their work, I mean yea u hear that it’s MDF, yea we know MDF swells up, but I also heard you say that its guaranteed for 30 years or whatever it was, I suppose what I’m saying is, you’re very good at what u do, I doubt you’re using standard MDF outside 🤣🤣🤦♂️
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As a former builder of speaker boxes using mdf I used a biscuit joiner to assemble those and never had problems having to use screws or pilot holes for those. The biscuits also made sure the edges were flush with each panel. My finish for those were a textured paint that easily covered up any “flaws” in the edges and the seams never showed back up later as they aged. Your mileage may vary.
I’m not a woodworker. I made some shelves with MDF. My tip is to buy it cut to size to avoid the whole problem of dust. I did cover them myself with Formica, bonded with Roo Glue, which I highly recommend. It is much easier to work with than contact cement. The end result was excellent, because MDF is such a flat, stable material.
Burnishing the edges via higher grits or dull sand paper. Also works wonders for preventing how much mdf edges soak up. This is a technique we relied on heavy when making Veneer sandwiched mdf cabinet doors, with a routed edge profile. Its the complete opposite of when you work with maple that your intended to stain, where your opening the pores in the sanding process.
My tip for screwing any kind of fibreboard, chipboard, or strand board is to pour low viscosity superglue (CA) into your pilot hole, making sure to get some all the way around it. It’ll soak right into the fibres fast and cure up fast, so put the screw in immediately. This will bind the fibres that the threads cut into & make things far less likely to strip out. Of course you won’t ever be able to remove the screw again, but if you’re wanting to do that then you should really be using a bolt & an insert instead of a wood screw in the first place, otherwise it will strip out after a couple of times.
I built some cabinets from mdf recently and was pleasantly impressed with the “diluted wood glue” trick for edges … I first sanded the edges with 120 to remove any saw blade marks, then applied some diluted wood glue with a small roller and wipe away the excess immediately … After it dries hit it with some 220 and break the edges at this time as they will be solid now … At that time its ready to go but i did a second coat just for peace of mind … It turned out as smooth as the faces of the mdf – and i used the cheapest pva glue i could find !!! 😊
The drywall compound thing is from the 1980’s. Many cabinet shops have been using mdf for raised panels since the 1990’s. We use one of two products. BIN white shellac primer sealer or a catalysed solvent based primer. You sand to 240 grit apply two coats of sealer to the cut area one minute apart. You can use a brush. The BIN will soak in like water then harden. You then sand with 240 and prime the whole panel with your normal waterborne/solvent primer. No drywall compound or bondo.
To “waterproof” MDF, I mix 50% linseed oil with 50% mineral spirits and apply until the board no longer absorbs the material. After letting it dry, apply a second coat, 75% / 25% oil to spirits. Sand before final finish. This does not work over a sharp corner, so be sure to break edges. I used this technique to replace a long interior window sill that puddled water every winter and it has held for more than 25 years. The treatment creates a thin casing of waterproofing, so once applied, do not cut into it without repeating coverage.
MDF doesn’t just come in a single type. The stuff you get at the large box stores tends to be rather fluffy in the middle and doesn’t rout or mill very nicely. It’s also much harder to get a mirror finish on it. If you have access to a lumberyard that sells the nicer varieties (things like Glacier Green, Ranger Board, Medite, Arauco double refined, etc) you’ll get a better result in my experience.
I’ve made lots of shop fixtures and drawers out of MDF. Pocket hole joints. Have had them for years. Have moved them from one shop to another and all my tool stands are on casters so they move all the time. The biggest warning I’d have about using MDF is don’t let any part of the panel get wet. Cheers.
I wish I’d seen this a year ago. Had work done in the house and the builders used mdf for door facings, skirting boards and shelves. Painted them all with undercoat and gloss. Every single edge swelled up, looked terrible and felt rough. I sanded it all and redid it with different more expensive paint and the same happened. After the 3rd attempt led to the same rough finish I decided to spread a thin layer of filler, sand and repaint. Worked a treat but my wife wouldn’t believe it wasn’t my fault until she decided to add another shelf herself including painting.
A trick I learned from a luthier is to use Minwax Wood Hardener. This is a thin resin that soaks in and “hardens” the MDF when dry. This is especially useful when using MDF as router templates. Also, whenever I pre-drill MDF for screws or T-nuts, I soak the holes in this stuff. It really does work a treat. (Don’t get it on the surface if you can help it… it can be a bit sticky.)
I made a large desk top with 3/4″ MDF with a 1/4″ walnut plywood veneer and applied a solid walnut edge with a tongue and groove (the groove in the MDF). This has been a very stable top that has lasted many years with no problems. The biggest problem was that the glue in the edge joint swelled the MDF and made the joint difficult to make up. I would recommend a water free glue.
I had a recent project where i was installing a kitchen island made with cabinets from Wren, who makes them out of MDF. A couple fascia pieces were made of MDF as well and not really intended to be installed where rhe cut end would be visible but in my case rhey were. I was worried about cutting the mdf and finishing it so it wouldnt look super obvious what i did, so i looked online. After cutting the MDF and routing it (rounding the edge) i used a 50/50 cut of titebond glue to seal the exposed raw MDF edge. The MDF sucked it right up, turning dark. I applied 2 coats. Sure enough when dried it was super hard and easy to sand. After some regular prep i painted the edge with some colormatched (greenish) paint from HD and without someone telling you that the edges didnt come factory finished, you wouldn’t know the difference.
Another helpful article. The only thing I might add is that for years I’ve been using Confirmat screws to join pieces of MDF. After a pilot hole is drilled with a specialty pilot bit, these screws make the splitting in MDF a lot less likely. Confirmat screws are available in a couple of sizes, and Spax even makes a #6 size that I’ve used successfully in 1/2″ MDF.
I made a coffee table from MDF over 25 years ago that is still going strong. In that time it’s moved nine times (two of them international, one of those by sea), and survived three children who are now all teenagers. I also had a substantial table with full length multi-level hutch that was all MDF that was still going strong too after 13 years and was only scrapped because even dismantled we decided it was simply too big to bring with us overseas. It too had easily handled three domestic moves, and a few repositions, without any trouble. Maybe having worked in an MDF factory gave me an early insight into how to work with it on any project without trouble…but even durable furniture is quite possible with MDF if done right.
The screw you show has a “way to fine” thread, and the root diameter is too narrow. There are coarse thread screws available that are designed for this product. “HAFELE” is one supplier of these screws, and they call them CONFIRMAT screws. The proper screw has a rather wide diameter with a coarser thread. What this does is it allows the threads of the screw to be spread further apart from the fibers thereby minimizing the potential for failure. I have been using these screws since the 1980’s. The holding power is immense. If I’m not mistaken, I think they were originally designed for melamine sheet goods with a particle board sub-straight, but we found them to work well with a wide variety of man made sheet goods. I have an extensive background in commercial case goods and architectural millwork.
What so many fail to mention is that there are many grades of MDF. The premium grades and even some of the ultralight products have a more refined core (smaller particle size and consistent density). Forget the joint compound when sealing the edges. That is messy, takes a long time to dry and will be softer than the material itself. Fillers should harder to approximately the same hardness as the material you’re working with and MDF isn’t gypsum or paper. The absolute best method I have found over many years of trial and error is to apply Zinser B.I.N. primer with a foam roller. It is fast, not too messy and reliable. They key is to use firm pressure and multiple back and fourth passes, working the primer into the material. It’s ready to sand in about 45 minutes before applying a general primer coat and dries just hard enough that it sands perfectly flat.. For fasteners, confirmat screws are made for the application and work better than most screws. Knockdown fittings are the most reliable fastener I have found for MDF.
For MDF edges, I’ve been using an Abatron product—called Liquid Wood—which is a water-thin, 2-part epoxy created to absorb into rotted (“punky”) wood to stabilize and densitfy it. It creates a very solid, dent-averse edge that is waterproof and really tough. Abatron is a great company, too, focused on home restoration products.
If you’re looking for that smooth surface of MDF for painting, another good alternative is MDO (medium density overlay) or HDO (high density overlay). This is exterior grade fir plywood with one or both outer surfaces coated with a thin layer of MDF or HDF, so it has all the advantages of working with plywood but with that very smooth surface. It’s expensive, over $100 a sheet; I buy factory seconds for $15 a sheet that usually have one bad edge but the rest is good.
My best results for MDF edges is to not sand after cutting. Treat the cut edge off the saw with one to two coats of an acrylic primer undercoat (I use Layland which is made by PPG). Once dry sand lightly with 240 grit and you’re done. But like others said all MDF is not created the same so get the best you have available to you for best results.
The advantages of selling MDF furniture are mostly two: 1. It’s cheap and accessible, making it easier to sell. 2. It won’t last, ‘Planned obsolescence’, people think they save money, but actually, they need to keep buying new stuff every couple of years. So, you sell again. That second is also a good reason for you to avoid making your own stuff of MDF.
MDF certainly has its place in the building world. Like many, my biggest complaint is the weight. Another material I would like to see addressed is HDF or high density fiber board. I have only found it in thinner dimensions as it seems to be primarily for making peg board or used on the backs of cabinets, bookcases, etc. It appears to add some structural integrity without adding a lot of bulk or thickness to a project. But I would like to see any tips or other uses for HDF. Thanks for sharing all of your hard won knowledge.
I think MDF gets a bad rap in at least some cases because so many people use the term interchangeably with “particle board”. While it is technically true that MDF is a type of particle board, I suppose, the stuff you find inside most Ikea furniture that looks like compressed oatmeal isn’t the same beast as “proper” mdf. And don’t forget that there are moisture resistant versions of MDF, as well. Had a friend build a cabinet in his basement. He made the base out if resistant MDF, but the rest of the project out if regular mdf. His basement flooded by an inch, which never reached the cabinet itself, and the resistant mdf survived the flooding just fine.
There is one more disadvantage to MDF, they are heavy. Our house furniture apart from a few things I made are out of MDF. Almost all laminated, some have very nice textures too. They don’t look particularly good but let me tell you this, they are durable. I can actually use them to sand pine. They are incredible as long as they are dry and well built.
its heavy, doesnt flex, creates toxic dust that lingers in the air after cutting, dulls your tools, cant be fastened normally, cant get wet, and requires extra steps for basically everything making you not become a better woodworker in process what a great product i will say it takes acrylic paint decently and you can sell mini paintings on it
There are two places that it should NOT be used: 1.) anywhere that there is moisture or standing water. Unless thoroughly sealed mdf will absorb water, swell, and then breakdown. 2.) MDF’s inherent brittleness makes it a poor material for horizontal strength and load bearing. MDF boards used as shelves will now and break under much lighter loads than corresponding plywood or solid boards. MDF DOES make a fantastic base layer for paint and veneer if properly prepared.
I build a lot of MDF assemblies for the display industry. Don’t screw MDF- narrow crown staples and glue are as strong as any other method. I use 2P-10 on it or slightly thinned down aliphatic resin glue (so it penetrates the MDf) and narrow crown staples. Then spray it with two coats of shellac which seal the surface as well as the “end grain” so that it doesn’t suck up tons of paint- you can use a foam roller or brush for the shellac or the harbor freight $14 HPLV gun on even a pancake compressor works great. I never sand to 220 grit, (usually just pass a 120 block over it) and get up to a piano finish on it with precatalyzed lacquer. If you put drywall compoiund on it and sand to 220, and then spray waterborne on it, the fibers will just lift out and swell the edge anyway, don’t waste the time, use shellac instead. If you need to use an alcohol based finish like PVA over the shellac, spray a barrier coat of automotive primer. But I am usually spraying waterborne over the shellac.HD sells a 3lb cut dewaxed shellac as a sanding sealer by the gallon- great stuff, dries in 10m.
I’m glad I don’t have to handle or deal with MDF at all now. This is a very good article and highlights the dangers that I didn’t know it had. Although I knew it was too toxic to casually sand or saw it – the stuff is a bit of a toxic no-no. It ain’t worth the risk. I’d use solid wood or ply or veneered real wood. OK more expensive but safer. Good advice here about the atmospheric dust. It’s nasy stuff.
i didnt know that mdf dust is that bad that you recommend sealed safety goggles, but if thats also the case i recommend sealed earmuffs aswell, as the ears are also a way for airborn things to get into your body, a failry efficient way btw. and then if you dont want to carry it into your house but you have a beard and long hair, like i do you might aswell wear coverings for that, at best sealed coverings as you recommended for eyes and mouth. and now we are close to nbc safety equipment. so might just wear that. now, i think i’ve overdone it a bit, but it always is a case of how much are you gonna do with it -> if youre building a slotcartrack or what ever every 5 years and your cutting this stuff outside, well safety goggles, earprotection and a dustmask is recommended anyways, but you dont need to wear a full body condom. if youre in the shop for 8+hours a day tho, working with it all the time then absolutely. a good dust collection system takes a lot out of it, but still
MDF must be supported when using it for something that bares weight so that it does not warp. Unfortunatly when I stiffened my shelves with glued on strips of hard wood, it has a by-metalic effect. As the moisture changes throughout the year the MDF expands and contracts differnently than the hard wood strips. The shelves are streinght in the winter but bow up in the moist summer.
So time ago, a cabinet shop where I worked took on an outside job reducing MDF sheets into dimensional sizes using our sliding table panel saw. Hours of continuous ripping filled our shop with fine dust despite having a collector. Two blade changes and the dust collection machine completely filled several times were some of the highlights of that fiasco. I can still smell and taste the acrid dust to this day
Interesting about using drywall compound.. I was taught to use oil based paint as a way around the “sponginess” of both MDF and particle board. Agree that it is a material best used for non-moved objects.. but I don’t think i heard you mention this.. but MDF tends to have better vertical as opposed to horizontal strength.. Building shelves.. it’s very smart to put at least a 1×2 under the front edge of a shelf that has a span longer than 24″.. and will be supporting lots of heavy books, for instance. Glad to see someone talk sense about all the issues, though. Great article!
I used MDF for a book case and a computer desk over 20 years ago. The book case is still in use today, but it’s an absolute beast to move, weighing well over 100kg. I also used stain on it to give it an almost wood-like look and the trick was to brush the stain and lacquer mix on unevenly, and with a paintbrush that had been chopped up a little, to give a stripy and uneven look
James, could you do a article on applications where MDF is the preferred material? Everything about MDF (its weight, poor moisture resistance, no good outdoors, difficult to join, abrasive on cutting tools, harmful dust, cannot be stained, difficult to repair if damaged) seems like a big no to me. Plywood just seems like a far better alternative. Even PVC with its terrible environmental impact seems like a better alternative than MDF for trim and molding if the cost of solid wood is an issue.
I have to ask do you have MRMDF (Moisture Resistant)in the US? it takes a stronger screw joint is easier to paint and is sort of moisture resistant! It has a green core to it and is not so dusty when cutting it, I only use MRMDF now because just plain MDF is too soft (for my liking) it costs a bit more but like everything, you get what you pay for.
As someone who has had to rebuild cabinets that have been destroyed because a sink drain or supply valve leaked, I want to find whoever invented MDF and kick the living crap out of him. MDF SHOULD NEVER EVER BE USED WHERE THERE IS EVEN A REMOTE POSSIBILITY OF MOISTURE. Yes cabinet makers, I’m looking straight at you!
For utility use like workshop furniture MDF finishes very nicely with oil based polyurethane. My router table top is 2 layers of 3/4″ MDF and one of my cabinets has 21 drawer fronts of 3/4″ MDF. All sharp outside corners except the miter slots on the router table top are rounded over with a 1/8″ carbide roundover bit. In both builds oil based gloss Varathane was applied thinned 50/50 with mineral spirits for the first two coats. The MDF will soak it up like a sponge but it penetrates deep. After that the thinner was progressively reduced by about 10% for each subsequent coat but never below 10% thinner. Starting with the second or third coat a light, very quick 180-220 grit sanding to knock off the high spots helps with a nicer finish. When the poly no longer soaks in apply one more coat, sand lightly and finish off with a final coat of the same product from a spray can. It hardens the MDF into a seemingly different product. My router table is over 2 years old and still looks like new. It can be waxed to make wood glide over it smoothly. The 21 drawer cabinet is under a 10″x26″ metal lathe and is exposed to metal shavings and cutting oils. It’s a year old and holding up very well.
The only thing I don’t like about MDF is it’s tendency to bow under weight. If you don’ t put a bunch of hardwood support under it or make a hardwood cleat, the most it is good for is nicknacks. For example, those stuffed dolls or whatever kids have. So if you are going to use MDF, make sure it is not load bearing, this is where the cheap furniture manufacturers have failed for years.
We make quite a bit of trim from mdf (usually ultralight). Two improvements to what you describe are: Mdf should only be primed with oil primer. Water primer raises the grain on what was a very smooth face, requiring much more sanding. Filling the edge with drywall mud or spackle is best done after priming. It’s more steps, but the bond is superior.
It’s been quite a while since I’ve dealt with MDF. Last project I did was a sealed subwoofer box with a single 10″ in it. Routed the hole in a way where the front flange on the speaker was flush with the front of the box, and glued a piece of stained 1/4 ply to the front. The rest of the box was sprayed with plasti-dip. The dip adhered well and gives it a bit of grip on the trunk carpet.
I had to fabricate a new base for a pool table I inherited. I chose MDF for most of it, and it has held up nicely. I did a lot of routing edges and laminating pieces for thicker sections. It was mostly glued together, except for screws in a few areas. It came out nice, and has been moved once. It went back together well after the move. Thank you for all of the tips. I’ll do a better job next time.
MDF got it’s bad rep in the ways it has always irritated me. So many use it in areas that can get wet. Doorways, sink cabinet bases and areas near windows. The mobile home and motor home industry are the worse offenders but it happens in regular homes. The idea that those areas will never get wet is poor forward thinking for customers. It does provide work later for the replacement. I am not against never using it, but it’s limitations for long term should be taken in to consideration. It might be cheaper up front but cost more long term. Just things to stop and consider.
This was one of your funnier articles. You start with a statement or two about how MDF has its uses, then go on to explain, in detail and accurately, why it’s a horrible material for almost any purpose, and that it’s only virtue is that it’s flat when dry and not under any load at all, and that it’s cheap. If you value your time, health, and sanity, just avoid it. If you’re making furniture to give to people you don’t like or that will destroy it, and you work outside with someone else’s tools, sure…
One time when I was younger and less-experienced I was doing a remodel project where I was cutting a bunch of MDF out of the rain in a small garage area. I didn’t have any filtration or mask, and by the end of the day I had the worst headache and I felt so stupid. Don’t mess around with MDF unless you are protected
1. Never ever use MDF where it might get wet. Even with primer and paint on, I have had tiny pin holes that have been hit with just a little bit of water and ended up with a really large blister. 2. As for being fragile, I cut it into 2′ x 4′ sheets, bullnose the edges, and use it for panelling the lower half of my garage walls. Keep it about 1/4″ above the floor to avoid water, and it is just about bullet proof. 3. Finally, if you sand the edges well, and lightly sand the face to provide a bit of grip, just brush on a good clear coat with a quality brush. You’d be surprised at how nice it looks in the right setting.
You can temporarily clamp a strip off material on each side of the mdf edge that is receiving the screw. Then it will not split. For SUPERIOR strength on a 90 degree edge, use a barrel nut and a bolt. The longer the bolt the stronger the joint. I normally use about a 1 1/4 inch bolt. You can countersink the bolt head if needed. I fill the hole with Bondo if it will be painted or veneered. Nasty MDF dust will also ruin your shop vac motor, so be sure and use a dust separator. Thanks for article.
There is a special polyurethane filler for mdf that does not powder like drywall mud….much better and holds. An expensive option is bondo but wow it’s tough. You can also make a filler with flour and wood glue (PVA best)(6-1~!)…starch is less desirable. Mud won’t stick or hold…just fill. jpk PS. I’ve cut millions of pieces without mask and still alive @68(in ’70-75). Still not wise.❤️
If you use Ridgid 18v Cordless Drills drop your chuck setting from the Drill symbol down to 12 (roughly half), I find that setting prevents you from over torquing the screw when using coarse thread drywall screws, I have decade old speaker boxes put together this way then used caulk to seal the joints that are still rock solid, but then again I cut them so perfectly (as I plan out my cuts so all cuts of the same length are done on the table saw before changing to the next dimension) you can stack the pieces into their positions and stand on the box with no screws and it will hold you up. Lately i’ve been tempted to try doing drawer joiner to connect panels together to reduce reliance on screws in the visible areas.
Hmmm, well…almost right. Yes the BOTTOM piece should have a hole drilled the size of the body of the screw, but (he neglects to mention) the TOP piece needs a clearance hole that’s larger than the major diameter of the threaded part of the screw. That’s the only way the screw can re relied upon to actually pull the two parts together. Doh!
You silly Americans. How long do you guys know MDF? Here in Europe it is been used over 30 years. More then 80% of all buit-in cabinets / doors are MFD. Lots of furniture is MFD and finished in a high quality spray paint. You can move them as much as you want. They will last for ever. It’s the best product and available in so many thicknesses from 3mm to 50mm. There is a BIG difference in qualities of MDF. The one you show is very poor of quality and cheap (ikea quality). I can see it on the structure. Sometimes in the cheap ones there are little particles of metal in it, thats why your saw blade does not last long. Most brown MDF here, are pre primed, so white on the outside, and perfect to finish them in 2 layers of paint. Then you have green (more waterproof and most used allround. It’s stronger, better and much more density then the brown one, also you can get them pre primed), black (you just varnish it as a finish) and red (fireproof) MDF. The edges, you avoid painting them. You put them trough an edgebander for a thin piece of paper band, 2 layers of paint and you have a perfect finish in no time, instead of all the work you do and still end up with a poor look. You never ever put screws in them for the construction you show. You miter and glue them. They will be very very strong for decades, and it’s the best finish you can dream of. (you have no edges) And all that panic about MDF dust??? I should already be dead now after 30y with zero sec of mask on my face.
20 years ago I was given the suggestion to use a diluted PVA (Type 1 or 2) wood glue and water (about 1/1) as a binding sealer. This is used instead of the shellac. The benefit of this is mostly $. I don’t know about y’all, but the price of BIN primer is through the roof and it can sometimes be hard to find. The fumes are another benefit. The wood glue binder soaks in on the first pass then about 5-10 minutes later you can do a second pass. I usually brush it on but you could certainly spray it with a cheap cup gun since it isn’t a problem getting it on the MDF face. It’s non-reactive with lacquers, conversion varnish, oil/latex paint once it’s dry. I typically only sand it to 180 but to each their own.
Another downside is the weight. Honestly I’ve just moved away from MDF entirely. The upside used to be cost; you could get a full sized sheet for anywhere from 25-50% less than a full sheet of cabinet-grade plywood in my area. But COVID changed that and it hasn’t normalized since. It’s like an extra five bucks per full sheet for a good quality ply now vs. the same amount of MDF. Why would I ever go with MDF with the weight, dust, fragile edges, and joinery problems again in that case?
Hola! 🖐WOW! So many MDF haters out there, you really woke them up with this one, haha! 😂😂 Like everything else, there are good and bad attributes to anything such as wood, glue, screws, finishes, etc. I don’t think I could say I’ll “NEVER” because you never know when such a thing might just be the correct solution to a situation. Thanks for this article, lots of good info on it. I especially like the cross section view of the screw onto the joined MDF, that gave a good look at what’s really going on in there when you use this jointing method. Take care and have a good one, Adios!👊
MDF medite is a lot better than the hobby stuff. Even better, always go with MDFv313 its a lot tougher and a bit moisture resistant. And for cutting and sanding mdf… or anything Please use a dust collector. And I mean a proper one. Like the Felder RL series ore SCM Vacumobil. And in my case the sawblades I use for cutting MDF and melamine partial board are the most expensive a have… around 260 dollar each. The are special blades for dealing with these products and keep a clean ede for a very long time. Look them up, kanefusa board pro. 😉
Building some simple MDF cabinets into my workbench and I was thinking of painting with milk paint. I’ve read that folks recommend priming the surface of the MDF with Kilz or Bin 123 Primer. Anyone have any experience with these approaches? I’m not looking for beautiful kitchen cabinets, just liking the idea of adding some color to my workbench. Sounds like sealing the edges with BIN shellac is the way to go for that part of the process.
For paint grade MDF always use a premium grade; also known as door grade MDF. It’s higher quality and more dense. The face is smoother and edges are less porous. Sand the face and polish the edges with 320 grit, not 220. Also break the edges using 320. It burnishes the pores closed eliminating the need for an edge sealer. Primer will build nicely with minimal soak. It paints way nicer than standard MDF. This is also true for door panels where edges aren’t exposed. The increased cost for premium is more than offset in labor savings and better quality
Classic core MDF is plywood cores with 1/8″ MDF for the surface. Great for paint grade cabnets. Strength of plywood and smooth surface of MDF. Cabnets were faseframed with solid wood and cabnets tops were solid wood. Doors and drawer fronts are shaker style with 1/2″ MDF rabited panels and solid wood frames.
Things I hate about MDF: The weight – may not be as expensive or strong as hardwood, but it’s just about as heavy. When lifting sheets to pre-stage for the tablesaw I use a long flatbar to hold the bottom edge and extend my grip to make them easy to carry. Sharp edges – wear gloves when handling! Factory or fresh cut edges can be very sharp.
I have found a really effective way to treat the edges of MDF is to give them 2 coats of PVA wood glue, allowing the first coat to dry before lightly sanding then applying a thin second coat, usually with my finger for smaller pieces. This leaves a super smooth edge that won’t soak up paint. PVA glue will take a latex based primer/undercoat well. I wouldn’t use this method for an oil based primer/undercoat.
If you are making any kind of furniture (built-in etc) then I would strongly recommend moisture resistant MDF (MrMDF). Also the quality of the stuff you get from big box stores is likely not to be as good as that from a reputable timber merchant. I would never screw MDF as you have shown. If you need to joint it, then use dowels, biscuits or loose tenons. If I may recommend another website here, then @10minuteworkshop / Peter Millard is worth a look if you are considering using MDF for projects. He goes into painting etc etc in detail.
Uncommon Common Sense! This chemist can tell you the resins used in making MDF must partially dissolve cellulose (ionic bonds) so burning MDF becomes a no-no, including the smoke as you are playing Mexican with your skillsaw. Mostly, it is just better to buy MDF to size, and other than screwnglue don’t try to join it. Also from an adhesives/coatings chemist: painting this material is expensive because of the density. On the positive side it accepts epoxies without priming, so is better for industrial applications than residential. If you wish to apply residential coatings on MDF, please know that Sherwin Williams bought Zinnsser, who controls the shellac market in the US. BIN and BullsEye are watered down versions of their previous incarnations. I suggest you use your favorite urethane sanding sealer, wiping with mineral spirits. Do not be afraid of the dryers unless you are staying green.
I don’t know about the USA building supply places, but European places mostly carry some of the mechanical fasteners, and specialized screws, for working with MDF and similar products…the screws typically have a sharp, thin thread, on a body that is about 2x the size of a wood screw, and the threaded inserts with internal threads for metallic screws, are also normally in stock.
I used to do QC for a business that put decorative laminate on MDF and particle board. When we’d QC incoming lots of panels for screwholding strength, the ANSI method called for machine screws. They hold better than wood screws in MDF. Pre drilling is an absolute must. I can not remember the exact screw after 30 years, but I am pretty sure it called for an 8-32. It might have been 10-32. The taper on a traditional wood screw doesn’t do anything to reduce splitting or increase holding power in this application. It is also true that the quality of MDF and particle board varies greatly. The big box stores sell the bottom of the barrel stuff. Sauder bought a lot of stuff from us, and usually, they wanted the cheapest panel we would laminate. If you put a good finish on good MDF, it will last a long time, even in applications where it gets wet occasionally.
Regarding the dust problem. Let me start by saying “I CAN’T” for certain blame this product as my previous life has included experiencing times of interaction with airborne asbestos dust from brake linings as an apprentice mechanic back in the late 60’s, coal dust from mine work and concrete dust from cutting in building work. But I’m currently undergoing diagnostic tests for pulmonary fibrosis. I had quadruple bypass surgery CABG done back in 2009. Up until the last two years I was great no breathing problems to mention. However it was during the years between my surgery and now we have had ongoing renovations in our home. We have installed a lot of MDF preformed trim in every room. We also have cut up many 8×4 boards of 1/2″ MDF boards for paneling and styles. No external shop available, it was all done indoors on a table and mitre saws. Despite using a large shop vac on both saws when cutting, the dust was an enormous problem. I was foolish enough to not wear any form of masks, just kept windows open when and were I could, and was constantly cleaning up to keep it to a minimum. Regular shop vac filters changed etc but it didn’t completely stop dust. Add also the forced air heating would recirculate the dust into every room. It’s been a nightmare. I wished we hadn’t started this renovation, or even buy a house that needed so much work. But we live and we learn. Personally this product should be banned. You can’t even call it wood. It’s hard cardboard at best, edges are easily chipped or broken, every Brad nail fired in causes a mound around the hole or puffing if that’s a better explanation, which required sanding before filling and caused lots of extra work sanding to reduce blemishes in the finished paint.
I have given up using MDF for any projects, and I have only been slowly using up the remaining scraps and off cuts to make jigs. But when using MDF I have always used a quality respirator mask to save my lungs but after finishing with the MDF I will vacuum the workshop and all tooling, and then vacuum myself, clothes, mask and hair until dust free before removing the mask. The filters are not reused. I can’t stand the stuff any more. Even the dust on the workshop floor makes it so slippery and dangerous.
Dear Sir, this is AGAIN an excellent info and demo article. Lots of info. I have watched maybe four or five of your articles and each one has taught me alot. Question …planing on using MDF to make a couple shelves and cubicles for closet organizer. CAN you use pocket holes ??? And how does the glue react ? Meaning will it soak and spill over into the next piece of wood? Thank you !
Not all MDF is created equal. When I use MDF, I never built my Fine Koa pieces with it. In my shop, there are as a wonderful place for MEF as a pattern material. Using it repeatedly without reinforcing it first would have meant wear on the pattern, so soaking the shaped edges with crazy glue (thin grade) and spraying it with the kicker beefed up the MDF.
Here is a technique I tried for a project I was working on. Stabilizing MDF with Cactus Juice…. What I learned…. overcut your project by 1/8 inch all the way around for final shaping after it comes out of the oven. MDF will suck up a lot of juice and when baked is extremely heavy. Cured MDF will sink in water but otherwise unaffected. I found that MDF shrinks in the vacuum and cure process, i.e. 3/4″ becomes 11/16″ . Bits and blades dull quickly.
I’ve built a few speaker boxes using drywall screws. I do predrill. I’ve not had a failure yet on my box that has 2 2k watt RMS stubs. But I did go a bit overboard on the screws and I did a lot of glued in 45’s in the corners. I also built a triple monitor stand for 27″ monitors. It amazed me that it never sagged. I used it for about 5 years before tossing it. I also have a MDF top on my workbench. It’s got a 3 inch unsupported overhang. My wife has stood on it and it’s not snapped. There’s no way it will hold me lol. I have been up on top of the table accessing our above garage door storage and nada. My “temporary” top seems like it’s going to be there forever. It’s 7 years old and still going.
As Stumpy points out, It does not paint well, splits very easily in the center, blunt’s saw blades badly, and is unhealthy. In addition, from a lifetime as a fully qualified cabinetmaker, I have experienced the following. 1 If you spend a whole day cutting MDF your face will feel like it has sunburn. 2 It definitely does bow, the thinner the sheet the more it will bow even when left in storage under ideal conditions. Or simply painted, even both sides. 3 Starts to reject most types of glue bonds after a period of a few months. 4 Deteriates worse than anything near water.
I enjoy your articles but I’m not a fan of the title of this one. It sounds a little like click-bait. As you said in your article, if you want anything that will last longer than the current average consumer product life-cycle then you’d better use wood. However, I fell for the bait, and clicked, because I wondered what on earth could he be smearing on MDF to make a woodworker find this stuff useful. I didn’t learn anything this time and I don’t think it changed your mind. Anyways, I typically enjoy your articles, so keep up that great work.
It’s worth noting that MDF is not a uniform density all through. The smooth surface is considerably firmer than the underlying structure. If you sand or plane it thinner, you’ll loose much of its structural integrity, and just as a melamine coating will make fibreboard much stiffer, so does the outer smooth surface of MDF. Another piece of trivia is its permeability. A strong vacuum applied on one side will pull air from the other side. In this way, MDF can be used as a hold-down for sheet materials on a CNC machine. This works even better once you take the smooth, denser surface off one side.
I found a way to seal MDF and make it much more moisture resistant and stable, especially on the edges. I was restoring some cast iron frame industrial grade park benches with 2×3 wooden slats, I had to restore the wood slats, which were pretty compromised after over 10 years outside. I bought some stuff called TotalBoat penetrating epoxy. It is a two-part 2:1 epoxy and it has the consistency water basically. I wanted to protect some MDF boards on a workmate type workbench. I put a couple of coats on that MDF and really soaked it with it. The stuff penetrates into the MDF and makes it harder and more water resistant. It penetrates wood, fills voids and then hardens. The product is made for restoring wood boats. If you are exposing it to the Sun you still have to put varnish on it because epoxy is not resistant to UV light. Use a mechanical mixer on a drill. I’m not affiliated with the company but it is a good product.
I “wood” never use MDF even for kindling to start a fire. This the most useless short life product imaginable for timber wood working. Looks great in kitchen cabinets when it is new. Finely sanded to perfection in an Epoxy paint finish it looks a million dollars. Any moisture and it swells and the product falls apart. I have just torn kitchen benches in a kitchen renovation apart. The dishwasher flooded the kitchen many times creating cupped floorboards. The cabinets were made of chipboard in all fairness. MDF would have been 10 times worse. Why on earth would anybody skimp using timber to use a product that in more akin to Paper Mache than real wood.
I worked with 1 inch thick 4×12 sheets of MDF years ago. I always primed it with 5% thinned oil primer as per the advice from the manufacturer. We were laminating two 1 inch sheets to make a hard sturdy bar/commercial counter tops. several coats of laquer with wet sanding between coats then crinkled up plastic bags dipped in paint to make marble look then several more coats of clear epoxy. bulletproof unless it was in a flood yet i still to this day detest MDF
Laminate a couple of layers of MDF together, make at least 2 of them. Then cut out round and turn to true round discs. Mount the discs onto a bench grinder 8″ is good. Mount the grinder so the top of the discs runs away from you. Work fine valve grinding paste into the rim of one disc and knife polish into the other. Don’t allow moisture anywhere near the discs and you will have a knife sharpener that doesn’t wear out your knives, cleans off damaged edge material gently while polishing a sharp durable edge. Now you finally have a use for MDF, blotting paper if you prefer its more accurate name.
I regularly make cabinets with MDF and leave it for curing for a week and then quote it with PU Paint. I run into a problem where no matter how good the work is, after a few days the joints just starts to show through the paint. I only wish I could show the picture of the failure and my disheartened face. Hoping you understood what I am trying to explain. Can you please give me a tip on how to address that issue.
I have a huge piece of furniture made entirely from MDF that has four 6ft brass doors that took 3 guys to fit each door due to the weight yet the screws are only 1/2″ long, how this works is beyond my understanding yet I know of 3 more identical units all working well, I think they are at the limit of what is possible but equally very surprising the weight MDF can hold
I regularly acquire 3/4 through 5/4 MDF in “shelf” sized pieces, as cut-offs from an industrial cabinet maker. I absolutely hated the idea at first, but after 20 years, the on-wall cabinets I built as a first-run trial are still strong and tight to the wall, and I’m in the process now of moving them to a new shop. I used a healthy 2-3 coats of mis-mixed paint I got cheap at the time- I didn’t even want to take the risk of spending good money for paint for them. I fastened the shell (box frame) together exactly as you showed in the article- coarse drywall screws with a right sized bit and countersink. The center shelf was dadoed into the uprights, glued and screwed after. MDF in this manner was an EXCELLENT way to hone my cabinet making skills- I got lucky with “free,” but another advantage of MDF is that you start out every panel with a laser-straight edge or edges. Like reloading your own b |_| llets, when you start with a good baseline, you know any error is yours, the tools, and/or the technique. I found this to be SO beneficial!! Great article, I’ll try the joint compound trick!
What I hate most about MDF is that any time water gets on it then it will swell and start falling apart. Just looks awful. You cannot sand it and fix it. It will always look swollen. I remember a job site I worked at used an MDF that was waterproof. We used it outside. It was also very strong. You could not snap a two inch strip. That was the only time I ever saw waterproof MDF. Home Depot/Lowes does not sell it. Why is it when they finally make something great that it has to disappear and never be found again?
There was no mention of the flammability of MDF, I had a part time job on my days off years ago and one of my jobs was to service or replace used fire extinguishers. I used to make at least 3 trips a week to my local MDF manufacturer and on occasion, multiple times a day. This stuff burns baby! On the other hand, it doesn’t like steam, water, rain or any moisture at all… keep it away from projects that might be exposed to moisture, even if it has been treated. Good article.
I worked with MDF extensively – read that literally hundreds of tons. Best fastener? Cam locks. MDF is quite strong, and has quite a bit of spring in larger panels, making it quite impact resistant. However, moisture is the arch enemy of the stuff. While it is great in constantly dry settings, it is a disaster if it gets wet. As much of the stuff I have used, in 16, 25, and especially 19 millimeter thickness, around 99% was covered with a laminate of some type. The smooth face provides a great surface for applying a wide variety of laminates.
That sentence towards the end about overusing MDF is funny to me. In Poland, where I come from, MDF is the better material used to build cabinets and wardrobes. More precisely, the ones that are too expensive for most people to afford. Kitchen cabinets, wardrobes, chests of drawers, desks and other furniture are made of chipboard, in case someone didn’t know, they are thick sawdust glued together with resin/glue and laminated on the surface. It must be honestly admitted that the choice of laminate colors is huge, from uniform colors to imitations of every wood I know. It’s funny to me that a board with laminate imitating pine is cheaper than the same board with laminate imitating oak or mahogany 🙂 Such a board is durable enough to withstand a dozen or so years and does not cost three monthly salaries for the material for one piece of furniture. Wood meets sporadically, max a few pieces of furniture in one house, I have no more than three pieces of wooden furniture myself and it’s only because I love wood (table, desk where I work, chest of drawers)
I worked at the Queens Museum of Art in the early 2000’s and one show required a lot of specialty vitrines and displays – all made of MDF. They must’ve gone through 50 sheets of MDF – I kid you not! I was working there renovating the museum gift shop and was “sharing” the shop with the outside crew they brought in to do most of the MDF stuff and I walked into it one afternoon and it was like a London fog in there. Except it was toxic and you could practically touch it! So gnarly. I saw one of the guy NOT wearing a mask! I hope he’s still with us!
If you really have to screw into mdf: pilot full depthbof screw, use long screw with wide thread, preferably a wax coated screw, use drill with such a low torque setting that you have to increase the setting to finish the driving. Possibly add glue of some type, but I don’t do that. Of course, screwing through the mdf into batten is preferable
I have used various kinds of MDF over the years. Likely started with MDF baseboards and doorway casings in the 80s. MDF pieces were obviously cheaper than solid wood, but most were also thinner, which looks very cheap to me. So I switched to hardwood. I built some custom built-in cabinets and spray painted them with latex BM paint. I did use drywall compound on any exposed edges to cover, but also sprayed the paint extra thick These were cheap and functional cabinets that looked good. I used scraps of MDF to make shelfs in my workshop- but these all deform badly under even a light load, so they got replaced by plywood. More recently, I made two doors to fit a custom doorway space, (both height and width were odd dimensions), which turned out okay. I had just made another door out of SPF 2x6s. The SPF was easier to work with, with way less dust, but ultimately, the door is warped. The MDF did not warp, but making a full size door with huge raised panels generates mountains of dust, which all starts out in the air, and eventually lands on everything in your shop. It’s not great wearing a half-respirator all day so not sure I will do anymore full sized house doors now, I’ve had my fun. Also did make custom shaker style columns for my porch. I used exterior grade MDF, (Extira) painted it, and 3 years later its fine. No machining, only long cuts, so no dust issues for these columns. Good application of the product. Exterior grade is hard to find though, it’s not at the big box stores, and only a few lumber stores.