A continuous span joist may require web stiffeners to increase internal load capacity at the intermediate bearing. When joist hangers are used and the top flange is not lateral supported, the joist can rotate. To modify existing joists to increase load-carrying capacity, several methods and practices can be used. Open web steel joist framing systems have their history, unique features, and challenges associated with evaluation and strengthening.
Strengthening of open web steel joists is often required due to the addition of rooftop units, underhung conveyors, or other loading increases not contemplated in the original design. Intermediate transverse web stiffeners are needed for plate girders. Joist with double angle webs may be necessary in remodels where additional equipment is installed and supported by the joists.
In place joists are key characteristics that eliminate the need to pre-insert traditional web stiffeners prior to joist installation. They can be easily rotated in-place for a tight fit. Bridging between open web floor trusses does not add much strength for bending anyway. Construction adhesive and 3″ construction screws are used to attach the joists, which form an “inverted T” once completed.
Sistering a single 2×8 to each existing joist will roughly double the strength and stiffness of the existing floor. Double 2×8’s will be used to provide additional strength. If stiffening is needed, adding 2 layers of 3/4″ plywood to the bottom of the joist can form box beams. Bracing the joists together, gluing and screwing sheets of plywood to the sides of the joists, and plywooding the entire ceiling from below can help stiffen the joists.
📹 Open Web Floor Trusses, One Year Review – Would We Use Them Again?
No posts, no beams, no wall, no bulkheads…our main floor and our basement are totally open concept with flat ceilings thanks to …
Does sistering a joist make it stronger?
Joists can sag over time, causing gaps between ceiling and walls. To fix this, professionals often add a sister to an existing joist, adding the full strength of the new joist to the existing support. This method requires some prep work before installing the sister onto the floor joist. It is crucial not to add a sister to a sagging floor joist, as this will make the sag permanent. Instead, professionals should consider nailing two boards together to create a double girder.
How do you reinforce an old floor joist?
Sagging or bouncy floors can be caused by various factors, including cracked joists, poor construction, wood rot or termite damage, issues with the beams supporting the joists, and notches in the joists. Cracked joists can lead to instability and weaken the flooring structure, while poor construction may result in an insufficient number of joists or too small joists. Inadequate support can also occur from subpar materials or improper renovations. Wood rot or termite damage can cause wet wood to lose its strength and become less stable, while termites can consume the wood, creating tunnels and compromising the floor’s structural integrity.
The beams supporting the joists can also be a culprit, as they may have shifted due to settled support posts or suffer from wood rot, termite damage, or other issues. Cutting notches into joists for electrical wiring can weaken the joists and make them less capable of supporting the floor. To strengthen floor joists from beneath, it is essential to address these issues and ensure the floor’s stability and stability.
How do you reinforce old joists?
Sagging or bouncy floors can be caused by various factors, including cracked joists, poor construction, wood rot or termite damage, issues with the beams supporting the joists, and notches in the joists. Cracked joists can lead to instability and weaken the flooring structure, while poor construction may result in an insufficient number of joists or too small joists. Inadequate support can also occur from subpar materials or improper renovations. Wood rot or termite damage can cause wet wood to lose its strength and become less stable, while termites can consume the wood, creating tunnels and compromising the floor’s structural integrity.
The beams supporting the joists can also be a culprit, as they may have shifted due to settled support posts or suffer from wood rot, termite damage, or other issues. Cutting notches into joists for electrical wiring can weaken the joists and make them less capable of supporting the floor. To strengthen floor joists from beneath, it is essential to address these issues and ensure the floor’s stability and stability.
Can existing trusses be modified?
Attic roof trusses can be modified to suit conversion needs, but the process is complex and requires careful planning. Hiring a specialized contractor with relevant experience is necessary due to the delicate nature of the process. They will evaluate the existing roof structure to determine which attic truss will be removed. The precise methods for modifying trussed roof conversions vary depending on the condition, size, and other factors, but a general overview is provided.
Can you reinforce a truss?
It is recommended that construction adhesive be applied along the edges of the roof trusses in order to strengthen their connection to the roof deck. This process is analogous to the application of caulk. It is recommended that trusses be secured to walls in order to provide additional support, particularly in the event of strong winds. It is recommended that trusses be connected to walls whenever possible and that wood trusses be reinforced by joining them with additional webs running from one end of the house to the other.
How do I stop my joist from sagging?
To prevent sagging and bounce in floors, install blocking that fits snugly perpendicular to the joists, cut solid wood pieces the same width as the joists, and secure them with nails. If floors are sagging due to poor structural design, consider installing structural jack posts to gradually raise support pillars to apply pressure under the sagging beams. To prop up the bowing floor, install a concrete footing on the foundation to act as a pillar base, as the pressure needed to prop up the floor transfers the weight down to the floor.
How would you stiffen a webbed floor truss?
The truss manufacturer suggests adding 2x4s parallel to the top chord of the trusses every 3rd or 4th truss to provide additional stiffness. This will help the existing strong backer bracing distribute deflection. The 2x4s are oriented 2 inches wide and 4 inches tall/deep, unlike the top chord which is 4 inches wide and 2 inches deep. The manufacturer raises concerns about the potential negative effects of having every 4th truss stiffer than neighbors, as tile is not a fan of movement.
Can floor trusses be modified?
Trusses can be modified or repaired due to various reasons, such as accidental damage, trades-made holes, design errors, or customer requests. These repairs must be analyzed on a case-by-case basis to ensure the truss can safely carry all intended loads. Some trusses may not be repairable and require replacement, depending on the extent of damage. More information about truss repairs and modifications can be found below.
How do you strengthen existing joists?
Sistering is the process of strengthening existing attic floor joists by adding a new joist or a “sister” next to the existing joist. This is particularly important for loft conversions, as many attics were not designed to support additional weight than necessary. Attic floor joists are typically designed to hold the weight of the ceiling below and related elements.
There are different types of attic joists and constructions that need to be considered when converting a loft. Most attics are built without flooring, as they are not designed to carry the heavy load of a finished room and its associated items. If you find your attic has a floor, it is likely that the joists won’t be able to carry the weight of a room. The floor may have been boarded with plywood to store seasonal items.
Attic joists for live loads may be made with 2 x 8 attic joists, which may be acceptable for building a habitable room upon, but there is no guarantee. It is essential to consider the specific type of attic joists and construction before converting your loft into a habitable space.
How do you sister joists to stiffen floors?
Sistering a floor joist is a common solution for older homes with weakened or damaged floor joists and new constructions requiring additional support. It is an effective way to repair and reinforce weak spots in the structure. Reasons for needing sistering include aging, termite damage, and improper installation. Aging and moisture can weaken the wood fibers, causing the joist to support less weight. Termite infestations can also damage the joist, compromising its load-bearing capacity. Improper installation can also cause excessive stress on the joist, causing it to sag or deflect under loads.
📹 Web Stiffeners, Solid Blocking And Squash Blocks Installation Examples For Trus Floor Joist
Examples of assemblies came from illustrations in this guide book – INSTALLATION GUIDE FOR FLOOR AND ROOF FRAMING …
The engineered trusses can be designed for all types of flooring applications. These trusses are probably designed at code min which is a LL Deflection criteria of L/360 (or 1″ over a 30′ span.) Most of our floor truss designs are utilizing L/480, and if you have any type of stone tile such as marble or slate, it is required to have a L/600 plus requirement under Total Loads (some applications require less than 1/8″ over the span of the floor.) Gypcrete which is used in most commercial buildings requires a total load deflection of L/360 which is also high standard than normal code. The Total Load deflection Criteria under Code is L/240. You also have to consider that you are clear spanning over 30 feet. The material in the trusses could have been increased to a high MSR material or even double chords which would also take away some of that bounce. There should also be three rows of strongback bracing which will aid in vibration and “bounce.” This is the “best” system for any application that you want to have less beams and posts, but it does cost more in the beginning (or is was until fire codes required that the basement ceiling be finished if installing them in this area.) The look good, and everything is able to be hidden. Some of the other trades need to be involved during installation to allow them to install the long runs while installing the trusses. This will eliminate the need to drill or cut out holes later. I enjoyed your article.
Great article – I like these “one year later” articles by the owner as once you lived in the house its a great time to review what you would have done differently. As an owner builder – twice – you are always thinking about what you would do differently if you would do it again knowing that there are a lot of decisions you need to make up front – so you would never build a “perfect” house and I think that is one of the more enjoyable aspects of a custom build and sharing it with others and learning from others. In regards to a basement – I would agree that you don’t need open truss design. More than any other floor in the house you know there are going to be internal walls and you know where they are going to be up front. The furnace/hot water heater area and any storage area, any rough in bathroom areas, and any areas with windows that would meet code for a bedroom.
I am considering doing this to my main floor in the basement, as I want to do a home theater in the basement in the future, and I think this would allow an optimal HVAC design for house while allowing me a flexible future layout of a rather large (28’x20′) high ceiling home theater room with soundproof wall and ceiling design. Also, why didn’t you have these trusses designed with a built in return slot? I’ve seen some like that, they frame a very large hole through the entire run in one section that the HVAC guys can then box in as the cold air return.
Truss design has 3 criteria for stiffness. Depth of truss, spacing of trusses and grade of lumber used. If you do not want a bounce in your floor, design it better! L360 is a very low design for stiffness. You should have used L480 or L600 for your design if you did not want a bounce. Its not the trusses, its the design. No matter what floor system you use, if not designed correctly will have bounce.
I was a mechanical contractor for 32 years with a large, one stop shop, mechanical contractor. Open web truss systems, of any type, including TJL’s are preferred to TJI’s. The key with mechanical contractors is preplanning and coordination meetings to square up routes. Working on the commercial side, we BIM everything and I do know, BIM is becoming a thing in residential markets. In general, the truss company should provide truss drawings to the subs long before the slab is poured or the trusses are even in production. Designs are coordinated, pipe, ducts, are prefabbed and when the trusses are rolled and set, pipe is placed in the appropriate void and life moves on. All of that is done prior to “dry in.” Once dried in, installers come back and slap the systems together. It’s actually a fast process if guys are smart enough to prefab and the HVAC contractor uses a shop to seal the ends and seam of the duct work. Fire sprinkler guys have no issue if they are installing steel, as that’s the norm or CPVC. Long runs of cast for DWV or copper, if the building is secure, for the plumber’s supply lines is also no issue. These systems shouldn’t be any problem for a experienced tradesman, even in residential construction. Also, there should be savings in the mechanical systems due to less drilling but, then again, residential is a different animal.
I have no idea if you made the right decision or not but I have to really say the ductwork and wiring seems to be something to consider. I’m new to construction but wouldn’t you have to make your basement about a foot deeper with other products to support the ductwork and also make your stairwell longer or make the steps shorter. Also you’d need a lot more support columns.
Not much of a comment more a question not usually a 2 story builder I’m doing a metal i beam construction with 20 inch metals trusses spanning 32 ft trusses are 24 inches apart. I don’t know how to put a floor over the top. And on tight budget I’ve been looking and see where they have products for pouring concrete but wanted a wood style floor without concrete. Not hitting the right key words on Google for what I’m looking to do i guess. Thanks for any direction on matter if even on internet. This is for myself
I recently bought a newly constructed home. The second floor of the house has squeaking sound, builder told me it is normal and it may reduce once furniture is on the floor. I don’t agree and I told him that it is not normal, I have seen many house like that. After discussion they agreed to review, they were thinking it has I-joist but they found open web truss joist. Now the y are telling web truss is expensive and strong but sound is expected. I find the sound very annoying, is there a way to reduce it. Builder tried multiple time and saying all is good and this cannot be perfect. Floor is little bouncy too. Please suggest
3:45 I totally agree. In a “modern ranch” or “modern prairie” type of home that I’m envisioning, even though the viewout or walkout basement is very important, I don’t think it’s SO important that the main level should have flooring issues. And you’re not going to have an extremely open basement layout – it’s going to be relatively boxy because you want several bedrooms down there as well as a bathroom and kitchenette. I think I’ll just do much shorter trusses to ensure the floor of the main level is ultra stiff.
Hi I have these type trusses in a garage addition we had built.. we are re-doing an upper deck that was poorly installed. My question is to properly attach the ledger do I drill and bolt through the end of the truss? Or do I have to avoid the truss completely and not touch it as it is “engineered” . The idiots i had hired only attached the ledger to the bloody OSB and used scrap wood as blocks behind to keep the bolt from pulling through the OSB I am getting mixed answers online
Insurance on these beams is higher due to total write offs in case of fire. Solid wood beans take longer to burn through, engineered lumber has a better rating than most and of course metal has the highest. Firemen hate them due to their inability to carry a load once damaged. Always a tough decision and I’m not sure one is a better choice over another, guess it comes down to what’s the best choice for you.
Interesting article, I am looking at making some home made ones for a 26′ span. I can’t understand why the top and bottom 2×4’s are on the flat though, is that for duct work access? It seems like turning those on their sides would take away the bounce a whole lot! All floor trusses are on the flat for some reason though, I don’t get it. Roof trusses never use wood on the flat, just on edge. I wonder if there is a space in your trusses where you could slide a beam in though, so it doesn’t stick down? Also if you went with 7’5″ cielings, you would still have plenty of headroom in the basement without so many stairs…
Great article. Just moved into a 3 year old home. The open web joists are 14″ tall on 24″ centers. They are bouncy in the middle which is not too troubling. The biggest concern is when approaching and standing near the toilets The toilets rattle and I’m afraid that the toilet seal could be affected. Thank you.
Me, my brother and my father have these in our houses and they are absolutely worth the cost. Finish that ceiling and seal in off and the entire volume between the top and bottom of your trusses becomes a return plenum and a conditioned space. No need for return trunk-lines or ducting, just cut a hole for a register anywhere you need a return vent, same for return air drops.
I Used 2×4\\2×6 swash blocks with 1×4 or 1×6 for TJIs as the fit flush with standard TJIs. For “But” framing, I used LVLs with the the joist hangers and 1×4 for spacers (web stiffeners) for the fastening the hangers for the TJI’s. I wouldn’t but join TJI to TJI. Only TJI to LVL or LSL, & I would always use joist hangers in the invent of severe wind or seismic movement. For but joints with Steel I-beams, you have to install LSL or LVL in between the steel flanges and fasten them top and bottom with structural screws for the joist hangers (That’s what the TJI mfg engineer told me how to do it properly). I believe I used 3/8″ by 8 inch structural screws, but recommend you check with the TJI mfg for your application. Note with LSL is that they swell a lot if they get wet which is common during framing construction (rain) unless you building in a desert. LVL so not swell if they get wet, so I recommend avoiding them.