Truss Uplift Cause and Solutions

TRUSS RAFTER
What is a Truss Rafter? Trusses are pre-engineered and manufactured assemblies that take the place of conventional rafter, ceiling joist – roof construction. Trusses are usually installed across the entire width of a home and transfer the load to the outside walls and through them to the foundation. Houses that are constructed using trusses seldom have internal load bearing walls. They are often a less expensive faster method than stick built roof framing. The trusses are a combination of wood members connected together with metal plates.

TRUSS UPLIFT
When a newer house shows signs of interior ceiling corner cracking at the top floor in the winter, this can normally be associated with truss uplift. Roof truss uplift occurs when the bottom chord of the truss is exposed to significantly different moisture and/or temperature conditions than the rest of the roof truss. The bottom chords of the truss are buried in heavy insulation, 12 inches or more thick. In the winter the warm temperature from the ceiling below and the thickness of the insulation keeps the bottom chord dry, causing them to shrink. The top chords (above the insulation) are absorbing moisture and being kept damp with the higher humidity in the attic. The dampness of the top chords of the trusses causes them to expand. This differential movement in the top and bottom chord of the trusses causes them to arch up in the center. Because the truss ends are secured to building exterior walls, (a location that resists outward thrust), as the truss bottom chord wants to expand along its length, the force pushes it upwards into the attic space. When the trusses arch up they pull away from the top plates at the ceiling-wall juncture of central interior wall partitions that run at right angles to the direction of the roof trusses, (predominately at interior partitions in the center of a building).  The ceiling/wall juncture cracks typically open in the winter and close in the summer.  As a result the problem is often an ongoing problem. The building contractor will be held responsible and in turn the drywall contractor will be called in to re-tape the corners and popped screws, only to have the problem reappear next season. If damage to the drywall occurs I am tempted to say that the drywall can’t be just repaired and refastened.  (See below for some possible preventative practices and ways to minimize the problem). Whatever the reason, the problem is real, but truss uplift is not a structural problem. This movement which can just cause a simple hairline crack or create large gaps and cracks along the corners is a cosmetic problem mostly in homes in cold climates.  I think the best approach is to stop the truss uplift action from having any effect on the ceiling and wall drywall joints that exist throughout the home. Remember, truss uplift is not truss uplift if the owner can’t see it. Let the trusses move.  The truss moves, the drywall bends, no crack, happy customer.

NOTE: Most truss movement occurs over a period of time, the preventive techniques listed below will allow the drywall to flex near the corners preventing cracking. In other words the truss does not just pop up or slam

PREVENTION
When building a new house the framing contractor should secure the interior partitions to the trusses with truss clips. The clips attach to the tops of the interior wall partitions and are then fastened through the slots to the trusses. The fasteners are not driven tight so as to allow for movement of the truss. This keeps the partition wall stable and plumb and secures the rafters at the proper on center spacing. The drywall installer must then install the drywall properly to prevent cracking. A common method of attaching the drywall is to use floating interior angle method. This helps minimize the possibility of fasteners popping in areas adjacent to the wall and ceiling intersection and cracking due to the truss moving upwards. The drywall installers should not screw or nail the drywall to the trusses within 16 inches of an interior wall and within 8 inches of the ceilings on the interior walls. The ceiling drywall panel is fastened to blocks of wood nailed between the trusses to the top plates of the walls or to metal clips or continuous angles that are attached along the top of the interior walls.

Note:The key to eliminating truss uplift cracks and screw pops is to connect the ceiling and wall drywall while avoiding nailing or screwing the ceiling drywall panel to the bottom of the trusses at or near the intersectiondown. The movement is gradual so the drywall can just flex slowly as the rafter moves up but the drywall along the wall/ceiling intersection stays in place.

 

Figure 1 – Ceiling and wall damage caused by roof truss uplift.  Truss uplift occurs in homes when the bottom of the trusses separate from interior partition walls during winter months. This separation breaks the taped joints between ceiling and wall drywall as shown in Figure 3. The wider the span of the truss, the more often the problem seems to present itself

Photo_Crack

 

Figure 2 – Roof truss in normal position.

Truss Photo_01

 

Figure 3 – Roof truss in “uplift” position. NOTE: The walls that are prone to the problem are the interior walls that run at right angles to the trusses, but walls that run parallel to trusses especially those close to trusses are also in danger of being effected by truss uplift. 

Truss Photo_02

 

CORRECTIONS – REPAIRS:
1. The solution to an existing condition: The tops of the interior walls should be un-nailed from the trusses. Remove or cut free the nails from inside the attic. Then remove all the ceiling screws within 16 inches of the corners at the center partitions and all the wall screws within 8 inches of the ceiling along the wall. The holes in the drywall should then be patched with dry wall joint compound and the walls and ceilings repainted. This solution will be difficult to accomplish and will be costly.

2.Install crown molding around all the second floor ceilings, nailing the trim only to the ceilings. This procedure would cover the cracks and maintain a good looking ceiling corner. Note:  When installing the crown molding in this manner, remember to paint the trim and drywall in the winter months so that there is no paint stripe at the bottom of the trim when the trusses lift next winter.

3. Change the way we insulate attics. Insulate against the roof plywood. This will create a conditioned attic so the temperature and humidity will be better controlled. In homes where the attic is part of the conditioned space, typically where expanded foam is sprayed against the roof sheathing, truss uplift problems are less likely.

4. TRUSS BACKING ANGLE:
Trim-Tex has a product called a “Truss Backing Angle” which is installed before the drywall is hung which helps prevent truss uplift.

Trim_Tex Solution_Truss Uplift

The idea is not really new; Trim-Tex is just trying to offer a better alternative that is also available at the numerous suppliers that carry their products. The backing angle is made out of vinyl, which is plenty strong enough. It just needs to hold the drywall edge in place along the top edge of the wall. It is attached the entire length of the walls being treated. This means that the drywall is backed for its entire length and can easily be fastened anywhere along the edge as long as the fasteners don’t go through the angle and into the truss. The screws start very easily in the vinyl engineered extrusions which speeds up production.

Truss Backing Angle: Eliminates inside ceiling corner cracking due to truss uplift at interior partition walls. The rigid PVC Framing Angle keeps the inside corner stationary during truss uplift.

Truss Photo_03

 

© Myron R. Ferguson 2014

 

 

21 thoughts on “Truss Uplift Cause and Solutions

  1. Hi Myron, It looks like we have this Truss Uplift problem in our 18 month old third floor condo. The builder sent an engineer today to look at the problem. He’s suggesting covering the problem with crown molding. I would prefer they remove the ceiling screws first then put up the molding. Should they do both? Or will the crown molding be enough to fix/hide the problem? Thanks.

    • Hi Michael, I would say removing the ceiling screw is a good idea otherwise the drywall will just keep moving and crack along the top of the crown. I would say you also could not fasten the crown to the rafters either. But I am still afraid that the ceiling drywall will still pull upwards.
      > I don’t know how bad the movement is but maybe attaching only to the rafters is a better option. That way you don’t have to remove the drywall screws and the crown will just slide up and down on the wall where it will not be very noticeable. Paint when the trusses are up.
      > Myron

  2. Hi Myron, Boy are you the guy I have been looking for , we turned our attached garage into part of the house 8 years ago and ever since I get ceiling cracks in the winter and they close up in the summer but they have done it so much that the screws are popping and it looks bad , I blew in about 22 inches of insulation but the roof plywood and trusses are still exposed to the cool temps from our south Dakota winters , would it help if I went up and spray foamed everything in the attic above the blown insulation to keep it from absorbing the humidity on top ? If so can I do it in the winter or not ?Thanks Mike

    • Hi Mike, The spray foam may help but it will be expensive typically around $2 per bd ft. If you choose tto do this i would do before the weather gets too cold.
      Truss uplift occurs along the ceiling at center located partition walls. Is the room just one big space or are there partition walls?
      My guess is that there is just structural movement. How good is the foundation of the old garage?
      If most of your problems are along the wall/ ceiling where the garage attaches to the house then the two buildings could just be moving independently of each other.
      Myron

      • Hi Myron , It is pretty much all 1 room 14 x 18 with a hip roof 1 closet at the end of the room , most all cracks are in the center of the room running parallel with the rafters from wall to wall but not along any wall to ceiling joints . I did have pillars installed because a contractor thought it would help but it did not change a thing soon as fall comes.The cracks start to open . This always starts way before the hard freezing starts . Thanks Mike

  3. Hi Mike. Can i just use long nails or screws to secure the truss more to the interior walls? Like 3″-6″ pole barn nails for instance

    • Hi Brandon, I think there is a lot of force when the trusses pull upwards. The extra strong fasteners may hold and who knows maybe the wall itself will pull up a little. The cracking may not be as bad.
      Really good insulation and a well vented attic is best and if possible insulating the rafters against the roof and as a result having the attic as part of the conditioned space is also a good idea.

      • I have a friend that had a contractor nail the truss cords to the interior walls trying to make the connections stronger. Now they have wall movement which causes problems with the interior wall doors which will not close correctly. They rub the door casings.

  4. Myron,

    In 2013 I built a high end custom home directly on the intracoastal here in Florida. I used open cell spray foam throughout the walls and roof system. This is the second winter and the uplift is so significant that in several areas the cracks/openings are 5/8 to 3/4 inches. Last summar everything fully settled which confirms the uplift theory, however my conditions don’t seem to. Furthermore I anticipate adding crown in the coming months, but the movement during the winter months makes so much noise at night if often times can wake you up. There is a lot of popping and cracking. Please let me know your thoughts on this home specifically as it appears you are very familiar with the uplift phenomenon.

    Best

    Josh

  5. Hi
    I was recently pointed to this article by a friend when i asked him about nail pops and cracks in ceilings. However I have now also noticed that there is a small gap between my kitchen cabinets on first floor and the sidewall. On that same sidewall, I notice gaps between bathroom cabinets on second floor and the sidewall. Also for that same sidewall, i notice a little gap between baseboard and floor.
    could all these be due to truss uplift or is there a structural issue that I need to be worried about?

    Regards
    vikas

  6. My home is 3 years old and still under structural warranty from the builder. The second winter, there were just a couple tiny cracks in where the center wall touches the ceiling. However, this year there are several, and they are bigger. I used a magnet to find the sheet-rock screws and most are only 2″ from the wall. So, I’m now waiting for the builder to schedule a time to have a look.

    In the mean time, I’ve been looking up the building codes to see how it was supposed to be done. I found the part about using the special L bracket to attach the Truss to the wall frame to allow flex. However, I haven’t found any code about not putting any attachment within a length of the wall (to allow it to flex with truss movement).

    Do you know if the IRC code even mentions this? Thanks for your feedback.

  7. Hi Mike,

    I have been searching the internet and stumbled on your website. Now I know what my problem is – Truss Uplift. We had a home build in 2014 and have the winter cracking problem. I want to do crown molding but see that I could still have a problem in the winter because this will continue to occur every year. I want to do two or three piece molding and don’t want to keep having to caulk either because that buildup will start to be unsightly. Also, I don’t want to take out any screws. Where should I nail the moldings? I plan to have a runner on the top nailed to the ceiling about 2 inches away from the inside corner of the ceiling – and – a runner along the wall about 3 inches or so down from the ceiling. So, then I will have a piece that would normally be nailed to the top runner and the bottom runner on an angle. What should I do to minimize the cracking in this case and is there another kind of molding design I should use? I am assuming this is just an unsightly problem since one of your posts above said that it is not a structural problem.

    Also, another problem I have you may be able to help with. In my bathroom on the first floor, some bonehead didn’t put a nailer stud in the corner and the drywall on the outside wall is free floating by about 10 inches coming to the inside corner. Should I cut out a section and put a nailer and then re-drywall (a lot of work) or is there another product that will allow a better solution?

    Thanks

    • I would try to just fasten to the ceiling which will let the molding along the wall slide up and down.
      Truss uplift does not compromise the structural strength but the structure is moving.
      Did you investigate the quality of the insulation in the attic and also the humidity levels in the house and attic?
      Is the drywall moving or cracked in the wall corner where there is no nailer?
      If it is just a reoccurring small crack you can install Magic corner instead of paper tape. The magic corner flexes and moves without cracking http://www.trim-tex.com
      Myron

  8. We’ve got a two flat condo and there’s uplift on almost all the interior walls of the top floor. Has anyone tried paintable caulk? I’m just trying to avoid having to do crown molding in each room.
    Thanks
    Tom in Chicago

  9. I am having a problem with what I assume is truss uplift. My house is 2 year old, and in my ensuite I have a full height glass shower enclosure. There is a small bulkhead across the front of the shower and the glass is attached up to that bulkhead, in a small chrome channel. There is also channel at the bottom and the glass also fits into that. Usually there are no screws in the bottom piece of channel as it could lead to water leaking below over time, so the channel is simply siliconed at the bottom and screwed dow the side. What is happening is in the summer, the panel fits perfectly and is tight on all three sides. However, during the winter, the glass and channel pull up at the bottom and breaks the silicone seal, leaving the glass swinging. Wile it is attached up the side it can be pushed back and forth. I am also having a problem in the kitchen with the crown moulding around the top of the cabinets pulling again in the winter and perfect in the summer. How can this be fixed so that this no longer happens?

    Thanks
    Debra

    • The problem is that the rafters are lifting and taking the interior wall it is attached to with it. Increasing insulation and controlling humidity in the attic will most likely help. Also removing the nails that attach the rafters to the top plate of the wall affected will help but keep in mind that the drywall or even the crown molding is attached to the rafters so those fasteners may have to be removed as well. Myron

  10. I have read many sites concerning truss uplift and your explanation is hands down the best. I have been battling it for years and I am looking for a long term solution. I live in a small 1200 square foot ranch with s low pitch roof. The hall and one small bedroom towards the center of the house have been the worst. I am contemplating removing the drywall in the small 9’x9′ bedroom and installing new drywall based on your recommendations. This is not however a great solution for the entire house. I can see the drywall tape pulling in other locations in the winter, so I am looking for a larger solution. The attic has 16″ spaced 2″x4″ rafters with blown insulation and no vapor barrier on the ceilings. There are gable vents with vented soffit, but no ridge vent. I am considering your idea of insulating with a radiant barrier insulation against the roof rafters and taping all of the seams. Then, possibly a humidistat controlled gable fan. To make things more difficult, I have textured ceiling, so removing drywall screws and moving them is not ideal. I am considering hiding the cathedral ceiling cracks with wood flooring, but I have no solid plan yet. Any additional details related to the idea of insulating the roof trusses would be greatly appreciated. Thank you!

    • Hi Aaron, Sounds like you have your hands full but have some good ideas. Prevention is the key because it is very difficult to fix after drywall work is complete. The angle piece that attaches to the top plate works great.
      For minor movement the Trim-Tex Magic corner is a good solution.
      Myron

  11. You made a good point that the bottoms of the roof trusses are buried insulation. I would think it’s important to make sure and find the right truss contractor so that you can be confident with your trusses. I bet it would be hard to repair, seeing as it’s buried in that insulation.

    • Your right, problems created by truss uplift are very difficult to correct. Lucky for me that I have been called in for only a few problems over all these years. I think most are just small cracks.
      I think the companies who build trusses know about the potential problems but it would be interesting to know what if anything they have tried to do to eliminate the problems.

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