Cracks Forming In Between The Ceilings & Walls Of Your Home? Here's What You Need To Know

If you've noticed cracks forming in between your ceilings and walls, you may have a problem in your attic with a phenomenon known as truss uplift. A family in Indiana had this problem and found three broken trusses above their children's bedroom. Since trusses are designed to hold the weight of the roof and any snow that falls on the roof, you can imagine how dangerous of a situation this can be. Here's what you need to know about truss uplift and what you can do to fix the problem before your trusses break.

The dynamics of wood trusses

Trusses are designed to transfer the load of the roof and snow to the exterior walls with a system of wood cords that are configured in a triangular shape. The tops of the triangles transfer the weight to the bottom sections, using the laws of statics and geometry. Trusses are designed by structural engineers and should not be altered in any way or your roofing structure could be compromised. One thing that can alter wood trusses is humidity.

Wood trusses expand when there's humidity

Wood expands when it is wet or there is moisture in the air. Now consider that the bottom cords of the trusses are typically underneath attic insulation and the tops of the trusses are not insulated at all, this means that the bottoms and tops are subjected to different humidity levels.

This can result in the expansion of the wood cords at the top of the trusses while the bottom cords remain constant. With the top cords expanding, force is exerted inward to the bottom cords. This causes the bottom cords to bow upward and lift, which gives the phenomenon the term truss uplift.

Ceiling drywall is attached to the bottom cords of trusses

The drywall of the ceilings on the top or only floor of your home is likely attached directly to the bottom cords of the trusses. When these cords lift upwards, the ceilings in your rooms also lift upward because they are attached. This is what causes cracks to form in between the ceilings and walls of your home.

Conceal the cracks with molding

Instead of trying to repair the cracks in between your ceilings and walls, conceal them with molding. However, be sure to attach the molding to the ceilings and not to the walls. That way, the molding will move with the ceilings if truss uplift occurs again.

Control humidity in your attic with ventilation

Now that you understand why and how there are cracks forming in between your ceilings and walls, you are probably wondering what you can do to fix the problem. You'll need to control the humidity level in your attic to prevent truss uplift. This can be done with ventilation through your fascia and a vent in the top of your roof. These vents can work together to allow fresh air to enter through the fascia vents and exit through the vent in the roof. The draft this venting creates can effectively remove humid air from your attic and away from the trusses.

The fascia is located underneath the eaves of your roof. It should have vents that provide the necessary ventilation to protect your home from truss uplift. You'll need to make sure these vents are not blocked. Sometimes, birds, squirrels, bees, and other pests can get into the vents and cause blockages. Also, you'll need to make sure your attic insulation does not cover these vents. If you are unsure whether or not your attic venting is adequate, ask a soffit and fascia specialist to conduct an inspection.