Truss Uplift

As a handyman I receive a great deal of questions having to do with cracks in drywall or plaster. In many cases these cracks only require cosmetic repairs. It is important to know what is causing the cracking before you start cosmetic repairs. You don’t want to have to make the same cosmetic repairs in two or three months.
Here is a question about a common cracking issue that often makes homeowners think they have a structural problem:

Question:

Recently my husband and I purchased a three-year-old ranch house. The house is beautiful and very obviously well maintained. However we have noticed a crack in the ceiling of the living room at the corner of the wall that separates the living room from the family room. On the other side of this wall is the family room, where there is a crack in the ceiling against the same wall. The cracks are not very wide, but they do run almost the entire length of this center wall, on both sides.
Our concern is this wall runs long ways down the center of our house, does this mean that our house is settling? Is our house going to fall down? Is this a major structural problem? What can we do?


Answer:

From your description of the problem, what you have is a typical case of Truss Uplift. This is not the first time I have had this question. To explain this, I will have to give you a brief explanation of your roof structure.
To start your roof structure is a truss type. To put this simply, the frame for your roof and the frame for your ceiling are all connected, this makes a truss. These trusses are spaced about sixteen to twenty-four inches apart, to span the length of your house. The top wood of the truss is called the upper cord, to that your roof sheathing and shingles are attached. The wood that runs along the bottom is called the lower cord, to that your ceiling is attached.

Trusses structurally span the entire width of the house, there for they require no load-bearing wall in the center. The center wall that divides your rooms is a non-load bearing wall, the lower cords of the trusses simply pass over the wall.

Now getting back to your problem “truss uplift”. This type of cracking or separation while being unattractive it does not usually indicate a structural problem.

Since the trusses are all one unit connected together to form the ceiling and the roof structure, as the parts cure and shrink all parts of the truss is affected. The wood starts drying and shrinking the attachments that hold the top cord to the bottom cord, causing the bottom cord to crown or rise up in the middle. This causes the ceiling to raise and lift from the center wall, thus causing the cracks between the wall and the ceiling.

In your case, since the house is three years old, the moisture content of the truss members is at a stable level, and will not get worse.

Cosmetic repair of the cracks should take of this problem. In most cases a paintable calk and some paint is an easy and inexpensive cure.

Call your local handyman to evaluate the best repair methods. In some cases a floating ceiling trim offers the best cosmetic repair.

While major and persistent cracking may indicate structural problems, in your case the cracking is a common and normal occurrence in new houses. With new construction it is likely to have slight settling and shrinkage of building materials, which will cause some slight cracking in your drywall mainly at the corners of openings.