Let’s talk about truss lifts

Let’s talk about truss lifts.

Do you have roof trusses in your house? Well if you do, there is something that you should know (especially in very cold weather).

A truss is a prefabricated wood framing member. They are most often used to save time, labor, and money during the construction process. They look like a large wooden triangle skeleton and are placed on top of the walls to form the roof. Plywood or similar materials are then nailed to the trusses to create the roof sheathing which then receives the shingles. They have been commonly used in houses since the ’60s.

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When the weather gets really cold I have received calls where the homeowner wanted me to come out and look at cracks that they recently discovered in the walls and ceiling areas of their homes. People often call about cracks which are usually exaggerated. I asked this on lady, “How big are the cracks?”. She said they were quite large. I asked her if she could give me an idea of how large they were. She said, “I can slide my hand into some of them.”. My first thought was that this was a gross exaggeration. However, after visiting this house, I came to realize that her observations were true. This was the first time I had seen this condition and within a few days, our office received similar calls.

The cracks were located on the inside walls and were primarily occurring where the walls meet the ceilings. In some cases, they were so severe that some of the ceramic in the adjacent bathroom shower stall was pulling apart and actually lifted approximately ¼” off the floor. How could this happen?

After analyzing the condition, this is my opinion of what occurred. There are certain necessary ingredients that can aggravate this “sudden” movement and cracking:

1. The roof framing must be made of wood trusses;
2. The attic/ceiling insulation has to be abundant (which is typically recommended today);
3. The attic must be well vented;
4. The outside temperature must be very cold;
5. The ceiling drywall has to be nailed to the bottom of the trusses.
6. The inside house temperature must be warm.

The bottom of the trusses are buried in the attic insulation and the bottom “cord” of the truss is probably near the interior warm temperature of the residence. The top portion of the truss is exposed and unprotected in the well-ventilated attic and the “top cords” are near the exterior temperature and typically are very cold. The trusses are sitting and bearing only on the outside walls of the house. The top section of the truss contracts with the cold while the bottom expands with the warmth. The truss contorts due to the extremely dissimilar temperatures (sometimes as much as 90 degrees between the inside and outside environments) of its members. The bottom part of the truss raises up in the middle (arching the bottom cord member of the triangle) AND in so doing, pulls the drywall ceiling and anything else attached up with it. The drywall ceiling being pulled up separates from the wall drywall and then cracks in that area.

The first question is, “How can this be corrected?”. Honestly, this cannot be easily remedied. When the outside temperature warms up, the condition often subsides, but can return again when it gets real cold.

The construction industry has come up with some alternative methods of attaching drywall which are not always used and do not exist in many of homes that are already built.

In my experience, the condition appears to surface when the outside temperature is approx. 80 degrees different from the inside (example: inside plus 70 degrees, outside negative 10 degrees). If that is the case, the best thing that I can currently recommend is to cool your interior temperature down in the real cold weather (which is usually at its lowest at night). In other words, turn your thermostat down in real down weather. Other remedies such as changing truss design, heating the attic, removing attic insulation, installing suspended ceilings, etc., can be difficult to do, impractical and expensive.

Mitchell Kuffa Jr. is a licensed builder who performs private home inspections.

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