By Mitch Kuffa
Do you have roof trusses in your house? Well if you do, there is something you should know (especially in very cold weather)!
A “truss” is a prefabricated wood framing member. They are used by the construction industry to save time and money during the construction process. In general, they look like large wooden triangular skeletons and are placed on top of the house walls to form the roof. Plywood or similar material is then nailed to the top of the trusses to create the wood sheathing and receive the shingles. One of the big claims to fame about trusses in that, in general, they are only “2-point bearing” which means that they sit down heavily on the outside walls of the house and don’t need to be attached to any of the interior walls. They have been commonly used in houses which were built beginning in the ’60s.
A while back I had a call from a lady who wanted me to come out and look at some cracks that she recently discovered in the drywall. People often call about cracks and these are usually exaggerated or are considered common. I asked the lady, “How big are these cracks?” she said, “They are 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 her house, I came to realize that her observations were true. This was the first time that I had seen this condition, but within a few days, our office received other similar calls.
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The cracks were located where the inside walls meet the ceilings. In some cases, they were so severe that ceramic tile in the bathrooms were actually pulling apart. How could this occur?
After analyzing the condition, this is what appears to have occurred. There are certain necessary ingredients that can aggravate this type of movement or cracking:
- The roof framing must be comprised of roof trusses;
- The attic/ceiling insulation has to be abundant;
- The attic must be well vented;
- The outside temperature must be very cold;
- The ceiling drywall has to be nailed to the bottom of the trusses.
Here is what occurs. The bottoms of the trusses are buried in attic insulation and the “bottom cord” of the truss is therefore probably quite warm. The top portion of the same trusses are exposed in the well-ventilated attic and the “top cords” become very cold. The trusses themselves are sitting and bearing down on the outside walls of the house. The top section contracts with the cold temperature while the bottom expands since it is buried in insulation. The truss contorts due to the extremely dissimilar temperatures (sometimes as much as a 90-degree difference between the inside/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 doing so, pulls the drywall ceiling up with it. The drywall ceiling separates from the wall drywall and causes cracks.
The first question is, “How can this be corrected?” Honestly, you cannot easily remedy this condition. When the outside temperature warms up, the problem sometimes subsides, but then can return again when it gets really cold.
In my experience, the condition appears to surface when outside temperatures are approximately 80 degrees different than the inside (ex. Inside is approx. 70 degrees and the outside is approx. -10 degrees). If this is the case, the common thing that I can recommend is to cool the interior temperature down in real cold weather if you have an older truss built roof.
The construction industry has come up with some alternatives in more recently built homes with truss roofs that allow for suspended ceilings, methods of heating the attic, changing truss design at interior bearing walls, etc.., but not all houses have these updates and they can be both burdensome and expensive. If you don’t have any cracks in these areas, don’t worry about it. If they show up in very cold weather this could be the problem.
Mitchell J. Kuffa Jr. has been in the construction industry since 1967. In that time, he was worked as a construction superintendent, general superintendent and construction manager for several large developers in the state of Michigan.
He has been a licensed Michigan residential builder since 1977, was an incorporated general contractor for 11 years and has built and/or run the construction of approx. 3,500 residential houses, apartments, commercial structures and/or light industrial buildings.
In 1981 he started the first private home inspection agency in Michigan and to date has personally performed approx. 16,000 inspections for a fee.
Since 1981, Mr. Kuffa, inspects properties and acts as a construction consultant for the Michigan Department of Mental Health (group homes), UAW Legal Services, numerous lenders, several non-profit organizations and for the US Department of Housing and Urban Development.
Mr. Kuffa is a federal housing fee inspector and FHA 203K mortgage loan consultant, works with several attorney’s as an “expert witness”, has been appointed by the Michigan circuit court system to act as a Receiver in several cases concerning construction litigation and teaches a series of construction classes (for misc. school districts, community colleges. Michigan state housing authority, etc.).
Mr. Kuffa has been a member of the National Association of Home Inspectors, in good standing, since 1983.
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