T/f: truss uplift is a major structural problem.

Recommendation. Redecorating the ceiling wall intersection is an easy fix. Molding attached to the wall only.

William,

Sistering onto the bottom chord, would not help, the truss works as as system. Since the mechanism that causes the truss to rise and fall is due to the coefficient of linear thermal expansion (CLTE) combined with shrink/swell due to changes in moisture content. One other factor you must consider is temperature and moisture content of the truss changes constantly, so you have to guess what the temperature and moisture content of the truss members where when the ceiling/wall drywall joint was taped. For the examples below I will assume at the time of construction the temperature was 70° and the moisture content was 15%. On the winter day we see the crack the temperature was 0° and the moisture content was 5%, i.e. lower humidity dries out the lumber.

The CLTE for pine is approximately 0.0000028 in/in/°F, so a 96" 2x4 that measured 96" at 70° would be how long at 0°?

The answer is 96 + [0.0000028] x 96 x (-70°) = 95.98"

Now to adjust for moisture. Pine will expand as the moisture content rises and shrinks as the wood dries out, however wood shrinks/swells differently in all three directions. Changes in length (96" direction) is very small and can be ignored. The coefficient for changes in the width (4" direction) is 0.00259. The coefficient for changes in the thickness (2" direction) can be ignored since changes in this direction does not effect what we are trying to solve.

The change in the width of a 2x4 due to a 10% reduction in moisture would be?

The answer is 3.5 - 3.5 x [0.00259 x (15 - 5)] = 3.41"

Now a computer program is needed to calculate the amount of truss uplift based on the shorter member lengths and widths. The geometry of the truss also has an impact, therefore a 24’ scissor truss will move differently than a 24’ standard truss.

I know this is probably more than you wanted to know, but I hope it gives you some idea of the complexity of this issue.

William,

Sistering onto the bottom chord, would not help, the truss works as as system. Since the mechanism that causes the truss to rise and fall is due to the coefficient of linear thermal expansion (CLTE) combined with shrink/swell due to changes in moisture content. One other factor you must consider is temperature and moisture content of the truss changes constantly, so you have to guess what the temperature and moisture content of the truss members where when the ceiling/wall drywall joint was taped. For the examples below I will assume at the time of construction the temperature was 70° and the moisture content was 15%. On the winter day we see the crack the temperature was 0° and the moisture content was 5%, i.e. lower humidity dries out the lumber.

The CLTE for pine is approximately 0.0000028 in/in/°F, so a 96" 2x4 that measured 96" at 70° would be how long at 0°?

The answer is 96 + [0.0000028] x 96 x (-70°) = 95.98"

Now to adjust for moisture. Pine will expand as the moisture content rises and shrinks as the wood dries out, however wood shrinks/swells differently in all three directions. Changes in length (96" direction) is very small and can be ignored. The coefficient for changes in the width (4" direction) is 0.00259. The coefficient for changes in the thickness (2" direction) can be ignored since changes in this direction does not effect what we are trying to solve.

The change in the width of a 2x4 due to a 10% reduction in moisture would be?

The answer is 3.5 - 3.5 x [0.00259 x (15 - 5)] = 3.41"

Now a computer program is needed to calculate the amount of truss uplift based on the shorter member lengths and widths. The geometry of the truss also has an impact, therefore a 24’ scissor truss will move differently than a 24’ standard truss.

I know this is probably more than you wanted to know, but I hope it gives you some idea of the complexity of this issue.

William:
You see why I suggested that you speak with an enginer?

Thanks for the explanation Randy:cool:

Cheers

Morning, William. Hope you are well and in good health today.
I posted Classic Truss Uplift on the open forum to express to other inspectors, what you sometimes come across during a home inspection maybe more than meets the eye. Look closely at things out of the ordinary. Ask questions to anyone present during the evaluation.

You can follow more of what I had to say on classic truss up on the closed for member only forum.

I experienced truss uplift in a rental property that I own which eventually resulted in the detachment of the ceiling drywall from the trusses. Bit of a mess. And yes, I had added about 6" of insulation on top of the bottom chords of the trusses.

You could have addressed the truss uplift or decorated around the symptom.

Truss Uplift | This Is Drywall

I purchased a home to flip about ten years ago that exhibited similar symptoms to those shown in the photos presented by the OP, along with other symptoms of foundation movement. The inspector I hired postulated that it was a result of heaving and settling of the structure, and recommended I have the plumbing tested. Indeed, there were numerous plumbing leaks. That inspector saved my bacon and became the only inspector I referred from that point on.

May I ask, did you purchase the home? And if so, what was done to correct the structural defects?

Real estate agents refer to purchasing homes undervalued, due to structural defects mostly, as Flips. Not a choice word.

Not to say that what the OP is presenting is not 100% correct, but that, at least in my case, it seemed that a similar symptom might have a different cause. The house had rafters, BTW.

Which roof framing members reduce rafter spread?

Rafter ties help resist the outward thrust that rafters exert on the exterior walls. They help keep walls from spreading due to the weight of the roof.

Which roof framing members reduce rafter separation from the ridge?

Collar ties (or ridge straps) prevent the ridge from separating due to uplift pressure from wind (top drawing, right). Rafter ties or ceiling joists support the rafters and sidewalls under gravity loads, including the dead load of the roof structure and live loads such as snow (above drawing).

What describes an assembly of three or four vertical studs nailed together to make up a corner framing element?

Corner Post This describes an assembly of perhaps three or even four vertical studs nailed together tightly to make up a corner framing element in a dwelling.

Is a horizontally placed wooden steel or engineered member which supports floor framing members?

Typically, a header is a horizontally placed wooden framing member that is made to support the load when an opening is made in a load-‐bearing wall.