Ceilings separating from wall headers

[jay156]

Hi, I just looked at an interesting problem and I have a theory, but it has me kinda confused.

This guy's slab-on-grade ranch house has a problem where the ceilings are separating from the tops of the walls (see the attached picture). There are also numerous diagonal cracks at just about every door opening in the place and tiles are popping off the shower and kitchen backsplash.

My first thought was the exterior walls must be frost-heaving and lifting the roof trusses, and differential heaving is causing the diagonal cracks and other problems. The separation of the ceiling and walls is most pronounced on walls that are perpendicular to the direction of the trusses. I know the footers around the perimeter are way too shallow. He had the ground opened to put tile along one side and they were only 18" to 24" deep (in Cleveland, OH). So that further supports the idea it's frost heave.

But one thing the homeowner said perplexed me. He said that in the summer, the cracks close back up, and in the winter they widen. Okay, that makes perfect sense assuming it's frost heave, but he said the problem starts getting worse even before the ground has frozen, in the fall.

My first thought of how to explain this would be the cooler temperatures and drier air causing the various building materials to contract, opening the cracks. Does that sound like a plausible explanation?

And then my final question to you is what are some options for fixing this problem? I guess they could dig down and try to underpin the foundation, but that's a huge undertaking to do it to the entire house. Is there any other way to remedy this problem? He doesn't really have a lot of water next to the foundation from what I could see, but would pumping out any traces of water below the sub-grade possibly help?

Thanks,

Jay

 

[ishvaaag]

From your description I think that you are right in your assumption of differential temperature between inner elements and wall and roof (even structural) elements are making the cracks appear. Then it would be one more case of seasonal movement. Maybe in the summer the windows are more open and the agreement between interior and exterior temperatures is bigger. Once closed in autumn, the differential behaviour would appear, the cracks closing a bit when in winter the envelope closes on the inner core materials.

Were such the case, a solution would mean identification of the structural and non-structural attachments, then creating 2 independent systems of the same, and then creating architecturally open and aesthetically acceptable joints.

 

[JAE]

Expansive clay - moisture variations causing shrink/swell behavior?

 

[Ron]

jay156...you might have all those possibilities working against you. My first impression was possibly arching of the trusses due to thermal and moisture changes, but frost heave is a clear possibility from your description. As JAE noted, you might have expansive soils as well.

This one will require a rather thorough investigation to get it all in perspective.

 

[ACtrafficengr]

If you can't fix the root cause, attach crown molding to the ceiling, but not the wall. At least it will cover up the gap as it expands and contracts.

I'd hate to have their winter heating bill. I would not be suprised if a lot of warm air is escaping through those cracks. I'm not sure how you could seal them. Perhaps some sort of flexible membrane, installed when the cracks are at their widest, and concealed by the crown molding.

Whether it's frost heave or expansive clay, you'd have to lower the water table to below the capilary rise of the soil. That's something like 6 feet for frost-susceptable silts, and 10-12 feet for clays. Underpinning may be easier.

"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

 

[ToadJones]

truss uplift may be part of the problem. Extremely common problem.

 

[a2mfk]

Wood frame house with what type of cladding?

Exterior distress?

I'd have a few hand augers down to 10ft to see what type of soil you are dealing with. Have them done near the worse exterior distress.

Agree with others ideas above too, interior separations especially at wall-ceiling joints are many times due to truss bottom chord movements.

Here is a layperson article explaining the phenomenon:

http://www.askthebuilder.com/169_Truss_Uplift_and_Ceiling_Cracks.shtml