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expansion and contraction of exterior walls

Posted by bbmanty (My Page) on
Thu, Dec 12, 13 at 15:47

I have a problem with some exterior walls in my home. The first is in the kitchen, the exterior wall moves when the temp drops outside. I end up with a 1/2 gap behind my countertop. The second is a seam in the corner of my bedroom that will open up when the temp cools off outside. In spring both areas return to normal. I would like to put tile in my kitchen but am concerned that the tile will crack with the movement. What is the cause of this and is there a way to repair this situation so it doesn't happen?


Follow-Up Postings:

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RE: expansion and contraction of exterior walls

At first knee jerk,I would guess your foundation footing isn't below the frost line and is heaving. If that's true you have a big problem which requires professionals to correct. I hope someone has a less serious reason it might be.


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RE: expansion and contraction of exterior walls

I don't think it's a footing issue, this is an in and out expansion and contraction not up and down besides it only effects those two areas of the house.


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RE: expansion and contraction of exterior walls

Is your house on "clay" soil?
Is your kitchen and bedroom on same side of the house?

If so, it could be soil expansion and contraction. To correct this, water the foundation using a soaker hose around the outside about a foot away from the foundation on a regular basis to keep house from shifting so much.

We had a house that had plenty of moisture in front but back of the house water ran away from the house.


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RE: expansion and contraction of exterior walls

If the shrinkage is in the wood framing it is more likely to be from dry air in the winter rather than the direct effect of the temperature drop.


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RE: expansion and contraction of exterior walls

Get a HVAC contractor to install some humidity control in the home. And use your AC in the summer.


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RE: expansion and contraction of exterior walls

•Posted by Renovator8 (My Page) on
Fri, Dec 13, 13 at 21:33
If the shrinkage is in the wood framing it is more likely to be from dry air in the winter rather than the direct effect of the temperature drop.

•Posted by GreenDesigns (My Page) on
Sat, Dec 14, 13 at 16:51
Get a HVAC contractor to install some humidity control in the home. And use your AC in the summer.

I am keenly interested in what you all are saying and can't find research that has been done. Please expound.


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RE: expansion and contraction of exterior walls

Wood does two things. expand/contract as the temperature changes and expand/contract as the moisture content in the wood changes.

Those changes are mostly to width and thickness, not length. Any experienced craftsman that works with wood knows how to allow for that movement---when building furniture, for instance.

Walls and roof support structures can have a different movement---one that involves the wood construction members moving as a unit. That happens mostly with walls and trusses built with improperly dried wood---or wood that got very wet and was closed in(under exterior/interior sheathing.

The wood moves similarly to how a bow works by bending. The movement is actually called 'bowing'.

Conditioning the inside air creates large differences in temperature. A normal house wall is about 3" thick. The wall studs are 1&1/2" thick. If the outside temp is 20 degrees and the inside is 75, those differences meet in those wall studs. That causes tension in the studs.

Now factor in the humidity changes and that tension is increased even more.

That seems to be what is happening in your situation. Air conditioning removes humidity from the inside of a structure by lowering the temperature compared to ambient---by condensation. However, on a day when ambient humidity is low, the inside humidity may stay basically the same. That creates a big swing in moisture affecting the wood and causes bowing/warping/waning/etc.

What the advice about HVAC and humidity control is advising is to create an environment inside the house that provides a constant level of humidity.

Short of replacing the wood that is causing the problem---wall studs and possible roof trusses----the best way to minimize wood movement is to create a stable humidity environment---and have a humidity control system installed. That minimizes the wood movement caused by changes in humidity.


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RE: expansion and contraction of exterior walls

And check your attic for adequate ventilation getting rid of the moisture up there. You want continuous soffit and ridge vents, as well as attic interior chutes that keep the insulation channels clear for the air to flow.


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RE: expansion and contraction of exterior walls

I live in a cold climate (Minnesota). If your wall is really contracting by 1/2" there's something wrong.


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