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Question DetailsAsked on 11/9/2016

Boards/siding(?) of house separating and showing gaps. how to approach

It looks to be wooden boards with vertical metal strips where 2 boards connect(ed).
A few months ago we repainted house from white to brown, recently we noticed white areas to the left and right of the metal strips. Visible gaps now, up to 3/8"

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3 Answers


normal expansion and contraction, cold shrinks the wood and the gaps widen, paint the gaps and keep an eye on things after that

Answered 3 years ago by the new window man


Thermal expansion and contraction, as NewWindowMan said, can cause gaps like this to open up - though in wood, the maximum thermal change over a 50 long house and 180 degree F temperature variation (think Fairbanks Ak, 120F summer to -60F winter) would only be about 1/4 to 1/2" depending on wood species - so unlikely that is your case because that variation would be distributed over several joints, and you undoubtedly have not seen anything like that temperature variation.

One other possibility - moisture changes if wood siding - which from kiln-dried condition to saturated wood could expand as much as 6 inches over a 50 foot house face - or about an inch per 8-10 foot board. While the moisture in the siding (especialluy if painted) normally changes only about 1/4 that much, that is in the range of 1/4-3/8" per board - about what you are seeing, so could be the change from humid summer conditions to dry early winter conditions caused what you are seeing.

I suspect, especially since you have metal slips (butt end covers or joint covers) that you have wood-textured aluminum or possibly vinyl siding - which has about 10 and up to 15 times as much thermal expansion as wood - so 1/8-1/4" "reveals" like this after painting are common with them.

As he says - clean surface as necessary and ensure it is thoroughly dried out, then touch up paint in fall or spring when humidity is below 80% and temperature is above about 45 if temp is rising, or above about 55 if temp is falling. OR see if your joint covers are the snap-on type - just grip the siding like a "claw" shaped hand - with that type you push in on center and pry out on one end to pop off, similar to the covers on many household digital thermostats.

Answered 3 years ago by LCD



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Answered 3 years ago by Member Services

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