# Cracks in drywall under window sill



## HomeBody119 (Aug 13, 2017)

Gents, looking for some help with this one. We turned out heat on about 2 weeks ago when I got cold here in the northeast. We have old steam radiators on first floor of house. I’ve noticed an expanding cracking in the drywall under the window sill in the last few weeks as well. Not sure if the two are related (is it possible the steam is causing this cracking)? I’ve also noticed the decorative sill is coming off the wall now. Any thoughts on what’s causing this? Can it be remedied?


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## Nealtw (Jun 22, 2017)

I would suspect water leaking in around the window. I would remove some drywall or rent a moisture meter to check the wall.


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## HomeBody119 (Aug 13, 2017)

Nealtw said:


> I would suspect water leaking in around the window. I would remove some drywall or rent a moisture meter to check the wall.


I had a sinking suspicion this was the case. I had caulked earlier in the fall. May go out tomorrow and caulk all over again. It is an old wooden window and the siding is old cedar shakes (all of which are being replaced this spring - new windows and hardy plank all around).

I’ll remove a bit of the drywall to check. Apart from caulking anything else you recommend? I imagine when the window is replaced they will do new weatherstripping, etc.

Appreciate the help!


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## Nealtw (Jun 22, 2017)

HomeBody119 said:


> I had a sinking suspicion this was the case. I had caulked earlier in the fall. May go out tomorrow and caulk all over again. It is an old wooden window and the siding is old cedar shakes (all of which are being replaced this spring - new windows and hardy plank all around).
> 
> I’ll remove a bit of the drywall to check. Apart from caulking anything else you recommend? I imagine when the window is replaced they will do new weatherstripping, etc.
> 
> Appreciate the help!





If you are going to do, do it right.


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## ClarenceBauer (Mar 4, 2005)

My guess is those walls are Plaster & NOT drywall.
Between the moisture form the warm summer & moisture from leaks when the Radiators were heated it caused the moisture to be extracted from the Plaster causing some of the cracking. The cracks were already there only smaller & increased in size when the heat was turned on. It should be noted that plaster will start to fail when temperature exceed 125 deg. for an extended period of time & if you consider the age of that plaster it has performed very well for at least 50 years.


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## mark sr (Jun 13, 2017)

I also think it looks like plaster. A good siliconized acrylic latex caulk is correct for fixing the gaps with the wood but caulking isn't what you'd use to repair the wall. For that you want plaster or Durabond.


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## Guap0_ (Dec 2, 2017)

3rd vote for plaster here. It also appears that there is a steam radiator with an air valve that doesn't match the system. It could be throwing moisture against the wall.


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