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Discussion Starter #1
The drywall under a bedroom window has been slowly degrading and falling apart. It looks like water damage, but it hasn't been getting water in it since I dealt with the gutter and storm window last year. It has just been crumbling and peeling off in layers ever since then.

I'd like to figure out the cause before I replace that section so I don't have to do it again later :)
 

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retired painter
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I agree, that looks like plaster. Once it's dried out well assuming the leak has been fixed it shouldn't be too hard to fix.
 

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Any way to check whether its drywall or plaster? House was built in 67, so unlikely to be plaster...The other rooms where I've cut into the walls it is drywall not plaster.

I don't think there is any new water coming in, so maybe just old water migrating out... I'll try cutting that section out to see what is behind it. It is not soft at all (like I'd expect for a wet spot), just keeps crumbling over time when I poke at it.
 

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In your location it could be Veneer Plaster which would consist of A Gypsum Lath ( Blue Board ) with a thin base coat about 1/16" & a finish coat 3/32".
Question is the gray area in the photo a paper facing?
 

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In your location it could be Veneer Plaster which would consist of A Gypsum Lath ( Blue Board ) with a thin base coat about 1/16" & a finish coat 3/32".
Question is the gray area in the photo a paper facing?
Interesting. Very possible that was the original material and I just happened to cut into later installs thus far.

The gray is not a paper facing. The wall has been crumbling and peeling off, so that gray section is actually what is revealed when the surface (about 1/16-1/8 inch of what feels like joint compound) peels away.

I dealt with the water issue about 18 months ago and noticed what looked like mineral deposits. Of course I started poking and prodding and it's been crumbling away... oops
 

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Interesting. Very possible that was the original material and I just happened to cut into later installs thus far.

The gray is not a paper facing. The wall has been crumbling and peeling off, so that gray section is actually what is revealed when the surface (about 1/16-1/8 inch of what feels like joint compound) peels away.

I dealt with the water issue about 18 months ago and noticed what looked like mineral deposits. Of course I started poking and prodding and it's been crumbling away... oops
Just basing this on the photo , year & location I would say it is a Plaster system of some king.
1 Rock lath with a base coat & White coat finish.
2 Veneer Plaster over a gypsum base.
3 Plaster over Lath.
My guess is number 1 due to the gray sandy base texture.
If it was 2 a Veneer system the gray area in the photo would be an off White.
3 conventional Plaster very possible due to how tight the base coat material is to the electrical box.
If it is a Plaster system remove all loose or delaminated material including the gray material. For the repair material use a setting compound like Durock fill all base coat areas that was removed. For the Finish coat sift the setting compound through a screen wire mix as per instructions on bag than trowel on & trowel smooth.
 

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Just basing this on the photo , year & location I would say it is a Plaster system of some king.
1 Rock lath with a base coat & White coat finish.
2 Veneer Plaster over a gypsum base.
3 Plaster over Lath.
My guess is number 1 due to the gray sandy base texture.
If it was 2 a Veneer system the gray area in the photo would be an off White.
3 conventional Plaster very possible due to how tight the base coat material is to the electrical box.
If it is a Plaster system remove all loose or delaminated material including the gray material. For the repair material use a setting compound like Durock fill all base coat areas that was removed. For the Finish coat sift the setting compound through a screen wire mix as per instructions on bag than trowel on & trowel smooth.
Fascinating. Thank you very much for the info! I didn't realize there were so many types of plaster.

For repair, the gray material is not loose at all. Should I try to cut it out or just leave it? Also for the setting compound, do I need something different since it is plaster? I have a bunch of the normal joint compound, I think with the 20 minute setting time.
 

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That wall material is not dry wall, or also known as sheetrock. I see no paper or gypsum material. That is simply concrete or plaster. Most likely concrete.
But the issue is that water is coming in from some where and leaking out around that wall box. Find the water intrusion and fix that issue, then come back to this problem and repair it. How you fix it depends on what you find that is allowing water to come in. Joint compound of not for concrete. Read the container. Plaster is what will stick to concrete. Try to use the same as what is already there. Stop thinking about how to fix this issue quickly and concentrate on how to stop the water from coming in to the structure.
 

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Discussion Starter #12
That wall material is not dry wall, or also known as sheetrock. I see no paper or gypsum material. That is simply concrete or plaster. Most likely concrete.
But the issue is that water is coming in from some where and leaking out around that wall box. Find the water intrusion and fix that issue, then come back to this problem and repair it. How you fix it depends on what you find that is allowing water to come in. Joint compound of not for concrete. Read the container. Plaster is what will stick to concrete. Try to use the same as what is already there. Stop thinking about how to fix this issue quickly and concentrate on how to stop the water from coming in to the structure.
Yep, that is my goal, not going for a quick fix here. Previously water was getting into the window above this crack cause it was pouring over the edge of a clogged gutter. That's been fixed. No more water in the window sill. Problem is I still see this flaking off.

The flaking problem is local to under the window only, which makes me think it is window related. Only other thing I can think of is that the window isn't flashed properly, which I'll check into when it warms up.
 

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The plaster and concrete soaked up a lot of water, and that's what's causing your skim coat to blister and peel. If you say you've solved the water problem, I think you could wait a little while for it to finish drying out, and then skim and repaint. Since it's right near an outlet, it might be worth turning off the fuse and taking a look inside there with a cheap endoscope.
 

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The plaster and concrete soaked up a lot of water, and that's what's causing your skim coat to blister and peel. If you say you've solved the water problem, I think you could wait a little while for it to finish drying out, and then skim and repaint. Since it's right near an outlet, it might be worth turning off the fuse and taking a look inside there with a cheap endoscope.
I solved the obvious water problem, but there was definitely a lot getting in at the beginning. I was thinking of cutting a hole there to see how wet it is and then just replacing the section, but that doesn't sound as easy since it isnt drywall.

I like the endoscope idea... I'll look into it!
 

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I would agree with Handy Andy on making sure the moisture problem is taken care of.
I will disagree on it being a cement base coat again based on your location.
During the period of construction in that location there were many very good qualified Plasters working there an again back to the photo that is very neat work around that electrical box. " Instructions for Plaster Gypsum or Lime based finishes, including Keenes Cement, should not be used directly over a Portland Cement basecoat or over concrete block or other masonry surfaces."
As for using a Joint Compound as a repair material from my experience is a bad idea due to moisture reacting between a Plaster base & the Mud based Joint Compound it will fail over an extended period of time.
Other ways to check the existing material.
1 At the base check to see if there is a screed board this would also be used as a nailer, the same for around window & doors if this is found than you would have a conventional Plaster system. For repair of the finish coat use a setting compound & trowel it smooth. If all the WATER leaking has been corrected you can drill a couple of holes say about 6 inches above the finished floor & also drill some at the top of the damaged area this will allow air to travel up & behind the existing Plaster bring the moisture out. MAKE SURE you don't hit any ELECTRICAL wiring or Plumbing when drilling the holes. Also purchase a moisture meter for checking the affected area against other areas.
 

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Leak really fixed?

Yep, that is my goal, not going for a quick fix here. Previously water was getting into the window above this crack cause it was pouring over the edge of a clogged gutter. That's been fixed. No more water in the window sill. Problem is I still see this flaking off.

The flaking problem is local to under the window only, which makes me think it is window related. Only other thing I can think of is that the window isn't flashed properly, which I'll check into when it warms up.
gjones8131, you say you fixed the leak by making sure that water stopped pouring over the edge of a clogged gutter? You may have stopped water from flowing over the gutter and down into your house, but it doesn't sound like you fixed the leak where the water was getting through your window and into your exterior wall. A driving rain might also get water into the leak that is still there. The water pouring over the gutter wasn't the leak, it was just a source of water that pointed out the leak. It seems to me that you still have a leak where a driving rain can still cause damage.

I agree with those that feel you need to make sure that the affected area is properly dried out before you attempt repairs to the wall. My concern about residual moisture is whether it is causing any mold growth. If there is still an avenue for water to leak into your house, this avenue might also allow moisture to constantly move into the wall.

If you find that you have mold growth inside the wall you might have to think about how to treat the mold. One possibility is to spray a product called Concrobium into the outlet hole using a fogging machine so it will saturate all the surfaces it comes in contact with. Concrobium is sold at Home Depot. Home Depot also rents a fogging machine to fog the Concrobium.

I was thinking that if you temporarily removed the wall socket and hooked up a wet vac exhaust to the hole, the warm and dry interior air (amplified by the wet vac to be hotter) might push enough dry air into the area to dry it out faster than leaving it to do so gradually. I would also scout around outside the window to find where the water came in - and may still come in during a driving rain!

When the area is dry enough to repair, I would scrape away as much loose material off of the grayish material in the photo. I would then coat this grayish material with 2 or 3 good coats of Gardz sealer (originally designed as a concrete sealer) and let dry thoroughly between each coat. The Gardz will soak in and solidify any loose material and give a good base for spackling.

I would then skim the coated area with USG Durabond 20. USG also makes a product called Easy Sand. If you dropped a clump of Easy Sand on a concrete floor and let it dry, you can come back and slice it off with your mud knife. If you try to do the same thing with a clump of Durabond, you might damage your mud knife! Durabond sticks like crazy to most surfaces. I would put 2 or 3 coats of Durabond on, taking care not to build up the Durabond, but keeping it as flush to the wall as possible. When each coat dries, all you should have to do is take your mud knife and scrape/slice off any lines or nubs, then skim again. The idea of doing it this way is so you have minimal Durabond build up to sand. I have gotten surfaces smoother than a baby's a__ doing it this way. When the patched area is smooth enough to paint, I would sand lightly, then apply another good coat of Gardz, let dry thoroughly, then paint. If you don't want to buy a large bag of Durabond you could probably buy a small container of USG's Green Top mud. Be careful not to overfill this as it is also difficult to sand.

Without being there and seeing things for myself, this is how I might do it.

siffleur
 

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Discussion Starter #17
I would agree with Handy Andy on making sure the moisture problem is taken care of.
I will disagree on it being a cement base coat again based on your location.
During the period of construction in that location there were many very good qualified Plasters working there an again back to the photo that is very neat work around that electrical box. " Instructions for Plaster Gypsum or Lime based finishes, including Keenes Cement, should not be used directly over a Portland Cement basecoat or over concrete block or other masonry surfaces."
As for using a Joint Compound as a repair material from my experience is a bad idea due to moisture reacting between a Plaster base & the Mud based Joint Compound it will fail over an extended period of time.
Other ways to check the existing material.
1 At the base check to see if there is a screed board this would also be used as a nailer, the same for around window & doors if this is found than you would have a conventional Plaster system. For repair of the finish coat use a setting compound & trowel it smooth. If all the WATER leaking has been corrected you can drill a couple of holes say about 6 inches above the finished floor & also drill some at the top of the damaged area this will allow air to travel up & behind the existing Plaster bring the moisture out. MAKE SURE you don't hit any ELECTRICAL wiring or Plumbing when drilling the holes. Also purchase a moisture meter for checking the affected area against other areas.
ok, I like the ideas about the moisture meter and the holes for airflow. I gotta check the flashing on top the window first...the PO had the house rush-repainted and they mighta sealed the flashing in.

2 maybe dumb questions. 1. what is a screed board? 2. would it be easier to just cut out the entire effected area and replace with drywall and just feather in the edges? Never worked with plaster before so that'd be a bit of a learning curve :)
 

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NO don't use drywall.
Think about it this way.
If you can trowel drywall mud on a sheet of drywall you can do the same with any Plaster product. The setting compound can be used to eliminate the sanding when applying your finish coat use a misting spray bottle & mist as you trowel NO SANDING REQUIRED.
A screed board is what the Plaster would have used to rod the plaster off of for a true & plumb wall. The boards are covered by your trim boards.
 
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