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What can I plaster over?


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05-29-09, 12:31 PM   #1  
What can I plaster over?

Hi all --
I've been reading all the posts and while some have provided me with ideas, I'm still a bit lost as to how to handle my circa 1938 interior wall in my apartment (I own it) that has had water damage and has been patched with something (it's greyish white and powders off when I scrape it). Under that, there's some very old paint (some flakes off, and some not), then the original plaster -- most of which appears to be in good shape with some cracks. However, there are places where the original plaster has been replaced by what looks to be softened plaster -- it appears white and powdery (though different from the later patch). And under that, there's something that looks like cinder block. In some places there's as much as a 1/2 inch difference between levels.

So, what should I use to fix this? I do have a rather large area that needs fixing (4 ft wide and 6 ft high). I have both the DAP drydax and patching plaster -- are these good products or shall I return them? I also have the fiberglass tape (which apparently isn't the best thing). Can I apply one of these to any/all of the layers indicated above? Do I wet all of it down first? Do I have to try to remove all the layers down to the plaster? Have I gotten in way over my head?

Thanks!

 
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05-29-09, 09:46 PM   #2  
Can you show us some pictures?

A good rule of thumb is if something is soft it should come off.

If what you have is indeed cinder block and if the area to patch is only 4 X 6 you should scrape or chop off everything down to the block. Then clean the block with a wire brush. If there is some efflorecense you should wash the block with a solution of about 3 parts vinegar to one part water then rinse it with clean water.

Do this then report back and tell us what you find and we can tell you how to fix it. It's pretty simple.

Take back the material you mentioned and try to get some gypsum plaster hardcoat. You might have to settle for
Gypsolite or StructoLite.

Let us know what you find.

 
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05-30-09, 02:14 PM   #3  
Pictures and such

Thanks for the reply -- I know you're the plastering celebrity. I'm including pictures of what I had hoped was going to be a straight-forward task. Now I have a wall-sized image of what appears to be a map of the UK and the beginning of Scandinavia. Clearly there's been water damage that has been patched over repeatedly.

I've gotten rid of most anything that comes off easily -- the grey stuff comes off, but it does so as a powdery substance and not in chunks. I'm hoping I don't have to get all of that stuff off the wall.

Here's the website with the pictures -- hopefully this will work.
http://diydont.shutterfly.com/

Thanks again!!!

 
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05-30-09, 06:40 PM   #4  
OK, the pictures help.
Yes you have water damage. What is on the outside of these walls?
What is above the ceiling? Roof? Another floor?

I would sure like to see a mortar joint in the cinder block? Do you know from looking at the outside walls that this is a block building?

It's a little unclear to m but maybe what you have is spalling finish over the gypsum plaster brown coat. Or, less likely, a Portland cement plaster basecoat with plaster finish.

This is a mess but I think I would approach it either of two ways.

The first is more radical and more work. That is to chop and or scrape off a defined area that includes all of the defective plaster down to the block, if indeed it is block.
The fix is more work but not necessarily more complicated. You would wire brush the exposed block then paint on some bonding agent. The standard of the industry is Plaster Weld by Larsen's Products. There are other brands. You would pay special attention to the edges of the remaining existing plaster. A new plaster brown coat would be applied and screeded flush to the existing surrounding plaster then the outer edges of the perimeter would be cut back 1/16" to 1/8" to allow room for a finish coat and the finish would be applied.
Should you go this route there is more you ought to know but let's explore the other option.

Scrape off everything that is loose or soft.
Wash it with that 3 parts white vinegar : 1 part water solution and scrub it pretty hard then rinse it with clean water. Yes, it's a little messy, but you need to do this.
Then Paint everything with bonding agent.
The difference is you are not chopping everything down to the block. Instead of plaster get some setting joint compound. One common brand is EasySand by USG. There are other brands. It is in formulas that set in 5 min. 20 min. 45 min and 90 min. Mix it with water in the amount you think you can apply in the amount of time you have before it sets. Spread it tightly and neatly. The less sanding you have to do the better you will like it. As soon as one coat is hard you can give it another coat. When everything is smooth and level you let it dry a day or to then sand it and prime and paint.

 
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05-30-09, 07:45 PM   #5  
there's another apartment above me. The wall that's most affected separates the bedroom from the bathroom. There have been plumbing issues, but theoretically, these have been fixed. In addition, the adjacent wall is the building exterior on the other side, and it's brick. We had BAD water damage throughout the building and that wall was essentially torn out and replaced. The exterior brick was sealed and I don't think we've really had any water problems since. Why they didn't address the ceiling is beyond me, but there you go.

I suspect I will opt for solution B -- A sounds like it's way out of my skill set (and B might even be a stretch). Or there's option C -- hire someone to do it for me. How difficult do you anticipate solution B proving to be? I'm hoping that this is the only wall with this level of damage, but you never know once you start removing the peeling paint.

BTW, would I tape up the cracks first before applying the EasySand? And would I need to do multiple layers?

Thanks again. Love these prewar buildings but the upkeep can be daunting.

 
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05-31-09, 03:57 AM   #6  
Tightcoat's the pro but I'll give my 2 cents

I don't often patch plaster but when I do, I use durabond [similiar to easy sand] IMO a setting compound is more diy friendly. Even though easy sand says easy - setting compounds don't sand very easy, so be sure to apply neatly! If you can't, just leave the setting compound coat a little shy and finish with regular joint compound - it sands easy. I usually only tape plaster when it's a crack I'm concerned will return.

I'm sure tightcoat will chime in shortly with some more top notch advice


retired painter/contractor avid DIYer

 
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05-31-09, 10:17 PM   #7  
No more advice really but an observation or two. It looks like some of your problems are due to repairs made with joint compound that got wet. If the JC had not gotten wet it would still be fine but it softens more easily and more quickly when it gets wet than does plaster. Don't misunderstand me here. The plaster would have done the same thing only maybe not the first time it got wet or the second but if it stayed wet for a feew days or a couple weeks it would have done what you see.

So before you spend a lot of effort make sure as much as possible that all the water problems are solved.

Let us know how it turns out.

 
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06-01-09, 07:39 AM   #8  
Ok. So let me make sure I have all the things I need to do:
Make sure there's no ongoing leaks (I don't think there are -- everything is dry -- just ugly).
Scrape off any soft damaged stuff. Use wire brush on cinderblock if necessary.
Wash area w/ 3 parts vinegar to 1 part water
Apply bonding agent (Plaster Weld)
Tape large cracks
Apply easysand. Dry and reapply as necessary.
Apply regular joint compound if I wasn't as neat with the easy sand.

Do I have all the steps?

Thanks again!!!

 
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06-01-09, 08:57 PM   #9  
You forgot one thing:

Let us know how it goes.

 
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06-01-09, 08:59 PM   #10  
New and exciting pictures of destruction

So I resumed scraping the loose soft stuff of the wall. I found LOTS of mildew on the ceiling beams. Again, nothing feels wet to the touch but there's been some serious, unresolved water damage. You asked for a bigger picture of the so-called cinderblocks -- be careful what you wish for, because you got it. http://diydont.shutterfly.com/

A 20 in high, 12 in wide section of the white plaster came off with little to no force on my part. I've added the pictures to my diydont website. Have I breached the line between diy and hire a professional? I'm certain I won't be able to get to the cinderblock level for the entire wall. Not all of it is that loose. And the white, chalky stuff when wet (I used a bleach mix to kill the mildew) turn grey and became rather gooey.

Anyhow, if these new lovely pictures alter any of the previous advice, let me know. If not, I've got my easy sand and my float. At this point, I don't think I can make the situation worse.

Thanks!

 
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06-01-09, 09:19 PM   #11  
Well, I'm still not sure what I am seeing. The dark grey area, how thick is the plaster on it? Does the plaster seem to be in more than one layer probably of different colors?

I would expect to see a mortar joint or two in that area. How hard is the darker grey material?

Is it possible that this is a poured concrete wall?

Do you want to explore a little deeper?

Maybe what you are showing is is the plaster brown coat. Behind that could be wood lath or masonry or possible, (but I doubt it) metal lath. Maybe, but I doubt it, you have Portland cement plaster for a basecoat.

Good move to use the bleach on the mildew.
Now if that darker grey area is shallow by a half inch or more you should use plaster to fix it. Gypsum plaster like Two Way Hard wall by Gold Bond or RedTop Gypsum Plaster by USG or some other hard coat plaster is best. You can use Gypsolite by Gold Bond or Structolite by USG. If that is what you have to use let us know for there are a couple tricks. Spread it on a little fuller than the existing then screed it off level with the existing then cut it back 1/16" to 1/8" to leave room for the finish. it isn't ideal but you can use the EasySand for the finish. it is a bit more amateur friendly than anything else and you won't have to deal with yet another kind of material. If you dampen with water for lubrication and keep your trowel clean and wet you can trowel the EasySand almost as slick as finish plaster if you hit it just as it sets. Then if you still need to you can sand it when it is dry. Don't try to sand it when it has set but not dried..

No, I don't think you are beyond your skill level but I sure am more curious what I am looking at in the new pictures.

All of the above is void if what we are looking at is only shallow by 1/8" or 1/4". If that is the case use the EasySand.

That the stuff turns gooey when you get it wet indicates that it is conventional drywall mud and not a setting compound. That is why when it got wet it went bad. That is why you want to make sure everything is dry and not going to get wet again as soon as you paint. Furthermore that is why I encourage you not to use regular joint compound. The setting compounds can stand a little getting wet if they dry again quickly. If they sit there a few days wet all is lost again.

 
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06-02-09, 07:20 AM   #12  
I think it's more in the 1/8 to 1/4 in range. Once my bonding agent arrives (had to order that), I'll give it a whirl and see what happens. Like I said, it can't get any worse. The grey cinderblock level generally appears to be solid. I haven't hit lath yet, but if I do y'all will the be the first to know!

Thanks so much. I'll report back soon.

 
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06-02-09, 08:55 PM   #13  
more pictures -- now with additional colors

like pink and rust. hopefully this will give a better indication what the heck this stuff is.

http://diydont.shutterfly.com

 
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06-02-09, 09:46 PM   #14  
I refer you back to an earlier post

Scrape off everything that is loose or soft.
Wash it with that 3 parts white vinegar : 1 part water solution and scrub it pretty hard then rinse it with clean water. Yes, it's a little messy, but you need to do this.
Then Paint everything with bonding agent.
The difference is you are not chopping everything down to the block. Instead of plaster get some setting joint compound. One common brand is EasySand by USG. There are other brands. It is in formulas that set in 5 min. 20 min. 45 min and 90 min. Mix it with water in the amount you think you can apply in the amount of time you have before it sets. Spread it tightly and neatly. The less sanding you have to do the better you will like it. As soon as one coat is hard you can give it another coat. When everything is smooth and level you let it dry a day or to then sand it and prime and paint.

This is still not the best way but it is an amateur friendly way and should work. Mix up some quick setting joint compound and fill in the deep hole and before it sets screed it off level. Then smooth it down some with the idea not to have it higher than the surrounding and not to have any gobs that you will have to sand late. You want to sand this stuff as little as possible. They might call it EasySand but it's all relative.

Smooth over all you can on the rest of the areas with the same setting compound. If you want you can do the last coat with topping for it sands more easily. But if you do that remember the gooey stuff? That is what you are putting back on.

 
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07-06-09, 12:06 PM   #15  
We haven't heard from you in a while. How is it going? Do you have some in progress and after pictures?

 
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