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mnp13 11-18-2011 09:23 PM

Fixing damaged 130 year old plaster
Our house was built in 1873, and still has the original walls. The quality of the plaster work varies widely between rooms.

One of the bedrooms has had some water damage, and the skim coat over the cement layer has bubbled. The room was painted a couple years ago, and it was just painted over the weak spots. In the process of trying to run wires tonight, we put a few large holes in the wall - and I'm not going to be able to patch them with all the loose stuff.

So, I scraped the loose stuff off, and the cement has a layer of sort of sparkly efflorescence. There are areas where the paint is directly on the cement, but I'd rather patch the spots that I scraped off and smooth them over before I repaint. It's not going to look perfect, but it will look better and most importantly I won't have to think about it.

So anyway...

What should I use to clean off the sparkles before I re-plaster?

Snav 11-18-2011 09:30 PM

Are you using the term cement and plaster to mean the same thing? Knowing just what substance are you referring to, here, would be key in figuring out the solution.

Pictures - if you can - would be awesome.

mnp13 11-18-2011 10:08 PM

Cement - gray layer that goes through lath, coarse texture, looks like it has sand in it

Plaster - the thin, smooth skim coat that gets the final finish

Pictures tomorrow!!

Brushjockey 11-19-2011 06:27 AM

What you're calling the cement coat is usually called the brown coat, and then finishing plaster.
I have repaired plaster very often.
Here is a quick rundown of procedure
remove and dust out loose material from holes. if large enough and lath is removed- cut back to halfway into studs and cut a piece of sheetrock that is flush or slightly less than flush.
use 1 1/4 sheetrock screws and attach rock and with a touch of not over spinning them -also screw to reattach plaster around hole to lathe.
do the screws on either side of major cracks also
screen tape over cracks and around sheetrock.
Set tape and any major fills with powdered hot mud.
second coat with same. use a 12' blade and fan out
if there is enough of them on a wall, I will take the second step over the whole wall.
finish skim all with a sandable topping.
sand. prime, look over and spot whatever is needed, reprime those and finish paint.

It has a lot to learn, but becomes a routine once you have it down.
good luck!

mnp13 11-19-2011 08:33 AM

2 Attachment(s)
Here are a couple.

What's hot mud?

mnp13 11-25-2011 11:20 AM

Ok, I'm guessing hot mud is the stuff that you mix with water, that generates heat as it cures - like plaster? As opposed to the pre-mixed stuff in a bucket that dries from evaporation? Where can I get it?

Brushjockey 11-25-2011 11:30 AM

Exactly! One thing to know- it dries very hard and is difficult to sand ( even though the most popular brand calls it "Easy Sand..)
Comes in setting speeds- 90 min, 45 min, 20 min and 5.
Don't mix more than you will be able to use in a little less than that time, and clean equipment completely before it turns to a rock. But it is strong and works very well. You can recoat after it turns hard, but before all the moisture evaporates. In fact- I find topping at this stage is good- less bubbles appear.
See other thread about damaged walls for more how to tips..
All Box stores and paint stores carry this. It is an essential.

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