Strange Wall Construction


Old 12-08-05, 06:53 PM
kolias's Avatar
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Strange Wall Construction

I renovate this second floor bathroom and I have never seen before the construction of these walls. The walls and ceiling in this bathroom are now glossy white and when I removed the wall tiles and other wall accessories, the paint peels away in flat sheets of various shapes. I can see that the walls are built with or 3/8 gyproc but on top of the gyproc there is a white like plaster coat about thick and hard like a rock. My questions:

What kind of wall construction is this?

Do I have to do any special preparation to repaint the walls and ceiling so the new paint will not peel away? I have been able to scrape all the old paint which comes off very easy with a putty knife.

Thank you
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Old 12-08-05, 08:19 PM
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Sounds like a 1940-50 home that used 2' sheets of gypsum as backer for a thin plaster coat. It could be that on top of the plaster is a hard oil enamel, which would explain why the succeeding layers of paint (likely latex) are peeling off so easily. Latex paint does not stick well to those old high gloss oil enamels.

Keep in mind the warnings regarding safety when working around lead based paint, as it sounds like you've probably hit the mother load. The dust is harmful to both children and adults.

If you are actually down to the plaster, it could be that humidity in the walls has caused the lime in the plaster to become powdery and repel the layers of paint. This sometimes occurs in plaster houses that have had cellulose blown into the wall cavities. If that's the case, the wall would probably need to be dusted or sanded, then coated with durabond and skimmed out in order to be ready for paint.

Regarding how to best paint over your surface, whether it is oil paint or plaster you are down to, you might try the Decorate > Painting forum.
Old 12-10-05, 04:33 PM
Join Date: Jul 2003
Location: California
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This is my response to an earlier post which describes similar walls. The advice given previously about painting is right on. You have good walls. Take care of them.

I think what you have, given the age of the house and your description, is gypsum, plaster over gypsum lath. The stuff you think is concrete is the gypsum plaster brown coat. What you think is drywall is gypsum lath. USG called theirs RockLath. It is in sheets 48" long and 16" wide. I think mybe they made it in 24" widths as well, it is 3/8" thick, the plaster is about 3/8' - 1/2". There is probably metal lath reinforcement in the angles and short pieces diagonally across the corners of the openings. The finish is probably whitecoat which is a misture of lime and gauging plaster ( similar in nature and behavior to moulding plaster) It could be Keenes cement, a harder, stronger more moisture resistant finish.

This is a good system. It should last.

How did I do?

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