Patching and Plastering - Replacing thin veneer layer on lath&plaster wall?

A couple of years ago, an upstairs shower leaked onto one side of a downstairs lath-and-plaster wall. When the wall dried, the veneer layer debonded from the rough coat and large cracks appeared.

Yesterday, I inserted a putty knife under the cracks and, amazingly, the veneer layer (less than 1/16" thick) came off in large sheets. The rough undercoat of plaster is still firm, and the underlying lath feels (and sounds) solid.

I now need to reapply the veneer coat to the affected area (roughy 4 feet by 2 feet).

Can someone tell me where to purchase veneer plaster mix (Home Depot?), and give pointers or techniques for applying it?


Thanks,

Joe

maybe i am an idiiot, but what the heck is a "lath"
barry

Lath is the name of the strips of wood that were attached to the building's framing to give the plaster something to bond to when it was originally installed.

Regarding a skim coat, I think that you can use a premix joint compound for that, although the dry mix drywall compounds usually contain a bit of gypsum in them to help them set up.

Your other alternative is to contact an organization like US Heritage and talk to them about a Lime putty based skim coat. This is really only necessary if your house dates back to before 1900.

I would recommend that you try a patch in a small area first to see how it goes.

Good Luck.

HB

If the ceiling is smooth and in an area that small you can use vener plaster finish to do it. Use Diamond by USG or Unical or Kal-Cote by GoldBond. I don't know if you can get that at HD or Lowe's My local Lowes used to have Diamond. Mix it with a drill in a bucket the consistency should be like peanut butter at room temperature or a little thinner. Either of those materials will set in a little more than half an hour. A key to a good patch is to keep the existing plaster clean. Don't try to lap the new work onto the old but keep it exactly flush. Use a mist of water and trowel the work through the set and then trowel it until it is as smooth as the surrounding. You can make it as smooth as glass if you trowel it a couple extra times.

Now if you have a texture you can use the same material. But first experiment on some drywall or something until you can match the texture.

If you can't find real plastering material on a patch this small use a settint type of joint compound like EasySand by USG or another brand. Get some 20 min or 40 min set material. You can't trowel it down quite as slick as the real plaster material but it is much more sandable and if you don't get it right you can recoat it again as soon as it sets. When you sand it try to sand it exactly flush with the existing. It will probabaly bond if you let it lap a little.
Sand with very fine sand paper so you don't have scratches showing through the paint.

Priming and painting should be the same for either material

Let us know which you use and how you do it and how it turns out.

I thought of something else. If you use setting joint compound you can embed some mesh tape in some of it before you do the whole field. Maybe you can use a little setting mud and embed some tape over the cracks then still use real plaster material if you decide to go that way. If you do this make sure that you don't get any material projecting beyond the surface of the existing finish or you will have a hump.

The more I think about this the more I lean toward using setting joint compound. It is more amateur friendly and might be easier for you to find. I would use some plaster material but then I have some on hand and that after all is what I do.