How to patch a large hole in plaster and lath


I am having some plumbing repaired in my 1913 house that will result in a large access hole (2' x 16") on the first floor. The wall is currently plaster and lath and I'm trying to get a handle on the best way to repair the damage after the plaster and lath are removed. From what I've read so far, plaster of Paris hardens too fast, making it difficult to work with so I'm leaning towards DAP® Plaster Wall Patch (Dry Mix). I know I need to provide some backing material either metal or wooden lath but I'm not sure what else is needed. Do I need to use any fiberglass mesh to put over the lathe or can I just start with the plaster. Does anyone have any experience with the Plaster Wall Patch? Is there something better that would work? When applying plaster it sounds like I need at least two layers, once base and another finishing. Should I build up a first layer, let it dry and then another layer level with the existing surface or is there a technique that would be better. Do you think I can paint over the Plaster Wall Patch or is something else needed to prepare the surface for painting?

I can't wait to get started, I just need a little help in putting a plan together.

Best Answer

What I have done on my 1909 house (I am in the U.S.) in the same exact situation is clear a wider area of the lath and plaster and replace it with drywall. To do that, you will need to add some padding over the studs because the lath&plaster is thicker than 1/2" -- what I did was pad it with 3/8" plywood, then drywall over plywood to achieve approximately an even joint between the new drywall and the old plaster. Then you tape and sand the joints like you would with regular drywall, prime and paint it later.