DIY Plaster Project?

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Old 01-11-20, 04:18 PM
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DIY Plaster Project?

Iím redoing the facade and mantel for my fireplace because it was ugly and a fire hazard. I finished the demo and have a couple small repairs to make before I rebuild. I probably am going to finish it with a simple tile and a non-combustible mantel.

I think the wall is plaster, with a wire mesh. Is that what I am seeing, the concrete looking material? Can I fill in the gap with layers of plaster and mesh? Itís about 2 1/4Ē at the thickest. After that I think I can just lay tile up the wall.
 
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Old 01-12-20, 06:26 PM
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Let's let some tile people weigh in on that part. Like how to tile over painted surfaces, special considerations if any fora fireplace.
About the plaster. Yes this is very doable.
Since you intend to tile I think you have a couple options: You can use gypsum plaster or Portland cement plaster. If the only gypsum plaster you can get is Gypsolite of StructoLite you can use them. To each 50" gag of plaster you should add about a half gallon to a gallon of mason or plaster sand. If you don't do this it will probably shrink crack and might even curl and debond. If you use sanded plaster which is available in some places you should mix it 2 parts by volume sand: 1 part by volume plaster. Mix according to the instructions on the bag. It might take two or three coats to build up to your thickness.
If you use Portland cement plaster it will take maybe three or four coats to build it to your desired thickness. Maybe the brick will have good suction and you can build it up in fewer coats. If so good. If your material starts to slump and slide down the wall stop, leave it rough enough that the next coat has some mechanical bond, let it set then put on the next coat. Maybe you dcan get stucco basecoat or mortar mix so all you have to do is mix it with water.

The preparation for either material is about the same.
First wire brush all the brick to get any dust or loose mortar off. Maybe you should paint a bonding agent on the brick but I think it is probably only critical to paint the edges of the existing plaster. Bend the wall ties until they break off.

This is important. You can't stop plastering in mid air. You must stop against something. The existing plaster if it is straight and plumb will work on that side but you must install by wedging or temporary fastening of some kind a stop around the fire box. This could be a 1 X 4 or if the plaster will be too thick a 1X 6 so you can put it around the inside of the firebox and have it project so it will be even with the desired thickness of plaster and straight and plumb while still supported by the edge of the firebox.. After your plaster has set and dried a little it should separate from your wood stop and you can remove it.
So apply your plaster in as many coats as it takes until the last coat is flush with the existing. Use some kind of straigtedge that will span the whole width of the opening across the top and from plaster edge to wood stop on the sides and across the top. You will screed both vertically and horizontally. You want your new work to end up exactly flush with the existing all the way across and around. Leave your last coat perfect with no humps or holes. If you are going to tile Leaving it the way it is left behind the screed is probably good enough as long as it is flat and even If you think it is too rough to tile you can float it with a red sponge float to smooth it a little and still leave enough roughness for the tile adhesive of thinset to bond. but check for humps or holes again after you do this. If your existing is gypsum plaster and if you use Portland cement plaster there will be a crack between the new and existing. The bonding agent will help here it is not guaranteed. Actually this may happen even if you use gypsum plaster. Not too serious a problem only best you can lay out the tile so a joint is not in line with the joints between the old and new plaster.

This is how I would plaster it. A drywaller will tell you to fur it out and drywall. I don't know just what a tile setter will tell you. I will watch this for more information.

There might be some youtube videos about plastering over masonry. Not a big secret.
 
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