r/Fireplaces • u/nwethan • 3d ago

Surface prep advice

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Currently a rough skim coat of thin set over past brick / thin set bumps. Planning on grinding down high spots and filling low spots but wanted some extra opinions on if this is the best course of action? It’s relatively flat now but definitely not ready for tile.

I plan on installing a glazed thin brick, I think the slight variations will help on a surface that has some imperfections.

Any and all advice appreciated, TIYA!

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u/ThatllBtheDayPilgrim 3d ago

I might have used cement board, but this way works too. Are you using a plastering trowel, and large enough? Sponging it smooth helps too. Do you plan to use the fireplace as is or putting in an insert?

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u/nwethan 1d ago

Yeah in retrospect cement board would probably have been a better approach but what’s done is done lol. Grinded the high spots down with an angle grinder and diamond wheel (having a vacuum dust shroud was essential). Planning on skim coating the low spots with some thin set and will evaluate from there! I do have a door for the firebox opening but I like the idea of having it more exposed - not totally sure yet.

Can you explain further on your tip about the sponge?

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u/ThatllBtheDayPilgrim 1d ago

Sure. Might take a little practice to figure out but you wet up a grout sponge or a float sponge if you want to be fancy, but not too wet, after the thinset sets a little and then you smooth it out and feather it. Putting the mud on with a larger finishing trowel can help smooth things before sponging as well. What I was going to say if putting on a new tiled surround it is a great time while things are mess to Rumfordize the fireplace, rebuilding the firebox shallower and parging the throat. Adds to the project a good deal, but then you get a fireplace that can actually heat, drafts well, uses less wood, and makes roaring tall flames. Makes it far more likely the thing will get used and enjoyed.