Replacing hearth tile

[MattBD]

I am replacing the hearth tile in a house that was built in 1940. To my knowledge, the tile has been in place the entire time. I was able to remove the old tile with a cold chisel and hand sledge. The surface underneath is as shown in the attached image. It's pretty solid in most places and I vacuumed up all the loose stuff. I have no idea what is underneath it as the basement ceiling is finished.

Should I take up that surface as well? If yes, what should my subsequent steps be?

If I can work with the surface in the image, the old tile was about 3/4" thick. The new tile is about 5/16" thick. Is the 7/16" difference too much for thinset to make up? If so, how should I build it up?


Thanks,
Matt

[cx]

Welcome back, Matt.

It'll help if you'll post your photos as attachments from storage on your computer so they appear in your post and remain a permanent part of your thread for future visitors. Links to third party storage tend to disappear after a while.

[MattBD]

Thanks for the reminder. I edited the original post to add the attachment.

[John Bridge]

Hi Matt,

If that's thinset on the floor it wasn't done in 1940. Thinset wasn't around then.

I don't see a problem with going over the stuff with more thinset.

[Davy]

We usually want the tiles flush with the hardwood. Have you checked for that? If the thinset isn't flat enough, go over it with a rub brick.

[MattBD]

We usually want the tiles flush with the hardwood. Have you checked for that? If the thinset isn't flat enough, go over it with a rub brick.

The new tile is thinner, so would be a bit low. I'll have to build it up by about 1/4". If as John said I can do that with thinset, then I'm good to go. If thinset is not the right product, it looks like a troweled on or self-leveling underlayment would be the way to go.

[Davy]

What size tiles are you installing? Even though thinset isn't the correct material to use, many installers use it to butter up 1/4 inch. It can be done much easier when installing large tiles than small tiles. If your tiles are 5/16 thick, I assume they're pretty small. In that case it's safest to use a self leveling cement or bust out the old mud and mud it up to the height you want, which is what I would do.

[MattBD]

They are pretty small; about 4x4 inches. I'll do what you suggest. I've done that before and it was pretty easy to work with.