More newbie hearth pad questions!

[a_saccharum]

We're building a hearth pad by laying flagstone on cement board over plywood. The installers recommended using S type mortar, but the folks at Lowes are recommending thinset. Are both appropriate for this use? What are the pros and cons? For the S type mortar, there were two "S type" products on the shelf at Lowes- S type cement and S type mortar/stucco mix. I'm guessing I want the second, is that correct? Or am I looking for something completely different?

Also, is it necessary to use grout over top of the mortar, or is that more for aesthetic purposes?

Thanks to everyone who replied to my previous thread! This forum sure is a great resource.

Thanks,
Sarah

 

[firefighterjake]

I'm no expert at tiling to be sure . . . but I do know that the advice I had here was to use modified thinset to stick tile to the cement board . . . three years in, no cracking, no movement and no worries. If I was to do this again I would go with the same stuff.

As for grout . . . I believe the grout is more for the aesthetic look so you don't have tiles sticking up above the cement board/thinset . . . however I think you would want to take the time to grout between the tiles anyways to keep dirt, sawdust, etc. from getting stuck between the tiles . . . besides it would look a bit unfinished if you didn't grout between the tiles . . . and it is an easy job to do.

 

[a_saccharum]

Thanks for the feedback on the thinset! About the grout, I'm not sure if I really phrased that question the way I meant it. I know that after I put the stone down on the thinset, I will want to fill in (grout) between the stone with the thinset. Will I need to put a separate product on top of the thinset (like the grout you would use on ceramic tile) assuming I am happy with the color of the thinset?

 

[Intheswamp]

Like Jake, I'm no tiling pro, either, but I think there might be a "sealer" that is put on the grout to keep it from getting stained...or maybe I dreamed it. :gulp:

Ed

 

[woodywilson]

Stick with the thin set (no-pun intended) for laying the flagstone. Use sanded grout to finish as it will clean off the stone proper. Use the appropriate mortars for their application-- in the long run you will be happy!!

 

[a_saccharum]

One other question- the folks at Lowe's said that I needed to seal the individual stones before laying them, or they would absorb water out of the mortar and cause it to not set properly. Is that correct, or are they just trying to sell me something I don't need?

Thanks, everyone, for all your help!

 

[firefighterjake]

One other question- the folks at Lowe's said that I needed to seal the individual stones before laying them, or they would absorb water out of the mortar and cause it to not set properly. Is that correct, or are they just trying to sell me something I don't need?

Thanks, everyone, for all your help!

All I can tell you is the way I did it . . . and it works . . . after letting the thinset "harden" up for a day or so I sealed the stone (slate tiles in my case) . . . for some reason I don't think I sealed my grout . . . however I usually put a coat or two of sealant on the entire hearth before the start of the burning season.