Laying a limestone hearth for a fireplace

[secteur]

Hello,

I am looking for some advice about laying a fireplace front hearth of Porto Beige limestone and very much hope someone could help.

I have some 20mm thick slabs which are 600mm square and are leftovers from our kitchen floor which was laid by a true craftsman ten years ago. The surface finish is honed but not polished and I am going to finish the stone with Lithofin StainStop MN. The hearth will be rectangular, about 850mm wide and 350mm deep and will stick out 350mm in front of the fireplace opening but will not extend back into the fireplace recess. I have cut the stones on a diamond saw with water cooling, two pieces 175mm by 350mm, and a middle piece that is 500mm by 350mm. The substrate is a well-cured, flat concrete screed. I'd like to go with a solid bed, fast setting adhesive layer about 3 or 4mm thick.

I've read a lot on this forum about limestone being stained by the adhesive, and I'm looking for advice about whether I should use some Stainstop to seal the stone all over before laying. If I use a white, fast setting adhesive, do I need to bother given that the stone is beige, and I believe, quite hard for a limestone? What adhesive would you recommend. I'd rather not buy a 20kg bag given that the area is only a third of a square metre so something that comes in small 5kg bags would be ideal. Alternatively, ready mixed in a tub. The grout is a powdered grout that is beige in colour. I know it is suitable because I cadged it off the guy who laid our kitchen floor. I think I should seal the stone before and after grouting.

I would really welcome any advice and any doubts that you may have about what I intend to do.

Thank you very much.

 

[White Room]

You can get 10kg bags from B&Q which has the markings of mapei, don't use tubbed for the stone.

 

[kilty55]

as above use a rapid setting white addy like you suggest,use a combed trowel also no blob and dabs

sounds nice
btw is this an open fire

 

[secteur]

Thank you both. Do you think I need to seal the stone all over before laying?

10kg at B&Q will cost more than 20kg at a merchant, I suspect!

Yes, the fire will probably be logs.

 

[kilty55]

yes i would seal the tiles,my only thought about it being an open fire with logs is any ash/embers with limestone being pale

most fires i have done or seen are slate or a grey travertine

 

[secteur]

Thanks.

I'm not too worried about the ash/embers. I have seen fireplaces made of Porto Beige on Google. Certainly, it will not look surgically clean after a while, but that's half the fun of stone, isn't it? I'm more worried about the adhesive staining the stone when it is laid. Others have had this experience hereabouts.

 

[kilty55]

white rapid setting addy is fine

grey addy may stain it as will dot and dabbing with a slow adhesive possiblt stain it

 

[White Room]

Back skim the tile with your adhesive.

 

[secteur]

Thank you all.

I'll go for white , fast setting, cement-based flexible adhesive and no sealing before laying, and back skim.
If it all goes wrong, I have a demolition hammer drill that could destroy the evidence. I will probably buy a bag of stuff tomorrow. If you have further advice, please tell me.

Thanks. Your help is appreciated .

 

[secteur]

Well, I used Wickes Natural Stone and Porcelaine tile adhesive. It is re-badged as "Flexible rapid setting tile adhesive". I only needed a couple of kilos but I had to buy a 20 kg sack. Places to buy that kind of stuff are a bit limited on Saturdays. If anybody wants 18kg of the remainder, they are welcome to it. It goes in the skip otherwise.

I back skimmed it using a squeegy and it went down well with a 3mm solid bed. A couple of coats of Stain-Stop MN went on today, and it should be good to grout soon.

Sorry, I just love the look of limestone. Look at those fossil shells from a few million years ago.....

Best wishes,

Martin