laying limestone hearth

I've got 4 lovely pieces of 30mm thick black limestone to lay on a concrete hearth. The builders opening is plastered. down to the hearth. I intend to lay these slabs on a regular mortar and point them up later. I was going to point them with regular mortar mixed with some ash. Trialed for effect first. I was going to go for a 5mm gap between them, will that be okay pointed with mortar? Should I butt them against the plastered opening or leave a 5mm gap at the back and sides? I was going to just butt them. There is a 20mm or so overlap where the front pieces go onto the floorboarded floor. Will mortar be okay here, or should I rake it out a little ready for some kind of sealent later. I'm sure the usual method is just mortar.

Thanks,

Reply to
visionset
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indoors you can use anything you like because it's not affected by weather like mortar dyes etc....I've even seen shoe polish used on white grout between black tiles and it worked a treat, still there 5 years later.

Often, a contrasting grout looks better, white grout on black, or any colour on white!

If carpetting up to it at the front edge you can use mortar, if wooden flooring, I'd use black silicone but it's up to you at the end of the day...it's not the end of the world if the mortar cracks out at a later date, or one of the floorboards needs to be lifted and it has to be raked out.

Reply to
Phil L

Thanks, another thing, I'm sure I've read that the hearth should be raised

50mm or something similar. But the only thing I can find in the regs is that it should be obvious what is hearth and what is not. Hearths at the same level as the floor I'm sure are allowed as long as the perimieter stops things being pushed on to the hearth like e.g. a foot stool. My hearth will be raised, I was hoping about 30mm. That will comply with regs won't it? All other dimensions are correct ofcourse.
Reply to
visionset

Who's going to check?

This is the only safety feature of a hearth, apart from catching hot coals before they roll onto a carpet/wood etc, anything is sufficient, and I've never heard of anyone ever checking a hearth WRT building regs etc.

I thought the slabs were 30mm? - plus the mortar?....it's basically as you say, to stop someone sliding a stool or chair into the fireplace, although whether they would want to sit so close to a roaring fire is another question :-p

Reply to
Phil L

I made my own superimposed hearth from marble slabs. The concrete hearth level with the floor is the constructional hearth. There are regs about that as well, like it being at least 18" front to back, but like people say, who's going to check.

However, to meet regs your superimposed hearth needs to extend at least 6" to either side of the fireplace opening, but if the fire surround is wider than that, it must extend to the edges of the fire surround, and be at least

12" front to back.

The superimposed hearth ( SH ) is normally at least 2" thick, but I'm not sure if this is a regulation.

I built mine by laying three slabs on top of a mortar bed. Mostly this mortar went over the original constructional hearth, but some mortar went directly over floorboards ( NB: I wasn't going to use this particular fireplace for a fire anyway ). NB: soft sand is a litle easier to mortar with and handle than if you use sharp sand.

My slabs were maybe 30mm thick, but what I did was cut some slivers off a spare slab with a wet flat bed diamond wheel cutter ( inexpensive ) and used them to form a facing for the bed of mortar that showed underneath the marble slabs ( total SH thickness was about 2" ). That way you couldn't see the thick bed of mortar at the front any more.

I left gaps where the facing strips of mortar butted together and also I left a gap unerneath them, like tiling, by inserting matchsticks underneath. That gave me the room later when the mortar had set to grout the marble strips/tiles together.

Mortar is too coarse for fine work like grouting small gaps. I butted the three main slabs together, but since they hand rounded edges, I made up a matching mortar out of marble dust I collected when cutting up a slab, and white and grey cement, and grouted them using that. There was a little lifting of the grout off the floorboards at one end, but it was minute and not visible without close inspection.

If you haven't a flat bed cutter, or don't want to bother, another idea to make the hearth 2" thick would be to sit your slabs on an appropriate thickness of mortar like I did, and just tidy it up as it sets to give a fair and true face underneath the slabs. Not really visible anyway, and by going over it with dark grout or whatecer you could achieve a good match perhaps to your limestone slabs.

Andy.

Reply to
Andy

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