what stone is safe to use as a stove hearth?

[dcraven]

hey

im building a hearth for a stove (6.7kw if it makes a difference) using bricks round the front and filled with concrete or cement (open to suggestions on that one) but i want to then put either slate or black sandstone paving slabs on top to pretty it up.

does anyone know anything about heat tolerances of these stones? will i be safe with those? its going to be directly below the stove so will be taking alot of heat and heat change.

many thanks for the advice in advance

dave

 

[PrenticeBoyofDerry]

natural stone or slate will be fine.

 

[noseall]

A PBD has said you would need some serious heat to exceed the temperature tolerances of most stone or even cement based products for that matter.

 

[Richard C]

The heat generated by a solid fuel fire is well within the tolerance of most natural stone & concrete but it’s important not to lay a one piece hearth for solid fuel. These stoves can generate very high temperatures in the hearth immediately underneath & in front of the stove & need the provision of expansion gaps to counter the effects of differential expansion between this very hot area & the much cooler outer perimeter of the hearth. This will expand at a much smaller rate & is like putting a restrictive band around the hearth, if there is nothing to accommodate the greater expansion of the bit in front of the fire, the stone will very likely crack. Take a look at the difference in construction between “over the counter” one piece decorative stone hearths & those constructed for use with solid fuel.

I don’t install stoves but I’ve finished off several hearths & surrounds. I usually buy in the hearth as they come pre-fabricated on a 50mm bed of concrete & at a cost of around £160-£180, it’s not worth the hassle unless you want something bespoke. I’ve used 600 x 300 x 10mm polished black granite tiles to fabricate surrounds & they look really good but at around £20 each retail (£15 trade) you don’t want to be making any mistakes cutting them. If making your own hearth, close butting the stone is sufficient to allow for expansion, were not talking gaps here unless you want them; in fact pointing/grout in any gaps may well crack & fail. You can lay your chosen stone on a bed of concrete but I would be inclined to cast the sub hearth in concrete & then fix the stone to this with a decent powdered cement tile adhesive, which I use for the surrounds; the one I use is good up to 150 degrees C but check the suitability of individual adhesive brand.

Be careful with the wall finish surrounding the fire; don’t use Gypsum plaster products either as base or finish coat in the area 500mm either side or 800mm above the stove, it won’t stand temperatures much in excess of 50 degrees & I can almost guarantee it will crack & blow off the wall.