Black Limestone Hearth

[nordberg73]

Hi,

I'm after some advice on laying a black limestone hearth which will be home to a wood burner.

The hearth will be 1.4metres wide beyond the chimney recess and 1metre inside the chimney. The new hearth will sit on top of what's left of the concrete constructional hearth.

Firstly, I doubt I will be able to find the exact size flags I need, so will need them cutting and dressing. Is this something a stone supplier should be able to do? (I'm in West Yorks if anyone can recommend a supplier)

Secondly, I have read elsewhere that I should lay the flags on a fairly soft bet of sand and cement. What mix should I use? A friend suggest 1:4 using river sand? The constructional hearth is not symmetrical - one side of is about 4cm longer than the other. The end result is that the flag will be seated on the wooden floorboards. Is this going to be a problem?

Next, I'm conscious that these flags can be easily stained. Should I seal them before I start any work with them - ie before I even lay them on the base? I've read that Aqua Mix Enrich & Seal is a good solution. I don't want a sheen on the flags, just to protect them and if there's a colour enricher, then great.

Finally, do I grout them with tile grout or traditional cement based?

Many Thanks!

 

[hotrod]

I've just laid some limestone although they were imperial blue. They do a "Midnight Black" in the same range - nice stuff.
http://www.globalstonepaving.co.uk/global-range/limestone-collection/midnight-black-paving/

Cut with a 9" diamond disc, bed on a semi wet 4:1 grit sand:cement.

No need to seal the flags - point up using soft sand / cement. Consider using white cement to lighten the mortar or lime if that's the effect you want. Add a splash of feb to the mortar to help workability - I put it in the bedding layer for the flags too

I would try and avoid bedding them on your floor boards - can you not lift them, shutter, bit of DPM, pour a bit of concrete then lay your flags?

 

[nordberg73]

Thanks!

I would try and avoid bedding them on your floor boards - can you not lift them, shutter, bit of DPM, pour a bit of concrete then lay your flags?

In English please I'm a complete novice....

 

[hotrod]

In English please I'm a complete novice....

Sorry - my fault description was a tad brief. This all depends on how deep the void is below your suspended timber floor (floor boards / floor joists), the deeper the void the more concrete you will have to use. You can lay flags on floorboards but in imho it's not the proper way to do it because of the expansion / contraction differential movement betwixt the two materials - you are asking for problems down the line. Anyway, I digress, so:-

1. Remove floor boards where the flag(s) will be seated.
2. form a "box" out of plywood to match the footprint or slightly larger than the area you want the flag to cover. This is your "shuttering". You may need to reinforce the outside of it with additional timber depending on the size prior to step 4.
3. Line the plywood box with a DPM (Damp Proof Membrane) - think, lining a baking tin with grease proof paper .
4. fill the plywood box with concrete to a level that marries up with the existing hearth level.
5. Once the concrete has cured you can "strike" the formwork - remove the plywood "mould" from the concrete
6. You can now use a bedding thickness of your choice to match the 2 surfaces together and lay the flags.
7. Lay flags in the morning, point up in the afternoon.
8. Sit back, crack open a cold beer and admire your handy work.

hth