We had a wood burning stove installed a couple of months ago. It is a 5KW stove and was put on a one piece Brazilian slate hearth which must be at least 25mm thick. It was installed by a HETAS registered company with a good reputation etc. We discovered at the weekend there is a crack in the slate hearth. Looks as though it runs from near the corner of one of the stove feet until the fireboard at the side. One side is about 1mm higher than the other side, so its cracked and moved.
We have sent them an email to the company for them to come and have a look but no reply yet, but just wondered what could cause this. We haven't stood on the hearth (even though it should be ok to do so I guess). We haven't over fired the stove to our knowledge.
Is this something to do with the installation or material?
I would say that 25mm is not thick enough for what is, essentially, quite a fragile material in a place where there are huge thermal differences.
...and Brazilian? What's wrong with Welsh or Lake District slate? Surely price wasn't an issue for such a relatively small piece?
But yes, from your description of the crack it sounds as if part of the slate wasn't adequately supported.
Yep, what globalti said.... sounds like they put it down on dabs that didn't support the slate in the right place.
I very much doubt it's been caused by thermal difference as stoves tend not to send that much heat down (stove specific though) and most can get away with a 12mm hearth nowadays.
The fact that the crack is right next to one of the legs would point towards the hearth not being supported properly. Stoves are heavy there there can be some proper point loading.
Our installer refused to fit a one piece slate hearth… insisted it would have to be two smaller pieces to guard against it cracking long term. We ended up with one piece stone instead.
Hasn't been installed properly, as above.
I will be interested in what kind of creative BS the installer comes up with to try to wiggle out of having to sort it.
I am away from the house so cannot measure the thickness but it could be approx 30mm, will measure later.
I'd be surprised at a 25-30mm slate slab cracking under what is essentially a static load of not very much weight.
If they've used dabs of mortar rather than a full bed then I'd get them to come back and do it properly.
And if you want to find out how much UK produced slate costs then give Burlington Slate a ring and ask for a quote! Just be sat down when you are doing it.
Heat cracking, installer should replace foc.
Chase it up if they mess you around.
Happened to me a couple of times in my early days installing.
Small, short legged stoves are the worst for it as they give a very intense concentration of heat.
I always use two piece, unless it's a long legged / heatshielded stove.
And yea, I also use 30mm Brazilian slate. I agree it's insane that it is less than half the price of slate from 80 miles away. As well as being available and consistent quality.