Black limestone hearth - cracked joints & lifted flags.

JustAnotherSaver

teddysmum wrote: »

We have a slate fireplace, which gets quite warm on the section in front of the gas fire.


Did you light your fire shortly after fitting, when the plaster (?) was still wet, thus drying it out quickly and unevenly ?

We were advised to light it after it was fitted, although to keep the fires small for the first few times of lighting. This is also repeated in the handbook.

It was about 3 days or so before i lit it for the first time & i kept it small & not burning for very long.

I did this for about the first 3 times, 4th & 5th got steadily bigger & longer before burning 'as normal' after that.

In all that time there was no problem with the hearth.

I've only had the hearth covered up the past week or two & that's when it's happened.

With it being covered, i'm wondering if one of us has just stepped on the edge of the flag & lifted it. I've been painting the chimney breast so even i may have done it & not noticed. I don't know.

Just seems very strange to me that for 3 months it was perfectly fine, then i cover it & work around that area & all of a sudden it's like this as if by magic. That's what makes me think it's been stepped on. I've knelt on it, maybe i did too close to the edge & as it was covered i didn't notice.


Thanks for the reply.

Ruski

JAS: step on the floorboard in front of the lifted slab, does it lift the slab slightly when you put your weight on the floorboard (between the joists)

I have a feeling that a springy floorboard may be acting as a lever under the very front of the slab, even if it only 20mm under the mortar...

Let us know. Even if it doesn't move, there's one more thing you can discount being the cause

HTH

Russ

JustAnotherSaver

Thanks Ruski.

No - stepped on each board next to the flag, up close, a little distance off, stepping on 2 boards at a time, 3 boards, i checked with wife doing it, wife checked with me doing it.

The flag itself didn't move at all throughout. Just tested it now that you've said.

cyclonebri1

I've just realised why there is confusion about the thanks is, you've quoted from an entirely different topic/thread. What you said to me wasn't anything to do with this post of yours at all.

If your dealing with your contractor in as muddled and confusing manner, well.
It have been like pulling teeth, every few posts there are more pictures and information and given the number of pictures taken, (very admirable and should advise everyone to do this), I can't understand how difficult it has been and how.

You are still getting sensible advice, I've edited post # as I feel this may now be your issue, but there is only 1 solution and it's been told to you several times, the base isn't supportive enough and if it feels springy it has failed, get your man in and hopefully he will sort it for you.
This is the only advice you need as clearly it's his responsibility even if you had asked for something incorrectly specified, any builder should have balked at it.

DaftyDuck

There are several problems with how it's been done, and I'm not reading all of the riot above to discover what has or has not been suggested, and there's little point in "who's to blame", more a point in how to fix it.

Having the cement underbase cross from the hearth to floorboards will always cause a failure at some point: ALWAYS! There'll be vastly differential heating, flexing and drying when the fire is alight/cooling. It will fail. You may have a minor earthquake (I've had two!), or the rumblings from lorries; it WILL FAIL! The mix for the underbase looks poor - it's dusty and crumbling, cracked in many places, lifted from the boards (no surprise there), separated from the slate, still on the side of the slate... it's been appallingly done. The underbase also doesn't appear to extend fully to the right hand corner and, if you zoom in there, it looks like the cement has been slightly crushed by a pivot action on the corner of the slate. Shouldn't be possible, as slate should be fully supported underneath, and with a frame around to protect the corner... Nice bit of wood, contrasting colours, bevelled edges, say.

It does really need a frame around it, wooden, metal, tile, whatever. Having the hearth exposed like that, it will fail, and it's a trip hazard. There's no spread for any pressure on the large slate tile, and... well, I could moan on...

Solution? Get the bloke back to fix it, and do a proper job. One solution (still not ideal) is for a single large sheet of slate, supported on the underhearth, surrounded by a frame, supported on the floorboards, the two closely fitted, but not fixed together, allowing some movement without failure. Better would be to increase the sub hearth size, but that'd be costly and messy. But, the point of a deep, wide, stone-based hearth is to absorb all that heat and stop the wooden floor bursting into flames....

I've put in a number of fireplaces (eight or nine, plus two or three solid fuel stoves) in older properties myself (before regulation madness) but I'm no professional. I'd certainly expect a more... rugged job to be done. Personally, I'd have had no compunction not to stand, jump or put a ladder on a hearth when I'd done it. Yours, I'd be wary of standing on it even when just done.

So, get your bloke to come back and expect him to patch it up, or get someone more professional in, and pay more for a good job, or leave it for now, and work out how to do a good DIY job in a few months or years. Choices, choices....

The "Thanks" button is there ˅˅˅˅˅˅ Luckily, no "hate" button!

JustAnotherSaver

Thanks Dafty. You can have a thanks button click for that lol

Just a few things...

1) It likely wont matter, but just to say that a carpet will be fitted at some point. We're not having exposed boards. This will take away the lip sort of to minimise the trip hazard. And at any rate, on the topic of trip hazards, i'm not getting in to health & safety nonsense thankfully. If you can't see two whopping slabs & mind your footing around them then you deserve to trip over them.
Call it poor attitude, but i'll take my chances as far as tripping goes I'll contact you in 30 years & let you know how many times i've tripped & i'll buy you a pint if it's even once. Can't say any fairer than that

2) I haven't really shown a shot of the left hand side.

But it makes me ask ........ if having it slightly on to the floorboards or up to the floorboards WILL make it crack, and we have seen the right hand side crack.....
...then why hasn't the left hand side cracked?

I don't mean that in a "you are wrong" sense. Just a - if it's going to crack, then why hasn't the left side done it?

cyclonebri1

But it's not just the floorboards, lets get this straight once and for all;

You now say the brickwork is built off a solid once tiled floor?, so how come there are joists above that?, has the floor been raised by 9" or so?

The brickwork extends to the level of the joist, yes? then it's also sat on the joists and just the same thing, they will swell and shrink with humidity and heat, thing about the effect of all that plastering you have had down, every timber in the house will have swollen then shrunk to some extent.

Why has only 1 side failed?, well luck, the other probably will given the way it has been done.

This is the reason for flexible tile cement, not to cover incorrect installations but to allow for the inevitable differing expansion rates of timber substrates and if he has not altered the joists to allow the brickwork to be totally independent then whether you accept it or not, it is actually sat on the joists, doesn't mater if there's a bed of mortar on top it will and has failed do to wrong installation.

(Not for a minute suggesting it wouldn't have failed if flexible addy had been used, I'just giving an example of why these measures have to be taken).

JustAnotherSaver

Unfortunately i don't have a photograph of when all the joists were ripped out in order to show you that the joists are not on top of the hearth.

They run length ways & fit into the side of the chimney breast.

I know you think i'm being hard headed. I think perhaps more it's just a misunderstanding between us. We don't seem to be 'getting' each other. For example ... i've said numerous times that he hasn't & can't touch the joists but you keep mentioning them. Perhaps that's my fault. Perhaps i'm describing it poorly. I must be if you think that he can access the joists. Trust me though when i say ... he can't access the joists. Not unless he rips up the floorboards, which he has NOT done.

You have the joists running the length of the room. Into the window wall, onto a sleeper wall & from the opposite wall back on to the sleeper wall. The joists up against the party wall run in to the chimney breast SIDES.

On to these joists go the floorboards running WIDTH ways of the room.

One end of the floorboard butts up against the wall (a little gap before anyone 'starts') facing the chimney breast whereas the other end of the SAME floorboard butts up against (again a gap was left, but please don't ask how big of a gap - i never measured) what was the hearth platform or whatever it's called that my lack of knowledge just doesn't know. The bit that the wood & hi viz jacket was sat on.

So basically that hearth area (or whatever it's called) is not touched by anything at THAT moment in time other than the face of the chimney breast itself - the brickwork runs down on to it. No wood is touching it.

If i've lead to you believe that joists & floorboards are covering it then i apologise but i honestly don't know how i did that. Again, if i did, then i apologise.

So on to this hearth area (or whatever it's called) they cemented & laid flags, which ended up touching the ends of the floorboards but NOT the joists since the floorboards extended a little over the joists. Again ... NOT NOT NOT the joists.

And that is how it was done.

JustAnotherSaver

I'd had enough of it this evening. So i lifted the flag to see how much it'd lift off.

It actually lifted clean off without any fight whatsoever.



Oh & what i thought were wet patches at the ends of the floorboards where the mortar met the floorboards actually aren't wet patches it seems.

I bought a moisture meter some time ago & jabbed various areas of the floor ... 18% throughout. I then jabbed these areas where the mortar meets floorboard & varies between 18% & 19% so looks like it's just staining from when the mortar was drying out.



^^ What i'm pointing at here is the tiled area in that little gap. Shows you the boards don't stretch a million miles in to the mortar.



Looks like the rear flag is bedded on something different to the front 2 flags.
If not a different bedding then at least it's a different colour.

Silver-Surfer_2

Chop it out and rebed it then. Nice little bank holiday weekend job.:beer: