Hearth splitting badly after one year. Is this acceptable.?

[mikefanta]

I had my hi spec wood burner, and slate hearth installed 13 months a go, by the same company. The slate hearth split badly down the middle after 12 months. The company that installed it have spoken to their 'slate suppliers' who have said, basically 'tough luck'. I appreciate slate is a natural product, but is it reasonable to expect a slate hearth 20mm thick to last more than one year without splitting.? The hearth has been fitted properly, with an expansion gap around the edges.

The installers have offered me a discount on a new hearth, but to spend another £165 on another piece of slate supplied by the same company, with no guarantee that it won't split in two, three, or twelve months time seems a waste of money.

Any advice would be greatfully appreciated. Also any advice on any way to mask the split. The crack is such that I can't put a coal bucket etc over it. The split is from the middle of the rear of the hearth to about half way and then accross, ie about 1/4 roughly.

 

[Adios Pantalones]

I would bet they didn't do a good job leveling and supporting it underneath- that's what often causes cracks. Think about it- if the slate was firmly and evenly supported, it would handle that sort of stress really well.

 

[begreen]

I have to agree. It doesn't sound like the fault of the slate. The stone should have been nicely bedded in mortar or thinset and allowed to properly dry up. Sounds like some corners were cut here unless something heavy dropped on the slate.

Is the stone still cemented in back or can it lift out? How large is the gap? Maybe post a picture of the problem?

 

[Dakotas Dad]

If this is a single piece of slate, with heavy stove on top of it, 20mm or.8 inch is not very thick, I would want it about twice that thick, considering how fragile slate is..

A picture would be nice, to see how, and in what manner it split.. probably a poor bedding, but.. it is slate..

 

[Thistle]

Definitely a sub-standard installation.Slate even just 20mm or approx. 3/4" thick is plenty tough enough to withstand any foot traffic with a proper mortar bed underneath.Its not like you're parking a car or driving over it.

 

[fishingpol]

Put a level across the crack. See if the crack is at the high point and if it slopes down either side of it. If there is a basement below, was this hearth built over a support beam for the house? A few factors can affect this, but I would think a bad install. I just re-did my hearth last fall. I pulled all of the old framing out. Put in new framing with joist hangers and toenailed the framing into the headers. Construction adhesive on the framing, put 3/4" plywood down and good screws . I put a few inches of concrete over plastic sheeting. After the concrete set up in a few days, thinset and slate. Grouted a day or two later. Rock solid. No movement.

Any minor deflection in the floor and she will crack somewhere. Where's the beef?(In the framing that is.)

 

[CarbonNeutral]

I have natural slate - no problems. +1 to the poor substrate

 

[firefighterjake]

I agree with Adios P . . . my hearth consists of slate tile that are only 1/4 inch thick . . . no cracking whatsoever . . . of course I have the slate on two layers of 3/4 inch plywood and a 1/2 inch of concrete backer board . . . I have very little to no flex and made sure the slate was well supported underneath.