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Posted: Fri Apr 05, 2013 1:29 pm
by MartinL
I will be laying a new 2 piece 45mm deep slate hearth onto an old brickwork hearth base having lifted up the slabs that were installed previously. An 8kw wood/coal burning stove will be installed on top of the hearth so it will be exposed to quite a bit of heat especially underneath the stove itself.

The room itself is ground floor with wooden floorboards fitted flush to the existing brickwork hearth base. Airbricks ventilate the underfloor space. Fitted carpets will be fitted up to the hearth which will cover the bedding mortar base.

(1) What mix should I use for the mortar/bedding base. Should it include Lime/Sharp Sand/Building Sand?
(2) Is it necessary to provided some kind of key on the underside of the slate so that it sticks better to the bedding mix? e.g. maybe coat it with a PVA mix with a bit if sand mixed in?
(3) I was thinking of having quite a small gap (maybe 2mm) between the rear and front slate slabs so I was thinking of a dark grout. Any recommendations for grouting bearing in mind that it will be pretty hot down there?

Posted: Fri Apr 05, 2013 7:16 pm
by lutonlagerlout
the guys installing the stove who must be "hetas" registered can advice you on the grout
I would use 3:1 grit sand:cement for bedding the slate
you can use a bond bridge painted on the back of the slate to aid adhesion
this is a slurry or 1:1 sbr:cement
just paint it on the back of the slate before you lay it
cheers LLL

Posted: Sat Apr 06, 2013 1:37 pm
by MartinL
Cheers LLL for the advice on. I dont know what "sbr" is yet (for the bonding mix) but I'm sure I'll find out if I look around on this site. I have used this site several years ago when Tony started it up as I was doing a massive DIY project and this site is top notch.

The guy installing my stove is hetas registered but he charges a fortune per day so I thought I would do the more basic work of bedding the slate hearth myself. He is rendering the back of the chimney brickwork in heat resistant render then installing the stove and he says he wants the slate installed at least 4 days before his work begins.

Posted: Sat Apr 06, 2013 1:45 pm
by MartinL
I have googled SBR bonding and found a good link explaining all

http://www.permagard.co.uk/media....eet.pdf

Posted: Sat Apr 06, 2013 3:23 pm
by Carberry
MartinL wrote:I have googled SBR bonding and found a good link explaining all

http://www.permagard.co.uk/media....eet.pdf


Bond bridge

Posted: Sat Apr 06, 2013 10:30 pm
by MartinL
Carberry, thanks for the link to the bond bridge section.