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Posted: Tue Aug 16, 2011 1:24 pm
by bokbevok
Hi
A builder friend is helping me build a patio. We have layed a concrete base and he has said that we can lay the Indian Sandstone slabs on top of that using Tile Adhesive. Does this sound like an ok thing to do, as I haven't seen it mentioned anywhere on any web-sites?
Thanks.
Posted: Tue Aug 16, 2011 2:20 pm
by GB_Groundworks
Think you answered your own question there, are they sawn six side calabriated? But it's still a no. See the main site for how to do it properly
Posted: Tue Aug 16, 2011 2:51 pm
by DNgroundworks
Why have you installed a concrete base?
Posted: Tue Aug 16, 2011 2:58 pm
by local patios and driveway
odd not to bed the stone in to the base.. is your mate a labourer or something?
Posted: Tue Aug 16, 2011 3:13 pm
by Bilabonic
No nails is much better :laugh:
Posted: Tue Aug 16, 2011 4:58 pm
by lutonlagerlout
even with calibrated stone there is too much difference for tile adhesive
if it was 6 sided sawn calibrated to +/- 1mm you might be ok
but i doubt it
should have laid the flags onto the plastic concrete
LLL
Posted: Tue Aug 16, 2011 5:43 pm
by msh paving
Last spring i laid a calibrated stonemarket slate slab ,in the same way 70mm concrete base laid to falls ,stuck slabs on with tile adesive, 4 size slabs no probs , pointed up with GfTK 800
MSH 
Posted: Tue Aug 16, 2011 8:39 pm
by lutonlagerlout
any progress reports after 16 months mark?
cheers LLL
Posted: Tue Aug 16, 2011 9:49 pm
by London Stone Paving
I've got a real aversion to natural stone being laid on concrete bases. Its usually done by builders and it always ends in a cock up (no offence to builders in general). You wont get sawn stone +/- 1mm. The standard spec is +/- 2mm but even then there will still be be 3 or 4 slabs outside that tolerance.
The amount of times a customer has bought stone and then had to return it because the builder/tiler has installed a concrete base and not considered the thickness tolerance of the stone
Also, in my experience patios laid on concrete bases will retain water and damp patches will pop up.
Posted: Tue Aug 16, 2011 10:09 pm
by lutonlagerlout
its just plain wrong
total waste of tile adhesive
LLL
Posted: Tue Aug 16, 2011 10:28 pm
by London Stone Paving
lutonlagerlout wrote:its just plain wrong
Done by people who dont understand what they are doing, but with the best of intentions.
Posted: Tue Aug 16, 2011 10:58 pm
by local patios and driveway
ok boys so we are done slating off the guy and his mate, whats the solution now? im thinking dry bed with a slurry but im not sure how thin they could go for the bed?
Posted: Tue Aug 16, 2011 11:06 pm
by London Stone Paving
Surely any bed needs to be at least 40mm thick. Cant see it lasting otherwise.
1. would be good to know the exact spec of the paving material7
2. Also does the paving join up to the house? If so what is the finished height thats been allowed for. I.e how many bricks below damp course. Might ne able to nick a bit of height there
3. Also sounds a bit bodgy put could you not leave a gap of 100mm arround the house to keep the damp course free. Then lay the paving on a proper bed
Thats why I hate the things so much because your just forced to start compromsing on the construction methods
Posted: Thu Aug 25, 2011 2:54 pm
by bokbevok
The slabs are hand cut calibrated (22mm thick). The patio is at the end of the garden and so not connected to the house. Don't know if it matters but the concrete base is raised about 1 brick above the ground as we don't want the patio to be level with the ground.
Cheers.
Posted: Thu Aug 25, 2011 7:31 pm
by lutonlagerlout
if the concrete is good and true,and is clean and dry ,
you should prime it with sbr then knock up a wettish bricklaying mortar mix 3:1 with 100ml of sbr in the mix
lay the flags on this bed from 10-20 mm
cheers LLL