Hire a tradesperson!

Our tradespeople are ready to help. Post a job for free, read reviews and hire today.

Need some tips or advice?

Stonemasonry

Do I need to apply SBR to underside of INDIAN SANDSTONE patio slabs?

Anonymous user 23 February 2024 - 3.31 PM

I plan to put down 100mm type 1 MOT and whacker plate it with a 1:80 fall sloping away from the house, followed by 50mm mortar which will be 4:1 sharp sand to cement, as long as this is all correct, please can someone advice if I actually need to apply SBR to the underside of the INDIAN SANDSTONE slabs prior to laying them on the mortar bed? I've tried looking online but get various answers which also depend of the type of stone used, and some saying it'll be ok if you just wet the underside of the slab with water first which will stop the slab absorbing all the moister out of the mortar . A definitive answer would be much appreciated.

Are you a tradesperson and able to answer this question?

Log in

6 Answers

S.h.y property maintenance

No reviews yet

Cramlington
I think it's just to stop the initial suction so it wont dry to quickly, if you apply sbr you could do all the stones then lay them. If you use water then you will have to damp every stone down as your going to make sure they all stay damp as there being layed. If you use a feb in your sand and cement mix also it will keep it more plyable for longer
Answered5 May 2020
9
Chris Rajek stonemason
Rating: 4 out of 5454 reviews
Kirkcaldy
In my opinion the answer is yes !it only takes seconds to do each slab give's better adhesion /blood bridge from slab to mortar ,can also stop any mortar staining seeping through to top face of slab . Thanks Chris
Answered3 May 2020
7
Buildtech
Rating: 5 out of 5551 review
Felixstowe
In my personal opinion as long as you have a good solid level bed of mortar and is of a damp consistency but not to wet i brush the back with water on all the Indian sandstone being bedded, you can lay straight down, never had a problem..
Answered21 December 2020
5
A & D Stonemasonry
Rating: 5 out of 55539 reviews
Bristol
With Indian sand stone and any natural Portland, forest of dean etc, I always brush a cement slurry to the bed of the slab either white or grey cement depending the stone used. Make sure the bed is full not a dot and dap.
Answered5 May 2020
4

Anonymous user

Firstly sandstone, whether Indian sandstone or not sandstone will vary in its porosity, and ideally a sandstone with low porosity, is preferred for external paving, I would personally apply a bonding coat of PVA and cement to guarantee a bond between bedding material and stone especially on thinner materials, as they are prone to popping free, and of course a full bed, no mortar dabs.
Answered6 May 2020
3
KB Building
Rating: 5 out of 5552 reviews
Stroud
Depends on the current climate. As it's currently hot we normally give thinner slabs, like indian sandstone, a quick brush with a pva and water mix. Helps with suction as previously mentioned by another comment. On thicker slabs we have scored the underneath as well as pva'd them before for extra grip. Works, no complaints.
Answered5 May 2020
1