diy related: Laying granite on concrete - Page 3 - TilersForums.co.uk | Tile Forums

**grumpygrouter** · 23-09-2008

Zygo, DO NOT USE PVA as a sealant. It has no place in tiling. If you need to seal your concrete and you can't get SBR of any sort - trade tiler do it - than you should obtain an acrylic primer of some sort. If you use Mapei adhesive they have their own preferred primer, check it out. If you use PVA you expensive tiles will be secured to nothing more than a thin layer of PVA, NOT your concrete floor. If moisture penetrates through to the pva layer for some reason, your tiles will come up!!

zygo · 23-09-2008

Thanks for the warning grumpygrouter. This could be the best bit of advice I have had. The concrete subfloor is about 80mm thick and lies on top of 80mm of Celcon, which has a dp membrane below it placed on top of the original garage concrete base. I don't know if that original base was laid on a dpc but it never showed signs of any dampness in 25 years. However, I will heed your advice because the extra protection I have since read about is well worth the few quid it wall cost to buy SBR. Would five litres be enough for 8/9 square metres?

z

**grumpygrouter** · 24-09-2008

Hi Zygo, glad to hear you have taken on board the advice re SBR. 5ltr will be plenty. It needs to be diluted 4parts water to 1 part SBR (this is BAL Bond SBR) and then brushed or rollered on. Allow to dry and then tile. you must commence tiling within 24 hrs.

You can get BAL stuff in 1 ltr packs wich will be plenty for your job I should think. if you have difficutly obtaining it where you are, Trade Tiler (our sponsors) sell 5 ltrs of an equivalent and can be delivered to you.

zygo · 24-09-2008

Sh**! That was close.

I was gonna apply the SBR to the subfloor BEFORE spreading the self-levelling screed. Should I be doing it the other way round then?

z

**grumpygrouter** · 24-09-2008

No you were right the first time Zygo. Concrete or screed generally doesn't need priming (unless your adhesive manufacturer says so) but it can be a good idea to do so as it helps to "lock in" any residual dust. Have you ever swept a concrete floor? There always seems to be more sweeping required.........

Seal the floor with SBR and then level it. No need to prime the leveller (usually) you can tile straight on top of it.

zygo · 24-09-2008

Phew!
Just one more point on this topic, Grumps. You mentioned that I should lay tiles on the sealed subfloor "within 24 hrs". Does this mean that I should apply the SL screed within 24 hours of painting the subfloor with the SBR?

Thanks for the advice on needing only 1 litre of SBR for 8sm of floor area diluted 4:1.

Z

**grumpygrouter** · 24-09-2008

Quote:

Originally Posted by zygo

Phew!
Just one more point on this topic, Grumps. You mentioned that I should lay tiles on the sealed subfloor "within 24 hrs". Does this mean that I should apply the SL screed within 24 hours of painting the subfloor with the SBR?

Thanks for the advice on needing only 1 litre of SBR for 8sm of floor area diluted 4:1.

Z

Correct.