Is Palace PVA suitable for adding to mortar for external re-pointing?

TuppenceHapenny · 16 May 2018 at 9:23PM

I bought some cheap Palace PVA 'Multi-Purpose Adhesive and Sealer'. If it's suitable, I would like to add it to mortar to be used for re-pointing a roof verge (which is obviously exposed to the elements). Instructions on the bottle of PVA seem to imply it is suitable for external use but are not entirely clear (at least, not to me):

"Ideal for DIY Hobbies and Crafts"
"USES: ... Priming cement etc; for painting, dilute 5 parts with 1 part water. ... Palace PVA can also be used as a bonding aid and admix."

I tried testing the PVA by applying some to a surface, leaving it to dry (so it turned clear), then wetting it and it returned to being white and slightly tacky. Does this show it is not suitable for external use?

(Many sources on the Internet say PVA can be added to mortar, but at least one I've seen says PVA is not waterproof, not suitable for external use and instead EVA should be used, not PVA)

AndyMc..... · 16 May 2018 at 9:43PM

Is it waterprooof? It should say on the container.

Furts · 17 May 2018 at 7:58AM

Screwfix sell waterproof pva, and this is twice the price of ordinary pva. This makes me suspicious of your pva - though I am aware of the brand.

As stated above, look closely at the label but an obvious point arises. Just because your product can be added to mortar, or concrete, or screed, does not mean it can be used in all situations. Many walls and slabs remain permanently dry - think of all your internal walls and the inner leaf of cavity walls. Your pva is clearly suitable here - it says so on the container. Is it suitable for use outside? Your shout, but I would not risk it.

TuppenceHapenny · 17 May 2018 at 11:04AM

Thanks for the replies. No, the container doesn't mention waterproofness at all, so I'll assume the PVA isn't suitable and get something different.

garrysibbald · 22 May 2018 at 7:02PM

Instead of using a PVA glue, I'd suggest that you used SBR.
See this website for a comparison: https://www.sikaproducts.com/shop/admixtures-and-building-chemicals/pva-and-sbr/

TuppenceHapenny · 7 June 2018 at 7:20PM

If I do use PVA (rather than SBR), can anybody advise how much PVA should be mixed with the water to be used for making the mortar? I can't find a clear answer. Also, can anybody suggest how much PVA I'm likely to need (should I buy a 1L, 2.5L or 5L bottle) - it's for repointing both roof verges on an average-sized bungalow?

Do others agree SBR would be more suitable than waterproof PVA? If there's not much difference I would be inclined to get whatever is cheaper.

eamon · 7 June 2018 at 8:27PM

I know the thread is getting old and the job has probably been done. But for future readers Palace Chemicals are probably the last remaining UK building product maufacturer left. The rest have been gobbled up by multinationals. They have a web site for info and tend to be bought direct by large individual customers and distributed to independent merchants .

TuppenceHapenny · 7 June 2018 at 8:45PM

eamon wrote: »

I know the thread is getting old and the job has probably been done.

Job hasn't been done yet so further advice would still be welcome.

ceredigion · 7 June 2018 at 9:09PM

General rule of thumb. PVA, internal as a primer prior to the application of plaster. SBR, external with cement based mortars.
I would prime the area first with SBR but use an integral water proofer as an additive for the mortar. Obviously cant see your job so cant be certain of your requirements but there is a product called renderaid. which is a polymer based gritty stabilizing solution. Very much like blue grit but for outside work that you might find useful.

garrysibbald · 11 June 2018 at 4:18PM

It seems from your post like you just want to go ahead with PVA because it's cheaper?
It's always better to ask the manufacturer than take second guesses from the internet (see the link in my earlier post) but as a pointing company we have never used pva instead of sbr because sbr is recognised as more suitable.
As ceredigion has stated pva for inside and sbr for outside is advisable.
Remember, it's never cheaper if you have to do the job twice ;-)

TuppenceHapenny · 12 June 2018 at 8:13PM

garrysibbald wrote: »

It seems from your post like you just want to go ahead with PVA because it's cheaper?
It's always better to ask the manufacturer than take second guesses from the internet (see the link in my earlier post) but as a pointing company we have never used pva instead of sbr because sbr is recognised as more suitable.
As ceredigion has stated pva for inside and sbr for outside is advisable.
Remember, it's never cheaper if you have to do the job twice ;-)

Didn't mean to suggest I would go with PVA jut because it is cheaper if, in fact, it is not particularly suitable. Would only have used waterproof PVA if I had good reason to believe it was suitable and was noticeably cheaper than alternatives. If others more knowledgeable than me (such as yourself) recommend SBR (or something else) in preference to waterproof PVA then I'm more than willing to accept that advice. Thanks for your replies.

Is Palace PVA suitable for adding to mortar for external re-pointing?

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