P.v.a. Versus Primers...... - Page 5 - TilersForums.co.uk | Tile Forums

**whitebeam** · 18-07-2008

I've done site work for a contractor and never saw a bottle of primer although everything was dry lined, On a another job the walls was bucket gear (some tub gear state that no primer required) and that was on new plaster in a new private housing, Again no primer supplied. If your using cement addy on walls then it must be primed. I've used a mist coat of emulsion, artex sealer and sbr before and had no problems. The trouble with new plaster it's so absorbent and sucks the moisture from the adhesive giving it no time to cure properly, Thus giving in to failures at a later date.

Viceroy · 30-07-2008

I,m totally confused with this !
I always used to pva diluted 1-4 plywood overlays (Never Had A Floor Fail)
then i was working with another tiler who used bal bond !
I Thought it was much better,so i started using that .
Talking to another tiler about it ,he told me the bal instructions on back of floor adhesive state you should only seal the sides and back face of ply ?
I now can't bring myself to tile directly onto a newly plyed floor without priming it !!!!!! so what do you fellas do on a newly plyed floor bond or no bond ?

Cheers

Viceroy

**Dave** · 30-07-2008

BAL say you don't need to using there cement adhesives.......but other manufactures will say to prime...so always check on the bag.......

Viceroy · 30-07-2008

Think youre right there !
Because Flexible profix (Dunlop) Say to use suitable primer !
Next job is with PCI
Tilefast 6 Rapidflex

The surface should be prepared to provide a rigid and secure base without deflection and suitable to support the
intended weight. Tongue and Groove/Chipboard must be over-boarded with exterior grade plywood which is at least
15mm thick and given time to find equilibrium with its surroundings. Plywood floors must be 18mm thick and all joints
must be supported. All must be screwed down every 300mm centers. The reverse face and edges of the boards must
be primed with Primer W to prevent the ingress of ambient moisture while the exposed face should be unprimed and
clean. Any existing wooden floor may also be over boarded with PCI Pecidur: minimum 10mm thick or PCI Polysilent:

4mm or 7mm thick

Still not convinced about no primer !!!

Viceroy

**Dave** · 30-07-2008

That also sez no primer...trust me i use BAL day in day out and it is fine......

Like i said if it sez prime then prime it if not then don't.......

..

Viceroy · 30-07-2008

Cheers Dave !

**sWe** · 30-07-2008

Many/most modern cement based adhesives are "primer free" to some extent. That means they don't require normally encountered surfaces, such as plasterboard or concrete, to be primed, BUT, there are almost always exceptions. The obvious ones are gypsum/anhydrite surfaces, (partly for the reaction risk, partly because they're very absorbant) and other surfaces which may react in some way when in contact with cement based materials.

Very absorbant or very non-absorbant surfaces may need to be primed.

Very absorbant surfaces can include certain light weight concretes and LECA, because otherwise they'll absorb too much moisture from the adhesive, thus preventing it from curing properly.

Very non-absorbant surfaces include already tiled surfaces, plastics, and metals, becuase the adhesive may not bond properly to them otherwise.

Always check the manufacturer instructions on wether or not an adhesive is suitable for the surface you intend to tile, and if your specific surface needs priming or not when using your chosen adhesive. It should say so on the bag. If it doesn't, don't risk it.

dptiling · 02-08-2008

the pva my tile shop sells .has pva sealer and pimer on the front.
confused dot com or what.

Gazzatile · 03-09-2008

Dave very good article hopefuly this will mean fewer jobs failing

Gazza

handyrabbit · 09-09-2008

brilliant! saves me asking the question why!!

glad i've moved house - pva'd a wall in my bathroom b4 tiling it!!

was there for 3 years after but i wonder mmmm???!!!

**David - Tradetiler** · 09-09-2008

Just in case anyone missed it, because of this thread, we now stock SBR (at a really good price too)

TradeTiler.Ltd Siliconing sealers/primers

pt44 · 13-09-2008

So, have I understood correctly - that SBR is a proper primer? not a PVA.

Also - from the small plastering knowledge and mortar knowledge that I have. I would normal pva seal a brick wall, with 1:4 pva mix. Let it dry, then redo it, with a 1:1 pva mix, and either plaster over it or render it with mortar, while the second mix is still tacky.

Can't beat PVA for plastering/rendering & patching in mortar or concrete (from my experience)

However, really interesting about why not to use it for Tiling.

Paul