As everyone here knows, diluted-down PVA is the best thing since sliced bread for sealing crappy surfaces prior to repair, right?!
What I'm unclear about is after you've applied the stuff, do you let it dry thoroughly before proceeding with the repair, or crack on quickly before it dries? I'm sure the answer is different depending on the circumstances, but which?
(As it happens, my next project is levelling a yucky, dust-shedding concrete floor with self-levelling compound - for this application the PVA should be still wet I think?)
I was on a series of shop refurbs recently and the flooring specialists/carpet fitters were using latex under the self levelling not pva. (Don't ask me why it is required, just follow the instructions.)
I'm going to do the room in my flat with it, directly over vinyl tiles. I dare say I could use PVA, I certainly wouldn't consider not using something on a dusty concrete substrate. Why ask for problems when a few quid should sort it?
Even if you are correct and it isn't necessary, he won't be out of pocket by much. And if you have set him wrong how much are you going to pay him for your poor advice?
Your opinion; I and I think a large number of uk.d-i-y regulars would disagree with you on that (I don't know where they're all hiding now!)
Sorry, but total nonsense. First time I ever used self-levelling compound I came a right cropper; it all cracked and eventually lifted off the original substrate and I had to redo it. In fact I asked here what the problem was, and was advised to pre-treat the dusty, friable concrete surface with PVA. Did that, and next time it worked a treat, and I always use this method now.
Last time I used SLC I'm almost certain that the mfr's instructions recommended sealing first (I don't have a bag on me right now so can't confirm that one).
We had somebody in a thread only a couple of days ago having problems painting a PVA'ed wall. The stuff has its uses but is not a universal panecea. It should also NOT be used on walls or floors using lime mortars under any circumstances as it affects the damp transfer characteristics. This isn't my opinion, it's that of English Heritage and most conservation officers.
I laid a bag only yesterday (Wickes). No mention of PVA anywhere - just clean the surface and lightly dampen. Just because you failed to do it correctly does not make my advice not to use PVA nonsense.
I'm aware of that, my original comment was intended to be slightly tongue in cheek. I was a contributor to the thread on PVA-ing prior to painting, pointing out tat it was a Bas Idea.
Well, I bought my bag today - also Wickes as it happens. I'll do no more than reproduce the relevant text from the back of the bag below, as obviously you missed the salient points when you read it:
"Dense Concrete: Prime with Wickes Building Adhesive mixed with water in the ratio of
1:1. Allow to dry before laying levelling compound.
Porous Concrete: Just before application of the levelling compound, lightly dampen the concrete surface with clean water but avoid leaving pools of free water.
Very Porous Base Concret and Lightweight Screeds: Prime the surface with Wickes Building Adhesive dliluted with 3 parts of water to 1 part building adhesive and allow to dry."
I will certainly use PVA solution first before laying the compound, and will be sure that the floor will be OK.
Meanwhile I'd still like to hear a response to my original question! which was under what circumstances you should allow the PVA to dry first, and when you should press on with plaster/mortar whatever while it's still damp.
I levelled a few square metres just before Christmas, used a bag of B&Q's "value". It recommended 1+4 PVA first. Never done this before and surprised how easy it was.
Obviously they have changed the bag design or havc two suppliers or something. Have just checked on the other two I have and there is no mention of this. What counts as "dense concrete" ? I still would have thought most examples were in the second case and so no PVA is required.
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