TheMitchells Posted March 19, 2017 Share Posted March 19, 2017 While renovating our house, I am finding I am using quite a lot of PVA glue, watered down on brickwork before filling holes with plaster. now I plan to try my hand at plastering one of the rough walls, before we get a chap in to make all the walls look nice. Seems an ideal place to have a go as its going to end up in a cupboard. However, I dont know whether I need to pva the wall again and if I do, it is still watered down stuff? or Neat? I thought it would be quite handy for a post on PVA rules. I am sure its something most builder people know but us newbies do not. so has anyone got rules that I would find useful - when do you use pva? what other things can it be used for and how should I use it? Ideas please. 1 Link to comment Share on other sites More sharing options...
Onoff Posted March 19, 2017 Share Posted March 19, 2017 With my first house I was buying waterproof PVA (the "black" as opposed to "red" container) by the gallon from Wickes and putting it in EVERYTHING, from mortar, to render to concrete and even plaster. If in doubt.....5:1 was the moto! I still own the place and everything's still standing and that was 25 years ago. As to the rules??? Link to comment Share on other sites More sharing options...
Oz07 Posted March 19, 2017 Share Posted March 19, 2017 Patching plaster it's lean and weak to seal dust. Then slightly stronger and tacky before filling with plaster Link to comment Share on other sites More sharing options...
TheMitchells Posted March 19, 2017 Author Share Posted March 19, 2017 I have a wall where i have removed the loose plaster. so now I have areas about an inch less than the rest. Should I build up layers, painting with weak pva beforehand? Or should I stick pieces of plasterboard into the large areas and then patch it to the rest? Link to comment Share on other sites More sharing options...
TheMitchells Posted March 19, 2017 Author Share Posted March 19, 2017 Fill in with plaster layers or plasterboard then patch? Above was half way stage. Below was after all loose plaster removed. Link to comment Share on other sites More sharing options...
Nickfromwales Posted March 19, 2017 Share Posted March 19, 2017 PVA is used for many things build related. In the instance of plastering over it, regardless of it being cement render or gypsum plaster, the PVA must be tacky. Not wet, and most definitely not dry as that is like trying to get something to stick to plastic. If you wish to plaster then typically you need to ascertain the background ( type of surface upon which you wish to apply it ) and work out if it's high or low suction. For eg, painted walls it would be low suction ( near zero porosity) but for old black mortar it would be high suction. The difference is which will 'suck' the moisture out of the plaster faster or slower. 1 Link to comment Share on other sites More sharing options...
TheMitchells Posted March 19, 2017 Author Share Posted March 19, 2017 okay - work out if low or high suction, then what?? sorry for being dim. if high suction, like my brick walls, tacky pva - if low suction, dont bother?? Link to comment Share on other sites More sharing options...
TheMitchells Posted March 19, 2017 Author Share Posted March 19, 2017 And I have been watching youtube clips to see what people do. Watched one where they just sprayed the area with water before filling holes with plaster. they took 4 coats to get it finished. it was american though - they may have different plaster? no pva used there. Link to comment Share on other sites More sharing options...
Steptoe Posted March 19, 2017 Share Posted March 19, 2017 If it's more than maybe 3/16th" then I'd suggest probably bonding it first, skim doesn't really like anything more than 3-5mm depth to get a nice finish. Brick/mortar, then yes, a 5:1 PVA first, give it a good scrub with a wire brush first if in doubt, then a good brush out to get rid of any loose dust/debris, Link to comment Share on other sites More sharing options...
jfb Posted March 20, 2017 Share Posted March 20, 2017 yes to bonding with tacky pva then finish with skim (no need for pva when skimming onto bonding) Link to comment Share on other sites More sharing options...
Nickfromwales Posted March 20, 2017 Share Posted March 20, 2017 Firstly you need to make the affected areas more or less flush with the surrounding existing plaster / other, and then you need to prep the whole wall for skimming ( plastering ). Don't for a minute think that you'll get away with just patching in and painting as that's not going to be a practical option IMO . 9 hours ago, TheMitchells said: if high suction, like my brick walls, tacky pva - if low suction, dont bother?? Over the bricks I'd first apply a PVA solution, 60% water 40% PVA, and saturate it, paying particular attention to the open edges of the existing mortar which will be loose and dry as a bone. After a couple of applications go over the bricks with neat PVA and then start building the gap up with bonding coat. You'll prob need to do that over two applications as its quite deep. Get that flush with the surrounding plaster and allow to dry. Prior to plastering the whole wall, I'd neat PVA the lot and allow to go tacky before skimming. If you PVA bits of the wall the skim will start drying out at different times and make skimming a pita. Link to comment Share on other sites More sharing options...
TheMitchells Posted March 20, 2017 Author Share Posted March 20, 2017 All sounds like good advice. will do it in layers over neat pva - think I'll need to go and get some more pva!. I have Thistle hardwall plaster - is that the same as bonding? So forget sticking plasterboard into the cleared area - just build up the layers with the bonding plaster?? Link to comment Share on other sites More sharing options...
Onoff Posted March 20, 2017 Share Posted March 20, 2017 3 hours ago, TheMitchells said: All sounds like good advice. will do it in layers over neat pva - think I'll need to go and get some more pva!. I have Thistle hardwall plaster - is that the same as bonding? So forget sticking plasterboard into the cleared area - just build up the layers with the bonding plaster?? Loads of info here: https://www.google.co.uk/url?sa=t&source=web&rct=j&url=http://www.british-gypsum.com/~/media/Files/British-Gypsum/Brochures-and-Leaflets/Product-information/Thistle-Plaster-Selector-Guide.pdf&ved=0ahUKEwid6s-fyOXSAhWBNJoKHSGOAmcQFgguMAE&usg=AFQjCNHfn6-ODbRgINp7O2aYtdLIaRpKkA 1 Link to comment Share on other sites More sharing options...
Steptoe Posted March 20, 2017 Share Posted March 20, 2017 7 hours ago, TheMitchells said: All sounds like good advice. will do it in layers over neat pva - think I'll need to go and get some more pva!. I have Thistle hardwall plaster - is that the same as bonding? So forget sticking plasterboard into the cleared area - just build up the layers with the bonding plaster?? No, hardwall is simply hardwall, a finishing plaster, bonding is a lot different, http://www.diy.com/departments/thistle-bonding-coat-undercoat-plaster-25kg/35814_BQ.prd Link to comment Share on other sites More sharing options...
Steptoe Posted March 20, 2017 Share Posted March 20, 2017 Browning may actually be better if you are unsure about the suction, it holds its water better than bonding, but, can be a bit harder to work with. Link to comment Share on other sites More sharing options...
Nickfromwales Posted March 20, 2017 Share Posted March 20, 2017 48 minutes ago, Steptoe said: Browning may actually be better if you are unsure about the suction, it holds its water better than bonding, but, can be a bit harder to work with. Browning is pretty good for bulking out actually, so I'd second that. Get the second coat on when the first goes hard, but not when the first is dry otherwise you'll have to PVA between coats. Link to comment Share on other sites More sharing options...
TheMitchells Posted March 21, 2017 Author Share Posted March 21, 2017 Okay - I'll get some Browning and use that to build up the layers. And on the leaflet that OnOff suggests, they say use GypPrime and Bond-It for high suction areas - but I can use PVA as an altenative? Thanks for all the advice. I'll take photo's of my attempts. Link to comment Share on other sites More sharing options...
PeterW Posted March 21, 2017 Share Posted March 21, 2017 GypPrime = PVA + Brand Markup.. Link to comment Share on other sites More sharing options...
Nickfromwales Posted March 21, 2017 Share Posted March 21, 2017 Pva for everything . Just different dilutions, through to neat, to suit each situation. If you want to go mental you can use "blue grit" and that'll stick anything with everything. Link Link to comment Share on other sites More sharing options...
TheMitchells Posted March 21, 2017 Author Share Posted March 21, 2017 Not heard of that before. So what else can I use PVA for? Keep the answers legal please!!....... Link to comment Share on other sites More sharing options...
CC45 Posted March 21, 2017 Share Posted March 21, 2017 Used blue grit in the past - to skim onto a painted wall. Rough as hell when dry. Plasterers loved it. Link to comment Share on other sites More sharing options...
Nickfromwales Posted March 21, 2017 Share Posted March 21, 2017 1 hour ago, TheMitchells said: Not heard of that before. So what else can I use PVA for? Keep the answers legal please!!....... Everything plaster / render / brick / stone I meant . A lot of people will do all the heavy work and clean up and then mop all the floors / floorboards with a weak pva solution to 'size' all the surfaces and lock the dust down. Link to comment Share on other sites More sharing options...
Onoff Posted March 22, 2017 Share Posted March 22, 2017 Shouldn't we touch on the waterproof "exterior" and the more general (and cheaper) everyday versions of PVA? Big difference in price. I know back when I temporarily dust proofed my concrete floor in the bathroom I used dilute SBR bonding agent on advice here rather than PVA. This on the basis that when tiling later there's a risk of water getting under the tiles and affecting normal PVA. It was cheaper using SBR than buying exterior PVA. I do know some on here have dust proofed say their new garage floors with dilute PVA. I've certainly glued T&G chipboard flooring together with it. I'll often use it when doing noggins before I screw them in. Doing it throughout boxing in in my bathroom. I've used it btw when the kids have run out of "craft glue" and topped the bottle up. Made many a paper mache'd balloon head when they were younger! 1 Link to comment Share on other sites More sharing options...
Thedreamer Posted October 10, 2019 Share Posted October 10, 2019 Old thread. I have some concrete sills with mortar joints that I want to water proof. Could I brush PVA over the top would this seal them? I plan in long term to paint the cills would the PVA cause a problem here with painting? Any advice much appreciated. Link to comment Share on other sites More sharing options...
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