wallpapering on fresh plaster

[Fred]

Hi,

I have plastered a room as best as I could ;)

I hope to hang wallpaper but I am not sure whether I need to apply something to the plaster first. I understand if painting the plaster you should use a mist coat of either water or 50:50 water/emulsion but I am unsure what the rules are when papering?

Can I just size it with watered-down wallpaper paste or should I use

50:50 water/emulsion as for painting?

In the past I have used 2.5L tubs of plaster primer but I noticed at B&Q these are now quite expensive. (£10ish for 2.5L IIRC)

I have heard people say that B&Q value emulsion is very watery and no use for painting with! I don't know how true that is, but I thought it might do as a cheaper alternative for priming. I think the price is about the same except you get 5L for your money rather than 2.5L. I suppose that if you are diluting the paint, you actually get 10L for the price of 2.5L of primer.

What does the group recommend?

TIA

[Martin Bonner]

I am not a wallpapering expert (I leave that to SWMBO), but I would tend to= either not worry about it, or just splash a bucket of water on with a big = brush first (depending on how hard the dry plaster "sucks"). I certainly w= ouldn't bother with sizing; if I had some old emulsion, I might well mix it= up with some water and splash it on first.

[Andrew Gabriel]

Depends on the paper, but you probably want to paint it, or you may end up being able to see the patterns on the plaster through the paper afterwards. Something similar happened to a friend who spent weeks stripping back and preparing the room first, and then basically had to strip off all the new paper again.

[stuart noble]

Alas viscosity isn't a good guide to solids content. I've used the Screwfix brand diluted with 4 parts water for sealing new plaster, and the paper slid about beautifully.

[Phil L]

Don't use emulsion. It needs sizing, either use normal paste (solvite etc) mixed as per instructions on pack for sizing. Or if you have any old pva knocking about, you can use a weak solution to do the same job - it basically puts a film on the plaster so as to improve slide and final adhesion, emulsion won't do either very well. If you don't size it, as soon as the pasted wallpaper touches the wall it's dry, meaning you can't slide it, nor re-position it without creating bubbles and creases

[Him & Her]

2.5L. I : > suppose that if you are diluting the paint, you actually get 10L for : > the price of 2.5L of primer. : > What does the group recommend? : Don't use emulsion. : It needs sizing, either use normal paste (solvite etc) mixed as per : instructions on pack for sizing. : Or if you have any old pva knocking about, you can use a weak solution to do : the same job - it basically puts a film on the plaster so as to improve : slide and final adhesion, emulsion won't do either very well. : If you don't size it, as soon as the pasted wallpaper touches the wall it's : dry, meaning you can't slide it, nor re-position it without creating bubbles : and creases

+1. Always size new plaster. Not worth the risk of spoiled paper for the sake of a couple of quids worth of paste.

Regards,

[Rick]

Here is something I wrote earlier ... "New plaster is highly absorbent. Non-thinned emulsion cannot be brushed out neatly as it sets straight into the plaster leaving streaks which would show. You would also use a lot of paint. The first coat, thinned with water, has enough liquidity to brush/roll on and seals the surface so further (normal, unthinned) coats may be applied. Good practise is to use 5:1 water:pva adhesive to seal the surface first. "

I now you want to wallpaper so once dry you should seal it with PVA.

[Fred]

Thanks for all the replies.

SWMBO has chosen blown-vinyl that will be overpainted, so hopefully this will prevent anything showing through.

I have some spare bags of wallpaper paste, so since this is to hand, it makes sense to use this rather than anything else.

Does the size soak into the plaster so that it only needs to be applied once, or would I have to reapply it every time I strip the wallpaper? I'm thinking that particularly with steam strippers, a lot of paste gets scraped off.

TIA

[Phil L]

It's good practice to apply new size each time you re-decorate. I always allow the wall to fully dry after stripping, then give it all a light sanding by hand - this removes 'snots' of old paste and smooths everything out, then re-size than paper as normal

[Fred]

Thanks, I'll give that a go.