Help! Didnt seal plaster before we painted

aboard_epsilon

Invention of the devil and the paste won't bond with it. Slightest bit of mositure or condensation and off comes the paper. How do you expect the paste to dry out properly if you've got vinyl silk underneath and a vinyl wallpaper on top?

Cheers

yup, you have a point there ..

and you're probably right //

but the vinyl silk is as hard has hell like i said ...and does make it easier to remove wall paper no gashing into the plaster with a scraper..thats normal wall paper ..normal wall paper and aneglipta sticks ok ...no condensation problems here ..but i supose youre right ..stay away from it if you have those problems.

all the best.markj

aboard_epsilon

cyclonebri1 wrote: »

For year now when plasterers are re skimming old finished plaster they precoat the walls in a weak pva solution. They all do this as it makes their job easier, it ensures the plaster sticks as both the pva dries and the plaster cures at the same rate.

Unfortunately pva is reactivated by water so here are 2 real issues.
Tilers know to their cost the effect of applying wet adhesive and heavy tiles over newly or old skimmed surfaces. The pva melts and you can have a very dangerous situation:eek:.

Also if the householder papers and eventually strips skimmed walls where pva has been used, and the chances are they will never know untill it happens, the use of a steam wallpaper stripper will again reactivate the pva and the skim will "blow" from the wall.:eek:

Repair time again:A

Ive seen a few plasterers not washing the walls down before applying pva

i know from my own experience some 25 years ago ..that pva does not work on top of wall paper paste laden walls..once the skim jobs finished and dried.find an edge and you can scrape the whole lot off like wall paper....that happened to me ...and i lost confidence in pva ...untill stripping wall paper a few years later discoverd the stickiness of the old wall paper paste that was still on the wall...and then things started to make sense..i then knew why the job failed .and Ive had no trouble with pva since...i make sure the walls are well and truely cleaned of all wall paper paste..

just look at the walls once the paper is off .you cant see the wall paper paste its translucent ..its like dried snot ..that becomes sticky when wet...and before it just looks like a normal painted wall.

what about this fellow here

http://www.youtube.com/watch?v=rO4orltyxfk

i think that lot will be falling off in a couple of years ..nice as it looks



plaster isn't all that resilient to water either ..plonk a piece of hardened plaster outside in the rain for a couple of days ..and it reverts to a granular form.

all the best.markj

cyclonebri1

aboard_epsilon wrote: »

Ive seen a few plasterers not washing the walls down before applying pva

i know from my own experience some 25 years ago ..that pva does not work on top of wall paper paste laden walls..once the skim jobs finished and dried.find an edge and you can scrape the whole lot off like wall paper....that happened to me ...and i lost confidence in pva ...untill stripping wall paper a few years later discoverd the stickiness of the old wall paper paste that was still on the wall...and then things started to make sense..i then knew why the job failed .and Ive had no trouble with pva since...i make sure the walls are well and truely cleaned of all wall paper paste..

just look at the walls once the paper is off .you cant see the wall paper paste its translucent ..its like dried snot ..that becomes sticky when wet...and before it just looks like a normal painted wall.

what about this fellow here

http://www.youtube.com/watch?v=rO4orltyxfk

i think that lot will be falling off in a couple of years ..nice as it looks



plaster isn't all that resilient to water either ..plonk a piece of hardened plaster outside in the rain for a couple of days ..and it reverts to a granular form.

all the best.markj

:T:T

Nice to see you understand chap, pity many don't :o

scunny89

WhiteHorse wrote: »

New plaster shouldn't need sealing at all. What you should do is put on a couple of coats of watered emulsion (this is called a 'mist coat'). This soaks right in, bonds and seals. Further normal coats will cling to this nicely.

If you put paint straight on from the tin, it's too thick and dries quickly on the surface, rather than sinking in. Thus, it forms a layer that can peel off.

Exactly as above. I normaly do a 50/50 water and cheap matt emulsion coat. Then another virtualy straight away. After that its normaly good to go.

nickj_2

i'm not sure where the pva to seal new plaster myth comes from , especially as paint manufacturers give instructions about thinned paint on the side of the tin , and if i remember correctly pva has the warning , do not use with water based paints on the side of their tins ,

misgrace

Kaz2904 wrote: »

I never knew the advice to make your masking tape unsticky by sticking it to your trousers first. Thankfully, I was having a break before I went back to do the cutting in and read this. I tried it (I used my carpet because I had no trousers on). It worked a treat and now I have a quick and easy way of making sure my edges are neat. Thanks very much for the tip.
No need to buy low tack masking tape again (especially as it doesn't work because it's too sticky ).

Am so pleased you tried it and it worked, as I always do this, sometimes before I paint the frames I put the strips on that, pull off and on a couple of times, still has enough stickyness to do the job.:D

Leif

daveyjp wrote: »

Sealing is only really necessary if you are going to wallpaper straight onto the new plaster. Using an emulsion wash or PVA as a first coat is cheaper than the more coats of the final emulsion, so this method is often used on new plaster.

Read around on forums such as https://www.UltimateHandyMan.co.uk and you will learn that PVA should not be used on new plaster. Just use white emulsion diluted 20% with water as a primer. As other have said.

Leif

cyclonebri1 wrote: »

PS,
A wallpaper steamer makes removing wrongly applied emulsion so so easy;);)

Be very careful. It can also remove large areas of plaster, as I found when using a streamer on walls to remove wall paper. It is possible that the plaster was already blown, but application of the steamer caused plaster to balloon out, even though it was not held against the wall for long. It is possible it is okay on fresh plaster, but I would be careful.

I do agree that a steamer can remove emulsion. Today I removed emulsion from a plasterboard ceiling with a steamer and a scraper. Worked a treat. Wish I'd read your post yesterday instead of discovering this for myself today when 2/3 of the way through the job.

cyclonebri1

Leif wrote: »

Be very careful. It can also remove large areas of plaster, as I found when using a streamer on walls to remove wall paper. It is possible that the plaster was already blown, but application of the steamer caused plaster to balloon out, even though it was not held against the wall for long. It is possible it is okay on fresh plaster, but I would be careful.

I do agree that a steamer can remove emulsion. Today I removed emulsion from a plasterboard ceiling with a steamer and a scraper. Worked a treat. Wish I'd read your post yesterday instead of discovering this for myself today when 2/3 of the way through the job.

This is what I was saying in post#30, if the walls are pva'd or plastered on wall paper paste steaming isn't a good idea, trouble is you don't know untill you try it.

As you found on sound walls it's the best method, just don't hang around in 1 place too long,

Jebrelli

cyclonebri1 wrote: »

Also if the householder papers and eventually strips skimmed walls where pva has been used, and the chances are they will never know untill it happens, the use of a steam wallpaper stripper will again reactivate the pva and the skim will "blow" from the wall.:eek:

Repair time again:A

Absolutely right. My lounge walls are now a patchwork of old lime/horsehair mortar and newer plaster because the new layer lifted off the old one as I was stripping the wallpaper.

Trying to figure out what the last owner did - looks like they decided to skim the walls after removing wallpaper as the wall underneath was in a bad condition, but halfway through got bored stripping the wallpaper and decided to PVA over it then skim. :rotfl: