Treating walls before wallpapering

[AMS1]

Hello

I'm about to wallpaper a couple of our bedrooms.

The house is about 70 years old and the walls have been papered in the past. However, a few months ago I got a plasterer in to improve the appearance of some of the walls as a lot of the original plaster had blown in places and was in general need of repair.

However, some of the plaster he used wasn't the browny/pinky stuff, but white; this stuff also seems 'softer' ie you can run your nail down it and it'll leave a mark. This isn't really a problem as I'm wallpapering over it, but how do I treat it before decorating, as it seems very porous?

I've already sized the whole bedroom but I'm wondering if I need to do anything more to the sections of the walls that has this white plaster covering over it?

 

[kjacko]

Sounds like he's used easyfill, which a lot of decorators used to smooth out walls (or part of) prior to wallpapering.
When i've prepped walls with easyfil i just put a little watered down paper paste onto it to avoid it sucking too much of the moisture out of the pasted paper.
I guess general wall sizing would incorporate this, but i'm no pro decorator.
That said, my paper is still up 4 years later with no ill effects.

 

[opps]

Hmnnnn.... it does sound like easyfill.

Whilst not wanting to malign your fellow I would never expect a "proper" plasterer to use it. I did work in a hose recently where the other "supposed" decorators used the stuff to dry line the ceiling (tape and join), i wonder how long it will take to crack...

If you have sized the wall you should be ok. Did you use real size or watered down starch based paste? I only ask because I once made the mistake of using real sizing (BeeLine), the stuff stank the whole house out.

To check that all is as it should be, spit on your finger (or use a wet rag) and rub it over the filler, if it turns darker instantly then the level of suction is still too high.

Good luck

 

[AMS1]

Hmnnnn.... it does sound like easyfill.

Whilst not wanting to malign your fellow I would never expect a "proper" plasterer to use it. I did work in a hose recently where the other "supposed" decorators used the stuff to dry line the ceiling (tape and join), i wonder how long it will take to crack...

If you have sized the wall you should be ok. Did you use real size or watered down starch based paste? I only ask because I once made the mistake of using real sizing (BeeLine), the stuff stank the whole house out.

To check that all is as it should be, spit on your finger (or use a wet rag) and rub it over the filler, if it turns darker instantly then the level of suction is still too high.

Good luck

Thanks for your response. The stuff he used was called 'Sheetrock (presumably the brand?) Lightweight All Purpose Joint Compound' I know this because he left half a tub of it when he went. In fairness it was mostly used around the windows and the corners of the room where he'd 'sharpened' the corners with that metal edging stuff.

I've taken your advice, licked my finger and pressed it against the wall and has indeed left little darker fingerprint marks. Does this mean I have to re-size?

And the stuff I used was just a watered down version of wallpaper paste, following the instructions on the packet for making size.

 

[AMS1]

So, should I just re-size the 'joint compounded' bits?

Or should I invest in some proper wallpaper primer sealer like Zinsser Gardz?

 

[kjacko]

personally, fwiw i'd dilute some wallpaper paste and just size the whole wall. It doesn't always need to be rocket science with specialised products. I've never used them and not had any paper fall off yet.
No doubt i'll get scalded by a pro decorator now, lol.

 

[opps]

So, should I just re-size the 'joint compounded' bits?

Or should I invest in some proper wallpaper primer sealer like Zinsser Gardz?

just sizing the filled areas should suffice.

Personally when lining I paste both the wall and paper (full strength), helps to ensure that something is wet on very hot days. I use a roller to apply the paste

 

[AMS1]

personally, fwiw i'd dilute some wallpaper paste and just size the whole wall.

I've already sized all the walls, but the filled in bits still seem very porous.

just sizing the filled areas should suffice.

Personally when lining I paste both the wall and paper (full strength), helps to ensure that something is wet on very hot days. I use a roller to apply the paste

Thanks, opps.

 

[kjacko]

yeah, then maybe full strength paste on the filled in bits then.
But as opps said i've often not diluted at all when sizing whole walls AND i paste the wall and paper too.
I guess some pva wouldn't hurt it? I've seen guys put some gloss over filler too, but only smallish areas, cos of the drying time.