How to prepare walls before wallpapering
This is part of a series, How to prepare walls before wallpapering . Here I explain how to check walls before stripping off wallpaper; tips on how to strip wallpaper with a smile on your face…and now, how to make sure the “bare” walls (or ceiling) are ready for wallpapering or lining.
Unfortunately, once you have stripped the wallpaper, there is still more preparation work to do. Sorry! Please don’t jump the gun straight onto lining and painting, lining and wallpapering… tick off the sanding, filling, sanding, and sizing first.
Do not forget to sand before filling, sanding, filling, sanding
That wasn’t a typo! With the best will in the world, when you strip paper, there will be traces of the old paste left behind, plus little pimples and bumps and loose specks of plaster or traces of the wallpaper.
If you fill straight away, or even worse, if you get straight on with papering, you will probably end up with loads of imperfections.
You need to avoid this contamination, (and improve the finished look, and reduce time spent sanding and smoothing back over bumpy filler). Therefore I would recommend sanding the walls the moment the plaster has dried out. Use a coarse grit paper with a sanding block. Be vigorous and thorough, but not too mad! As a guide, this stage should take no more than 30 minutes. When sanded, you should brush or vacuum the surface for a dust free surface.
Do not forget the filling
Modern plaster(board) walls. Even though you have removed all the paper, sanded, and the plastered walls look ready to paper, I would still allow up to 2 hours to check over every surface, filling any small cracks and dings.
For me, filling means I fill once; sand; second fill; sand the walls again. I recommend vacuuming all the walls too, leaving the surface smooth, ready for further decoration.
In an older property with lath and plaster walls Even if the walls look OK, with the paper stripped, bagged and thrown out, I would still allow half a day for filling and sanding. And if the walls are in a bad way, (flapping, bulging and crumbly) I would make a call to an experienced plasterer to patch and match before any further decorating work was done.
Some tips about filling and sanding walls for wallpapering
Rake out cracks with the edge of a scraper. Take a blade and just slightly open up the joint. Clean it out with a vacuum or blow hard. You have given the filler something to grip to. Deep cracks should be dampened before filling in layers. Or 2-pack Dulux filler will work in one swipe plus a quick skim.
Fill each crack slightly proud of the surface.
Sand with a sanding block Once the filler has dried hard, sand the whole wall area with 80 grade abrasive paper on a sanding block attached to a vacuum extractor. The sanding block I use is 4 x 10 and is preferable to holding the sandpaper in your hand. Not because it is so kind to your hands, but because it levels out the surface better.
Last step, vacuum the tops of skirting boards and clean the floor. Repeat the filling, sanding, cleaning process.
As professionals, we are beholden to make sure a job lasts, and looks good too. 70% of my work is prep. It is easy to undercut someone who does a thorough job of preparation. That’ll do attitudes are cheap in the short run… but you pay for it in the medium and long run.
Sizing – Next step on How to prepare walls before wallpapering
Once cleaned, filled, and sanded, the walls are ready to size!
Traditionally, size is a glue-based liquid made from melted-down horses hoofs. It prevents plaster from sucking the moisture straight out the wallpaper paste. (If paper dries too quickly, or unevenly you get bubbles and stretches and creases.)
The modern way of sizing is to prepare a runny mix of paste, roll the wall area and brush in around the edges. You’ll see the filler darken when you apply the paste. This is good because the filler is absorbing the paste now, and won’t be able to suck the paste off the back of the wallpaper later.
I don’t subscribe to the traditional or the conventional modern method of sizing. Primer sealer is the way to go!
In my experience, play safe when dealing with older properties. There have been so many experiments conducted over the decades by previous tradesmen and homeowners, that it is increasingly difficult to tell what you are actually being asked to wallpaper over.
Unless you have access to the sort of equipment and analytical skills of companies like Patrick Baty, I think it makes sense to use a product that is more sophisticated than glue size or watered-down paste.
You want a sealer that, unlike diluted paste or glue, lays down a barrier over what has gone before, and actively prevents lifting joints / split seams and bubbles from occurring on any interior plaster-type surface.
The Beeline Primer Sealer way
To anticipate any potential problems, prior to wallpapering, I use Beeline Primer Sealer on all plaster surfaces. It is a wonderful product that smells like PVA glue but isn’t! It seals, evens out surface porosity, aids slip and slide when papering – but most importantly, it does what PVA or glue size can’t…
Beeline binds down any poorly adhering filler and prevents the impending paste on the back of the wallpaper from penetrating that filler, softening it up, loosening the bond on the substrate – making it prone to lifting it when it dries out.
This is a checklist for the whole process of How to prepare walls before wallpapering. Stripping wallpaper and preparing for re-papering / lining / lining and painting.
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