Fixing hairline cracks in old plaster

User1234

Hi all,

I've purchased a mid 50s property (belonged to a grandparent) which was wallpapered *everywhere* (solid walls). On stripping it off to paint, most of the underlying plaster has hairline cracks that intersect and follow irregular patterns (i.e. no solid vertical or horizontal cracks following pipes).

On some walls steaming made the cracks worse, to the point of plaster popping up, and falling off - these will definitely need skimming over.

I'm left with a lot of hairline cracks which I'd like to tackle myself, like these (skinny finger for a little reference):

https://onedrive.live.com/redir?resid=F3655909A8A57112!75754&authkey=!ALgYu_X2c2r93BQ&ithint=file%2cjpg

There are also some slightly larger ones like this:

https://onedrive.live.com/redir?resid=F3655909A8A57112!75755&authkey=!AAtzT6lsIxT7ykY&v=3&ithint=photo%2cjpg

Tapping the wall doesn't sound hollow so I'm guessing it's not 'blown' (I think that's the correct term) and there are no damp problems. After spending probably hours reading threads on here/elsewhere and watching videos there appear to be a few ways to deal with it but I'm not sure what would be best.

1. Fill with flexible "decorator's" filler/caulk.
2. Fill with powder filler (the mix with water kind).
3. Lining paper.
4. Open out cracks using some sort of tool, then fill.

From what I can tell, it seems the easiest and quickest way to remedy the situation would be to use a premixed filler. The brand beginning with P offer both a spray for thin cracks and a hairline crack filler that's liquid, both of which sound incredibly convenient, but then I've seen some criticism of their products (can't tell if snobbery or not). Perhaps some of the slightly wider ones should be opened and definitely use a filler. Would anyone fault this idea?

There are lots of videos online where people are mixing powdered filler, even putting joint tape over gaps and filling on top. Joint tape makes sense if it's to hold cracks together, but I don't see why it's worth the effort of mixing your own filler?

I've seen suggestions that you should wet the crack slightly to 'prevent the plaster from sucking the moisture out of the filler too quickly'.

I've also seen people open up cracks that look to be only 2mm to 10mm to fill!

Finally, should the filled cracks be primed afterwards? I've noticed before that filler tends to look a different colour when painted over, even in white, sometimes.

Thoughts very much appreciated, thank you!

phil24_7

The correct way to repair the crack would be to chisel the cracks out wide enough to use scrim tape in (to strengthen the crack) and then fill and sand level. A quicker and easier way of doing it would be to rake the crack out a fair bit, then fill and sand this.

An easy sand filler would be your best bet.

konark

If the plaster is bad maybe you could put anaglypta on the wall before painting or just paper them with a patterned wallpaper.

keith969

"but I don't see why it's worth the effort of mixing your own filler? "

Because it's cheaper (why don't plasterers use ready mix plaster?), you're not paying for water. Of course it depends how much you have to fill...

Problem with hairline cracks is that they can have a habit of reappearing after filling.

User1234

konark wrote: »

If the plaster is bad maybe you could put anaglypta on the wall before painting or just paper them with a patterned wallpaper.

:rotfl:I've spent about 25 hours so far taking that off the walls and I'm only half done!

User1234

phil24_7 wrote: »

The correct way to repair the crack would be to chisel the cracks out wide enough to use scrim tape in (to strengthen the crack) and then fill and sand level. A quicker and easier way of doing it would be to rake the crack out a fair bit, then fill and sand this.

An easy sand filler would be your best bet.

If any bigger ones appear I'll definitely get some scrim tape, thanks. I think the others can probably be raked out. Someone at work sold me on easi-fill today.

User1234

keith969 wrote: »

"but I don't see why it's worth the effort of mixing your own filler? "

Because it's cheaper (why don't plasterers use ready mix plaster?), you're not paying for water. Of course it depends how much you have to fill...

Problem with hairline cracks is that they can have a habit of reappearing after filling.

That makes sense. I don't think there's *that* much to do but it'll depend how much I scrape out the cracks, most likely.

konark

User1234 wrote: »

:rotfl:I've spent about 25 hours so far taking that off the walls and I'm only half done!

Now you know why they put it on!