Filling cracks advice ?

Shimmyhill

I am after some specific crack filling advice !

Said cracks are where a fireplace and window used to be and have been plastered over - having removed woodchip paper have discovered these cracks.

I presume i will need something more flexible than polyfilla and see they do a flexible filler - is this the way to go ?

LandyAndy

I think you should be OK with polyfilla. Work well into the cracks and then use either an electric sander or sandpaper wrapped around a wooden block to flat it back. It might take a couple of applications to get it properly smooth. This approach worked for me in my latest house where there was quite extensive cosmetic cracking.

misgrace

I agree that filler is the way to go, but not the one that comes in a tube, however, it will solve the problem for a while but the crack will come back.
I know this first hand, and I am sorry if I have mentioned this a few times lately lol, but I am a professional decorator, but by telling you this, means that I have worked on problems like this quite a bit.
This year alone I have had 3 jobs where they have bricked up doorways, serving hatches etc, and plastered, a couple months later it has cracked and you can see the outline.
Even in the last few years I have seen quite a few like this, where even the client, or they have called the plasterer back to repair it, but still it cracks a few months down the line.:(
I have no idea why this happens, but it does, am not saying it happens all the time, but I have seen it loads of times, and am sure other decs will say the same.

What I do in this situation, as really have no other choice, unless they get another skim on the original skim :eek: is that I cut out the cracks a bit wider, then I fill using a suitable powder filler, I sand, then apply some diluted PVA on the actual filler, then I fill again, as obviously there still will be an indent from the crack.
Once I second fill, and the filler feels flush, I PVA again, this gives the filler a hard eggshell protection, hardens it for a better word, and less prone to crack.
But I know eventually it will, so I then line that wall with a 1200/1400 grade lining paper, this on top of the PVA will hold the crack back (Sounds rude doesnt it) lol, therefore if and when it does crack again it will be some years before it actually shows through the lining paper.
You can either paint the lining paper, or hang a finish paper on top of the lining paper, so now you have more protection and a much longer time factor before the crack will show.

Take note though that I only PVA if I am hanging paper, never apply PVA on new plastered walls if your going to paint, as it can cause you no end of trouble.

Hope this helps.

wallbash

Most comprehensive 'crack' reply I have ever read . Now need to find a crack to fix

Thanks

LandyAndy

I agree with misgrace (but didn't put in my first post:o) that you need to rake out cracks so that the edges are solid and not flaky. Cracks in walls that I filled 4 years ago and then emulsioned over are still showing no signs of reopening. Ceiling cracks are not doing quite so well (but still much better than what I repaired) but then there is much more flexing in a ceiling than a wall.

misgrace

Hi Landyandy, cracks in ordinary situations are easy to sort out, but its different when you have blocked in a structure, ie, fireplace, door, hatch.
Thats when you have problems, now, you would think that by plastering over this would solve the problem, but like I said earlier,sometimes it does do, but in most cases, the majority of these the cracks will appear, and you actually see the outline of the thing you tried to block off after a bit of time :eek:

I know that the PVA and lining paper works, as 99% of the people I work for call me back, so I always have a nose and see the work I have done before, and I am smiling cause there is no cracks showing.:D

keystone

Excellent advice from MisG.

Cheers

Shimmyhill

Thanks for the advise, im not a fan of lining paper and have removed lots in this house already - i suspect when done well you would not know it was there but the stuff here had the tell tale lines etc The walls are actually very good underneath so it sees it was lined as prep rather than hiding bad walls and not needing to be skimmed as i feared !

I presume if the walls were skimmed then the cracks would need to be taped to prevent them coming back, im not sure i want to have the room skimmed as the other walls are decent and of course the perfect wall SWMBO wants wall paper !!!

Will have to have a think on it but again thanks for the write up on a solution

LandyAndy

misgrace wrote: »

its different when you have blocked in a structure, ie, fireplace, door, hatch.
Thats when you have problems, now, you would think that by plastering over this would solve the problem, but like I said earlier,sometimes it does do, but in most cases, the majority of these the cracks will appear, and you actually see the outline of the thing you tried to block off after a bit of time :eek:

I think this happens because the blocked off area is not properly tied in to the surrounding block work and so there is a small amount of differential movement that causes cracks to appear. If the new blocks were tied in to the remaining wall it should make it all move as one and prevent cracks reappearing.