Filler keeps cracking

Zaphan58 · 4 Apr 2020 at 21:36

Hi all, I had a large crack in a bedroom wall. I filled it in, sanded over and painted. It looked good for a couple of weeks but now I notice hairline cracks at the edges of where the original crack was. Any suggestions? I'm now thinking I should have taped it before filling? Or maybe I should use a better filler? I used a Screwfix no nonsense filler.

BigBoy · 4 Apr 2020 at 21:46

How big a crack are we talking? Also did you PVA the surrounding material before filling? (Stops the filler drying out too quick)

What caused the crack? If it's.movement and the crack keeps.opening up then you have potential subsidence issue that will need looking at.

Zaphan58 · 4 Apr 2020 at 21:54

It was pretty big, could get your finger in it. It was more of a loose plaster that came off. I believe caused by damp that was coming in around a window that has since been replaced and resealed. So hopefully the cause is gone.

No I did not PVA. I tried putting more filler on top but it just cracks again in a day or two. Room gets a lot of sun so I think it dries the filler out.

LOAM · 4 Apr 2020 at 23:11

Are you absolutely sure it's not structural movement? Usually cracks that crack after filling is because it's still moving. We had a broken drain that caused cracks to appear in one of our walls because water (mainly bath water) was destabilising the ground. Once that was fixed and the ground dried out, the filled crack has never reappeared.

Zaphan58 · 5 Apr 2020 at 11:26

Yes pretty sure it's not moving. The house was surveyed last year and nothing came up anyway. Though I guess things can be missed. Pretty sure the crack was caused by damp though.

fezster · 5 Apr 2020 at 18:15

Make sure you use a knife to expand the crack enough to fill it properly. Make it a v shape when cutting it out. Preferably, use some scrim tape, and then fill.

Fluke? · 5 Apr 2020 at 19:46

LOAM said:
Are you absolutely sure it's not structural movement? Usually cracks that crack after filling is because it's still moving. We had a broken drain that caused cracks to appear in one of our walls because water (mainly bath water) was destabilising the ground. Once that was fixed and the ground dried out, the filled crack has never reappeared.

I hope you handled this without involving the insurance company? When you get a subsidence marker on your property then its goodnight Vienna as far as reasonable insurance premiums are concerned.

Zaphan58 · 5 Apr 2020 at 20:55

fezster said:
Make sure you use a knife to expand the crack enough to fill it properly. Make it a v shape when cutting it out. Preferably, use some scrim tape, and then fill.

Thanks I am going to have another go at it. I have bought some Toupret filler and scrim tape this time. I'll tidy it up, cut it as suggested and see what happens.

LOAM · 5 Apr 2020 at 21:24

Fluke? said:
I hope you handled this without involving the insurance company? When you get a subsidence marker on your property then its goodnight Vienna as far as reasonable insurance premiums are concerned.

Yeah I'm in construction industry (architecture). Had a good mate who's a structural engineer look at it, it was caused entirely by the blocked drain destabilising the ground. As soon as that was resolved it's back to normal again, albeit in an ever so slightly different position

No insurance was needed, it didn't need underpinning or anything, just a mate to expose a drain and put a plastic inspection chamber in.