Flexible sealer for plaster repair

Leif

I have stripped wallpaper, lining paper, and paint from the lounge ceiling, as the wallpaper was vile. Beneath the wallpaper I found bad plaster repairs where cracks had appeared. The plaster repairs had cracked. Not surprising as plaster is rigid, and the ceiling flexes ever so slightly where the plasterboards are butted together. They were not taped before skimming. Anyway, now I am back to skimmed plasterboard, with some cracks, mostly very small, but one really weird crack tracing a rectangle about 30cm by 60cm. I intend to repair the cracks with a flexible filler. The best I have found is Evo Stik flexible filler, which is rather like caulk. Is there anything better, a bit firmer, more sandable?

As an aside, that rectangular crack is weird. Other cracks are narrow, no big deal, and easily filled with a caulk filler. But this one has strange edges, quite wide, and irregular. Anyone got any ideas why this one is so different?

Finally, yes I know some builders will say to tape and skim, or to overboard, but to be honest 95% of the cracks are tiny and caulk will do the business, and not crumble as the ceiling flexes over the years.

Widelats

Most brand names are more or less the same, bond it, unibond etc, not much difference between them. No i dea what the rectangle is, can't even guess. I'm having same problem as you my plasterwork needs a re plaster and i have to fill the smaller cracks, i'm going to use unibond interior flexible filler.

Leif

Widelats wrote: »

Most brand names are more or less the same, bond it, unibond etc, not much difference between them. No i dea what the rectangle is, can't even guess. I'm having same problem as you my plasterwork needs a re plaster and i have to fill the smaller cracks, i'm going to use unibond interior flexible filler.

Cheers. Is that the stuff in the gun cartridge, or the self squirting can? Assuming they are not the same substance inside.

keystone

If the skim is cracking where the boards are joined that suggests that the board edges that are flexing are not screwed into a joist which is poor installation TBH.

The sort of interior flexible filler you are talking about is just what you suggest in the lead post - its caulk. Long term it won't be that effective but I can't see that you have much choice except to get the plasterboard fixed up properly. You could try raking the cracks out (ie make them bigger) and applying easifill or something similar. No filler works with small cracks - it just falls out. Howerver, thats not going to solve the underlying problem either.

Cheers

Leif

Using Easifill is the worst choice as will crumble at the slightest flex of the joists since it is brittle. That is in effect what happened originally, someone had used a thin band of plaster over the crack, and it too cracked. There is not much flex in the joists, but just enough that the edges of adjacent boards are put under pressure, and they fracture. Bear in mind this is over 40 years.

The ceiling was made in the late 60's I believe that it was normal to just butt boards together then skim them, as that is what was done. The problem is that very slight flexing of joists will cause the material in the join to fracture, due I guess to pressure from the boards either side (join is a weak spot), and the fracture will propagate to the surface. Modern practice is to tape the joints then skim. I do not understand with certainty the action of the tape, but I suspect it prevents cracks propagating into the skim layer. So it does not prevent cracks, but the cracks stay hidden. That is my guess.

I do not understand why you say the caulk will not be effective in the long term. It will not crumble under the slight flexing over the years. I have found a number of people who have done this and found it to last years. I have found no example of someone saying it did not work.

keystone

Leif wrote: »

Using Easifill is the worst choice as will crumble at the slightest flex of the joists since it is brittle......

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.................... I have found a number of people who have done this and found it to last years. I have found no example of someone saying it did not work.

Don't know why you bothered raising the thread then seeing as you have the answers already.

And I don't agree with you about easifill. Filling joints between sheets of plasterboard is what its designed for.

Cheers

misgrace

The only problem with caulking on a ceiling or wall is that the caulk will grin, (show through your paint) as you are painting with an emulsion over it, so if you caulk these cracks, then I would brush over some oil based undercoat, when dry, emulsion, the undercoat will seal it, and prevent it from flashing through your emulsion, but your caulk would have to be smooth as if not will show the caulk lump.

In all honesty, even the caulk will crack at some time, pressure from walking above wont help, it might pay you to get the ceiling skimmed.

If you cant afford skimming, how about lining the ceiling, do your repairs, cut out the cracks, caulk, but leave like an indent,then PVA over the caulk then when caulk is dry, fill over the top with a suitable powder filler till flush with the ceiling, sand down then PVA the filler, then line, this will hold back it opening up for a few years, other than that skim.

Leif

keystone wrote: »

Don't know why you bothered raising the thread then seeing as you have the answers already.

And I don't agree with you about easifill. Filling joints between sheets of plasterboard is what its designed for.

Cheers

No, I asked if someone knew a good flexible filler which can be sanded. Ideally I want something thicker than caulk which is a bit runny, and it is not sandable.

You are correct about Easi-fill but I suspect it is not good for ceilings without scrim tape. Of course I might be wrong.

Someone had previously repaired the cracks with a thin band of plaster, and over the years it had cracked, and ended up looking worse than the original cracks.

Leif

misgrace wrote: »

The only problem with caulking on a ceiling or wall is that the caulk will grin, (show through your paint) as you are painting with an emulsion over it, so if you caulk these cracks, then I would brush over some oil based undercoat, when dry, emulsion, the undercoat will seal it, and prevent it from flashing through your emulsion, but your caulk would have to be smooth as if not will show the caulk lump.

In all honesty, even the caulk will crack at some time, pressure from walking above wont help, it might pay you to get the ceiling skimmed.

If you cant afford skimming, how about lining the ceiling, do your repairs, cut out the cracks, caulk, but leave like an indent,then PVA over the caulk then when caulk is dry, fill over the top with a suitable powder filler till flush with the ceiling, sand down then PVA the filler, then line, this will hold back it opening up for a few years, other than that skim.

I can afford to have the ceiling taped and skimmed. I believe skimming on its own will not be effective, as that was in effect what was originally done. I am told that tape adds tensile strength, which eliminates or reduces cracks.

I have thought about lining paper, but I am not convinced I can do a good job. And if I pay someone to line, I might as well pay for the scrim and skim.

I am starting to think that tape and skim is the way to go.