How to repair hair line plaster cracks?

[PC Plod]

I have hire line cracks in a wall that was plastered a year ago. As it is only a hair line crack I can't seem to fill it. What is the secret of filling this sort of crack?

[Steve]

hairline crack polyfilla?

may be cheaper method, but that stuff work quite well.

Steve

[George]

Don't bother with any filler as they will come back immediatly or over time? Use a flexible sealant.

it in the crack and clean off excess with a damp rag. Leave it to set then lightly sand crack area with the finest wet&dry sand paper you can get before painting.

[George]

No type of powder filla works for hailine cracks at its too thin a fill for it to stay adhered to either side of the crack. Over time and specially were traffic is present or foundation movement it'll seperate and again will show up as a crack.

[Chris J Dixon]

Isn't the traditional technique to open up the crack first, so that the filler has somewhere to go?

Chris

[John Evans]

If it is a very fine hairline crack I've never found a filler to work unless I open the crack out slightly first. Even so it will appear again over time if it is caused by setlement or traffic. In which case a fexible sealer may work better.

[Dave Liquorice]

Decorators chaulk doesn't sand, indeed I can't think of any flexable sealant that will sand.

Hairline cracks are best dealt with by opening up with something sharp and pointed then filling with a stiff mix of ployfilla or similar. When about the stuff has set but is still soft, use a wet float to feather the edges properly. When fully dry they powder residue from the feathering can be wiped of with a damp cloth.

[George]

Disagree and how much are you advising to open up? if 1mm then its pointless because its to fine a filling as it will appear as a crack again.

For any plaster cracks that require filla has to be at least a quarter of an inch deep or more to get a successful job and even that might be prone to cracking on the edges if there is foundation movement or a bouncy type floor.

Been there done that and tried different methods and I went back to the caulk method.

[Dave Liquorice]

I normally use the point of an old trowel so 1 or 2mm and a good 5mm deep. Wet the opened up crack, as one would anyway, before applying the stiff mix of filler ensuring it fills the full depth of the crack.

[Chris J Dixon]

I have just noticed a few new hairline cracks after the recent earthquake :-(

Chris