Hair line cracks in old plaster

[ReidyRiot]

Hi, just looked at a job that needs surfaces skimmed over. The walls are plastered and have cement based render approx 25 years old. Majority of the surface has hairline cracks but has not blown. I would normally remove or tape the areas concerned but there are way to many. would these cracks occurred due to rapid drying times? I'm concerned that if i skim over without prior sorting that they will come through. ANY IDEAS.
Thanks for any comments regarding.

 

[steve1976]

Iv seen this before too, it should be ok to skim over just let the client aware that that theres a small chance they could come back.

 

[nicksey1401]

if the clients willing to pay you can use scrim cloth
https://www.warren.co.uk/Pricelist_pdfs/drylining/drylining_frames.htm page 39
you might be able to roll it in with a strong pva coat?.... never tried it though :-/ or just give it a tight coat of bonding and then skim, still wouldn't guarantee it though and then there's the price!!

 

[Steve28]

just give it a tight coat of bonding and then skim

What do you mean by a "tight coat of bonding?

 

[bodplasterer]

Thats why people dont use sand and cement for roughing any more as it shrinks and randomly cracks, we usually try to scrim it up and reskim. Its a bit of a nightmare job as you got to put little strips everywhere but it usually does the trick.

 

[nicksey1401]

just give it a tight coat of bonding and then skim

What do you mean by a "tight coat of bonding?

on top of the mesh mate if it won't stick with pva

 

[dpbeds]

A tight coat means a thin coat.
You can apply bonding as thin as skim.
It'll take out any unevenness before you skim.

 

[tree]

Hi, just looked at a job that needs surfaces skimmed over. The walls are plastered and have cement based render approx 25 years old. Majority of the surface has hairline cracks but has not blown. I would normally remove or tape the areas concerned but there are way to many. would these cracks occurred due to rapid drying times? I'm concerned that if i skim over without prior sorting that they will come through. ANY IDEAS.
Thanks for any comments regarding.

I reckon the cement backing was incorrectly gauged, too much cement that may account for the cracking/ movement. Just chip off any shitey bits with a floor scraper and then stanley V/ scrim the cracks before re skimming. Shoul;d do the trick, after initial movement the backing should have settled still no guarantee though :-/

 

[bigsegs]

ive come across this before...in a house of similar age which had forced air heating (the type with a huge electric heater in a cupboard and ducts in the walls leading to vents)
the cracks were all over, visible but you couldnt really feel em (looked almost like theyd been drawn on in pencil) and i put it down to the type of heating..
anyway, i basically ignored em due to the apparent age, pva'd the walls and gave it 2 coats of multi without any problems...
heard a story bout a builder a while ago who tried to dry out a house that had been flood damaged..
rented a massive industrial dehumidifier and left it running for a fortnight....killed the house, had to demolish it...what that basically means is theres always some water in a building even when its dry, remove ALL of it and you weaken the structure...think old lime mortar in old buildings...
i wouldnt waste my time and money on scrim unless you can really feel the cracks, if it looks like a crazy paved patio all over and there pretty flush id just pva and skim it...

 

[topmark]

My old house was like this, the walls were full of hairlines, about 40 years old, temperature varied a lot, warm through day, drop cold through night, built with very poor breeze block, shite house, got rid. ;D
Bigsegs seems to be the wise one on many issues, I'd never dry an house out too much, everything will shrink or crumble like f$*k.