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Plastering and cracks - to be expected?

S

StevieB

Nordic Pine
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We have recently had out hallway and stairs plastered. Good plasterer, used him for a long time (several houses) and no problem with his work previously. The hall and stairs are big - was a 5 day job to do a skim over the original horsehair plaster. All onto brick walls underneath rather than laths. Only problem with it was it required approx 3 coats of 4:1 PVA to prevent he plaster drying out too fast for him to work it properly.

Plastering was finished approx 4 weeks ago and since it was done large hairline cracks have begun appearing. By large I mean long rather than wide, not enough to fill properly but enough they will show when painted. Is this something others have come across? Only explanations I can come up with are too large an area so something has to give as it dries and therefore cracks, or it dried to quickly and therefore cracked as a consequence. From application to dry was typically 24-48 hours, which is fast. Usually it takes 3-5 days for a room to dry. There is certainly no movement in the brick walls, they have just been skimmed. I did try to take a pic but the cracks are not really visible in the photo. I haven't started painting yet but hope to in a couple of weeks time.

Questions then - what is the best way to fill these - simply polyfiller or some other method? And is this to be expected and if so anyone know why it has happened?

Cheers,

Steve
 
Not certain but it sounds like the horse hair layer is the problem. If it took 3 coats of diluted pva mix to seal it enough to work the top coat then it's probably dried unevenly, shrunk at different rates in weak spots and that's caused the cracking. I've built two new and renovated one 400 year old cottage. On the cottage we also had lime plaster with all sorts of stuff mixed in to help it bind including horse hair and straw. That was also over brickwork and it was a veritable sponge! In the end, we had to take it back to brick, pva the brickwork and then put a layer of bonding over the brickwork. (I mean carlite bonding...the product). Then I think the spread may have built it out with a layer of sand and cement before he skimmed it...or my memory might be failing and he skimmed on top of the bonding. But that original lime plaster had to go.

Anyway, when we plastered the house I'm in now directly over modern brickwork, the spreads used sand and cement direct on the blocks and then skimmed that. Took ages to dry.
 
Thanks Rob, not had it before on old plaster and it was fairly flat prior to skimming :eusa-think: but differential drying could indeed account for it. Ah well, bit of filler and a coat of paint, if all else fails then some wallpaper as a last resort should hide it a treat :D

Steve
 
I'm sure you can rescue it. One tip with the really fine cracks which sounds a little counter-intuitive. Dig them out first. Using something sharp like the tip of a scraper or an old bluntish knife tip, scrape the crack so you make the channel deeper and wider. This will provide a much better key for a larger volume of filler and its then less likely to re-split in no time. Don't worry too much about obsessively flattening the filler when wet, sand it back after its dried.
 
Rob":2j5o2bev said:
I'm sure you can rescue it. One tip with the really fine cracks which sounds a little counter-intuitive. Dig them out first. Using something sharp like the tip of a scraper or an old bluntish knife tip, scrape the crack so you make the channel deeper and wider. This will provide a much better key for a larger volume of filler and its then less likely to re-split in no time. Don't worry too much about obsessively flattening the filler when wet, sand it back after its dried.
Click to expand...

:text-+1: for widening hairline cracks. If the crack is too small, you will think you have filled it but when you sand it back it's still there because nothing actually entered the crack while spreading the filler.
 
I use an old screwdriver and follow the line of the crack.
I've also been using One Strike which is a ready made fine filler, easy to apply and seems to last for ages in the pot by adding water to keep it moist.
Around coving, skirting boards etc I use flexible decorators caulk.

Rod
 
That 400 year old cottage I mentioned earlier was pretty much held up by caulk :-)
 
Rob":7t3rd3m3 said:
That 400 year old cottage I mentioned earlier was pretty much held up by caulk :-)
Click to expand...

I know the feeling. Last house we did up, the timbers were only still there because the woodworms were holding hands.

StevieB - wouldn't it be easier to paint over the cracks with something like Zinsser CoverPlus which is a thick primer/undercoat. Filling in cracks and then sanding them down nearly always looks worse in my experience.
 
Do you have a link to that Roger? Cannot find it on the zinsser website. They do two types of filler and several stain blocking and priming paints, but no 'filling' paint that I can identify.

Cheers,

Steve
 
RogerS":2gi8bfux said:
Rob":2gi8bfux said:
That 400 year old cottage I mentioned earlier was pretty much held up by caulk :-)
Click to expand...

I know the feeling. Last house we did up, the timbers were only still there because the woodworms were holding hands.

StevieB - wouldn't it be easier to paint over the cracks with something like Zinsser CoverPlus which is a thick primer/undercoat. Filling in cracks and then sanding them down nearly always looks worse in my experience.
Click to expand...

Not heard the woodworm hands one before Roger......made I chuckle :-)
 
StevieB":29es53xo said:
Do you have a link to that Roger? Cannot find it on the zinsser website. They do two types of filler and several stain blocking and priming paints, but no 'filling' paint that I can identify.

Cheers,

Steve
Click to expand...

Sorry, my bad. It's Cover Stain. http://www.zinsseruk.com/product/cover-stain/#

The amount of solids in this paint is fantastic. It will paint over and fill your fine crack, I'm sure. It's about the same price as normal primer as well. Brilliant stuff.

Zinsser's range is the DB's. I'm always using BIN white primer. It's shellac based. Problem surface, Sir? Apply BIN. Crappy Farrow&Ball paint giving you grief? Cover it with BIN. Dries in minutes.

They also do a very handy free book for painting over/restoring bad surfaces.
 
Thanks Roger. Would you apply a mist coat of watered down generic emulsion prior to using this, or go straight onto new plaster with the Cover Stain? I note it is stocked in Screwfix so could get hold of some fairly easily.

steve
 
I'd go straight on.It is proper paint ie solvent based
 
I didn't :( Filler arrived but my local Screwfix was out of stock of the primer. It will now have to wait a couple of weeks due to other commitments next weekend (out and about with my sons at swimming, golf and cubs/scouts) and the following one (SWMBO has a birthday) - am aiming for the bank holiday weekend currently!

Steve
 
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