Cracking plaster

[kvasir]

Back in July I got the bathroom done up which included a skim coat of plaster and, about a week later, a couple of coats of paint. It's a flat in an 1890s tenement block.

Mid September, after a cold night, a couple of cracks appeared in the wall to the tenement stair, both about 3 feet long and wavy, one horizontal and one vertical; they don't quite meet at the top of the vertical one but not far off.

A couple of months on, and I thought that was as bad as it was going to get, but last night was another cold 'un and lo! another crack. Again, it's vertical and runs up from the tongue and groove panelling to the horizontal crack so there's pretty much a rectangle of cracks.

So, if we have a cold winter, am I likely to end up with crazy walling? Is what's happened par for the course? How long before I can be sure there will be no more and ask the firm back to patch it up?

Thanks for any advice.

 

[Richard C]

Were there cracks in the same place on the original plaster? If so, how bad were they? How bad are they now?

I reinforce any existing cracks in the plaster before re-skimming & they will not usually reappear. If, however, the cracks are a sign of something more substantial i.e. right through the base plaster & even extending to the blockwork/brickwork itself, they will ALWAYS reappear unless you repair & reinforce the cracks in the substrate. It sounds like you may have some movement going on there which is not surprising if the building is an 1890’s tenement block & extremes of temperature will bring it out. Dry lining the wall may help prevent it reoccurring but that’s not guaranteed either!

 

[kvasir]

Thanks for the reply.

The cracks are each about 2 feet long and, I dunno, half a mm wide. Whether they were there or not before I don't know, as the walls were wallpapered and tbh after that came off I was too busy keeping an eye on the plumbing goings on to think about checking out the walls!

I don't think I can face major restorative work (the revamp turned into a bit of a saga for various reasons). a bit of replastering and a paint over was what I had envisaged. In the light of that and what you said, is just painting over the cracks as they appear the best option?

 

[Richard C]

The cracks are each about 2 feet long and, I dunno, half a mm wide.

With cracks that wide, I would have had a dig back to the brickwork to see what was going on; if the crack is in the substrate you will never stop it reappearing without corrective work.

In the light of that and what you said, is just painting over the cracks as they appear the best option? :

As I said; if the cracks are in the substrate, you won’t stop them reappearing & painting over them every 2 weeks wont help much. You could try a flexible caulk; or lining paper may help but that rather defeats the object of having the wall re-skimmed! I’m afraid the cracks are always likely to reappear until you sort out the underlying problem.

Without seeing the problem, it’s difficult to criticise but I don’t really understand why your plasterer did not bring to your attention the fact that his skim, however perfect, would not stop the cracks reappearing. It’s the finished job that everyone sees & I certainly would not want to leave my work open to criticism when the real problem lies underneath; I would have brought it to your attention & given you the opportunity to do something about it!

 

[memor maplin]

They are just cosmetic.

Fill them in with polyfilla and paint over the top.
half a mm wide is nothing.
Memor

 

[Richard C]

They are just cosmetic.

Fill them in with polyfilla and paint over the top.
half a mm wide is nothing.
Memor

Try it, you might be lucky