Why is my plaster is cracking?

[pclayto]

Hi

I purchased a house nearly 5 years ago, and it was in good decorative order (and largely, still is), so much so that I have not decorated since I moved in.

Over the past 4 and a half years cracks have appeared in the plastered walls. The house is a 1930s semi. Ceilings are lath & plaster and walls are plaster straight onto brick for the external walls, or some kind of block for internal walls.

There are no cracks in the external walls outside, so I assume these cracks are a result of temperature changes over the seasons. I have filled a few cracks with polyfilla, but the crack just re-appears in the polyfilla after a few months. What can I do to get rid of these cracks and prevent then from re-appearing?


Any advice would be appreciated. Thanks.

 

[misterhelpful]

There's nothing unusual about those cracks, but they are the annoying kind that keep re-appearing after a while.

If the walls and ceilings had recently been skimmed, any underlying cracks should have been taped with scrim to avoid further cracking. If this wasn't done, the cracks are likely to always re-appear.

Along the ceiling and wall junction is just a natural place for a crack because of the different movement directions of the substrates. Flexible caulk is your best bet for those, and the same goes for the corner cracks between walls.

The cracks in the middle of walls should be filled with a flexible type of ready-mixed filler. Don't use caulk because it cannot be sanded properly and will not blend in with the surface.

The ceiling cracks are the worst to deal with. If there is excessive movement in the substrate, it must be remedied before filling, but even then you may still have issues if there is an underlying crack that wasn't taped. Again, use a flexible filler for this, not caulk.

 

[opps]

The cracks in the middle of walls should be filled with a flexible type of ready-mixed filler. Don't use caulk because it cannot be sanded properly and will not blend in with the surface.

The ceiling cracks are the worst to deal with. If there is excessive movement in the substrate, it must be remedied before filling, but even then you may still have issues if there is an underlying crack that wasn't taped. Again, use a flexible filler for this, not caulk.

Toupret Fibracryl is great for those kinds of cracks.

http://www.toupret.co.uk/business-customers/products/specialist-solutions/fibacryl-FIBACP01G.html

It shrinks back quite a lot. I use the caulking gun version, squeeze it into the cracks and remove the excess. Leave it to shrink back (a day or two depending on the depth/width of the crack) and then over fill with Toupret Redlite or Red Devil Onetime.

 

[misterhelpful]

Toupret Fibracryl is great for those kinds of cracks.

I'll tend to be avoiding recommending products, in any replies I make these days, because I can't be sure of how they may have changed over the last few years. It's good to hear Toupret is still a reliable brand.

Cheers, opps.

 

[pclayto]

Thanks for the replies. I have a bit of research to do in some of those products mentioned.