Reoccurring cracks in plaster (above windows)

23 Sep 2010
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United Kingdom
I have a problem where the plaster on my landing and bathroom windows continually cracks. Maybe it's a coincidence But the landing window is next to the bathroom(?).

The narrow cracks appear along the inner edges of the window then start to extend along the walls.

During summer we shower with the window open to aid ventilation. However plaster cracks in all seasons!!

I have filled the cracks on many occasions but cracks reoccur. Even one of the 'no more cracks' type paints was wasted effort. Any suggestions?

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Looking at that your walls are based coat and finish, rather than board and finish.
What space is above this windows? ie other rooms/loft.
Is the floor also supported from below?
Is there any evidence of these cracks on the other side of the walls?
it might be a case of raking the whole area out and starting a fresh or even applying some reinforced mesh over the area.
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Plaster,, on solid walls can quite often crack at the top, either side of windows/doors. It's where the concrete lintel meets the brick/blockwork.
For reference:

- bathroom is upstairs.
- approx 1 foot between window top and ceiling.

Will check outside tomorrow (too dark now!)
How old is the property? It’s almost certainly finish over base as PBD says & I’ll put my money on Roughcasters post. Check outside for corresponding cracks but hopefully there won’t be any.

It can be repaired but you’ll never do it with filler or paint; it will involve quiet a lot of work, removing the plaster & base coat (probably render) around 200mm either side of the crack, fixing a reinforcing metal lath, re-rendering & finally re-plastering; I usually re-plaster the whole wall which makes the repair totally invisible.

I’ve done loads of these repairs & if you look at the pics in my profile under “Building stuff”, you will see some examples of crack repairs including a couple similar to yours involving concrete lintels. Done properly the success rate is very high; some of my earliest repairs have been around since 2005 & still good but I will never guarantee it won’t crack again in the future.

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