Chimneys & Fireplaces Question

Are the hairline cracks in the wall to do with the chimney breast removal?

Hello all,

4 months ago I had the chimney breast removed from both floors, and some sort of metal bracket fitted in that bit of the roof (that bit of the roof is not accessible). The builder dealt with it all...I don't remember a structural engineer being involved, but I paid a (substantial) invoice for a party-wall surveyor. I don't have much contact with the people that put it in for various reasons, but that's another story!

A couple of weeks ago, I noticed quite a few hairline cracks in the wall on the 1st and the wall on the ground floor, where the chimney breast had been, in only what I can describe as crazy pavement type style. Not loads of them, and no wider than 1mm, just a few in a broad Blockbuster-style pattern (for those that remember) across the walls. Then I started to look all over the house, and saw that there was quite a lot of this going on all over, but mostly on these two walls.

Now....I did have the place skimmed recently, all over, so people have told me that these hairline cracks are most likely to be about the new plaster and the recent drop in temperatures.

But then I'm thinking that 70% of these hairline cracks happen to be on the (ground and 1st floor) walls under that chimney.

So...either it's a) the plaster and nothing to worry about, or b) the chimney removal is having some sort of impact/stress on the structure of the house, and this is manifesting in hairline cracks on those walls and elsewhere.

What I would really like to know from the assembled expertise is whether b), in the way I've described it, sounds plausible or familiar. Whether these hairline cracks appearing on those particular walls in that way is a common manifestation of a problem following chimney breast removal. Or not really, and therefore more like to a).

In the meantime, I'm making contact with the builder and seeing how we address etc, and making initial enquiries about getting a structural engineer around, I just thought it would be useful to get opinions off here too. (first time poster so apologies if I've broken all the rules!)

Thanks in advance for any help.

1 Answer

Best Answer

Are these cracks any deeper than the plaster?

If they are you need to act quickly to sort the problem out! Find your Local Planning Authority and find a construction engineer they recommend, they will have them for their planning stuff... Then act on their advice.

To check, simply put a pin or similar into as many cracks as you can reach and see how deep they are. The plaster on the whole should not be more than half to three quarters of an inch deep, but bear in mind that the cracks are likely to run in at angles not square against the wall. Bear in mind too that there might be the same thickness of old plaster underneath the new so you need to find the thickness of the plaster all the way back to the brick underneath and use that thickness as your reference point. If you go past that then your bricks/mortar are cracking and you need help PDQ!

It would also be worth checking them over several days to see if they are getting substantially bigger/deeper.

Another way to check is to run an old wooden broom handle along the wall. Hold the brush end about a metre away from the wall with the top of the handle hard against the wall. As you walk along it you will hear a change from what sounds solid to what sounds hollow. There should not be any areas that sound hollow if it is all new! Any old stuff that was not sound should have been removed before the new was put on. Otherwise they are effectively putting plaster on to thin air!

Plaster does crack but I have never heard or seen any with 'hairline' cracks a millimeter wide. That is a tad too wide for my liking. Hairline is literally meant to be the width of a hair, not 10 hairs.

Answered 28th Dec 2017

Sandau Enterprises UK

Member since 28 Feb 2017

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