Cracks keep opening: how to fill?

[Simon Elliott]

Our house is a three storey end terrace, built with brick end walls and with concrete lintels joining the end walls. The side walls (with the lintels) have a lot of very large windows. The remaining part is covered with upvc weatherboarding. The house is about 40 years old, and the lintels have sagged a bit.

Inside, on the top floor, on the side wall, a long horizontal crack has opened up. It was there when we bought the house, and the survey said it was nothing to worry about. Every time I fill this crack, it just opens up again. It's only a millimetre or two wide, and it's not getting any wider, but I think there must be a little bit of movement there.

The interior wall is I think some kind of plasterboard attached to the concrete lintels. The wall is just plastered and painted, there's no wallpaper.

Can anyone suggest a way of covering over this crack more permanently?

[Bert Coules]

What are you using to fill the crack? Some fillers are more flexible than others.

Bert

[Huge]

Cut out the plaster surrounding it, cover with metal mesh & replaster over the top. S'what the builders did with our "seasonal movement" cracks.

[The Natural Philosopher]

decorators caulk.

[bigcat]

Suggest exposing the brickwork and ensuring your pointing is good. And not covering it, as you need to know if it continues to move.

NT

[Simon Elliott]

Thanks for all the replies. I've bought some flexible filler from a local DIY shop, will try to remember to post here re whether it does the biz or not.

[Simon Elliott]

There's no brickwork. That wall of the house is a series of concrete lintels, with cladding where there aren't any windows. Whoever designed the lintels didn't do a very good job of calculating the serviceability limit state (I assume they had to do calcs for this in 1965?) as they have sagged a bit.

I think the cracks opened either to the sagging of the lintels or to settling back in the 1970s, as it seems the builders didn't do such a good job with the foundations either. Several of the houses in the block have had nasty settlement problems in the past. But I think the cracks are probably moving slightly due to thermal stresses: the concrete lintels and the stuff that was used for the cladding seem to have very different coefficients of expansion.

[bigcat]

Firstly we dont know what the wall is made from, I'm assuming theres more to it than just lintels, since they would not stay up on their own.

Unless Im mistaken, if a concrete lintel sags, it has failed. If this is your situation, I would not be looking to decorate over the cracks, as it may possibly be at risk of collapse. Without the necessary info, really we can not know what is going on, but sagging crete lintels does not sound good.

NT

[mark d]

1960's house then they are 13 to 14 ft wide and sit on the brick / sinderblock walls that form the side walls.

Doesnt concrete take a while to fully set? They would have been cast in situ and sagged over subsequent months. It seems very typical of

60's houses and flats and its not a major problem. If the OPs lintles have been covered in paslter board then the house has been replastered and the cracks are where no skrim was use. If it hasnt been replastered but merely sounds hollow like plaster board then the sand and cemet plaster is detatched and the fix is to replaster.

Those 13' wide windows present problems for window fitters who have measured the reveals at the side and not noticed the sag:)

[bigcat]

Concrete takes 6 days or so to cure. If it sags even a bit, it has sheared.

There are some situations in which broken lintels are not a significant safety issue, but I would not at all assume thats how it is without knowing the details. If I were the OP I'd want to find out. I dont think we have enough info to know.

NT