Cracking Concrete Lintels
Chris
building work finished about August.
A few weeks ago I happened to notice one of the concrete (actually
reinforced concrete with a fancy 'sandstone' finish to it) under one of the
windows had a crack in it. The lintel is only about 30 inches long. Checking
the one above the same window didn't reveal any other problems.
Out and about last weekend, I was having another look and now the top lintel
is cracked also. Quick, panicy inspection of other lintels revealed that 9
out of the 13 in the extension are now cracked, all with a single crack,
mostly hairline, but a few a bit bigger. But I can't see any trace of the
stonework or mortar cracking anywhere, not any cracks indoors apart from the
expected bit of plaster shinkage.
I am of course getting an expert out to have a look, but has anyone any
experience of concrete lintels cracking thus? Apart from the obvious, and
disturbing, conclusion, would there be anything else that could crack the
lintels? It may just be the fancy surface layer rather than the real
load-bearing part, possibly.
Regards
Chris
Charles DH Williams
<chr...@pussinboots.plus.exspam.com> wrote:
> Last year we had a two storey extension built on the sideof our house, the
> building work finished about August.
>
> A few weeks ago I happened to notice one of the concrete (actually
> reinforced concrete with a fancy 'sandstone' finish to it) under one of the
> windows had a crack in it. The lintel is only about 30 inches long. Checking
> the one above the same window didn't reveal any other problems.
What direction, length and size is this crack, and where exactly?
Charles
Alan McGowan
"Chris" <chr...@pussinboots.plus.exspam.com> wrote in message
news:fzU98.5664$k91.293449@wards...
Cracking in concrete is fairly common. The BS for water retaining structures
recommends a design crack width upto 0.2mm.
The crack you are seeing is probably due to flexure (I assume its mid
span?).
It's difficult to say if you should be concerned, but if you can see the
words top scribed into the ones above the window, then be worried as they
are upside down.
Quite often the precast yards that make these lintels lift then when they
are still 'green' (i.e. only cured for a day or so) and they quite often
crack. This crack reopens when they are loaded by the brickwork above, but
they usually have sufficient strength.
Sorry I can't provide any more definitive answers
Alan
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dg
Hairline cracking is common and does not necessarily mean a defect. It may
be just the sandstone face that has cracked due to differential expansion of
the two materials. Also the lintel and cills will settle with the new walls.
These lintels and cills are also frequently cracked during handling and
installation - these then enlarge as the building moves.
If there is reinforcement, then the lintels should be fine. The only concern
would be to seal the cracks to prevent water penetration and associated
rusting of the steel reinforcement.
However, all this really depends on the size, shape and location of the
cracks and if the surrounding walls are also in distress. Get the builder
back to confirm (via independent expert if needed) all is well.
dg
Chris
the span. The length is the entire lintel, top to bottom IE 6 inches or so.
Chris
Chris
by mishandling. He was very careful with them, storing on slats of wood and
protecting them from damage from above as the building rose. Afetr seeing
the first crack, I did look very carefully for any more, especially in the
lintel above the first detected cracked one. There was no sign.
As you say, I will be getting an expert in next week to look them over.
Thanks