How to make sure lintel is safely / correctly installed?

[mikengac]

Just started a major overhaul of the kitchen/downstairs extension and I've discovered a lintel that seems like it wasn't installed properly.

Probably easier to explain with a photo and diagram:

've been two single-storey extensions, firstly when the kitchen was extended (old extension) and then when a full-width extension was added which reused one wall of the old extension and totally enclosed the others.

Part of the old extension had been demolished and a stub wall "D" had been left which we'd like to remove so we've been taking out the old kitchen cabinets and boxing in to see what we'd find.

An 8.5" 22cm Catnic box lintel was installed when the old extension was built. The wall-to-wall span is 7'6" 230mm and there's 5.5" 14cm in contact where it sits on the old extension wall "D".

There's a crack running down the stub wall "D" where it meets the old wall "E" which suggest to me that the newer wall wasn't tied into the old wall properly, and that the stub wall has been left because removing it would have effectively left the end of the lintel on a column of dodgily-attached blocks.

Before I call in the builders (or surveyors), I'd like to have some idea of what would be involved in ensuring the whole thing ends up safe and sound.

Would the sequence of work be something like Acro-ing the existing joist, rebuilding the brickwork so that it's toothed in properly, ideally tying it in to both the old wall "E" and also the old external in picture A (effectively forming a new right angle corner, putting a spreader on top of the new brickwork and re-seating the lintel? Does that sound right?

Is it likely that the lintel would need to be replaced with a longer one so that it extends into the wall further? Ideally I'd like to avoid having an additional brick column built that protrudes into the kitchen as the old wall "E" is flat at the moment.

Thanks for any advice.

[Mark]

Lintels are supposed to have 150mm minimum support at each end. Trouble is the next size up will be 300mm longer and you are not supposed to cut them down. Also they are expensive. Cracks happen and most of the time they are nothing to worry about. I don't fully understand what you are dealing with but I'd have thought solving this would have been straight forward to most builders. A couple of acro props possibly , take out the stubwall, make good so that the existing lintel sits on 150mm of support.

I'd be inclined to get a builder round to quote. If what he suggests reassures you then it hasn't cost anything yet. A surveyor will cost.

mark

[Roger Mills]

You haven't said exactly what the lintel is supporting, but I assume that it's the upper storey - and maybe part of the roof - of the original house?

If so, simply having it resting on a block wall is totally inadequate - firstly because there is unsufficient bearing and secondly because blocks are not strong enough to take point loads and need some means - such as bricks or pad-stones - of spreading the load. The crack is almost certainly the result of the upper wall having settled as the blocks have partially collapsed.

You need to get advice from a structural engineer - and I imagine he will say that you need a longer lintel which is properly supported by being cut into the original brick wall.

Is the lintel above or below ceiling height. If below, when you replace it you may be able to install the new one higher up so as to achieve a flat ceiling.

[Rick]

lintel should sit on 150mm (min) of at least, on dence concrete bricks and or blocks at each end.

I have DIYed a fair few lintels, in your case I'd get accros in to hold the lintel in place, then rebuild the support under the end.

You need to make sure the accro is well supported at the bottom, and not resting on a silly bit of floorboard, actually renting acros is cheep, so I like to use plenty.

I'd rebuild the pillar with concrete bricks, let the bricks dry, then pack in bwteen the bricks and the lintel with mortar and/or slates, to finally fill the gap. When all dry, remove accros.

Of corse this assumes the lintel is the right size, which is possibly a bad assumption. Aslo can you remove the stub wall, and support the thing on other wall ?

An arctitectural technition who specalises in fixing screw-ups would be the best place to go for advice, or even a strutrial engineer. Many moonlight, and the costs are more reasonable when they are not working for a big company, but working for cash.

[Hugo Nebula]

On Thu, 30 Aug 2007 13:31:46 -0700, a particular chimpanzee, Rick randomly hit the keyboard and produced:

TBH, I would expect an archi-technician to suck air through their teeth & say, "we'll need an engineer for this".

If that back wall is to a two storey dwelling, I'd have expected to see a couple of UBs (RSJs in old money) in there.

I'd do ABD, with the proviso that I'd replace the Catnic with a couple of 152 x 102 or 178 x 102 UBs.