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Concrete lintel enough where external wall knocked through?

Discussion in 'Building' started by fuzzyducky, 26 Jul 2012.

  1. fuzzyducky

    fuzzyducky

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    Hi Guys,

    My first post on these forums, so hi.

    I've recently bought a 1930s semi-detached house which has various modifications that I'm suspicious of and have no supporting paperwork.

    The one that concerns me the most is a lintel used to support an external solid brick wall that has been knocked through on the ground floor.

    Below is my poor attempt at a diagram (not to scale) of the ground floor layout. The lines in black represent the original building, and those in brown represent the ground floor extension, of which I think the bathroom and toilet room were individual extensions that have been integrated into the overall extension at some point.

    The original external wall has been knocked through leaving a 2.1 meter span. From what I can see so far after pulling back a chunk of plasterboard, there is a 6.5mm thick (measured vertically, and I assume reinforced) concrete lintel with the brickwork neatly packed up to it. This is all I can see, and I'm not sure if there is any other support in there.

    [​IMG]

    After looking under the floorboards upstairs, I can see the floor joists run parallel to the wall that has been knocked through so I assume it doesn't take the floor weight, however I assume that wall supports the roof?

    I know there are complex calculations required to work out if this is enough, however at a glance does this seem adequate?

    I do have some paperwork about planning permission regarding the party wall act which dates back to a similar time the wall was knocked through, however it is titled "new windows" and has very vague content. The double glazing was fitted at about the same time, so I'd assume it has nothing to do with the wall and due to the title is for the windows, however would that be required for replacement windows?

    A tradesman I mentioned this to in passing said something about getting the council to look at it, where would I start with that and would it be expensive?

    As you can see guys, this is my first house and I'm new to all of this, any guidance would be greatly appreciated and I can supply any further info needed.

    Thanks in advance!
     
  2. tony1851

    tony1851

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    If its a 65mm deep pre-cast concrete lintel, that would not normally be regarded as acceptable on a 2.1m span, particularly as a retro-fit (ie these things are intended to be built in as brickwork proceeds, not put in for a knock-through).
    Having said that,in practice these things often work. If there are no cracks in it, and the floor joists run parallel, it could well last for ever.
    If you ask the Building Inspector, he will ask for structural calcs for it which
    would be almost impossible, and the manufacturers litrature would almost certainly not allow that beam on that span. The council would ask you to put another beam in.
    Why open a can of worms?
     
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  4. fuzzyducky

    fuzzyducky

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    Hi Tony,

    Thanks for the reply. I can't see any crack nor any movement in the house, however; is there any way that we can get some reassurance that the lintel is adequate?

    You say calling in the building inspector would only open a can of worms, but won't the lack of paperwork cause issues when we come to sell?

    Thanks Glyn
     
  5. tony1851

    tony1851

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    Probably not, with that size lintel on that span. Only the manufacturer will know the grade of concrete, strength/cross-sectional area of the steel, pre-stress in the steel and so on. Would you even be able to locate the manufacturer?
    But in practice, will it affect a future sale? You bought the house, and it didn't put you off. The longer these 'defects' go on, the more into the background they go, until one day it seems to be no longer an issue. As the beam is not supporting any floor load, one would assume if it was going to fail, it would have done so by now.
     
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