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Damp: concern or not?

Discussion in 'General DIY' started by DPJ, 22 Oct 2021.

  1. DPJ

    DPJ

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    AEAACD90-A947-4440-A49A-BA8D1EBC1C1F.jpeg 4774CC6F-D813-4C51-A62C-49D5AFBE0429.jpeg Hi,
    Have had a bit of damp under our stairs (it’s open, not a cupboard). It mostly shows on old rucksacks etc that hang there for years and then we notice they’re a bit moldy!

    It’s an external wall (we’re end of terrace 1930s, with solid brick wall - no cavity) and is rendered. The render is in good condition, but means I can’t see if there’s a DPC. The wall is about 150cm from the next house, so fairly sheltered.

    Yesterday I took the floorboards up to see if there’s an obvious cause and noticed that there’s about 150mm patch of ground next to the wall that when you scrape away the top level of debris is a bit damp (see photo). As far as I could see this is the same along the wall, including places that don’t appear to be damp.

    The bricks there read about 20% on my damp meter, compared to ~9% from the other bricks that I could see (the honeycomb walls that also support the joists). The joists are all ok and showing no sign of rot.

    Is this something I need to sort? If so any ideas about what I can do? Or can I just leave it and keep an eye on it?

    Also, would I be able to see the DPC from the inside?

    The path on the other side of the wall is cement and probably been there for a very long time - doesn’t look to me to be too high, but as I can’t see the DPC its hard to tell.

    Thanks for any answers / thoughts!
     
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  3. foxhole

    foxhole

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    Render traps water if there is slightest damage, if you cant see damp course likely to have been breeched.You can’t get accurate moisture reading from meter on brick , it only records surface moisture. Not allowing good air movement can cause condensation issue.
     
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  4. JobAndKnock

    JobAndKnock

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    If the walls are solid, not cavity, I suspect that the buildings may be older than 1930s but damp proof coursing was apparently made compulsory in 1875 in London and in many other parts if the UK before WWI AFAIK. The problem is that many early DPCs were laid shoddily and no longer fulfil their purpose. Old DPCs may consist of slate, butumen, lead or even tar impregnated hessian barriers, fitted into the walls to protect against rising damp at about 150mm above ground level. Over time these can crack as a result of settlement, or decay (bitumen and hesian), or (more likely) be bridged because of earth building up against outside walls. Cavity walls started to appear in the 1870s (our house is 1880s and has them, albeit too narrow by modern standards)
     
    Last edited: 24 Oct 2021
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