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Damp patches on chimney breast - loft bedroom

Discussion in 'Building' started by Russ11, 1 Sep 2020.

  1. Russ11

    Russ11

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    Hi,

    I'm about to buy a house. The home survey reported:

    "Using my moisture meter I tested the chimney breast to the ground floor and first floor and through the loft space. The chimney breast to the front of the house was dry on all elevations. The rear bedroom chimney breast tested positively for damp. The moisture is not causing blistering to the plaster or unsightly staining however the moisture is likely to be as a result of condensation formed from either cold bridging within the stack or possibly hygroscopic salts which attract moisture from the environment. The installation of an air vent in the chimney breast would likely remedy this."


    However, we went to view the property again last week whilst it was raining and had rained a lot during the week to find some damp patches on the chimney breast in the loft bedroom.

    I've attached photos of the damp patches and also google earth images of the loft conversion. Could the damp patches be due to a leak on the roof? Could this be causing the damp all the way down, or could this be a different issue, and both leak and air vent needs to be sorted?

    Oh and the house is 1930's build.

    Many thanks

    Russ
     

    Attached Files:

    Last edited: 1 Sep 2020
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  3. JohnD

    JohnD

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    if the chimneys have been blocked off, then they need to be ventilated top and bottom. This is a very common cause of damp.

    The photos are poor and I can't see the chimneys. But maybe they need some repair work at the top. This is also very common, and buying a house with chimneys it is something you will have to take care of from time to time. It is not much of a problem.

    If the chimneys are permanently out of use, I favour taking them down below the roofline, and reinstating the roof over them. This will remove the need for flashing and haunching in future, because rain won't get to them.
     
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  4. Russ11

    Russ11

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    Hi John,

    Thanks for the feedback. It's greatly appreciated. Sorry the photos aren't good quality.

    So even if there is no leak coming in, the lack of venting could cause patches like these to appear and then disappear?

    Normally, would the first action be to fix the air flow, or would the inspection on the roof be the first place to start?

    Thanks.
     
  5. JohnD

    JohnD

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    start with ventilation, because that is always needed.

    your pic shows two particular round damp spots, which is uncommon, so there might be a particular cause. Maybe rain is running down and penetrating through a bad joint in the brickwork or something. Sometimes builders throw rubble into fireplaces and down chimneys if they think no-one will see.
     
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  6. ^woody^

    ^woody^

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    You need to speak with your surveyor, give him the new information - particularly the weather, damp locations and type of staining, and ask him to confirm or revise the comments in his report.

    Also ask him to clarify his mention of hygroscopic salts. These salts wont exist in the plaster unless the wall has been previously saturated or suffering persistent dampness - and then it will be predominantly due to ground dampness not damp half-way up a chimney. These salts will also be very visible as salts or stains.

    Also his mention of cold-bridging is inaccurate, if he is referring to a flue stack, and I would not expect a surveyor to use that reference in this manner.

    IMO, if those stains are after rain, then its either a roof/flashing leak (stain near ceiling) and or a leak to the flue or stack (the two stains half way up the wall). You wont be getting flue condensation issues in the summer.
     
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  8. Russ11

    Russ11

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    Hi Woody,

    Thanks for your reply.

    Interesting that you say we wouldn't get condensation in summer.

    So from your opinion would you start with inspecting the roof and top of the chimney?

    What it is that is wrong with his reference to cold-bridging on the flue stack?

    Thanks
     
  9. Russ11

    Russ11

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    Thanks again John.

    Yeah, the two round spots do seem quite odd the way they have formed and both very similar. I really want to see what it's like on the roof.
     
  10. ted456

    ted456

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    In terms of buying the house the issues you raise are mickey mouse - buy the place if you want it, and deal with these issues later.
    If you still have concerns then It would be perhaps more worthwhile to have one of these drone inspection guys have a look at the roof, the stacks &, in particular, the Dormer detail.

    After ownership you can:
    Examine the terminals, flaunching and flashings on both stacks.
    The stack in question seems to be in a semi-demolished state?

    The twin circular stains might be D&D adhesive dabs allowing passage of moisture?
    Do the chimney breast flues, have open fireplaces on the floors below?
    Are there appliances in-situ now or do you propose to have appliances in the fireplaces in the future?
    Dont install a vent in the chimney breast in the loft - it could be dangerous if an appliance is working below.
    Sweep and smoke test the flue(s) and make sure they are through vented.
     
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  11. ^woody^

    ^woody^

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    Because it is the wrong use of the terminology from what should be a professional who should know better.

    It's a chimney with a flue, which is not something that could be experiencing cold bridging.
     
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  12. Russ11

    Russ11

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    Thanks for your reply Ted.

    The chimney stack in question is not is use and blocked off at the bottom.

    We are thinking the best way forward now would be to get a roofer up there to check it out.

    Interesting what you say about the D&D dabs. It does look like them.
     
    Last edited: 2 Sep 2020
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