1. Visiting from the US? Why not try DIYnot.US instead? Click here to continue to DIYnot.US.
    Dismiss Notice

Installing an airbrick - through the damp course????

Discussion in 'Building' started by mrbee, 18 Jun 2006.

  1. mrbee

    mrbee

    Joined:
    18 Jun 2006
    Messages:
    6
    Thanks Received:
    0
    Location:
    Manchester
    Country:
    United Kingdom
    Hi, :D

    I was advised to install an airbrick into our external wall to ventilate the area beneath a suspended tiber floor. I have stripped off the render in the area where the airbrick is to be installed. Unfortunately the course from which I have to remove a brick is where the chemical damp course has been injected. (the holes in the brick indicated this). I cannot go up a course as it will be too high and will penetrate the wall at the internal floor level. I cannot go down a course as it will be at the finished external floor level and will probably allow surface water through the airbrick. :confused:

    How do I install the airbrick without compromising the chemical DPC? Are there any additives I can mix with the mortar I use to fit the airbrick which will prevent damp rising around the airbrick?

    Any advice would be really appreciated as I do not want to make a costly mistake. :eek:

    Thanks,

    MC
     
  2. Sponsored Links
  3. Softus

    Softus

    Joined:
    21 Oct 2004
    Messages:
    19,558
    Thanks Received:
    12
    Country:
    United Kingdom
    This is all crazy. Firstly, you seem to have render at the height where the DPC should be - this is capable of causing damp to rise between the render and the brickwork, and should be removed.

    Secondly, a chemical DPC achieves virtually nothing. If the wall was found to be damp then the cause lay elsewhere.

    Thirdly, it sounds as thought the external ground level might be too high - depending on the composition of the ground, this can lead to damp penetration through the wall, above the DPC, when rain bounces off the ground.

    Do you have any photos of the area where you intend to install the airbrick?
     
  4. joe-90

    joe-90

    Joined:
    28 Oct 2005
    Messages:
    31,284
    Thanks Received:
    1,063
    Country:
    United Kingdom

    Have you contacted RICS and told them they've got it all wrong?



    joe
     
  5. Softus

    Softus

    Joined:
    21 Oct 2004
    Messages:
    19,558
    Thanks Received:
    12
    Country:
    United Kingdom
    I have no relationship with the RICS, have never corresponded with it, and have only ever referred to it once (by posting a link to the web site).

    If you think it's important to tell the RICS something, whatever that thing may be, then I suggest you go ahead and do it yourself.

    Edited as follows...

    The RICS web site has this to say:

    The remedial damp-proofing industry in the UK has reached an established position in the property/construction sector for a number of reasons, not all of which have been subject to analysis. The fundamental factors upon which the industry is based are, firstly, diagnosis of `rising damp' by the use of hand-held electrical conductance-type meters and, secondly, treatment by chemical injection.

    It is often assumed, within the industry and by outsiders, that these practices have been thoroughly researched and developed. However, by normal academic standards, very little work has been carried out in either of these fields, and what work has been published has tended to cast doubt upon the accuracy of diagnoses and the efficacy of the remedial treatments.


    Well then joe-90, it looks like the RICS already knows that chemical injection is useless, so there's no need for you to write in :D
     
  6. JohnD

    JohnD

    Joined:
    15 Nov 2005
    Messages:
    74,224
    Thanks Received:
    4,287
    Location:
    Crossgates, Europe
    Country:
    Cook Islands
    Mrbee:

    Putting in an airbrick (or, better, more than one to give a good airflow under the floor) is going to help remove dampness.

    If you say that the outside ground level is high (? how high below the floor joists is it?) and the dpc has render over it, these want looking at too. When you took the render off, was there any sign of an old dpc, such as a slate bed in the mortar?

    As you will have noticed, there is a lot of differing opinions about chemical treatments and don't mention rising damp.

    However, although I don't use them myself, you can buy the damp-proofing liquid in bottles, and if you are worried about the mortar around your new airbricks, you can drill a hole it and add some more. If you don't have a pressure injector you can get the bottles with a sort of tube on the spout (bit like those rabbit drinker bottles) and it will dribble out as it soaks into the brickwork.
     
  7. Softus

    Softus

    Joined:
    21 Oct 2004
    Messages:
    19,558
    Thanks Received:
    12
    Country:
    United Kingdom
    A good and balanced post from JohnD, as per usual :)

    However...

    OhMyGod! Lid off.... worms everywhere....

    ...then I'd suggest counselling, not chemical injection ;)
     
  8. JohnD

    JohnD

    Joined:
    15 Nov 2005
    Messages:
    74,224
    Thanks Received:
    4,287
    Location:
    Crossgates, Europe
    Country:
    Cook Islands
    :LOL: :LOL: :LOL:


    p.s. I forgot to say, you can get a stepped airbrick duct, where the outside is at one level, and the inside is at another. that would enable you to have the outside high enough to reduce rainwater splash, and the inside low enough to avoid the joists.

    I hope you have at least two on each side of that floor?

    Here we are - only £2 at screwyou. [​IMG]

    They do reduce the airflow a bit so have an extra one.
     
  9. mrbee

    mrbee

    Joined:
    18 Jun 2006
    Messages:
    6
    Thanks Received:
    0
    Location:
    Manchester
    Country:
    United Kingdom
    Thanks to you all for your input.

    The render on the wall goes all the way down to the external finished floor level. I assume the owner at the time rendered it after the dampwork but didn't realise it would be a problem.

    The chemical DPC is in the second course up from the ground. Which I assume may be too low? The internal suspended timber floor is about 3 courses high.

    I didn't see any sign of an existing physical DPC either.

    The house is about 125-130 years old.

    It has solid walls and I don't think that there is enough room to fit the offset airbrick (pictured).

    I can take a picture tonight and will post it tomorrow for more advice.

    I'm guessing that I'd be best stripping of the render to 150mm ish and fitting the straight through air brick as planned.

    I just don't want to stuff it up.
     
  10. Sponsored Links
  11. Softus

    Softus

    Joined:
    21 Oct 2004
    Messages:
    19,558
    Thanks Received:
    12
    Country:
    United Kingdom
    Render - bad. :cry:

    Not too low, just too irrelevant - it will do nothing to stop damp rising between the render and the brickwork, nor would it do anything to stop damp bouncing off the ground and hitting the brickwork.

    I have a hunch that the ground level has risen over the course (no pun intended) of that period.

    It's survived until now without one, so the solution ought to lie elsewhere.

    Picture - good.

    Maybe - let's see the piccy!
     
  12. mrbee

    mrbee

    Joined:
    18 Jun 2006
    Messages:
    6
    Thanks Received:
    0
    Location:
    Manchester
    Country:
    United Kingdom
    [/quote]Maybe - let's see the piccy![/quote]

    Tune in tomorrow for the photo diary of my dodgy damp course....
     
  13. Softus

    Softus

    Joined:
    21 Oct 2004
    Messages:
    19,558
    Thanks Received:
    12
    Country:
    United Kingdom
    You might well have damp, but I doubt that you have a dodgy DPC.
     
  14. mrbee

    mrbee

    Joined:
    18 Jun 2006
    Messages:
    6
    Thanks Received:
    0
    Location:
    Manchester
    Country:
    United Kingdom
    Have got the photos. How do I post them? :rolleyes:
     
  15. DIYnot

    DIYnot Staff Member

    Joined:
    17 Aug 2001
    Messages:
    2,456
    Thanks Received:
    516
    Country:
    United Kingdom
  16. JohnD

    JohnD

    Joined:
    15 Nov 2005
    Messages:
    74,224
    Thanks Received:
    4,287
    Location:
    Crossgates, Europe
    Country:
    Cook Islands
    In the centre of pic. 1 I think I spy the characteristic attempt to build a little wall round an existing air brick when the pavement/patio level is raised.

    Is that what it really is?

    Is the iron air brick, towards the left, higher up, for an old ventilated food cupboard/larder?

    It looks to me like the ground level has been raised (as Softus predicted) by that shingle/slab yard, and that may contribute to current dampness.

    I also see a garden wall which looks as if it abuts the house, and is probably damp.
     
  17. Softus

    Softus

    Joined:
    21 Oct 2004
    Messages:
    19,558
    Thanks Received:
    12
    Country:
    United Kingdom
    JohnD has asked an important question (at least one!), which is about that gully in the centre of the wall. Is this anything to do with what looks like a rainwater downpipe in the corner?

    Currently the render is ridiculously low wrt to external ground level. It looks like it's touching the ground, and it might even go below ground level! The problem this brings is, if any of the render is not fully attached, that water will creep up between brick and render by capillary action.

    So, back to basics...

    Who advised you to install an air brick?

    What problem is the air brick supposed to be solving?

    How long has the external ground level been that high?

    How much work is involved in lowering the ground by, oh, let's say three brick courses?
     
Loading...

Share This Page