Air brick causing damp?

Discussion in 'Builders' Talk' started by ConnorM, Aug 16, 2019.

  1. ConnorM

    ConnorM Member

    I’ve noticed some damp in the living room - went outside to see if I could spot anything causing it when I realised we have an air brick in the DPC...seems counterintuitive to have it there. Anyone think it’s likely the cause? Same spot on the wall where the damp is on the inside.

    Would DPC cream into the mortar joint above it resolve the problem do we think?

    You’ll also notice the DPC sits out from the wall - but has a mortar chamfer above

    6C727925-AAAE-4F0A-873B-64ED8AA9D088.jpeg 0D698D77-C275-4082-949C-C139A9D00965.jpeg
  2. gas monkey

    gas monkey Well-Known Member

    brick bit low may be allowing water in lower chippings etc
    make shore its clear
  3. CGN

    CGN Screwfix Select

    Majority of damp problems caused by either penetrating water or condensation.
    Injections damp courses are a big con.

    I’d be tempted to have a dig around that area to see how the wall fairs a few courses down, there maybe a way in for water. Also check the vent is clear of obstructions. Check guttering and down pipes for leaks and as gas says, lower chippings.
    KIAB and Joe the Plumber like this.
  4. Joe the Plumber

    Joe the Plumber Screwfix Select

    The mortar above the air brick looks a bit iffy. It may have a crack allowing water to run across onto the floor inside. If the mortar
    will come out easily, try replacing it with some new stuff and see if that sorts it out. You certainly don't want any DPC 'cream'
    (unless you fancy a trifle that is....)

    I notice your house has already been damaged by some idiot drilling holes in the bricks to install a chemical 'damp proof course'.
    As CGN says, they're all a big con.
  5. Bob Rathbone

    Bob Rathbone Screwfix Select

    The injected DPC seems a good idea, until you realize that the bricks need to breathe. They are porous by intention, this allows the moisture on one side to travel through the brick and evaporate on the other side. Looking at the inside of the house, the bricks there have probably also been treated with silicone based water proofer, this will stop the moisture in the warm air of the room travelling through the brick and dissipating in the cavity. Instead the moisture builds up in the fabric of the wall and you have Interstitial Condensation that can only move back into the room and cause the plaster to become damp. This is a low corner of the room, probably with furniture in front and close to it. This prevents adequate air circulation and leaves a cold spot on the wall. Solutions include, fitting an extractor over the cooker and shower, installing a de humidifier (this may only be needed for a few months) or just opening windows to ventilate the house. The damp in one room is not caused by an issue in that room, but more by issues across the whole house, it's just that the moisture has condensed out of the air at the coldest and least pervious point.
  6. ConnorM

    ConnorM Member

    Thanks for all the info guys - I’ve had a dig down and it looks like there’s a small moat around the house. It’s all paved and then this chippings border but there is no drainage and a good 5 inch mortar bed. Looking at houses round the area they have an entire course of bricks visible below their DPC.

    I’m thinking when it rains the water is sitting in this moat and just absorbing into the brick

    I won’t bother with the cream! Looks as if proper drainage and ventilation is required. Possibly lowering or removing the indian stone too - i think it's been poorly installed

    IMG_8093.jpg IMG_8094.JPG
    Jancat likes this.
  7. CGN

    CGN Screwfix Select

    Google french drains.

    Paving installed too high is a common cause of problems, so although a pain, a good idea to rectify.
  8. Jancat

    Jancat New Member

  9. Jancat

    Jancat New Member

    Did it work Connor? Did the internal plaster have to be removed? I've just viewed a house with similar issues and a ground level air brick with external cement floor. There's even half a slate up against it to redirect rain by the look of it!
  10. Akmb92

    Akmb92 New Member

    Very similar problem. We have been advised to get a new damp course but we are going to Try a French drain and repoint on the corner followed by spraying brickwork with sealant. driveway has been built up to the same level as the air bricks meaning that water can get in.
    Anyone else has this problem?
    Wondering whether to insert a pipe into the French drain so it can run off somewhere else or let the water absorb into the ground naturally?

    Attached Files:

  11. Astramax

    Astramax Super Member

    Does the problem area usually have furniture in front of it?
  12. Jancat

    Jancat New Member

    Probably but it's empty and for sale
  13. Akmb92

    Akmb92 New Member

    Yes, a sofa but we put legs on it to increase ventilation
    Also, warping to the laminate floor- scared to see what’s underneath as I fear the blocked vents are causing more problems!
  14. Astramax

    Astramax Super Member

    A common problem of which you obviously understand by attempting to increase the air flow, is the wall soaking wet or just damp to the feel. If you think it maybe a condensation problem use a suitable emulsion on the walls such as Dulux Trade Mouldshield, Crown Trade Streacryl both reasonably costly but very effective so could be an inexpensive way of eliminating condensation problems. If it is damp then you will have noticed a musty smell then further investigations on the exterior and lifting the floor may be required to pinpoint what's been going on.
    Jancat likes this.
  15. Akmb92

    Akmb92 New Member

    It’s not soaking wet but the skirting the lower section of the wall are damp. The walls get very cold due to no insulation and both external so it may well be a condensation problem. We are looking to buy a dehumidifier to see if that has an effect. Trying to decide which one at the moment.
    Thanks for the tip re paint.

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