Air bricks in conservatory now internal and letting in damp

Discussion in 'Builders' Talk' started by AJ.47, Nov 13, 2022.

  1. AJ.47

    AJ.47 New Member

    Hi, we've had a conservatory build on the back of our '99 built semi detached house with solid foam insulated cavity walls. The walls have plenty of external air bricks at low level but since building the conservatory some of the air bricks are now inside the conservatory and let in a draft as well as damp (see photos). I'm thinking of using silicone to seal the air brick & stop drafts and mould or is this a bad idea?

    Floor of house and conservatory is solid concrete btw. New conservatory walls are cavity insulated with rockwool and no air bricks although does partially cover an airbrick (wall on left)

    I work in construction but as a fire alarm engineer so no idea what I'm doing here but happy to give advice on fire alarms!
     

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  2. AnotherTopJob

    AnotherTopJob Screwfix Select

    I don't really see what the airbricks are achieving by coming inside the property. They're normally to ventilate a suspended floor or the cavity but in your case don't seem to achieve either of those things.
     
  3. Abrickie

    Abrickie Screwfix Select

    OP Are you absolutely sure you have a solid concrete floor ? As the airbricks would suggest block and beam.
    @AnotherTopJob absolutely no reason why they can’t be above DPC, hence the availability of telescopic sleeves ;)
     
  4. AnotherTopJob

    AnotherTopJob Screwfix Select

    Originally those airbricks vented to the outside atmosphere, so presumably to maintain that a sleeve should have been fitted to extend them?
     
  5. AJ.47

    AJ.47 New Member

    Thanks for the replies. Definitely concrete floor, changed the carpet to laminate recently. Pretty sure there's no sleeve fitted but the cavity of the new wall does go over an air brick so I think it could vent into the new walls only no air bricks in the new walls. Conservatory was built by a proper window/Conservatory company so I'd hope they knew what they where doing but no guarantee I guess!
     
  6. qwas123

    qwas123 Screwfix Select

    Is the photo the extent of the damp?

    Do you step down from the house FFL onto the conservatory FFL?
    I'd suspect that the house air bricks were originally built-in, and were left in to ventilate a suspended floor?
    Why do you say your house floor is solid?

    I can see weeps above both visible air bricks - suggesting cavity liners are in place above the a/b's?
    Are cav liners in place above the knock-thro lintel?

    FWIW: low level air bricks were intended to vent suspended floors - not to vent cavities.
    DPC's should be 150mm above ground level.
    Joist tails should sit on DPC's.
    Air Bricks should sit on the DPC & go in the joist bays between the tails.
    All the above detail takes place below FFL.
     
  7. Cris 11

    Cris 11 Active Member

    Most likely a block and beam floor no other reason for air brick vents, if your not a builder it will look like a solid concrete floor.
     
  8. AJ.47

    AJ.47 New Member

    Photo is the extent of the damp & conservatory has been there about 3 years now. It's level with the floor of the rest of the house

    Don't know for sure about cavity liner above knock through lintel but it also has weeps above so hopefully!

    Seems we must have block & beam with screed on top?

    Guess this all means sealing the air bricks is a bad idea, unless it's vented properly through the conservatory wall, which it isn't. Is just putting an air brick in the conservatory wall in the hope that the existing air brick (that's partly in the new wall cavity) will vent through the new cavity also a stupid idea?
     
  9. AnotherTopJob

    AnotherTopJob Screwfix Select

    The only way to restore their intended function would be to extend them directly to the outside atmosphere.
     
  10. Cris 11

    Cris 11 Active Member

    Is the damp patch just in the corner in photo, how many air bricks in the conservatory and how many in total for the property?

    Has the wall always been damp since the conservatory was built or is it recent?
    A few more pics might be helpful showing the complete back of the house and the whole wall that is damp.
     
  11. qwas123

    qwas123 Screwfix Select

    OP, the air brick that meets the new wall was there from the original build - it wasn't "put in".
    The only a/b's on view should be on the original house not the conservatory.

    Its possible that the new conservatory wall, & floor, maybe has introduced the rising damp in the photo?
    But without knowing if a membrane was used under the solid floor or where your DPC course is - & if the conservatory even has DPC's in the cavity wall - then its not possible, for me anyway, to be definite.

    Are there any signs of damp on the inside/interior of the wall - if not then just live with the small area of damp on the outside leaf of a cavity wall.
     
  12. Abrickie

    Abrickie Screwfix Select

    Not true, those airbricks in the photo should have been moved to the cavity wall of the conservatory, ducted under the new slab.
    As a side note the airbrick that is only partially visible as someone built a wall over it, although amusing, is not best practice ;)
     
    Last edited: Nov 15, 2022
    stevie22 likes this.
  13. qwas123

    qwas123 Screwfix Select

    Nope, I'm afraid you haven't got the hang of what i was saying - but, fair enough, I phrased what I was attempting to say very poorly. What I meant was that as things stood then the only air bricks to be seen would be on the house elevations not the conservatory.

    A properly built conservatory would have had ducted air bricks but the OP's conservatory doesn't have ducted a/b's.
    As far as we know, the conservatory builders relied on the two a/b's we can see, and any other a/b's that might be on that elevation.

    I dont understand your reference to the wall blocking the half visible a/b?
     
  14. Abrickie

    Abrickie Screwfix Select

    @qwas123
    Look really closely at the corner, it’s construction comedy gold, as well as the epicentre of the dampness
     
    Jord86 likes this.
  15. AnotherTopJob

    AnotherTopJob Screwfix Select

    The main problem with conservatories is you don't generally need any planning or building regs - almost anything goes. I've seen conservatories built on foundations only a few inches deep and with the floor built completely over air bricks.

    Most damp/structural issues etc take a few years to materialise, companies know that by the time it's an issue, the guarantee will have expired or will have become void because the house has changed ownership.
     
  16. qwas123

    qwas123 Screwfix Select

    Post # 14 what is your point? What is "construction comedy gold"?
     
  17. Cris 11

    Cris 11 Active Member

    Personally I would have replaced those a/b with ordinary bricks if its just a couple, and if completely paranoid would have let in some a/b somewhere else near bye (no point in a draughty conservatory especially as those a/b that are now in the conservatory are now doing nothing at all.

    This is why I asked for more pics, my first thought is the problem is else ware, very easy to get tunnel vision and convince yourself not to look any further.
    What is on the other side/ above the damp patch where does the water main/waste enter the property is it anywhere near the new conservatory slab?

    In my last property I blocked off two a/b to build an attached garage (fire regs) that had a suspended timber floor it didn't cause any problems and is still OK 30years on.
     
  18. AJ.47

    AJ.47 New Member

    Damp is mainly in the corner. There's 1 ½ air bricks in the conservatory (½ is in the new conservatory cavity wall) and 2 on the rest of the outside back wall. None down the side of the house and 4 along the front.

    I think there was a slight bit of damp before the works but is much worse now.

    It looks like the air bricks in the conservatory should be ducted back outside, probably through the conservatory wall to the left, how doable is that?
     

    Attached Files:

  19. Cris 11

    Cris 11 Active Member

    Does this conservatory back on to the kitchen or bathroom, your pics are not very helpful how about you put up about 7/8 pics showing the outside area where the damp patch is and the back wall from a bit more distance so we can get an overall picture of the set up. I dont think the two a/b have anything to do with the damp problem.
     
  20. qwas123

    qwas123 Screwfix Select

    OP, Why not read my post #11 & post #13 again?
    There are a few things that we readers of your thread dont know? eg DPC's and hopefully, a membrane?
    Neither do we know if a starter kit & a vertical strip of DPC material was used where the conservatory wall butts up?
    Neither do we know if debris in either cavity is bridging any DPC?
    Neither do we know if you have CWI - & if you do then is it wet?
    The conservatory builders lost the matching brick bond?
    Your new photo shows damp higher up the wall.

    Perhaps you will post a photo of the interior damp condition thats "much worse now"?
     

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