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Damp double brick wall

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  1. #1
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    Default Damp double brick wall

    This is the southern wall of our 80 yo house.

    There are damp readings on the inside walls along this wall.

    There is a bathroom which needs gutting and may be contributing to damp, roof seems ok but we will have it looked at.

    Obviously needs to clean out garden, you can see part of the huge concrete slab (6m x 10m?) which basically covers ground along entire side of house.

    We also know the brickwork needs repointing, could this be letting in water?

    Haven't been under house myself yet, but building inspection specifically states there is good ventilation and no evidence of drainage problems.

    I assume it's rising damp and we will need to have a barrier put in?

    Can someone talk me through how to best tackle the issue? Thanks
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  2. #2
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    Hi,

    I'm no expert but we have a similar aged house in Sydney and also have some damp issues I'm working through at the moment.

    First thing you need to do is determine what type of damp it is before you rush into any remedies. It may not be rising damp as the floor seems reasonably high and doesn't look like there are any signs of efflorescence on the outside bricks (although maybe the previous owners did a big clean and replaster like ours did). Is there a damp proof course, hard to see from the picture. Also check all the obvious things like gutters overflowing into the garden bed, leaking downpipe saturating the garden bed etc....

    Do you have any symtpoms inside or is it just something that was noted on the report. Any mould etc..? If you have mould the damp could be caused by condensation in the room if it is cold and lacks ventilation.

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    Southern walls get a lot of rain and very little sun, also a garden against a home is a no no, so get rid of the garden and also check the hottie is not leaking.

    You might then consider an aggie drain drained off to a lower point to get rid of any water falling against the wall.

    Once you get rid of the garden and install an aggie drain you can then fill the area with a nice stone to aid in diverting water to the drain, and also some large pots in lieu of what you have now.

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    Thanks for the quick replies.

    No mould or anything inside, just the damp readings from the inspection report. The house has hardly been lived in for two years (deceased estate with a family member staying a few nights per week) so not aired or heated well.

    There is no white line indicating rising damp and I don't think they've cleaned the brick or anything - in fact they were totally shocked when I said the report indicated damp on that wall (their parents lived there for 70 years, it's a well-loved house).

    The hot water system is 3 years old, looks in perfect condition but I'll check that too.

    We move in next week. My immediate plan will be to check for a damp-proof course, check the gutters (I think they'll be fine), have a crack at ripping out the garden along the house. Some air and heaters inside and I'll report back.

    cyclic, what's an aggie drain?

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    Another question, can we go ahead and do the repointing of the brick? or should we get to the bottom of this first?

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    Quote Originally Posted by unexpert View Post
    Thanks for the quick replies.

    No mould or anything inside, just the damp readings from the inspection report. The house has hardly been lived in for two years (deceased estate with a family member staying a few nights per week) so not aired or heated well.

    There is no white line indicating rising damp and I don't think they've cleaned the brick or anything - in fact they were totally shocked when I said the report indicated damp on that wall (their parents lived there for 70 years, it's a well-loved house).

    The hot water system is 3 years old, looks in perfect condition but I'll check that too.

    We move in next week. My immediate plan will be to check for a damp-proof course, check the gutters (I think they'll be fine), have a crack at ripping out the garden along the house. Some air and heaters inside and I'll report back.

    cyclic, what's an aggie drain?
    You don't need a white line to indicate rising damp, I'm sure I can see greening of the wall about 600mm above the garden.

    An aggie drain is a trench with slotted pipe in the bottom then filled with stone about 20 to 30mm rough diameter.
    The trench acts as the drain and as the trench fills the water gets into the slotted pipe through the slots/holes and is drained away to a point/drain lower than the base of the trench.

    Check the hottie valves are not relieving water at night into the garden, place a bucket under the valve outlet and see how much water is in it next morning, they can easily relieve up to 6 litres a night.

    Yes you can point up the bricks but I would be de moulding the wall first, Wet and Forget or similar.

  7. #7
    1K Club Member paddyjoy's Avatar
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    Quote Originally Posted by unexpert View Post
    Thanks for the quick replies.
    We move in next week.
    Congrats on the new house would be good if you could keep us posted on any fixes you do and how well they work!

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    Old Chippy 6K
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    As others have said - define the problem first. There might not be a dampcourse or it might be damaged. The garden next to the house is a bad idea - it might be the sole cause of 'damp on the day the inspection was done! But might not. Fix the damp issue before doing anything to make the brickwork look pretty . . . else you might find you ill be doubling your work.
    Advice from me on this forum is general and for guidance based on information given by the member posing the question. Not to be used in place of professional advice from people appropriately qualified in the relevant field. All structural work must be approved and constructed to the BCA or other relevant standards by suitably licensed persons. The person doing the work and reading my advice accepts responsibility for ensuring the work done accords with the applicable law.

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    So we've been here 3 weeks now and I have a bit of an update.

    There was actually a TINY bit of fine mould in the second bedroom, but we've kept an eye on it and it's not grown (I'm going to clean it off tomorrow). The rest of the rooms on that South wall had a bit of a musty smell, we've had windows open during the day and heaters on at night and the wet chilled feeling is gone.

    Today I pruned back a couple of trees outside on that wall, and ripped out all the greenery in the garden bed adjoining that wall. I noticed a few things:
    - there is a hell of a lot of external plumbing on that wall!
    - there appears to be clumsy attempts to repair/redo some of the pointing. I think they've used the wrong mortar as it's basically coming off in chunks, revealing old perished mortar underneath
    - the crawlspace door featured in many of the pics below has a steel lintel (?) that has rusted out and bowed. Fanning up the wall either side of this to the roof are fine-ish cracks along mortar lines. The stone (?) lintel (?) above the window ABOVE the crawlspace door has cracked and will need to be replaced

    At the front of the house on the same wall
    - there are still gardens I have to rip out
    - evidence of perished mortar
    - what looks to be an intact, healthy looking damp-proofing lining just below the inside floorboards

    Given that the pointing also needs to be redone on the north wall (the front wall was repointed and tucked more recently, the rear is a 60's extension that is fine) I'm thinking the following:
    - the damp or water is getting in through the perished pointing, and it's not drying out as it's the south wall etc etc
    - the steel lintel above crawlspace needs to be replaced (or this space bricked up with vents) to prevent more stress to the wall
    - the cracks from this stress will be repaired during repointing

    We do have a damp diagnostician coming out, but he won't get here till September. But I'm really beginning to feel like this damp problem is not THAT damp, more the problem outlined above plus the place being virtually empty for two years and two cold winters.

    Thoughts?
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  10. #10
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    Would be worthwhile to check out the plumbing, looks like there could be a lot of roots around the area where that downpipe goes into the ground. Once the roots get in there they will destroy the clay pipes and the water from the roof will just be going straight into the garden bed. Would be a good thing to rule out before the damp technician comes.

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    Looks almost exactly like a 1920's house built with the "Eastwood Browns".........spitting image of my house (or should I say the banks house....)....

    Let me guess the front of the house is dark brown bricks that were at one stage tuckpointed - mortar now looks like it has gone a bit purply/pink and tuckpointing ribbon almost worn off?

    The mortar dropping out is most probably cement mortar. If it is hard and will not crack apart/crumble when push hard with a screw driver - cement. Cement mortar and the old lime mortars do not mix very well, especially in areas of movement. The hard cement mortar will not move with the building and simply cracks and drops out.

    Depending on where you are - I would almost guess that the cracks radiating from the subfloor access point and the window could be related to reactive clay on which your house probably sits (....again the Eastwood brown bricks......from what I have seen around my area is generally highly reactive clay). Only caveat is that I could not see a clear picture of the lintel in the photos for both the window and the access point. The foundations for these building are not deep at all - in most cases it appears just excavated topsoil down to clay where the bricks formed the base. In this regard - vegetation in close proximity to the house will cause differential moisture levels in the clay (expansion and contraction) and differential movement as a result. First thing I did with my house was remove vegetation in close proximity.

    Lime mortars with this building design generally appears to have worked very well, as it is very forgiving, permeable, sacrificial in nature (so the bricks don't crack) and somewhat autogeneous healing with a free lime left in solution when moist to repair micro cracking. If you have not guessed after buying a lime mortar house and researching and using lime recently - I am now a huge fan of it. It is easy to repair/repoint.

    Regarding the moisture - is your bathroom located next to the damp area and is it still the old slag infill bathroom? I noticed my outside wall was damp with eroded mortar due to constant wicking when I had the slag infill bathroom. Removed the infill with a complete bathroom demolition / repair to someones previous dodgy work, and wall has now dried out.

    If that is not the case - rule out areas such as leaking roof down into the wall / or downpipe leak, plumbing leak etc. The dampcourse (if is the 1920's thingy) is most probably the hessian and bitumen method located just below the joists in the wall. So you can expect some moisture wicking right up to almost floor level.

    Hope it helps a little.

    Cheers

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    Quote Originally Posted by paddyjoy View Post
    Would be worthwhile to check out the plumbing, looks like there could be a lot of roots around the area where that downpipe goes into the ground. Once the roots get in there they will destroy the clay pipes and the water from the roof will just be going straight into the garden bed. Would be a good thing to rule out before the damp technician comes.
    Thanks Paddyjoy, I'll get on to it.

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    Thanks so much for your reply an3_bolt.

    Yep, house is a 1929 Bungalow on very Upper North Shore, Sydney. Are you nearby? I have no idea where the bricks are from but your description of the front made me laugh, it was so accurate. It's getting hard to find these old beauties now. They're mostly all done up or knocked down.

    I'm not sure about the clay base, but sounds right. Looks like I'm going to have kill my sons climbing tree (the camellia) and move the rhodos. I wonder if I can transplant those?

    Did you do your repairs/repointing yourself? I was going to outsource but a bit wary, many of the contractors seem to favour acid wash cleaning etc which I don't want to use on my lovely old bricks.

    Yes the bathroom is between the cracking and the master bed, so to our right as we look at the pics. The bathroom is ancient and only has a bath/shower and vanity. No loo. Seeing Paddy's point above and thinking it through, all the plumbing/clay pipes will have to be dug up when we do this bathroom, could replace the roof drainage pipes then? I have no idea what a slag infill bathroom is? Inside the house, any "damp" problem seems to be on the external wall rather than either of the walls common to the bathroom.

    The roof seems to be able to be ruled out at this point as a source of damp.

    The dampcourse looks to be a line of metal flashing? Is this not original? It looks in decent nick (not corroded or anything, from what I can see).

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    I wouldn't be worrying too much. That damp course will be lead (most likely) and likely will last a few thousand years . . . The mortar and brickwork looks in OK condition for a house of that age - the cracks are minor and the joints are loosening as it would be a lime mortar in the humid Sydney climate. The brickwork might be damp below the DPC, but the pics seem to show OK above it. Do the checks as advise above, but my guess is it is a job of raking out and re-pointing the joints - a job that can be DIYed over time. The pic showing underfloor access door looks like there isn't a lintel bar - or it has rusted. Again not hard to replace - search for 'lintel' on the forum and there is plenty of info.
    Advice from me on this forum is general and for guidance based on information given by the member posing the question. Not to be used in place of professional advice from people appropriately qualified in the relevant field. All structural work must be approved and constructed to the BCA or other relevant standards by suitably licensed persons. The person doing the work and reading my advice accepts responsibility for ensuring the work done accords with the applicable law.

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    .... Just Nextdoor over Ryde way.

    Yes - did repointing myself using a lime putty and washed sand mix. Also went to the extent of researching and teaching myself how to do traditional tuckpointing.......that took 2 years of trial and error and trips down into the British Library in London to access some of the old texts. Kind of went a bit obsesive perfectionist on that one.......

    It is all relatvely easy stuff to do and not to be afraid of. No need to get people in to do the repointng - using the old finger trowel and some lime putty/ sand will take awhile - bit of patience needed - but good for another 50-100 years when done correctly. The cracks in the photos easy to rake out and repair. If the rest needs repointing - generally do a whole wall as it will not match the old. So you only do walls that need it. If you get someone in they will most likely go for a compo mix of sand/cement/ lime- it will crack and fail with house movement. Best to replace like with like in this case.

    Generally not much of a need to acid wash the brickwork. If you rake out and repoint using lime mortar you do not smear it on the brick faces like a sloppy cement mix. If for any reason someone touches the bricks with an acid wash it needs to be neutralised with something like soda ash ( or the old washing soda ).

    Cheers

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    Quote Originally Posted by an3_bolt View Post
    .... Just Nextdoor over Ryde way.

    Yes - did repointing myself using a lime putty and washed sand mix. Also went to the extent of researching and teaching myself how to do traditional tuckpointing.......that took 2 years of trial and error and trips down into the British Library in London to access some of the old texts. Kind of went a bit obsesive perfectionist on that one.......
    That's awesome!!! Don't suppose you'd want to tuckpoint the front facade of our place? It definitely needs redoing!!

    The North and South walls are where I'm going to have to get stuck into it. I could do the raking ok, I think - more nervous about the mix and pointing. Are there guides for the lime putty/sand mix or do you have to work it out by trial and error? I guess my issue is, I'm not sure what it should look like.

    Thanks so much for your advice everyone, feeling quite a bit less daunted!

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    The lime putty sand mix is easy - about 2 sand / 1 lime putty will give you something similar to what is existing and reasonbly solid. This is a mix by volume. Sand is washed. You can adjust the sand colour to get close to your existing if required. No need to add any water when mixing lime putty and sand - it is hard going at first but as it is thrixotropic it gets easier the more you go. A cement mixer will not do he job. Alternatively a good drill with a plaster mixer attachment does a relatively good job.

    Regarding the tuckpointing - happy to show you how to do it - it is pretty slow going- get anywhere between 2-3m2 done on a day - so it really is a labour of love - or hate depending on how much patience you have! Between my day job and trying to finish off the renovation of our place - probably don't have time to do someone elses right at this moment - but happy to show you how!

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    OK, you're on! Give me a year or two to get the repointing done first though LOL

    Thanks so much - it's so awesome to know I'm not in the trenches by myself!

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