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Damp Proofing

Mould and wet cold walls

My husband and I own a ground floor 2 bed flat in a Victorian conversion. Our last two sets of tenants have found their clothes and shoes covered in mould . We got 2 damp specialists: One advising to put mechanical vents, no mention of rising damp. The other one found rising damp in the bedrooms and in a small section of the kitchen. So advised to get rid of the 2 built in wardrobe and do a dpc course. Also, mentioned that the single glazed windows weren't helping in keeping the place warm and was contributing to condensation. We removed the built-in wardrobes, so also had to re-carpet and paint. Put new double glazing windows, All of these within a month of being notified by the tenants of the problem! The job above was done between Nov 2021 and December 2021. So in March we paid an independent surveyor to inspect the property in and out. The first thing he said that we didn't need to replace the windows! Found that the vent in the bathroom was not extracting enough (no window) and thought that it was not extracting out but just into the internal wall. The solution was to get a new inline ceiling fan with a humidistat which would need to be ducted through the rear bedroom and out of the rear wall. Found that the kitchen was not ventilated enough and so the bedrooms. Also, said that the external rendered black plinth was serving no useful purpose and so to remove it. The rendered plinth was bridging the physical damp proof course and was causing moisture to bridge the existing dpc. So great, we have a true independent surveyor who is not try to sell any products. In April my tenants serve their notice to leave. We want to get the flat sorted for good and before the new tenants move in as we do not want to go through this nightmare again. We got the contractor to carry out all that was recommended in the surveyor's report. He looked at where the fan in the bathroom was extracting to and if it was indeed extracting into an internal wall. He was certain that the current fan was extracting out so he had to lift the carpet and floorboards in the bedroom to see if there was a connection to pull the air out... yes, the fan was ducted all across the bedroom and out through the brick vent of the external wall. We got a better vent. He removed the rendered plinth, installed a passive vent in each bedroom and a kair heat recovery ventilator K-HRV150 in the kitchen. All as recommended by the surveyor. Job finished and we have new tenants moving. I made them aware of what issues we had but we had done all the work and feel confident the problem is sorted. They move into the property in May and 3 weeks ago whilst I was at their flat to collect some mail I decided to check on the walls and they were covered in mould! The 2 walls where the mould is growing are cold and wet. These are external walls but there is no sign of water ingress. Before doing the dpc, should these walls be insulated, if so how? Thank you.

2 Answers from MyBuilder Damp Proofing Specialists

Best Answer

Your independent surveyor gave you instructions exactly as I would have .
Firstly I’d check that the HRV is actually on or set to the correct humidity.
You probably don’t have rising damp , it’s extremely rare and destructive, you don’t need a damp meter to find it !
Wet walls, mould and mildew are from internal high RH , not damp .
For some reason you’re still suffering poor air exchange.


Answered 21st Nov 2021

i am presuming it is a solid brick building built with lime mortar this allows the building to breathe if it has been re pointed or rendered with cement or plastered with gypsum plaster this will stop it breathing creating dampness,
bricks are porous not water proof, without looking at the flat in question its really impossible to say exactly what is happening but so far you have done everything you should not do to a solid brick building what you want is someone who specialists in older property, who can explain how all the materials used in the construction of your property work together to keep it water tight and dry,
insulation is only covering up the issue not solving it.
go onto the rising damp myth, or heritage property site to understand more about your property,

good luck Alex


Answered 5th Nov 2021

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