Mould and damp meter readings - cause?

hc25036

The DS is at uni and his basement room in a shared house is very damp and mouldy. It's a long-standing problem and after the previous tenants complained the room was stripped back to bare brick, "treated" (not sure what) and replastered about 4 weeks ago. The DS moved in 2 weeks ago and the room is already significantly mouldy and damp again. The builder came back and said it was condensation due to the plaster drying out and they will install a ventilation system.

DS has used a damp meter and the results are shown on the photos here:
http://i1093.photobucket.com/albums/i436/hc25036/99%20Bens%20room/photo1_zps191a316f.png

http://i1093.photobucket.com/albums/i436/hc25036/99%20Bens%20room/photo3_zpsd6fb3880.png

The first one probably fits with condensation, and a pipe runs down the outside wall where the figures are highest. The second picture is a fireplace on a shared wall with next door and I can't see why it would be so damp just due to condensation.

Any experts on here able to advise?

ka7e

Not an expert, but a builder's wife!
I'm pretty sure the best ventilation is to open the window a crack whenever possible. Plaster will dry slowly if it's humid/damp weather so a dehumidifier and gentle heat will help. Too much heat may crack the new plaster. Pipework in or behind a wall usually keeps that are cold, so it is more prone to condensation.
Finally, damp meters are nearly always calibrated for wood which is why damp-proofing salesman love them. They always register "dampness" on plaster.

hc25036

Thanks Ka7e. I knew about damp meters, but the relative readings do have some value (btw, 30% is the highest this meter will go). Other rooms in the house read in the teens except in a couple of places where mould is in those rooms as well.
I'm no more than a vaguely informed DIYer but this house seems to be in pretty poor condition to me and the agent seems to have applied sticking plaster remedies without identifying the real problem. Next stop is going to be Environmental Health I suspect

londonlydia

I think it does take a few weeks if not months for plaster to dry out properly, so I suspect it will be the moisture eeking its way out the plaster. They probably painted it too quickly too trying to get new tenants in.

Dehumidifier? I lived in a damp room at uni and I demanded my landlord get me one. I had it on 24/7 and put up with the noise, and I was emptying it twice a day at least...but I felt better for it. Not a permanent solution but then its not your DS's house, its more about him not getting ill whilst he's there. See if their landlord will get one, or maybe buy one if it takes too long. I would also avoid putting up the charlie chaplin poster artwork as it will get damaged if placed on a damp wall....

hc25036

Very true about painting too soon - it's falling off in places. The builder reckons some kind of active ventilation kit will do the job and is about to install one. According to them, a dehumidifier will simply drag more moisture in from outside (there is a large airbrick in the outside wall). We are going to ask the agent to cover any increased electricity costs so they may balk at paying for a dehumidifier anyway.

The mould is bad - his guitar is out of its bag as the bag was covered in mould within a week of moving in!

I guess what i'm hoping for is some advice about how quickly this will resolve - it's going to be tough living there like this for more than another couple of weeks.

glubalub

I would be surprised if this was sorted out quickly and it's probably a good idea to ask the accommodation officer at the uni to find alternative accommodation. Sometimes at this stage of the semester there are vacancies in the halls if some students who had booked a place don't turn up.


As other posters have commented the damp readings are not a good indication because condensation on the walls would increase the reading by increasing the conductivity between the probes. However, condensation is often a result of poor ventilation which if there is an air brick and if it isn't blocked wouldn't seem to be the case here. Condensation will generally occur at the coldest spots where the air movement is at its lowest such as in corners and behind furniture. Getting enough moisture on a guitar case, kept at room temperature, to make it go mouldy indicates a significant problem and suggests that there may be a problem with damp in the walls and or floor.

Curing damp in a basement is a specialist job and often beyond the expertise of a general builder who tends to rely on stripping back and applying chemicals to the brickwork to try and form a barrier. If the water pressure is too high, the surface unsuitable or the joint between floor and wall is not properly detailed then the system fails and the walls absorb ground water from outside. The evaporation of this water cools the walls which in turn encourages condensation.

One of the more common ways to damp proof a basement properly is to create a drained cavity between the existing outer wall and a new inner wall. Any water that seeps in is then pumped from a sump to a drain. The inner wall is often formed of stud and plasterboard so the wall will sound hollow if tapped. There are some proprietary systems in the form of a plastic profiled sheet that will accept direct plaster so the tap test is not conclusive.

Damp and mould whilst not horribly dangerous to a healthy adult is not a good environment to be exposed to for a long time and can lead to, or aggravate respiratory problems.

All in all, probably best to visit the accommodation officer tomorrow.

hc25036

Thanks glubalub for a very helpful reply. He's got a meeting with the accommodation service next week and will show them this thread.