damp problem - what's the cause?

[benpost]

hi, just moved into my 2 bed ground floor maisonette. however it has problems with damp, which i can't find the cause. the signs are black mould spots appearing on the walls (mostly outside walls) and in the bathroom (not an outside wall). it has double glazing and i can put windows on the latch setting. when i first enquired about the problem i was advised it was just condensation (this was just phone advice though).

my dad thinks it might be a problem with the roof as the tiles dont overhang the roof on part of it. also the porch area which has bad damp and the inside of the door gets dripping wet. the porch might need re felting possibly? also is it worth checking out the guttering?

am i right in saying the roof and guttering would be the upstairs flats responsibility, if it is the cause? any advice would be appreciated. thanks

[ac1951]

If the maisonettes are rented then it's the responsibility of the landlord. If you own the properties then I think you have joint responsibility for the roofing. When it comes to roofing I would get some quotes/advice from reputable builders. Show them what's happened and let them advice you, then compare what they say. This will give you a basis for going forward without committing any expence.

You should also check the outside ground level and make sure no-one has raised the level above the damp proof (built a patio etc).

[mail]

Dear Benpost [?} On the balance of probability it is condensation and the mould will be Aspergillus niger The likeliness of it being either damp from the roof or a bridged DPC will be remote but it would be sensible to check by visual assessment Whoever is responsible will be determined by the facts Landlord if rented! as determined by the rental agreement Landlord if leased! but under the terms of the lease Who is the landlord, if it is leased, could be you as shareholder of a Ltd company or any other You need to read the contract for your tenure!

Condensation is caused mainly by lifestyle and can be fixed by changing a whole variety of factors which can be looked up in Google Chris

[Stuart Noble]

You'll probably get loads of advice, and mine would be, firstly, not to pay for any of it. There's really no substitute for observing the symptoms yourself over a 12 month period and using a bit of commonsense. If things generally get better over the summer, condensation would be the likely cause, certainly in the bathroom. If they get worse again after summer rain, you might suspect penetrating damp. That being the case, it's likely to affect the walls that face south or south west because that's where our rain blows from most of the time.

That might be an issue if rain came straight down in an orderly fashion. Looking outside now, it's hitting my gable end wall almost horizontally. My roof tiles don't overhang by more than a couple of inches, which seems to be the norm round here.

also the porch area which has bad

I'd certainly try and strike up a working relationship with your upstairs neighbour at the outset. Hopefully there is already an agreement about who's responsible for what. At least you'll be able to see if they're suffering the same symptoms.

[dg]

Black mould is indicative of a condensation issue, and will appear on the coldest surfaces - typically exterior walls.

People generally think that just because they have double glazing, then condensation does not exist - because it does not show on the glass. But the humidity is still there and it condenses on the coolest surfaces - not the glass but the walls.

Just opening the window is not the answer. You have to get the balance of heating and ventilation, and try to remove all damp air from the property (cooking, bathing, clothes drying) and not let it travel around the flat.

It will take a good few months to balance the internal air. In the meantime you should clear any mould with a fungicidal wash.

If these walls are north facing or otherwise are predominantly in the shade all day, then they will be more prone to condensation.

With regards to the roof and guttering, these are not the responsibility of the person upstairs. You are in a communal block and pay a service charge for the upkeep of communal parts. If there is a problem with the external structure, then you should contact your landlord or service agent. You will pay for any external repairs on a pro-rata basis with the other leaseholders. Check your lease.

dg

[The Natural Philosopher]

Indeed, fitting DG without insulating walls ought to be a criminal offence.

Seen this so often. the old windows were draughty and kept the place dry, and ran with water which you simply took as a sign they needed opening.

With DG all that condenses on the walls. Result is mould,

All gooid advice.

[robgraham]

What hasn't been asked is what age of property ? My own experience might help to explain but won't necessarily help to cure if you aren't the owner.

I bought 30 years ago an old stone cottage - it had been dry lined in the 1920's (lathe and plaster), and it had also had properly suspended wooden floors fitted. With the logic available at the time, they vented the under floor ventilation up the dry lining. There was therefore zero insulation in the house and the bedrooms were a disaster for black mould as the warm air carried moisture from the living area and it condensed on the freezing cold walls, particularly the north ones. Heating the place was a headache, but we were young and just put on more jumpers !

The solution was to strip off all the lathe and plaster, add insulation and a dpm and re-dryline. Problem totally solved and comfort.

If it is an older property, then of course the double glazing compounds the problem by eliminating some of the air leakage that occurred in older windows - ie draughts !!

Rob

[benpost]

hi again, thanks for the responses so far. i have owned this maisonette for just over a year. it is part of a block of 4, 2 upstairs and 2 downstairs. there were signs of a problem when i bought it as there are air vents installed in the living room and bedrooms which are both on the outside wall side. there are fans on the walls where the vents are i presume to improve airflow. the property is about 25-30 years old. it is double glazed, i'm not sure how long ago the double glazing was installed, it was there when i bought the place. i have also checked and found that the outside wall is north facing. so all the facts so far point to condensation which is being attracted to the cold north facing wall and over a short time is causing these black mould spots to appear? i had rented the property out until now (moved in a few days ago). i was going to contact a professional company in the yellow pages as i was thinking the problem was more than just condensation but maybe it is not. i guess i should clean the walls properly and try and be as careful as i can to cut down on the condensation? if i am right, can anybody advise ways of cutting down the condensation? i always have 1 hot shower a day and i have to dry clothes near a radiator as i dont have a dryer ( i could get one if it would make a difference? ) there is a window in the kitchen for a dryer outlet or what about a condensing dryer? the cooker does not have a top so the steam is just going in the air if i use the hob. maybe this is another thing i could do and get one with extractor fan? well i hope to hear from you all again soon. thanks for information so far. ben

[mail]

Your life habits are a classic for condensation Read up on it on the internet Chris

[Stuart Noble]

It's a question of getting the heating/ventilation balance right. Vents in bedrooms and living rooms shouldn't be necessary if the place is properly heated and you open windows now and again. Ideally the rads should be on the outside walls. Showering and cooking shouldn't be that much of a problem, but soggy washing hanging about the place will be. If there's nowhere outside to hang it, a dryer would be a good idea.

[Pete C]

Hi,

Try a dehumidifier.

cheers, Pete.

[mail]

Dos and Don'ts

DO open the window at night such as to allow the 1.5 L per person H20 produced to go out use dry heating electric or gas not parafin heaters or calour gas heaters Turn the heat down once the cooking pan is at boiling point as more heat will only evaporate the water Use microwaves rather than boiling hang out washing to dry outside or in a ventilated open windowed space try to keep the walls dewpoint high by having them dry and hot - can perhaps put a lining on to check condensation can put on special anti mounld paint but this is not a cure of the cause only the symptom LOOK it up on the interet and work it out for yourself!

DO NOT Cook without lids on pans of boiling water dry washing inside on radiators seal all the windows - have tricle vents have the room temp too high relative to the outside allow any source of moisture to accumulate eg leave bath full of washing or in have large quantities of transpiring house plants Chris

[Maris]

I suspect, as nearly always in these cases, you have hard rendered walls with no breathability and with a surface temperature that attracts condensation. Best solution would be to hack of the hard render and replace with a lightweight plaster.

Maris

[Stuart Noble]

That'll be a nice little job for the weekend

[benpost]

thanks again for the replies. i suspect that the porch area is causing a problem, the walls and inside of the front door get wet, i think it may need re felting. maybe this could be causing a lot of damp to enter the flat and its moving to the other walls. the walls are brick and plaster, i'm not sure what type of plaster is there any way i can find out. seems like a big job to hack off and replaster!

radiators are not on the worst affected walls but the pipes are actually around the bottom of these walls so i guess they could be moved? what i am going to do is make sure the porch roof is sealed first and clean the existing mould, then see how i get on and see if the mould returns. i am leaving the smaller top windows on the latches permanently so there is always an escape for damp air. i have a small dehmidifier but it was only a =A320 one might give that a go too.

thanks again for replies

[Stuart Noble]

A big and a very dusty job!

Solid floors then? The pipes themselves will probably give enough heat, so I wouldn't bother moving them.

what i am going to do is make sure the porch roof is sealed

[Maris]

Rendered walls are generally very difficult to drive nails into. Usually need to use masonry nails.

Maris

[Appin]

The message

from [e-mail] contains these words:

Don't just TRY one -- buy a decent one with a built-in heater. And run it continuously for a week or two.

And before you eevn get that get a hygrometer and check your relative humidity. You're aiming to keep it between 40% and 60%. Over 80% and you've got real problems.

Buy pans with lids which have steam vents in them. That cuts down the steam enormously, strange though it may seem.

All valid points.

See above

Fair point, though dehumidifier works better at higher room temperatures.

[Appin]

The message

from benpost contains these words:

Think more in terms of spending £300 on a decent one. You won't regret it.

[Stuart Noble]

If you can find somewhere to put it