Damp!? Condensation or penetrating??

[Dave1104]

Hi guys,

Really hoping someone will be able to shed some light on my damp problem, as I'm getting tired of cleaning up all that black mould!

I'll try and set the scene as clearly as possible:

My flat: the building was built in the 1800s but extended (upwards by about 1/2 storey) and converted in to 2 flats in '87. Solid walls, box gutter. Since moving in we've made some improvements inc.
- double glazing
- extensive insulation including lining the interior rear wall with celotex and boarding
-lining the box gutter with isoflex (pretty sure that is now water tight)

The issue: damp on the end wall, on both corners of the gable end (exposed - there is another building abutted approx 4-6ft lower down). This comes and goes, and disappears completely in summer

velux window in bathroom: perhaps a no brainer, but always has condensation on it despite me installing a more than adequate extractor with a humidity sensor. Not really an issue in summer as it's open most of the time. The pane is blown, but would replacing make a difference?

front wall: damp, and all around the front door, with the ironmongery getting dripping wet on a regular basis.

My thoughts: Could this really all be caused by condensation?? Humidity is between 50-55%, especially now as we have a dehumidifier running regularly ...BUT...

- there are 2 of us
- that flat is tiny
- ventilation isn't great
- we cook, clean, hang washing, and have an open topped aquarium
...all that bad stuff.

Any advice would be greatly appreciated, as this definitely can't be good for out health, and if I shell out on something like a MVHR system I need to know it will cure the problem!

Also thinking about removing the plaster on the end wall, treating with Thompson's water seal and lining with British Gypsum thermal board, so yeh... desperate!

A fair amount to digest I know. Thanks in advance,

Dave

 

[JohnD]

//www.diynot.com/wiki/building:condensation_in_houses

 

[Dave1104]

very prompt JohnD - and some sound advice there. I will most certainly be trying the polythene trick!

So are you suggesting it's all condensation?

Unfortunately I can't see being able to reduce the source of moisture (would if we could!), warming up the wall is the cheap(er) but messier option, and the MVHR is the expensive choice, but would it be effective??

 

[JohnD]

It might not be 100% condensation. but if you don't stop making your home wet, you will never know. No landlord or surveyor will bother looking for any alternative cause if the primary one is so obvious. Ventilate. Then ventilate some more. Make a cover for your tank. Buy a washing line or a vented tumble drier and stop draping water round the house hidden in wet washing.

Look at gutters and downpipes as well.

 

[mointainwalker]

we cook

Ideally need extraction to exterior

hang washing

, probably 1-2 litres of water even in a spun load. Whilst you are still doing this, everything else is pretty pointless and you will have to wipe mould eternally.

Either a dryer venting to outside or the launderette.

Not clear from your post if you are getting any condensation/damp on the wall lined with Celotex

 

[Dave1104]

Ok the impression I'm getting is that I have to *ventilate*!

mointain walker - no damp on the insulated walls, but it's worst on the end wall which is exposed, and (I'm guessing) there is the greatest temp difference.

Thinking about it, the place is pretty much air tight... we have the velux open almost constantly in the summer, as well as the windows most of the time, and the problem goes away completely...!

So... would say a couple of passive air vents help when we seal the place up for winter? Or would I have to do more, like a mvhr system?

Thanks again

Dave

 

[alanrammel]

I would certainly check gutters, these are often the cause of repeated damp down walls and around windows. There's a good article on clearing your gutters here. Do you have any bay windows? If the problem exists here then blocked guttering can be the culprit. Maybe you have nearby trees that shed their leaves. Failing that I would get a local damp course contractor in. They'll be able to give you a good diagnosis, however get a few quotes! In my experience it can be easy and lucrative on their part to quickly diagnose rising damp when the root of the problem might be simple extraction.

Good luck

 

[mointainwalker]

"..Ok the impression I'm getting is that I have to *ventilate*! "

I said - and think JohnD agrees -that you should stop deliberately releasing litres of water from drying washimg into the house.

This would be a good example of treating the cause rather than the symtom.

 

[JohnD]

.... Ventilate. Then ventilate some more. Make a cover for your tank. Buy a washing line or a vented tumble drier and stop draping water round the house hidden in wet washing.

Look at gutters and downpipes as well.

 

[JohnD]

am I too slow?

or has he got a time machine?

 

[Dave1104]

Thanks guys,

alanrammel - sound advice but I'm afraid that's all covered - it's a first floor flat with clear gutters at the front and a sound box gutter on the back (or so I think... no evidence of damp on the box that I can see from inside, felt was old and a bit leaky but we treated that last summer). That and I'm in no position to pay anyone to do anything at the moment!

John D and mointainwalker - OK ventilate and stop making the place damp... sounds fairly simple when you put it that way! Although saying that, I'm staring at an airer full of washing as I'm typing...

Might be time to start using the dryer bit of my washer/dryer...

 

[alittlerespect]

Hi

My advice would be for you to start using the washer/dryer. The issue you have is with condensation and the dehumidifier can only do so much the real problem however is condensation caused through the temperature differential between surfaces i.e. your air humidity may be around 50% at say 20C, but when the air hits a cooler surface it reaches saturation point which is clearly evident by the problems that you are encountering.

If you indeed have a 'velux' window in the bathroom, this manufacturers opening lights have a trickle ventilation function, you just pull the opening handle back one notch without opening the window. Opening the trickle vent and leaving it open should improve conditions! You will also find that velux windows are double glazed units and it really depends on whether or not you can live with the condensation that may form in the air gap between the panes of glass.

One final comment: Passive air vents aren't going to be a solution to your problem, ideally what you need to do is clad all the walls with an insulated plasterboard in order to retain the heat within the wall surface and thereby avoid the temperature differentials that are causing the condensation. Even a relatively thin panel say 25mm PIR insulation with 12.5mm plasterboard finish would make a difference.

The other option would be to spend a relative fortune on heating the flat to the extent that the temperature of the surface of the walls are maintained above dew point, however, this would not get rid of interstitial condensation you would also need to maintain these conditions 24/7 during winter months, otherwise as soon as the walls cool down your condensation problem will be back to haunt you! Use your ironmongery as a barometer to know when conditions are right.

If you go for some additional heating go for radiant heaters as the radiant heat is not affected by air movement.

Regards

 

[Dave1104]

Just had a damp proofing company round for a survey - and the guy was stumped! He said there seemed to be too much damp for it to be condensation, even though those are the cold walls, and suggested I try a roofing company to see if they could identify any problems with the roof.

Still doesn't explain the random patches I have below my living room window... buy hey ho, might as well see what someone has to say on the roof!

P.S. alittlerespect - just figured that out about the velux - doy!