Pdoyle.net CSRT

Damp Problem

Thanking you in advance for this forum and would welcome any thoughts and suggestions.

Also thanking readers in advance for their patience in reading through the detail of this posting – quite a read though I have summarised quite a bit.

Three years ago a friend and I purchased a two bedroom semi detached bungalow.

Soon after purchase we noticed that the master bedroom [2 outside walls] was cooler than the other rooms and over a slightly longer period of time identified a “damp” smell as oppose to the room being cooler. We took advice from a plumber [known to us] who talked around a relatively old and decaying central heating system and that potentially the radiator in that room was the last on the circuit which may account for the cooler temperature. We also checked the pointing outside to check for any leaks not found.

We coped with this for a while but over time damp [black mould spores] appeared most obviously in two corners of the bedroom and a couple of places in the kitchen. Reading around the subject we identified symptoms of condensation. A fault with the central heating developed and we decided to take the plunge and replace the central heating throughout putting a double radiator in the bedroom. The plumber found a couple of small leaks in the pipework which were repaired or the pipes replaced. We treated the damp patches with a damp stop spray and paint and decided to install a home ventilation system which involved a powerful extractor fan essentially fitted into the ceiling in the hallway. That did initially help with condensation – water collecting on the windowsills – but on the recommended setting for optimum results created a cold draft. We then purchased a de-humidifier which we have found effective.

After all this the problem has still not gone away and there was a reoccurring damp smell in the bedroom. Most recently we found mould [dry dust spots] on the underneath of divan drawers within the double bed. The carpet is dry and there is no mould growth we can see on the carpet or back on the walls. We decided to have a look under the carpet and found the carpet and underlay to be dry. We took the carpet up last week and noticed some staining on the floor boards; almost like the appearance of a “dryer” square we could see on the floor boards directly under where the bed has been. There is the appearance of damper patches on the floorboards around the extremities of the room.

Friday of last week we took up a section of the floorboards allowing entry into the space beneath the bungalow. Essentially under the bungalow appears dry though what we have noticed on the joists under the floorboards seems to have a staining. If you can picture almost cutting the timber in half and the bottom half being a light wood and the top half closest to the floorboards being a darker shade. They appear dry to touch and there are no signs of damage to the wood, no droplets of water and no growth of mould.

Now to the point of the posting – three questions if I am allowed?

Does anyone have any experience of this?

Could anyone make a suggestion as to what they think may be causing this?

Could anyone suggest a treatment [we have chucked a lot of resource at this already!]?

Many thanks in advance and look forward to receiving any replies.

Suzanne.

Suzanne

A few questions first...

How old is the bungalow?

Do you know if it has solid walls or cavity walls. If the latter, do you have cavity wall insulation.

(If you can see the bricks, and you probably can because you mention re-pointing, are the bricks laid length-ways but with every sixth or so course laid a different way, so that they look shorter? Alternatively are they all laid end to end lengthways?) (See attached sketch)

This will determine if the wall is solid or has a cavity

Which way does the affected room face, i.e. North, south etc?

If you don't know, have a look at your house on Google Earth, the bottom of the screen is south.

Once we know this, we can have a go at the rest of it.

Thank you Patrick.

The bungalow was built in the late 1950s. It has cavity walls and we had cavity wall insulation installed just more than a year ago.

The room is south facing.

Look forward to hearing from you,

Suzanne.

This is one of those difficult situations where everything one would normally suggest has already been tried by the client, and it's probably time to go back to the basics. If you lose sight of these you could end up trying remedies that have nothing to do with the problem. The 'leaking' plumbing system being a prime example of the 'Red Herring' syndrome.

In the main there are only three forms of dampness that affect buildings: Rising Dampness, Penetrating Dampness, and that caused by condensation.

In this case I think we can pretty safely rule out the first two. The property will have been constructed and inspected in accordance with Building Regulations current in the fifties and the modern cavity fill should not allow penetrating dampness via the cavity walls. In any case, the symptoms you describe seem wholly related to condensation.

However, you are obviously aware of the dangers of this phenomenon and you seem to have done everything you can to reduce it. Unfortunately, if the symptoms of condensation are still persisting, even in this rather pleasant climate we are experiencing at the moment, your efforts have not been successful; and one can only conclude that the moisture you are producing (and apparently retaining) within the property is overwhelming your attempts to defeat the problem.

That this can occur is demonstrated by the example of the mirror in the bathroom. Sometimes, no matter how warm and well ventilated a bathroom is, when you get out of the bath you can't see yourself in the fogged up mirror; and this simply indicates that the relative humidity (rh) is so high that the surface temperature of the mirror is low enough to be below dew point temperature. This is an extreme example of course,but it demonstrates that most systems can be defeated if the conditions are right.

In your house, no matter how warm you are keeping the fabric of the building, and here I'm assuming that your loft is insulated too, the moisture inside the property is causing the rh to rise above the level where dew point occurs on affected surfaces, such as corners and sheltered furniture components.

Without actually seeing the house, and discussing in detail your life style, the only thing I can suggest is that you are ultra careful in removing moisture at source; and this means installing, and using effectively, good quality extractor fans in any of the moisture-producing areas, e.g bathroom, kitchen. The latter room should not rely on a cooker hood for ventilation as these are not only inefficient, they are seldom used as often they should be. I've never met anyone who switches one on when the washing machine or kettle are being used. They seem only to operate when the bacon is burning!

Not only should you use these devices effectively but you should make sure the doors to these rooms, and also the bedroom, are kept closed until the fans have had an opportunity to clear the air. This will help to ensure that moisture vapour cannot move easily around the house.

If, after re-appraising your situation, you are still producing mould colonies, and these colonies are the only symptoms you have, then they can be relieved by the use of fungicidal paints. If the symptoms are more serious, and decor/plaster etc is being damaged, you will need to ask someone such as myself to visit you and review the situation generally.

Sorry I cannot be more precise.

Regards

Patrick