Damp

[hariba]

Hi everyone,

I’d like a bit of advice about damp. The house is an old (1800’s) end terraced house.

My tenant told me this time last year that she was experiencing mould patches on the walls upstairs. I had a look and thought it to be caused by poor ventilation etc and advised her that it needed cleaning off and to open the windows on a regular basis. She told me at the time that that had rectified the problem. She has now, almost 1 year on, told me that the mould issues continue to be a problem and is saying that the problem never really went away and after cleaning off, it comes back again within 2 weeks. I have tried to explain to her that houses need adequate ventilation but she is adamant that there is a damp problem.

When I bought the house I did have the chemical injections in the brick work downstairs as the survey picked up some damp. This mould issue is in the 2 upsets bedrooms - it’s the outside walls of the house but internally where the mould is. My first thought is the roof or guttering. The roof was replaced about 5 years ago and is a slate roof. As it’s in 2 rooms, I think it’s unlikely to be the roof as that would mean a problem in 2 places in a relatively new roof. I have now called a roofer out to have a look and this is someone I’ve used before and trust, but he’s unable to go for a couple of weeks due to workload (meanwhile the tenant is unhappy that I’ve not arranged for someone to go straight away). I am reluctant to call out a damp specialist as I’m worried that they will absolutely ‘find’ an issue that may not be there. But I also do not want to leave my property with a potential damp problem.

I wondered if anyone could give any advice as I’m sure many of you will have dealt with damp problems. Thanks

[Berlingogirl]

I insulate external walls with that insulation on a roll that you put up like wallpaper (sorry I can't remember the name off hand) and find that does the trick. In my own house which is old, I keep the bedroom window open almost 24 hours a day but still have black mold grow between the wardrobe and external wall where the air doesn't circulate.

[boletus]

Assuming everything structural is in order I'd recommend fitting an envirovent/nuaire PIV type system. Worked every time for me.

[jpkeates]

My son's property has issues with mould and it starts at this time every year.
This year we decided to "sort it out once and for all" and got in a specialist.

If the problem is water coming in from outside, you'll notice damp patches and flaking paint and plaster, but there won't be any mould.
Any water that starts off as rain and penetrates brickwork is too acid to allow mould to form.
You might get a bit of mould eventually, but by then the property will be a real mess.

The mould will form wherever it's coldest in a room or where any condensation will pool and comes from damp caused by water that starts off inside the property and has been neutralised by being evaporated and is therefore perfect for mould.

The options are ventilating the property regularly (which costs the tenants in reheating the property), additional vents (which costs the tenants in reheating the property and make a noise), a complete PIV system (which costs the tenants in reheating the property) or a lifestyle change, with fewer showers and baths, no drying clothes indoors (which no one will admit to - including my son) and fewer boiling pans and kettles.

It's so obviously a lifestyle issue (although older properties simply aren't designed to cope with modern lifestyles), I'd suggest that you explain to the tenant that there's nothing wrong with the property, it's a lifestyle issue (ask them how they currently remove the moisture that they bring into the property*) and that, if they won't accept that, they can leave.

Or install a PIV system and let them complain about the cost of heating.

*A human being breathes out about 1/3 of a litre of water per day as they breathe, every shower generates steam which stays in the air, when wet clothing dries indoors the water goes into the atmosphere (not away). People struggle to understand this.

My son religiously wiped any damp surfaces every morning with a towel, which he then hung up to dry. Almost like recycling!

[hariba]

Thanks for the comments - hadn’t heard of a PIV system so useful to know.

jpkeates - I’m so glad you posted with your experience. I will get the external area checked as planned.....but I strongly believe it is a condensation issue. And tenants will never accept this and always think there’s a problem with a house. There is no window in the bathroom unfortunately but when I had the bathroom fitted out, they put an extractor fan in that vents up into the loft and out through the roof. This is probably not ideal for condensation build up but no other option without a window in there. The difficulty now (assuming nothing structural is picked up) will be getting the tenant to accept that she is actually the cause of it!

[leaseholder64]

The reason that rain is unlikely to cause mould is that it is intermittent. Mould can be caused by rising and penetrating damp. Plaster is very alkaline, so I doubt that the water getting through it will still be acid.

[AlexR]

Hi everyone,

The house is an old (1800’s) end terraced house............ mould patches on the walls upstairs

I did have the chemical injections in the brick work downstairs as the survey picked up some damp. This mould issue is in the 2 upsets bedrooms - it’s the outside walls of the house but internally where the mould is

I am reluctant to call out a damp specialist as I’m worried that they will absolutely ‘find’ an issue that may not be there

Your instincts are correct in that it won't be the DPC - you need to look at roof,chimney flashings,gutters and the gable end wall. I owned an end terrace house with a similar problem with tenants complaining about mould growing on clothes, walls etc and black patches on the walls.

The first thing is to look at the house carefully when it rains hard. Can you see any broken drains or water falling on brickwork? Is the end wall rendered - if so you may have cracks high up and water flowing down the inside of the cladding into the house. Or the wall may have lost its pointing . You have said that the damp appears against the outside wall so this is a likely problem area. If the damp is on the chimney wall then it could be the chimney flashing at fault.

In my house I re-rendered the end wall, replaced gutters all round and replaced chimney flashings and the problem disappeared. It took several months to dry out.

[jpkeates]

The reason that rain is unlikely to cause mould is that it is intermittent. Mould can be caused by rising and penetrating damp. Plaster is very alkaline, so I doubt that the water getting through it will still be acid.

I made a mistake in my post, mortar is also alkaline, I meant to say that the acid balance (the Ph level) is wrong for mould, but I got carried away.

Mould needs neutral water, so if the plaster is alkaline water coming through it won't support mould. Water condensing on a surface will.

No one has been able to show that there's such a thing as rising damp - there's almost no capillary action in bricks and mortar to wick the water up.
If you stand a brick "wall" in a pool of water, the damp doesn't rise.

Penetrating damp is an issue, particularly, as is leaking pipes. but (again) it's normally not a cause of mould; that might happen later if you don't fix it, because the more moisture coming in, the more moisture in the air. But anything that penetrates through mortar, brick or plaster is more likely to kill mould.

[hariba]

AlexR - good points, as yes it is rendered - again that was re done around 5/6 years ago but worth rechecking to see if there’s any cracks. And yes it is the chimney wall. The chimney is in the middle of the wall and the mould patches are on the 2 opposite ends. The wallpaper is the anaglypta type so the mould looks to be behind it in 1 room but showing through and on top in the other room. I’m going to try and attach 2 photos.

My my main concern is that the tenant won’t accept it’s condensation. And then you end up trying to justify it. If I bring in a damp specialist I am sure they will find thousands of pounds worth of work to ‘fix’ the problem but I don’t think the tenant will accept my word for it.

[leaseholder64]

If there is no such thing as rising damp, damp proof courses are a con, and the long multithread on the building without one is based on a false premise.

A very long time ago, I was in a seaside basement flat where a spare room had serious mould problems, because it was below ground and sea level.

[mariner]

Injectable DPC may last only 10 years or may have been 'bridged?
My builder prefers to 'chase out. the morter and insert a roof tile barrier.
Try fitting a pot chimney cowl to lessen amount of rain entering the chimney.
Many Victorian propeties may only be 'single skin', prone to conensation, so internal thermal insulation may be required.
I suggest a full external examination, as external mortar can crack over time.

[AlexR]

My my main concern is that the tenant won’t accept it’s condensation

Because you tried that last year and its back again! Unfortunately there is no one 'expert' who can help - they only deal with their own area of specialisation. You need to look at the whole picture yourself and take a view.

I had damp issues in many Victorian terraced houses and each case was solved by dealing with faulty chimney flashings,blocked or broken drainpipes and gutters and in one case faulty rendering.

[AlexR]

If there is no such thing as rising damp, damp proof courses are a con, and the long multithread on the building without one is based on a false premise..

There is a book called 'The Rising Damp Myth' by Jeff Howell in which he argues the case very convincingly

[nukecad]

Those photos don't look like a condensation problem.
I'd expect condensation on large flat surfaces rather than in the corners.

[OneSmallStep]

Unfortunately, some tenants do not understand how condensation is formed and how they are creating it. They see wet walls and automatically assume it is water coming in from outside. Obviously, in some cases it is a failing in the building structure or a simple fix like a blocked or faulty gutter.

However, this time of year and the location of the mould would indicate a condensation issue. (bottom corners of external walls are prime locations)

I understand you have a fan in the bathroom, don't take this the wrong way, but is it a good fan? a £10 Timer model just doesn't cut it to adequately ventilate a bathroom. To improve the condensation issue you should install a constant running fan in the bathroom with humidistat override. Circa £100-£150 plus install.
Also, if possible install a constant running fan in the kitchen, again with humidistat override.

Finally, a PIV on the landing. This will force air changes throughout the property and dilute the moisture laden air.

All the above have very low running costs. You can also programme them to let you know if the Tenant turns them off. (they think they cost a fortune to run, but actually the running cost is very low.)

In addition, some people assume that as the air changes it costs more to heat the building. It is actually cheaper to heat dry air that does not contain moisture,

Almost immediately you will notice a difference in the air quality. 2-3 weeks the walls will dry out. They will have to wash the walls with a mild bleach solution.