Remember mould behind bed in the bedroom?

[Howie]

Hi all. Originally, I had a problem with mould (caused by condensation hitting an outside wall) behind my bed in a modern house.

I have today discovered that, - contrary to my original belief, the wall in question is _actually_ a cavity wall!

The wall is the whole side of the house and is of concrete-block construction, rendered on the outside. The house is built into a hillside and can be seen here:-

I am still having a great deal of trouble with mould, - now apparent in both upstairs rooms against this wall. Also, inside the house the wall itself is very cold to the touch.

Can anyone tell me... is there an effective way to cavity-fill the wall, - and will this help cure my mould/condensation problem inside the house?

Appreciate all help offered....

H.

[Set Square]

Nice picture - but a bit more jpeg compression would have been good!

When you say that the house is built into the hillside, are you saying that there is soil in contact with the walls *above* the DPC? If so, the outer layer of blocks is going to absorb water from the soil, and it only takes a bit of mortar on the occasional tie to make a bridge to bring it to the inner layer.

You need first to address these issues to stop the water getting in. Then - and only then - will cavity wall insulation help to keep the inner layer warm. If you install it before curing the damp, it will make the damp worse!

[Peter Parry]

You appear to have double glazed windows and no ventilators. The first priority should be effective ventilation - without this no other solution will be particularly effective.

The mould is growing where moist air is condensing, having a cavity wall will reduce but not eliminate this. It will occur usually on the east side, or on exposed corners, or anywhere else the wall temperature can be a touch below everywhere else. Places where air is trapped (built in wardrobes, behind wardrobes, behind bed heads, anything against a wall) are particularly prone to condensation.

Anything which puts a lot of moisture into the atmosphere will make it much worse (showers in rooms where there is no ventilation or it doesn't run on for at least an hour after the shower, drying clothes, cooking) as will backing off the heating as you go out in the morning after all having showered. Closing bedroom doors is another dreadful thing - each person looses about a pint of water overnight in the form of vapour. Leaving bedrooms closed and unventilated invites mould growth.

The priority must be on getting rid of the moisture before indulging in other solutions. Try a medium sized dehumidifier running all day (they are usually too noisy to run all night) near the problem areas for a start. Invest in a whole house ventilation system before cavity insulation.

[Capitol]

Nice picture. Is the room in question the bit on the left with the ivy growing over it? Is there a flat roof? Was it an extension? If the answer to these questions is yes, then I'd grit my teeth and excavate the hillside so that I could get at the outside of the wall, strip the rendering if present, replace the rendering with a waterproofing additive and give it 3 coats of bitumen. Yuk! ( I'd also replace the flat roof with a pitched one) There is also the nasty thought that the extension has bridged the cavity of the main wall. Happy New Year? Regards Capitol

[Mary Fisher]

tarmac and other houses! Huge pictures like yours take a l-o-n-g time to load.

We had rockwool cavity wall insulation installed some years ago. We hadn't had a damp problem before this but afterwards the house had a more even temperature and we noticed that the windows were showing more condensation than before, presumably because the walls were then less cold than the glass (double glazed).

In case what I said is misinterpreted, we haven't had a damp problem since either. The house is a 1937 brick built semi.

Mary

[The Natural Philosopher]

And THEN put in 4-6" of plystyrene sheet OUTSIDE the house before backfilling with gravel, and then replacing topsoil.

I saw a cellared house being built in germany,. The whole underground section was surronded by insulation - possibley to protect against soil moivement, but certainly to keep it warm.

[Howie]

|Nice picture - but a bit more jpeg compression would have been good!

I know. - Sorry. I forget that most people don't have broadband! This is how the picture was taken and stored on my hard disk :-0

|When you say that the house is built into the hillside, are you saying that |there is soil in contact with the walls *above* the DPC?

No. It's not a rising damp problem. It's definately a condensation/mould problem.

| If so, the outer |layer of blocks is going to absorb water from the soil, and it only takes a |bit of mortar on the occasional tie to make a bridge to bring it to the |inner layer. | |You need first to address these issues to stop the water getting in. Then - |and only then - will cavity wall insulation help to keep the inner layer |warm. If you install it before curing the damp, it will make the damp worse!

Definately not water getting in. But, thanks.

[Howie]

|You appear to have double glazed windows and no ventilators. The |first priority should be effective ventilation - without this no |other solution will be particularly effective.

Sinc my original question a few weeks ago, I have been opening all the windows in the bedrooms during the day and been running the heating for an hour or so twice a day. This should be more than enough to make up for a lack of trickle vents (I was told),

- until I have time to fit some.

|The mould is growing where moist air is condensing, having a cavity |wall will reduce but not eliminate this. It will occur usually on |the east side, or on exposed corners, or anywhere else the wall |temperature can be a touch below everywhere else. Places where air is |trapped (built in wardrobes, behind wardrobes, behind bed heads, |anything against a wall) are particularly prone to condensation.

Yep. This is exactly what is happening. Mould behind furniture and in the corners higher up. | |Anything which puts a lot of moisture into the atmosphere will make |it much worse (showers in rooms where there is no ventilation or it |doesn't run on for at least an hour after the shower, drying clothes, |cooking) as will backing off the heating as you go out in the morning |after all having showered. Closing bedroom doors is another dreadful |thing - each person looses about a pint of water overnight in the |form of vapour. Leaving bedrooms closed and unventilated invites |mould growth.

I've eliminated those issues - I'm sure (see previous reply). However, the problem is still there after 6 weeks of open windows and heated bedrooms. I must point out that I have never actually seen or felt condensation on the walls. But the mould is growing :-0

|The priority must be on getting rid of the moisture before indulging |in other solutions. Try a medium sized dehumidifier running all day |(they are usually too noisy to run all night) near the problem areas |for a start. Invest in a whole house ventilation system before |cavity insulation.

OK. But I must say that the wall is _SO_ cold to the touch that I can't see how moisture can leave it alone! I am convinced that cavitly-filling is unavoidable, - eventually. However, I know nothing of the process or costs. Anyone have this info?

H.

[Howie]

|Nice picture. Is the room in question the bit on the left with the ivy |growing over it?

Ah, I see what you mean. It's an optical illusion. The ivy-covered wall is in the garden - not joined to the house wall at all! Between this and the house is a set of concrete steps all up the side of the property.

| Is there a flat roof?

No.

| Was it an extension?

No. The exterior of the house has had no modifications at all.

|If the answer to |these questions is yes, then I'd grit my teeth and excavate the hillside so |that I could get at the outside of the wall, strip the rendering if present, |replace the rendering with a waterproofing additive and give it 3 coats of |bitumen. Yuk!

Glad I don't have to do that then!

|( I'd also replace the flat roof with a pitched one) There is also the |nasty thought that the extension has bridged the cavity of the main wall.

At least your reply has made me feel a bit better. At least because I don't have to go to those lengths!

Thanks.

[Howie]

|Why on Earth didn't you crop that picture - we don't need all those trees, |tarmac and other houses! Huge pictures like yours take a l-o-n-g time to |load.

Yes, yes. I know. Sorry.

|We had rockwool cavity wall insulation installed some years ago. We hadn't |had a damp problem before this but afterwards the house had a more even |temperature and we noticed that the windows were showing more condensation |than before, presumably because the walls were then less cold than the glass |(double glazed). | |In case what I said is misinterpreted, we haven't had a damp problem since |either. The house is a 1937 brick built semi. | Thanks Mary. Looks like this is the answer. Is it a messy or very costly process?

H.

[Tim Hardisty]

We are having our 4 bed detached house done shortly, using the British Gas Offer. This is still running (until Jan 9th, the website says

It is costing us 200 GBP and, they say, will take about half a day to do.

The process is to drill 1" holes every 1.25m in the external walls, in a staggered pattern, and then for them to force rockwool bits into the cavity under pressure. They then make good the holes. I am expecting a polka dot effect :-)

In your case, if the offending wall cannot be accessed from outside then I imagine the holes would have to be made inside, meaning more mess and more involved making good. This would probably exclude it from the BG offer.

(As an aside, I am intrigued how a cavity wall could be as cold as you suggest yours is unless there's one heck of a draught in the cavity. Cavity walls have a reasonable U value to start with IIRC)

HTH.

Tim Hardisty. Remove HAT before replying

[BillR]

I had my house insulated under the same scheme. They won't do any walls that aren't easily accessible from the outside. Full cost for 4 bed detached house now is >£600.

What the OP has not shown us is the back of the house. If the outside wall is indeed in contact with the hillside and has not been tanked properly (or the tanking has failed) then that is where the problem lies...If so, expensive to put right. There was such a situation on Property Ladder not long ago and they ended up with a spring in the middle of the lounge floor.

[Mary Fisher]

|

Not at all messy. The Big Van stays in the street, it's a bit noisy and rumbly while the motor blows the stuff through holes pre-drilled at intervals by the contractor. There was absolutely no mess. Ours took a couple of hours I think, not much more. The holes were made good, we didn't think it was expensive as a long term insulation project.

I'd advise against taking a huge amount of notice of tempting information about how much you'll save in fuel, that depends on many variables. The overall comfort in our house, a more even temperature throughout the house with no cold patches, made it worthwhile without thinking of how much fuel we might or might not have saved.

Although I do hope that, on environmental grounds, we're not burning as much gas ...

Mary

[Mary Fisher]

You won't notice it unless you look hard. Our pointing is red mastic, they used regular mortar to make good. I thought it would be obvious but it isn't.

Mary

[Pete C]

Hi,

Is the render porous in any way? Any rain landing on a wall in that situation (surrounded by trees and sheltered by a hill) is not going to dry off quickly, and will soak into the render given the chance.

Something else to consider is that a wall has a high thermal mass so will remain cold for some time after the heating has switched on, especially if it is damp. Heating the house for short periods could make the problem worse as it will allow moisture removed from elsewhere in the house to condense on the walls before they have a chance to warm up.

A better way might be to continiously heat the rooms with sufficient background heat, leaving the doors partly open so the warm damp air can find it's way out of the room. Or, use a dehumidifier.

Mould also tends to thrive where there is a lack of air movement, so moving furniture away from outside walls will help. Even a few tube heaters below problem areas will greatly help air circulation.

I'd expect the same house in an open situation would not suffer damp problems, the developer probably used a standard design without tailoring it to the surroundings. Your roof looks like it has some moss on the top which indicates how damp the surrounding environment is.

Looks like cavity wall insulation could be the way to go, it will make the rooms easier and cheaper to heat too, but it might be worth consulting an expert on damp to get their opinion.

Anyway sorry for rambling on, hope this helps in some way, Pete

[Howie]

|I had my house insulated under the same scheme. They won't do any walls that |aren't easily accessible from the outside. |Full cost for 4 bed detached house now is >£600. | |What the OP has not shown us is the back of the house. |If the outside wall is indeed in contact with the hillside and has not been |tanked properly (or the tanking has failed) then that is where the problem |lies...If so, expensive to put right. |There was such a situation on Property Ladder not long ago and they ended up |with a spring in the middle of the lounge floor. | Hi,

Sorry, not familiar with the term 'tanking'. Could you explain what this is please? However, I am fairly sure that the rear of the house is fine. Also, it's 10 metres away from my furthermost mould problem! FYI, the rear is only one-story high because of the hillside. There is a utility room at underground level inside at the rear, and although parts of these walls below ground (huge exterior concrete blocks set on cast-concrete) are showing some dampness from the hillside, the room itself it's quite dry and well ventilated with eight (yes - eight) brick vents all around. Strangely though - the rear wall above ground level seems to be of timber construction with tile cladding over the top. Similar in looks to the picture of the front of the house. Sounds hollow (like a stud wall) when I knock on it from inside.

I have another (large, uncropped, and therefore downoad-time consuming) view of the rear of the property here:

these images are big - but I have piccies of the whole house stored in my web directory if you're REALLY bored you can look over the whole property inside and out!

Thinking about it, I suppose that the moisture inside the house could be higher than normal because of the hillside effectively evaporating run-off water through my rear 'foundation walls'. This could be adding to the condensation/mould problem. However, the house certainly does not feel damp anywhere, the walls are not wet to the touch and the mould itself is only really evident in the bedrooms - against my problematic outside side wall. The only place I can actually see and touch condensation is on the bedroom windows, - when I forget to open them!

Thanks again.

Howard.

[Howie]

| |Hi, | |Is the render porous in any way? Any rain landing on a wall in that |situation (surrounded by trees and sheltered by a hill) is not going |to dry off quickly, and will soak into the render given the chance.

I'm sure the render is fine. I drilled holes through it for aerial cables a few weeks ago and it was like reinforced concrete to drill through! Also, the drill-dust was very fine and very dry. The exterior paint is in A1 condition on top of the render. It all looks very new still (the house is only 35 years old).

|Something else to consider is that a wall has a high thermal mass so |will remain cold for some time after the heating has switched on, |especially if it is damp. Heating the house for short periods could |make the problem worse as it will allow moisture removed from |elsewhere in the house to condense on the walls before they have a |chance to warm up.

Ahh. This could be a contributor then. I hate Central Heating at the best of times and two hours a day is about all I can stand! | |A better way might be to continiously heat the rooms with sufficient |background heat, leaving the doors partly open so the warm damp air |can find it's way out of the room. Or, use a dehumidifier. | |Mould also tends to thrive where there is a lack of air movement, so |moving furniture away from outside walls will help. Even a few tube |heaters below problem areas will greatly help air circulation.

I will have a look at this as well, - in that case. | |I'd expect the same house in an open situation would not suffer damp |problems, the developer probably used a standard design without |tailoring it to the surroundings. Your roof looks like it has some |moss on the top which indicates how damp the surrounding environment |is.

True. In the winter this is obviously the case. Although, this _is_ a south-facing house in 'sunny' Devon, and I'm told by the neighbours that it's almost unbearable in Summer unless the front blinds are closed! I'm expecting to make good use of the terrace (shown on the picture mentioned earlier), throughout the spring, summer AND autumn!

|Looks like cavity wall insulation could be the way to go, it will make |the rooms easier and cheaper to heat too, but it might be worth |consulting an expert on damp to get their opinion. | |Anyway sorry for rambling on, hope this helps in some way, |Pete

Certainly does! Thanks very much for your contribution.

H.

[Robert]

In message , Peter Parry writes

Whilst I agree with Peter's advice I would add that we had a very similar problem with very cold interior walls and mould in two bedrooms. Our first action was to have cavity wall insulation installed which provided a dramatic improvement to the apparent temperature of the walls and ended the appearance of mould. This did, however, cause more condensation on the double glazed windows which requires additional ventilation to keep in check.

[Pet]

We recently moved to a house with full UPVC double glazing and restricted ventilation.

After about a month, mould was popping up all over, (esp.) behing the bed head. Made worse by cold non-insulated walls and the Mrs. drying washing on a clothes horse !!

Got one of them de-humidifer things from B&Q £149 (a faily beefy one as it's a large 4 bed detatched.)

Had to empty the tank every 6 hours or so for the first few days, then every day and withing a week condensation/mould vanished never to return.

It's also a real pearl for drying clothes. I shut it in the utility room sat under the clothes horse whith the Utility room rad. on No. 6 (on all time) and clothes come from machine and are dry in a couple of hours tops (even a machine full of towells). When we had high humidity it took about 2 days to dry the clothes !!

De-humidifiers rock. I am totally converted.

[Mary Fisher]

You're the only person who's agreed with me on that matter!

Thanks for making me confident that I wasn't imagining the situation.

Mary