Cavity Wall Insulation & DPC?

Hi All,

The OH and I noticed that npower are offering cavity wall insulation for £150 for existing customers (which we are):

http://www.npower.com/At_home/Energy_efficiency/Efficient_products/Home_Insulation_Offers.pdf

But before we jump in, my good lady mentioned about the green brickwork outside and damp patches inside and wondered if we had (rising?) damp?

See 3 x photos here:

//www.diynot.com/network/3rdWorldClassPlumber/albums/

Not sure if the damp on the kitchen wallpaper is due to damp penetrating from the outside green stained wall or due to the pipe that runs above the skirting in the kitchen cupboard and continues above the skirting (but behind the wall) in the kitchen.

OH reckons that the green staining and internal damp patches predate the driveway layed in 2003.

Last year a driveway contractor (not the original installer) lacquered the driveway and commented on the fact that the distance between the drive and DPC was too small - should be 150mm and it's more like 75mm. Oh bugger.

It's a shared drive and there is no such problem with staining on the neighbour's wall - probably due to a drainage channel put in along the base of the neighbour's wall.

Is it possible to have both a DPC & cavity wall insulation - and in which order? Do we really need a DPC anyway?

Perhaps we can use a stiff bristle brush and bleach/water solution to clean the brickwork?

Thanks,

3rd

First of all the DPC, best to remove the bricks along the wall to about 12 inches from the wall and to lower the base below 6 inches, 12 inches would be nice as heavy wind blown rain bounces quite high - then fill the space with shingle to make it look nice. (this will give the rain somewhere to go)

Cavity wall insulation. One of the earlier owners of this property took advantage of one of these cheap offers from ???
On subsequent examination I discovered that there are large spaces in the walls where the blown (looks like bits of yellow string) never made it.
I checked round the front windows there are large spaces more than 12 inches wide and 50 inches high.
Where I fitted fans in the bathroom and kitchen walls there were again large spaces where the stuff had caught on the ties and left large holes over 42 inches deep and 15 inches wide.
I would guess that being free and knowing that most people would never know how badly it was done, the installers just don't care.
Short of having a thermo graph camera test there is no way of knowing just how bad it is but, as I do more to the place this will become clear.

..what about 'sealing' the bricks as an interim/ middium term solution?
just a thought from a diy'ers perspective.

Perryone has given you some good advice re the dpc. It's highly unlikely that you have a rising damp problem but clear that you have a penetrating damp problem due to raised ground levels. You should have at least 2 bricks clear of the ground below dpc level to prevent rainsplash above the dpc, preferably I'd prefer 3 bricks below. You either reduce the level of the driveway or install a french drain on the side of the wall that's affected. Do not paint the wall with a sealer, this will prevent the wall drying out by evaporation.
I'm not sure what you're asking when you say, 'do we need a dpc'? You already have a physical dpc installed and there is little or no evidence to show that these fail. I'm sure the existing dpc is doing its job and installing a retrofit chemical dpc will serve no purpose whatsoever.
No reason why you can't install cavity wall insulation but as Perryone said; installation standards are hit and miss and there is increasing evidence to show that voids left in the fill material can form moisture pathways to the inner face of the wall.

Looks like the OP has a shaded or north facing wall for the algae to grow. In addition, the wall seems to be staying a bit damp for the algae to grow too.

Also, the algae seems the same above and below the DPC

Therefore, its highly likely that the wall is of more or less similar moisture content above and below the DPC

The internal wall has mould and signs of dampness, but not rising damp

So .....

There is no indicative sign on the external or internal face of moisture rising, but seems damp.

A raised ground level and water splash above the DPC does not, on its own, explain the mould and damp appearance internally

I would suspect debris in the cavity causing a breach of the DPC or a thermal bridge - causing the mould on the inside and moisture to be retained around the base of the wall just above the DPC causing the algae.

Or a leak from that copper pipe?

If you have a broken damp proof course, this will show by the wall being especially damp in one spot. It is unlikely that a whole damp proof course would go wrong.

Rising damp means, damp that comes up from the ground through or round a damp proof course (if there is one) usually it rises through the minute air spaces in the mortar to approximately 4 feet above the ground level where it levels off held down by gravity.

Hence expensive houses years ago having their living rooms above 4 feet to avoid this problem.

It is probable that the hight of the ground outside is causing the problem, this really must be sorted and the best way is to lower the ground.

A possibility is a leaking pipe or gutter high up the wall, where the water is making its way downwards arriving above the damp proof course and being trapped unable to sink any lower, relying on the effects of sun, cold and wind to move into the outside air.

A side issue is that with the wall being damp and therefore cold from one of the above reasons the water vapour inside the room is settling into the wall making its way from warm to cold.

Hi all,

I'm very grateful for your responses.

PerryOne Wrote:

First of all the DPC, best to remove the bricks along the wall to about 12 inches from the wall and to lower the base below 6 inches, 12 inches would be nice as heavy wind blown rain bounces quite high - then fill the space with shingle to make it look nice. (this will give the rain somewhere to go)

Click to expand...

This is certainly outside my capabilities and would need to get someone in. Hopefully there's some other remedy?

PerryOne Wrote:

Cavity wall insulation. One of the earlier owners of this property took advantage of one of these cheap offers from ???
On subsequent examination. I discovered that there are large spaces in the walls where the blown (looks like bits of yellow string) ...

Click to expand...

Having done some reading, I'm beginning to be put off a little from cavity wall insulation. OH wants it though as the house is rather cold in winter. I think the yellow string you refer to is the mineral fibre referred to here:

http://www.askjeff.co.uk/content.php?id=4

If (as is likely) we go for cavity wall insulation, perhaps foam or polystyrene beads are the best option (as per the previous link).

kitesurfer wrote:

..what about 'sealing' the bricks as an interim/ middium term solution?
just a thought from a diy'ers perspective.

Click to expand...

I'm all for the diyer's perspective being one myself!! I'm very tempted to follow the advice of Reader's Digest DIY, page 408 "Keeping out damp with silicone water repellent" It starts: "Silicone water repellent will normally cure damp problems on external walls. It stops rain from getting to the brick but lets the wall 'breathe' so that moisture already in the material can evaporate. If damp patches persist, you should get professional advice." It goes on to describe the straightforward application of Aquaseal 66 (or other silicone water repellent). This is my favoured first plan of attack. It's something I can do, and may prove to be a cost effective solution.

Joe Malone wrote:

Perryone has given you some good advice re the dpc. It's highly unlikely that you have a rising damp problem but clear that you have a penetrating damp problem due to raised ground levels. You should have at least 2 bricks clear of the ground below dpc level to prevent rainsplash above the dpc, preferably I'd prefer 3 bricks below. You either reduce the level of the driveway or install a french drain on the side of the wall that's affected. Do not paint the wall with a sealer, this will prevent the wall drying out by evaporation.

Click to expand...

Yup, I agree that rising damp is unlikely. I think it's rainsplash from the pattern imprinted concrete drive. My OH is absolutely certain that this green brickwork staining predates the driveway installation. Still, the driveway surface close to the DPC can't be helping. I wont be going for a chemical DPC. Hopefully the right choice of 'breathable' sealer will be ok.

^woody^ wrote:

Looks like the OP has a shaded or north facing wall for the algae to grow. In addition, the wall seems to be staying a bit damp for the algae to grow too. ... The internal wall has mould and signs of dampness, but not rising damp

Click to expand...

Yes, it's north facing. Never any sun on it.

I've uploaded another picture of the internal wall with wallpaper removed. I expected the wall to be much worse. Maybe condensation or moisture within the kitchen has caused the darkening/slight mould of the wallpaper? Maybe the pipe behind the wall is contributing - doubtful (?) as I'd expect more damage. ^woody^, maybe there is a breach in the cavity. Still, the internal wall ain't too bad.

PerryOne wrote:

If you have a broken damp proof course, this will show by the wall being especially damp in one spot. It is unlikely that a whole damp proof course would go wrong.

Click to expand...

Agreed, I don't think the whole damp proof course has failed.

PerryOne wrote:

It is probable that the hight of the ground outside is causing the problem, this really must be sorted and the best way is to lower the ground.

Click to expand...

The pattern imprinted concrete driveway was hugely expensive. As I say, the green staining was occurring before the driveway was installed. No doubt the hight of the driveway in relation to the DPC isn't helping. Lowering the driveway is definitely out. I've also uploaded a picture of the neighbour's wall - complete with drainage and stain free wall! My wall and the neighbour's wall are facing each other and are at opposite ends of the width of the driveway.

PerryOne wrote:

A possibility is a leaking pipe or gutter high up the wall, where the water is making its way downwards arriving above the damp proof course and being trapped unable to sink any lower, relying on the effects of sun, cold and wind to move into the outside air.

Click to expand...

Glad to say that the roofline was completely replaced last year - not that is was leaking in the region of the stained wall before (or since).

I'll clean it up and seal it. And cross my fingers. Failing that, we'll have to spend and get someone in (last resort!)

Cheers,

3rd.

Interesting series of comments.
I had an earlier house that was subject to water splash from next doors gutter, the wind would carry their water and dump it on my house.
Green mould started, I brushed it off and used silicone - it worked perfectly.
I have a gallon or so in my garage waiting for my lovely wife to paint the outside of our sun lounge, being high up and close to the sea we get more than our fair share of rain.