Mould and Damp problems - please help!

[bambam]

We moved into our new house at the beginning of May. In early August, I noticed that we had black and green mould growing around the skirting board and floor edge trim, all around the edges of the ground floor (on the walls to the outside and to the garage).

It's a four storey 'town house', and the ground floor is a garage, with a hall, utility room and understairs WC. The downstairs feels very cold and damp, even on a hot summer day.

When I found the mould, I reported it in writing to the developer. I photographed it, and e-mailed these. I got the site manager to come and have a look too.

I was advised by the developer that it was caused by two things - the house still drying out, and me hanging wet washing up to dry in the utility room with not enough ventilation. We agreed I would clean the mould off with a bleach solution, which I did, and see if it grows back, and in the meantime the site manager would get a brickie to remove some bricks to check the cavity is not blocked (which he is doing tomorrow morning while I am there too).

I work in the building industry so I know a bit about this. I've checked outside, and the DPC is, I think, at the requiremed minimum of 150mm above external ground level. The DPC level is only visible in one place, which is against NHBC regulations, but NHBC have advised me this is a guideline only. There is a cavity tray with weep holes that sits directly above the DPC level.

I think there is a chance battens were not used when building the external walls to ensure the cavity is free from obstruction (ie mortar dropping down inside the cavity), and the cavity is bridged at the cavity tray level (internal floor level is approx at the level of the DPC), so moisture is entering this way.

I guess we will find out tomorrow, when the bricks come out. My other concern is about the air bricks, as there is only one airbrick at that level, and to me that doesn't seem to be enough - surely there will be no through ventilation from this?

Other than that, does anyone have any suggestions? I thought perhaps the DPM has not been layed properly, or not dressed up the side of the floor structure (I think it's concrete beam and block).

I really would just like it sorted out. I'm worried that this is happening in summer, but could get so much worse in winter. I don't believe that it's being cause by the house drying out, and I always switch on the extract fan when I hang washing up in there, so if it's the washing causing the problem surely it's their fault for not providing adequate ventilation for the use of the room?

I feel so powerless aginst being fobbed off, when I know there is something wrong! Thanks.

[Tony]

What did they discover when the bricks came out? I guess the cavity was filled with mortar.

[bambam]

Aaaargh Ijust wrote a really long reply and then accidentally pressed back and need to start again!

Anyway, Yes, the cavity was blocked, it should now be cleared out, but unfortunately I couldn't stay to be sure of this. It was blocked to at least 2 brick courses above DPC level, so approx. 300mm above internal finished floor level.

I also could see into the cavity below the cavity tray, and there was no insulation here. There can not be any insulation until at least a couple of brick courses above DPC level because of all the mortar, I don't think anyway! It's supposed to be full fill insulation.

So, I think there's a cold bridge at DPC level as the insulation in the floor (it's a Jetfloor type system, so it must be insulated) and the insulation in the walls doesn't 'meet', so excess moisture in the air is condensing at skirting board level inside as it's cold there.

I have drawn this detail, and e-mailed it to the developer, asking them to either confirm what I have drawn is what has been built, or if I am wrong, to correct my drawing! I have tried before to get hold of the actual drawings but they have refused.

So, I suppose I just have to wait and see. Any suggestions? Not just about the problem, but about how to deal with them? I think they will tell me I am wrong, but as I have drawn it at 1:10 scale, I don't really see how they can fob me off.

If we don't get anywhere, I think the next step we will take is to employ a surveyor, experienced in dealing with new homes, but will this be worthwhile do you think?

They have given us a dehumidifier, which we are using, and we have made other arrangements for drying clothes for a while.

[Tony]

You seem to need little advice. I guess you are doing this already:

1. Keep meticulous records
2. Take photos
3. Get all verbal promises confirmed in writing

With regard to the surveyor, I would do this as a last resort.

[bambam]

Had some good news on this problem, the production manager admitted there was a cold bridge, as at least three brick courses had been blocked with mortar. They have agreed to come back and fill the gap with insulation, which I hope will help. I'm still worried, as I cleaned the mould off with bleach 5 weeks ago, and it's already starting to grow back.

When the house was built, they didn't use boards to prevent the mortar dropping into the cavity, and he said "No-one uses them", which is against the NHBC guidelines, and yet the NHBC just shrug their shoulders, as they are "just guidelines". s

[GKandR4CH]

The NHBC are useless they do not have a clue.
Give them a time limit to fix the problem and if they fail don't waste anytime taking them to court.
Developers do not like claims against them - trust me on this point.
Good luck.

GK