Mould on inside of flat roof.

Hi all.

I've done a search in the forum for this problem and now have a understanding of the problem and why it was caused but I still have some questions hopefully someone can help me with.

So had old flat roof replaced last Summer. Insulated with 70mm CeloTex, new OSB board and EPDM rubber over the lot. No vapour barrier.

While decorating yesterday around our burner flue I noticed a considerable patch of mould forming close to the flue (where there is no insulation) I understand why this is forming, warm air from the kitchen hitting the cold board and forming condensation and thus mould. Getting up the with head torch I can see the mould spreading.

The area around of the flue has no plasterboard as I was planning on cladded this area while decorating and is coldest part of room, which is a kitchen.

My question is, if the worst of the mould can be removed and the celing is sealed will this prevent the mould spreading? Alternatively I guess it either pulling the new roof off and redoing it with vapour barrier and pulling ceilings down inside?

I hope this all makes some sort of sense and greatful if anyone with experience in the field can help.

Cheers

Should use insulated flue for where it passes through the roof and insulate that part of the roof too.. You can touch insulated flues with your hands; they won’t set insulation on fire

You say there is no plasterboard and you mention cladding and sealing the ceiling. Does this mean you have no ceiling around the flue - just a gap and this mould is on the underside of the roof deck?

^woody^ said:

You say there is no plasterboard and you mention cladding and sealing the ceiling. Does this mean you have no ceiling around the flue - just a gap and this mould is on the underside of the roof deck?

Click to expand...

Yes this exactly.

The flue is obviously twin lined passing through celing and roof

Photos would help.

worzel_rummage said:

Yes this exactly.

The flue is obviously twin lined passing through celing and roof

Click to expand...

Then sterilise the mould, pack some rockwool into the ceiling void to deal with cold spot (the area affected by mould), and then fix the celling layer to match the rest.

This assumes that the mould is resulting from excess warm air getting to the roof deck via the lack of ceiling, and once you close off the ceiling that will stop it.

Thanks Woody, that was my plan you've confirmed.

However, upon further inspection today I can see the mold has spread, running possibly the length of kitchen. I am aware this is not a good situation. Contractor immediately asked if we have an extractor fan which we don't.

So what are my options moving forward? Should I still sealing the celing around the flue? Is there any way to stopping the mold or am I going to have to take more drastic action?

Cheers for anyone who can help.