Loft insulation and mould

maurice28

Hi all - please forgive me if this is a stupid question, or I use the wrong terms, I can't say I'm very DIY-minded!

In our home, we have a bit of an issue with black mould appearing on the edges of the rooms upstairs, next to the external walls. To varying degrees it appears in all rooms, only against the external walls. It wipes off fairly easily, but does seem to reoccur slowly.

I know ventilation is key to avoid this, but I'm wondering if it might be an issue with the guttering and lofts. The guttering doesn't appear to be blocked (no overflowing water, signs of sagging etc) but I'll certainly take a look to check.

We have had the loft insulated by British Gas a couple of years ago now, and I'm struggling to remember if this coincided with the appearance of the mould (likewise, we had double glazing installed perhaps five years ago, but I'm pretty sure the mould hasn't been appearing for that long).

I know insulation can also cause mould issues like this but before I go to the loft to check, what should I be looking for? The insulation is laid on the rafters, rather than the sloping roof. Should the insulation be right up to the sloping roof, or should there be a gap?

Any advice much appreciated!

Grenage

That's a common spot for mould to appear, especially when condensation is the cause.

Aylesbury_Duck

It may be entirely independent of your loft insulation and just the coldest spots where moisture condenses. Get to the source of the humidity first, then look at why those spots might be particularly cold and see if you can do anything about it.

The insulation should be laid in such a way that it doesn't go to the very edges of the loft, to allow airflow along the edges. A common mistake is to roll I out right to the edge which then reduces ventilation.