Mould on Roof Felt

revengep8nt14

Hi,

Bit of a tricky one here, we moved into a house last October and I have been keeping an eye on our loft space since as I noticed a lot of black mould marks. The first picture was taken in October 2020 and the second one in March 2021. I can't see any difference between the 2 pictures which makes me think that there is no damp in the loft anymore.

Before we moved in it was a rented property so makes me think that the tenants were drying clothes on the radiators etc. On top of that, I can hear scurrying in the roof and I thought it was rats (hence the rat trap) however it's actually birds getting underneath the tiles and moving along the roof felt. I am going to get someone out to block the entry off but could this mould be caused from the birds underneath the tiles?

We have 2 loft hatches so makes 1 big loft and the main area above the house has no mould whatsoever but then as you look towards the extension loft space it has all that mould.
The extension area has ridged roof tiles. The main house area has flat slate tiles.
Sorry for the long post! It's a bit of an odd one but what do you think its caused by?

Alter_ego

Is the loft properly ventilated?

Jeepers_Creepers

Thank you, Revenege, for posting photos of the problem - along with the almost certain cause :-)

The insulation has been pushed tightly against the bottom eaves, and that will hugely restrict air flow. You really need to keep that clear. You want that loft space to be howling with wind, bludy cold, and draughty. 'Cos that will make it dry.

Also make sure the two hatches have seals around them, and are also insulated.

The bird getting in is a slightly different problem - you don't want that 'cos you don't want noise and dead birds :-(  The birds haven't caused that mould, tho'.

As a first step, could you pull that insulation a few inches away from the eaves, pad it down more against the ceiling so's there's a nice open slope leading into an obvious horizontal gap along there - the gap only needs to be 2 or 3 inches high, and take another photo looking into the eaves line gap? The soffits outside - are they ventilated with long grills or with round vent discs?

The mould will naturally die off as the loft is ventilated dry, but you could always spray a light mist of mould killer/buster on to that 'felt' (breathable membrane) to clear the marks as well, but then you'll loft will smell 'chloriny' for a while before that, too, is ventilated away :-)

revengep8nt14

Jeepers_Creepers said:

Thank you, Revenege, for posting photos of the problem - along with the almost certain cause :-)

The insulation has been pushed tightly against the bottom eaves, and that will hugely restrict air flow. You really need to keep that clear. You want that loft space to be howling with wind, bludy cold, and draughty. 'Cos that will make it dry.

Also make sure the two hatches have seals around them, and are also insulated.

The bird getting in is a slightly different problem - you don't want that 'cos you don't want noise and dead birds :-(  The birds haven't caused that mould, tho'.

As a first step, could you pull that insulation a few inches away from the eaves, pad it down more against the ceiling so's there's a nice open slope leading into an obvious horizontal gap along there - the gap only needs to be 2 or 3 inches high, and take another photo looking into the eaves line gap? The soffits outside - are they ventilated with long grills or with round vent discs?

The mould will naturally die off as the loft is ventilated dry, but you could always spray a light mist of mould killer/buster on to that 'felt' (breathable membrane) to clear the marks as well, but then you'll loft will smell 'chloriny' for a while before that, too, is ventilated away :-)

Thanks for the replies. The loft is quite ventilated but perhaps not enough. You can feel the wind and breeze when you are up there on a not so stormy day. I will have a look at the soffits in a moment. I will try and take somemore pictures and show the difference in membrane to the main loft area.

The loft hatches are insulated but not sealed so that will help if I get that sorted. I will also take a pic of the eaves. Photo album coming your way lol

revengep8nt14

So the first picture is the main loft and where the arrow points is the ' extension' area that's riddled with mould. I'm just confused and grateful at the same time as why it hasn't reached this area eventhough it is all open? I havent got soffits and as far as I can see no roof vent either.
The second pic is an opening showing some form of air intake when the insulation is pulled away from the eaves (or just built shoddy).

Jeepers_Creepers

The only parts that'll be dry are the areas that have a through-flow of ventilating air. If an area is 'stagnant', it'll be a home for condensation.

I'm struggling to understand the first pic - is that fibre insulation peeking out of the cavity?  And the dark pic with the lines of daylight - is that the main or extension roof?

Any chance of some photos of the outside?

revengep8nt14

Jeepers_Creepers said:

The only parts that'll be dry and the areas that have a through-flow of ventilating air. Is an area is 'stagnant', it'll be a home for condensation.

I'm struggling to understand the first pic - is that fibre insulation peeking out of the cavity?  And the dark pic with the lines of daylight - is that the main or extension roof?

Any chance of some photos of the outside?

Yes that is fibre insulation in the cavity and the brick is obviously the external wall shown in the photo. I'm going to get someone out to have a look at putting in a roof vent as I can't see anything eventhough when I go up there it seems quite breezy. The dark pic is also the extension part of the building (I say extension but it's not - just easier to explain).

Boohoo

Looking at the last 2 photo's it looks like you do not have any facia or soffits where the guttering is.

Jeepers_Creepers

Boohoo said:

Looking at the last 2 photo's it looks like you do not have any facia or soffits where the guttering is.

So that line of light is presumably just a gap between the tiles and the wall?

Revengep, it might not be an issue at all - if these mould spots are the only sign and the membrane is otherwise dry - and the timbers certainly appear to be - then it could be as you said; poor practice by the previous occupants, with no longer-term problem.

No harm in having someone to check it out, tho'.

revengep8nt14

Yes sorry forgot to clarify that there are no soffits or fascias as the photo. Yes that's correct @Jeepers_Creepers, as you said too the timber hasn't been affected which made me think it was something to do with the birds lol!
On that note, I spoke with a guy and he said that sparrows are getting under the tiles and are likely to be nesting in the eaves and due to the protection laws, nothing can be done until the season is over. He reassured me though that they do not cause any structural harm except just bringing in a lot of material!