Mould on roof rafters ??

[liam546]

I am in the middle of renovating my house and have all ceilings down. The roof is slates with no felt so the rafters have a huge amount of ventilation currently as they are even open to the house, given no ceilings.

Yet whilst I have been renovating mould has started to grow on the rafters which are damp too. Now the slates are tight and I thought mould only occurred when there wasn't enough ventilation to take the moisture in the air away.

Why am I getting mould on these conditions?

 

[catlad]

Have you had plastering done that will add a lot of moisture to a building.

 

[liam546]

Hi Catlad, good to hear from you again.....

No plastering done or anything I can think of that would add moisture to the air. No heating on or anything. There is so much ventilation as I have no ceilings and openings everywhere.

All I can think of is that the minimal hot air the is in the building is setting on the cold slates as condensation and making the rafters damp. Then as they are damp mould is occurring.

The mould is more at the eaves on both sides as opposed to the higher part of the roof in the middle under the ridges.

Can't make sense of it

 

[catlad]

You are on the right track the slates will get very cold in the night and during the day they will condensate underneath, and without any heating to dry them out its creating the right enviroment for mould to grow.

 

[liam546]

Thanks, I will scrub the mould off and hopefully once I get ceiling and insulation back up I won't get mould growing back.