Increasing Loft Ventilation

pred02

Hi,

Living in 1900's Edwardian maisonette with a loft. The loft is unfinished with an old roof that is half clay tile with no liner and just wood sarking and the other half is slate with non-breathable felt. No insulation towards the roof but there is between the downstairs bedroom and loft. I lived there for 10 years, until last year had no problems but last year started to notice condensation in particular around the wood becoming moist. This is probably due to increasingly putting boxes and using the loft for storage as we had a kid and don't have much space in the flat. 

What can I do to increase the ventilation in the roof so reduce/eliminate condensation?

Bedroom is below with an ensuite bathroom but bathroom fan is going outside the property (not into the loft.

Thanks

ThisIsWeird

Two separate issues to look at. The first is the ventilation of that roof space, and the other is preventing excessive moist air getting there from the house.
Using the loft for storage, in itself, should not cause problems, unless it's piled so tightly that it blocks air flow - highly unlikely. So are you, perhaps, leaving the loft hatch open for long periods on a regular basis? Again, unlikely.
Have you added to the loft insulation? If so, did you keep the eaves gaps free - that's usually where the majority of cross-ventilation comes from?
Do the stored items themselves become damp? If the timbers are wet from a lack of vent, you should expect stored items to also show some signs of damp - cardboard boxes becoming weak, soft, sagging, distorting or discolouring, for example. If the boxes are crisp and bone dry when nearby timbers are wet, then that points more towards this being a leak.
Q's;
At what times of year, and weather conditions, do you notice this? Does the outside temp need to be below a certain figure? Have you noticed it during summer but following rain?
Any chance of photos of the wet timbers? 
Any darkening of the timber - black mould or similar?
Has anything changed up there other than increased storage?

Does the loft lid fit tightly?

And, on a breezy day, does it feel draughty up there (with the loft hatch closed)? 

(Many moons ago I was sent up into inlaw's loft to fetch stuff, and it was blowing a hoolie up there and bludy freezing. I was surprised - at the time - to find all their stored items, from electronics to pictures to soft furnishings, to be bone dry and completely unaffected. That was when the importance of ventilation became clear.)

Jonboy_1984

Has your change of storage habits resulted in any of the insulation being crushed?

markin

The forum had a flood of people with wet lofts early this year, the was unusual conditions, if the eves are clear and it looks dry it may be fine.

ThisIsWeird

markin said:

The forum had a flood of people with wet lofts early this year, the was unusual conditions, if the eves are clear and it looks dry it may be fine.

Good point!

pred02

Thanks everyone for your feedback, I will try to get some pictures this evening but have included a diagram of what it was before and after and provide clarifying questions below in hope for proper diagnostic and fix to the condensation problem. 

So are you, perhaps, leaving the loft hatch open for long periods on a regular basis? Again, unlikely.

I go into the loft about once per week depending on how long can stay anywhere between 2 and 10 minutes up there.

Have you added to the loft insulation? If so, did you keep the eaves gaps free - that's usually where the majority of cross-ventilation comes from?

I have not added to the loft insulation since moving in 10 years ago. The eaves gaps - where the roof meets the base of the loft have not been boarded up.

Do the stored items themselves become damp?

I don't think so but will check. I did notice moisture on a thin bag (actually proper droplets that was a bit oily in nature). Most storage is in boxes (paper and plastic) and I have not noticed items becoming damp or moist.

If the timbers are wet from a lack of vent, you should expect stored items to also show some signs of damp - cardboard boxes becoming weak, soft, sagging, distorting or discolouring, for example. If the boxes are crisp and bone dry when nearby timbers are wet, then that points more towards this being a leak.

I am struggling to diagnose if its water ingress or condensation. Last January we had a surveyor come in as we were in the process of selling (this felt through for various other reasons) who said it was condensation and moisture in rafters. I was dubious as it was particularly wet winter and the joists that were bit wet were touching adjacently directly to the outside. For example, one had metal flashing that is directly touching the wood joists and sarking. There is no felt on this side and no protection. 

I am also dubious as we have non breathable liner facing the right side (where the living room is) and this was dry - I would expect drops of water to be here but it was bone dry.

At what times of year, and weather conditions, do you notice this? Does the outside temp need to be below a certain figure? Have you noticed it during summer but following rain?

This I first saw last January / February. We had an unseasnoy cold and wet winter, with snow on for a couple of days. This summer it was bone dry up there even when it rained. Then I noticed it this weekend when I went up - first time temperatures feel.

Any chance of photos of the wet timbers? 

Later this week will take the photos and upload.

Any darkening of the timber - black mould or similar?

Bit water staining but no black mould. A bit white where there was water stain last winter. All dried over the summer.

Has anything changed up there other than increased storage?

And, on a breezy day, does it feel draughty up there (with the loft hatch closed)?

Yes it does feel breezy. When up there and its windy you can feel the wind and also there was traditionally lot of dust up there.

ThisIsWeird

Thanks for the comprehensive replies.
Great graphic. So, you've moved your boxes
That wall to the right of the new storage position, how high does that go?
I presume your living room has a vaulted ceiling? 
Where - exactly - does the 'wet' show?

pred02

Apologies for the delay - here are pictures of the loft. I went up there yesterday to take photos and I cannot see any condensation on the plastic boxes (you can see dust), paper boxes. There are areas where there seem to be patches of wet/damp on rafters I am not sure if these are old water stains or are wet around the rafters. What is interesting is there is no condensation on the non-breathable grey liner on half the roof which is where I assume I would see droplets. 

I am not sure if its a water leak or condensation but I do want to prevent damage to rafter/roof structure and am not sure how to go about next steps.