Damp rafters - no felt

[SamIAm93]

Hi all,

We have an old rosemary clay roof without any roof felt and have been getting damp spots on lots of the rafters, and now showing mould growth. All of the battens seem to be very damp/mouldy

We’ve not had any leaks or visible water trickling through just appears almost like penetrating damp through the tiles and battens into the rafters. No rafters feel
Rotten as in can’t push a screwdriver through.

We recently had any broken/slipped tiles replaced and the hips/ridges repointed but are still getting the issue. Don’t think it’s condensation as it’s very draughty in there.

If in summer when the rafters dry out properly I remove the mould and treat it with a mould/rot preventer, will the timbers last a whilst still?

Im just wondering if they’re okay to get damp but then dry and whether this will last us a few years still as can’t afford a full reroof

Pics taken after heavy rain during storm babet so at its worse!

Thanks

 

[freddiemercurystwin]

Better start saving then ....

 

[Notch7]

Porous tiles don’t really leak although I guess they can create some damp

the roof pitch looks reasonably steep and the battens are quite close so I doubt rain is getting blown upwards


Sadly if the tile battens are starting to rot, there’s only one long term solution.

I can’t see any harm with applying some timber preservative on

 

[^woody^]

Whilst timber can get wet and dry out, in a roof space, they are unlikely to dry out sufficiently to prevent mould or larvae taking hold. Further, there is a high chance that the humidity of the whole roof space is raised to cause mould spores to take hold in other areas not directly experiencing the damp - so applying preservative won't help. Preservative only tends to coat the surface anyway and does not penetrate deeper, so is not a viable solution.

You may find that the root cause is one or two locations or just a small section of tile or ridge, and if so these can have some repairs to deal with the problem in the short/ medium term.

 

[SamIAm93]

Thanks for the replies,

Did have someone redo all hips/ridges and replace the worst broken/slipped/shaled tiles but appreciate there are probably a lot more, and seems to be the covering is failing in general.

I get what you mean about general dampness in the loft and mould taking hold in other areas as we have found some spores on items in there.

In terms of the rafters getting damp/drying partially, will that actually rot the timbers to the point of needing replacing, is that a likely and quick thing? Or will then drying partially and then fully in the summer when it’s baking hot in there keep them structurally sound for a few years still?

Basically do I need to borrow some dollar and reroof now, or can it be a few years down the line (don’t want to leave it too long and end up having to replace lots of rotten rafters as well)

 

[SFK]

Just checking....
Are you sure that there is no warm are coming from your house into the loft?
For example arround down lights, your loft hatch, or the extractor fan and its tube.

Asking as that warm air from your house will be full of moisture that can condense in your cold loft space.

Sfk

 

[SamIAm93]

Don’t think it’s condensation, extractor fan is all secure and no leaks, same for lights and hatch.

Does just seem to feel damp in there after heavy rain

 

[tonyramponi]

Your pictures remind me of my own loft.

I've been living in my house for the last 10 years and only noticed after putting Christmas decorations away last year. After it snowed the backs of they tiles were all damp which I felt was probably condensation due to the cold temperatures.

I improved the seal around the loft hatch, checked the humidity levels on the upper floor and started to run a small dehumidifier as it was a bit high. I had also had a roofer come round who told me it was nothing to worry about.

However, I've just been up in the loft after heavy rain (storm Ciaran) and sure enough the rafters are now damp pretty much as per your picture. It's too warm at the moment for it be caused by condensation so I guess the construction of the tiles is breaking down in some way to let water through. Roof is now 90 years old so can't complain I guess.

Interestingly two sides of my Apex roof seem to be fine and it's just the front side which is getting damp.

I find it really odd that the whole length of some of the rafters is effected rather than localised spots.

Do the backs of your tiled feel damp to touch and how old is your roof?

I think my tiles are clay.

Tony.

 

[SamIAm93]

Hi Tony,

Yeah it’s an odd one, I have a hip roof and seems to only affect 2 sides, the side getting the most sunlight seems to be okay.

Had another look this morning and there is damp on the underside of quite a few tiles, did have rain last night so whether it is rain or condensation, I’m not too sure, but there are no obvious gaps or broken tiles that would let rain in.

And again seems to be across the length of the whole rafter on the sides effected, so starting to think maybe it is condensation after all as we had condensation on the windows this morning, and the upper floor is reading 75% humidity.

Pretty sure the roof is around 70-80 years old and is clay rosemary plain tiles.

Cheers
Sam

 

[Harry Bloomfield]

Had another look this morning and there is damp on the underside of quite a few tiles, did have rain last night so whether it is rain or condensation, I’m not too sure, but there are no obvious gaps or broken tiles that would let rain in.

My experience seems to suggest that the tiles themselves, deteriorate more quickly on the colder side of the roof, than the warmer, generally sun catching side.

I recently had to have around 50 clay tiles replaced, on the shady side, because they were becoming porous and breaking up at the exposed ends. The sunny side, had no such issues.

 

[tonyramponi]

Hmm, good point on the hot/cold side of the roof.

It is the cold side of my roof that is mainly effected. I guess it could still be condensation but there was pretty no sun to warm up anything on the warm side while it was raining so now working on the assumption that it must be penetrating somehow.

Tiles look ok from the ground but maybe they need a closer inspection. Perhaps there is a patch of tiles degrading.

 

[Harry Bloomfield]

Tiles look ok from the ground but maybe they need a closer inspection. Perhaps there is a patch of tiles degrading.

Mine were caught and replaced in time - the entire roof has a triple layer of tiles, only the very exposed upper 1/3rd had degraded, and become crumbly, in places.