Purlin bridging water from external wall?

[Dylan T]

Hi all - I’ve got a condensation issue in my loft which I’ve found to be a combination of a poorly fitted bathroom ceiling fan exhaust, loft hatch and lack of ventilation. So it’s a given there’s condensation as on cold days like we’ve had it collects and drips from the felt on the coldest side of the roof.

However I’ve noticed that on this same side one end of the purlin is very wet, and I’m trying to work out if this is related or a separate issue.

The west end of the purlin is in a lot of cement so I the theory I’m most hoping is right js that cement is just absorbing the moisture as perhaps there’s no retardant in it and therefore making the purlin wet. In this case hopefully sorting the condensation will fix it.

However I’m concerned it could be a sign of other water getting in - and hoping some kind folks could help give an opinion. I’ve had two roofers simply say they don’t know.

Thanks!

 

[blup]

Is there any sign of damp ingress via damage to the external wall? Or a flue? If not is there damage to the tiles or felt which is letting in the very heavy driving rain that is more common nowadays?

 

[catlad]

Is that the gable end?

 

[Dylan T]

Is there any sign of damp ingress via damage to the external wall? Or a flue? If not is there damage to the tiles or felt which is letting in the very heavy driving rain that is more common nowadays?

Is that the gable end?

No evidence of ingress from what I can see. The damp is isolated to that patch of concrete, and no cracks in render on other side. There is a flu on that side but its a couple of meters away and I can't see any link between the two. Does it seem more likely to be ingress rather than the absorption of condensation?

Yes that is the gable end, and probably the coldest portion of the house.

 

[wessex101]

Is it actually wet or just stained?
It doesn't look like the normal discolouration you see on damp wood. It looks like someone has just treated the end of the purlin with wood preservative to me.

 

[Dylan T]

Is it actually wet or just stained?
It doesn't look like the normal discolouration you see on damp wood. It looks like someone has just treated the end of the purlin with wood preservative to me.

It's wet

 

[blup]

The purlin end will be sitting on brick, the “concrete” is a mortar finish smeared over the brick. Its more likely to be condensation dripping from tne felt imo, particularly as this is a cold end. Regularly checking over the coming seasons will help to establish the cause(s). There is no rot so need immediate concern.

 

[Dylan T]

The purlin end will be sitting on brick, the “concrete” is a mortar finish smeared over the brick. Its more likely to be condensation dripping from tne felt imo, particularly as this is a cold end. Regularly checking over the coming seasons will help to establish the cause(s). There is no rot so need immediate concern.

Thanks so much, that's very helpful. I'm having vents added this weekend hopefully, and also adding a few other measures to reduce potential condensation. I'll get the dehumidifer up there and just have to keep an eye; hopefully it won't return!

 

[Ivor Windybottom]

If your bathroom fan was spewing damp air into the loft then this would have caused all kinds of horrible issues. That corner may have just been the cold spot where it all condensed.

Ensure the fan is 100% sorted and check again next year, once it's all had chance to recover from that.

 

[catlad]

If the purlin is covered by a bargeboard then check its doing its job.