Condensation in roof

Luke · 20 Dec 2009 at 14:31

I've just been up to our loft and have found that the entire underside of the roof is wet and is dripping along the length of the roof.
This has never happened, but I doubt it's a coincidence that we have a fair amount of snow on the roof at the moment.
The loft is insulated and is partially boarded.

I take it this is not normal and that it indicates there is some sort of significant problem? It's not a hole, there is no daylight, but it is absolutely slick with moisture underneath and a fair amount of my stuff up there is now water damaged.

Has anyone else got any experience of this sort of thing?

kwerk · 20 Dec 2009 at 16:30

How old is the roof?

john_s · 20 Dec 2009 at 16:38

Do you have a clear air gap along the eaves at both sides? Or is it stuffed with insulation?

PlacidCasual · 20 Dec 2009 at 16:56

I'll guess that lack of air flow in roof will be what most builders will respond.

*Moangroan* · 20 Dec 2009 at 17:11

I too wouls go for lack of airflow. You may or the previos owner may have stuck the boards or insulation right in the edges of the attic where the vents are restricting airflow.

beh · 21 Dec 2009 at 18:33

Similar problem, we've just had better insulation put in a couple weeks back (along with some flooring), and now there's a lot of condensation dripping off. Had the loft guy back and apparently partially due to the roof felt used being of an old type and not allowing much vapour to pass through or something, better ventilation in the form of a few vents being the solution I think.

LOAM · 21 Dec 2009 at 18:37

old roofing felt (type 2 IIRC) wont let any moisture through, that was its job. You need to have continuous eaves and ridge ventilation to prevent warm, moisture laden air condensing on the under side of the cold roof. Modern houses use a Dupont product called Tyvec which is a breather membrane and it lets the roof breathe.

As said above you need to ensure that the eaves vents arent blocked by new insulation and if possible look at getting some air bricks installed. Dont ignore it though as it can lead to timber rot, which is far more expensive than knocking a few bricks out.

http://www.glidevale.com/downloads/Roof Ventilation.pdf

if your interested

Duke · 21 Dec 2009 at 18:41

Does your shower/bathroom vent into the roof space?

moremoney · 21 Dec 2009 at 18:43

As already stated.
Lack of proper ventilation.

Without looking, it is hard to come up with anything else.

Just get up there and make sure there is nothing blocking the eaves, all round.

Stupot_ · 21 Dec 2009 at 18:52

When you say the loft is insulated... Do you mean the roof? or the floor?

If there is insulation on the floor and not the roof, then maybe there is a load of cold bridging across the roof, causing condensation on the underside. And yeh... ventilation too...

beh · 21 Dec 2009 at 19:18

LOAM said:
...

Good info, ta

Luke · 21 Dec 2009 at 19:29

Sorry, thought this had sunk unanswered!

The house is only 6-7 years old. The joists have rockwool between them, and in some areas I have boarded this to give an area to walk on (or dump boxes on!).
The underside of the roof appears to be some kind of bitumen/fabric material.

The bathroom has an extractor out through the wall, but it's rarely used. The room doesn't noticeably steam up when the shower is on.

I'll have to get back up there to see if the eaves are blocked.

Thanks

hybrid · 22 Dec 2009 at 09:38

We too have the same problem and our roof is only 2 weeks old. We're trying to chase the roofers up about this as our loft is actually dripping wet,

rossyl · 22 Dec 2009 at 09:59

It is due to a lack of ventilation.

Example.
You have a shower in an enclosed room. What happens? The room fills with steam, which eventually forms condensation on the walls etc.
What happens if you have a shower in a room with a window open, or an extractor fan? The moisture in the air escapes, or is extracted, resulting in less, if any, condensation.

Solution: roof vents, or openings near eaves.

wnb · 22 Dec 2009 at 10:08

I have this aswell, my house is about 50 years old, bought it two years ago and the surveyor said we needed to improve the ventilation. We have the builders put in two air breaks in to improve things. Last week when I got the xmas tree down i noticed that the roof was wet and dripping

I will have a look at the eaves to make sure noting is blocking the air flow.

StevieP · 22 Dec 2009 at 10:32

I'm having a similar problem - our house is about 8 months old and we've had the loft boarded out and when I went up to grab the xmas decorations I noticed a small drip coming from the inside apex of the roof!

I felt around and noticed it was damp in a few patches along the length of the roof, always in the apex!
The inside of the roof is lined with a black fabric type material!

I'm still in that period where the builder is doing various snagging bits and bobs for us - is it worth getting him round for this?

Thanks...

StevieP

LOAM · 22 Dec 2009 at 11:09

if your still in defects liability stage then yes, get him round

Cosmic182 · 22 Dec 2009 at 12:11

a lot of it will be to do with ventilation, and the felt your roof has... bitchumen roofing felt isnt breathable, whereas now when new houses/extensions are built, you use tyvek or simalar felt, as its breathable thus leaving you without the condensation.

rossyl · 22 Dec 2009 at 12:25

StevieP said:
I'm still in that period where the builder is doing various snagging bits and bobs for us - is it worth getting him round for this?

Thanks...

StevieP

YES

Condensation in roof

Wise Guy