Hi there, my warm flat roof is damp in lowest spot.

 

roof buildup:

 

-fibre glass

-200mm eps

-waterproof membrane (turned up and over insulation)

-18mm OSB 

-Timer I-beams

- VCL (pro clima intello)

 

It’s a new build and the joists are still bare inside. Fibreglass roof +insulation has been installed for over a year.

 

My theory is that the fibreglass installers used long fixings to fix into roof deck. This punctured the waterproof membrane (dpm) and has allowed the condensation present in the insulation to seep onto deck and collect at lowest point.

 

 

Solutions!?

 

maybe I should carefully cut this bad OSB out and stick some VCL (intello), fleece-side out to wick moisture into the house and evaporated by our ventilation?

 

 

thanks, any reply’s would be very much appreciated- bit of an emergency at the moment!!

 

J

 

 

Edited August 13, 20233 yr by westcoast

My guess is you have a leak not condensation. fibre glass is crap compared to EDPM.

Sorry to read of this.

 

A section drawing through the wall and roof would help.  Is this the only damp spot, or is it elsewhere?

Ugh... My sincere sympathy.....

 

In June, was the damp evident? 

 

If that is the case then, because June was so hot, it might hint at a leak rather than condensation. I accept that it's a rather shaky theory but it's a starting point for thinking

17 hours ago, Dave Jones said:

fibre glass is crap compared to EDPM.

I disagree, fibre glass is bullet proof if laid properly (how many boats are made of the stuff?). You say it was laid over a year ago, it would have leaked long ago if not laid properly.

1 hour ago, ToughButterCup said:

Ugh... My sincere sympathy.....

 

In June, was the damp evident? 

 

If that is the case then, because June was so hot, it might hint at a leak rather than condensation. I accept that it's a rather shaky theory but it's a starting point for thinking

But June was a very dry month.  July was very wet, so if it was a leak I would expected it to start showing when the rain came in July.

33 minutes ago, joe90 said:

I disagree, fibre glass is bullet proof if laid properly (how many boats are made of the stuff?). You say it was laid over a year ago, it would have leaked long ago if not laid properly.

The GRP used on my boat is almost an inch thick.  I doubt a GRP roof is anything like that thick.  It still should not leak if laid properly.

Assuming it was laid correctly (mat overlapped and not butted as I have seen) then you have to look at local damage .. ladders used on the roof or impact damage possibly. Appears too localised for condensation.

49 minutes ago, markc said:

Assuming it was laid correctly (mat overlapped and not butted as I have seen) then you have to look at local damage .. ladders used on the roof or impact damage possibly. Appears too localised for condensation.

The flat roof 9x9m has quite a good fall on it all converging at this point.

 

So my theory is all condensation will collect at this point too.

 

the fibreglass team seemed very professional, 30 year guarantee etc..

OK. Was the damp evident during the dry month, or did the damp patch first occur during a wet period?

Edited August 14, 20233 yr by ToughButterCup

I'd expect the damp area of osb to be greater with condensation.

I'm going for a leak, possibly tiny. On hands and knees look at all lips and seals at this point.

 

You say this is the lowest point on a big roof. What happens there? Puddling, drain or gutter. An open edge or a barrier? Photo of the top please?

5 minutes ago, ToughButterCup said:

OK. Was the damp evident during the dry month, or did the damp patch first occur during a wet period?

Hard to tell.

We had a quite a wet install so some mold was present immediately after install, after about 6 months I checked the dark area and it seemed bone-dry.

Since then I've always assumed it was dry.. but maybe it was getting a little damp on-and-off.

Very, very wet weather recently.

9 minutes ago, saveasteading said:

I'd expect the damp area of osb to be greater with condensation.

I'm going for a leak, possibly tiny. On hands and knees look at all lips and seals at this point.

 

You say this is the lowest point on a big roof. What happens there? Puddling, drain or gutter. An open edge or a barrier? Photo of the top please?

Scupper drain happens there through parapet wall - exit pipe fully fibre-glassed, I dont suspect drain to be leaking because wall is bone-dry.

Yes, some pooling happens around scupper drain, I will go up on roof for a look now for any problems.

 

BTW thanks everyone 

5 minutes ago, westcoast said:

I will go up on roof for a look now for any problems.

And take pics of the overall arrangement and at the pool. Try to get very close to it, nose in the puddle almost, to look for an joints, cracks or whatever. Eg at the drain.

A very local coat of sealer may resolve this.

11 minutes ago, westcoast said:

Scupper drain happens there through parapet wall

I had GRP laid a couple of weeks ago, with 3 outlets through parapet wall, also made out of fibreglass. These are not currently feeding into a hopper/downpipe, and I detected two bits dampness in the locality of two of these outlets. These two happen to be where most of the water is coming off the roof and a certain amount of pooling exists on the roof by them.

I think what is happening in my situation is that the water is tracking back on the underside of the outlets when we have had high winds and rain.

As a temporary attempt at fixing, I have made small cuts in the bottom edge of the outlet on the outside and bent the edge down a little to encourage the water to fall away quickly before it can track back along the underside.

I have also, on the one worst affected, now put some visqueen plastic along with some CT1 to provide a seal against any tracking back. I'll monitor over the next couple of weeks and may also make appropriate use of a new foam gun and expanding foam - old foam gun thrown away in disgust when it stopped me doing this at the weekend 🙂 

 

HTH

Expanding foam to be avoided  if at all possible. Likely to cause other problems. 

Still following up on possible leak but:

Although its been wet, its also been very warm and very humid at times. A LOT of variation in the weather right now.


The house is unfinished, but well insulated (200mm external insulation, 150mm kooltherm under screed).

Some hot days Ive open the door and been greeted with cool air from the day before

Some chilly mornings i've been met a nice warm air from previous day.


Is it possible condensation within insulation is the culprit?

 

47 minutes ago, westcoast said:

....
Is it possible condensation within insulation is the culprit?

 

Yes. The question you might consider asking is : how probable is it that condensation is the culprit.

Have you considered that  you might have two problems ? A leak and condensation problems.

 

I thought our 'leak' (more like a weep) was caused by the rats frolicking in our insulation. The weep seemed to coincide with the location that the rats entered the roof space. Rats problem fixed - to the extent that they ever can be considered 'fixed'. But still a very occasional  weep. Take today for example - very heavy rain for several hours - no water ingress at all. And there hasn't been for a while (i.e. for a few storms) now. Nulok tiles can be taken off very quickly and replaced just as fast.  So it's up on the scaff , a quick gander, and nothing - not a drop.

 

Debbie reminded me that it leaks when there's BOTH a strong easterly and heavy rain: fairly rare here. So I need to look for two things - rat penetration on the east face and a path for the water to flow.

My point? There are two factors at work. 

 

Try this stuff. Water tracing dye . Here's a playlist to help you decide.  I've lost mine - off to Screwies for another tub.

Edited August 14, 20233 yr by ToughButterCup

Which west coast you on, I like looking at GRP roofs.

Pictures will have to do.

4 hours ago, BotusBuild said:

had GRP laid a couple of weeks ago, with 3 outlets through parapet wall, also made out of fibreglass

Did you take pictures while it was being done?

It was raining 3 weeks ago, it's been wet for 5 weeks now.

1 hour ago, SteamyTea said:

Which west coast you on, I like looking at GRP roofs.

Pictures will have to do.

Irish west coast! will take some pics tomorrow 

Tomorrow is fine, probably going up country anyway.

4 hours ago, ToughButterCup said:

 

 

Debbie reminded me that it leaks when there's BOTH a strong easterly and heavy rain: fairly rare here. So I need to look for two things - rat penetration on the east face and a path for the water to flow.

My point? There are two factors at work. 

 

Try this stuff. Water tracing dye . Here's a playlist to help you decide.  I've lost mine - off to Screwies for another tub.

Thanks for this reply.

 

you’ve helped me come to the conclusion we will have to cut open the fibreglass at some point:

 

- Cut hole in fibreglass 

- Remove insulation 

- Cut out bad OSB 

- Replace with marine ply

- Repair DPM 

- Lay some kind of bituminous product in fixing line (pro clima naideck or similar)

- Replace insulation and get fibreglass people back to hopefully repair under warrantee!

 

This will solve both possible issues. Unfortunately I won’t be able to carry out this work until next summer, so for now it means continuing the build with a damp spot🫤

 

I will continue to check for any pinhole leaks tomorrow.

 

 

6 minutes ago, westcoast said:

you’ve helped me come to the conclusion we will have to cut open the fibreglass at some point:

 

- Cut hole in fibreglass 

- Remove insulation 

- Cut out bad OSB 

- Replace with marine ply

- Repair DPM 

- Lay some kind of bituminous product in fixing line (pro clima naideck or similar)

- Replace insulation and get fibreglass people back to hopefully repair under warrantee!

 

This will solve both possible issues. Unfortunately I won’t be able to carry out this work until next summer, so for now it means continuing the build with a damp spot🫤

 

I will continue to check for any pinhole leaks tomorrow.

To me, the obvious thing is cut a hole in the OSB, remove insulation from below and see if you can see a sign of a leak?  Less disruptive and easier to put back than cutting a hole in the GRP from above.