leaking fibre glass flat roof

[barber]

Hi

I have recently fibre glassed a flat roof on a new dormer loft conversion I am building and i have just notice today that the sterling boards are extremely wet in places! I have no previous experience with fibre glass but i felt with a bit of research it was possible to do it myself(maybe not eh!). I carried the work out when it was dry and I used 1 layer of fibre glass matt which i soaked thoroughly in resin, when the resin was slightly still sticky but not quite set I then poured and rolled out the top coat. It looks and feels great from above but is obvioulsy leaking in places. Any ideas much appreciated. Thanks

 

[SurreyRoofingEstimator]

We've not ventured into glass fibre ourselves but could it be a condensation issue where vapour is penetrating the boarding and condensing on the underside of the glass fibre?

 

[dilly]

Hi did you consolidate the resin and mat,what i mean by this is did you make sure there were no air and no pin holeing in the mat.Also why is the dormer not a warm roof constrution.

 

[barber]

Thanks to both for replying, much appreciated. I am pretty sure it is rain water because it is really wet in places and bone dry in others. I used a metal ridged roller to spread out the resin on the fibre glass. I actually poured the resin on the roof and then lay the mat ontop and then rollered it and if required added more resin. I suppose it could be pin holed if i didn't roller it enough?

Is it worth giving it another good thick covering of top coat. Will it bond to the roof now? In places you can see and feel the matting fibres...could this let in water?

Thanks again both

 

[Tuck1]

Fair do's for having a go but youve wasted your time and money.
You shouldnt really be able to see and feel the fibres after topcoating for one thing.

You should have applied the 1st coat of resin with a 9'' paint roller directly onto the boards, then mat, then more resin on top, then metal roller it firmly. Cut all your mat to length beforehand then roll it out while doing the above. When dry enough to walk on apply topcoat.

Did you fibreglass under the tiles & felt where they meet the flat roof, and is the felt ok? Water could be tracking from here, common cause?
Did you use pre-made edging trims and rear fillet?
Did you double seal any large joins in the boards?
What percent catalyst did you use?

You [i]may[/i] get away with sanding the topcoat and re-applying a new coat but its likely the fibreglass has lifted from the wet boards.
You should not fibreglass below +5c but if you must, add extra catalyst and hire a harrier jump jet to warm it up.

 

[barber]

Thanks Tuck for your reply. I did everything that you just said. I used winter catalyst and added 4 % to it. I warmed up the resin by leaving it in the aring cupbaord for a few hours before application. I used pre-moulded edges and corners. It didn't rain. The ridge tiles sit over leadflashing thats sits over the back end of the flat roof with a 2 x 1 batton under the lead flashing to create a raised edge. The ridge end of the roof is bone dry but it seems to be the sides where the moulded edges run. I think water must be tracking along somewhere there like you said. Thanks again, will let you know how i get on

 

[htgeng]

What is the weight of the matt? When did you lay it?

 

[barber]

not sure to be honest but was supplied with the resin from the roofing supplies people. It was quite thick though I would estimate about 3mm or something

 

[htgeng]

not sure to be honest but was supplied with the resin from the roofing supplies people. It was quite thick though I would estimate about 3mm or something

Its sold on the weight. You should check your invoice to see whats been provided. I think you're out of luck in this weather. Tarp it over till things warm up outside.

 

[barber]

i know, i was thinking that myself. What if you add too much catalyst? does it cause any problems?

 

[Tuck1]

How far onto the edging trims did you overlap the matting?
How did you fix down the trims?
Where the edging trims meet the rear roof edge how is that area sealed and how err high up is it sealed?
If you add way too much catalyst it can have a reverse effect but there is not a question here that the glass hasnt gone off.

If youre stuck pm me im not far from you. If im passing your area i can have a squint for you.

 

[barber]

Thanks Tuck your a star but don't want to inconvenience you but thanks again! I glued the trims down with grip fill and nailed them with 50mm galv nails. I actually ran the matt up and completely over the edge trims and at the front over so it is about 2 inch from touching the gutter. At the back of the roof I ran matt off the sterling boards and upto the main central ridge beam joist (300mm x 100mm). On top of this central ridge beam I fixed a 2 x 1 on its side and then ran 11" lead flashing over the batton and beat it into the the same shape as the batton and then ran it off the batton and the beam and ontop of the top coat of the fibre glassed roof. One thing i didn't do is tape or fill all of the joints between the sterling boards. Would this matter?

 

[Tuck1]

Thanks Tuck your a star but don't want to inconvenience you but thanks again! I glued the trims down with grip fill and nailed them with 50mm galv nails. I actually ran the matt up and completely over the edge trims and at the front over so it is about 2 inch from touching the gutter. At the back of the roof I ran matt off the sterling boards and upto the main central ridge beam joist (300mm x 100mm). On top of this central ridge beam I fixed a 2 x 1 on its side and then ran 11" lead flashing over the batton and beat it into the the same shape as the batton and then ran it off the batton and the beam and ontop of the top coat of the fibre glassed roof. One thing i didn't do is tape or fill all of the joints between the sterling boards. Would this matter?

No problem Barber. This fibreglassing is bloody easy isnt it!
Didnt need gripfill, just clout nails. Matt should finish on flat roof surface of trims not over them.
Lost me a little regards the rear of the roof. Havent you got a backboard behind the flat roof, normally 6x1 (2 of)? Doesnt the matt turn up at this edge at all??? Got any pics?! How are the edge trims finished and sealed at this rear point?
You only need to bandage joints in the boards is if they arent tight, say over 2mm gap.

 

[barber]

Sorry Tuck haven't had a chance to take photos in the light yet but tomorrow mill do. My flat roof is on a loft conversion dormer that I have built and the flat roof actually runs pretty much level with the ridge bean of the existing roof. There is no turned up matt at this point so that maybe worth a look now you mention it. I will take photos tomorrow which may help.
Thanks again

 

[alittlerespect]

Hi!

You failed to mention insulation in your thread!

What you should have done, perhaps in hindsight, which is a wonderful thing is created a warm roof design, this would then have eliminated the condensation problem, but there again there may have been reasons why a warm roof design could not be utilised.

Sounds like you have a cold roof design and the vapour control layer may have been ommitted in which case condensation can be a significant issue - you will need to ensure that you have a vapour barrier and adequate through ventilation above the insulation.

A question: Did you include a vapour barrier in the detailing?


As for the fibreglass process, I have specified a system on a number of occassions for quite large roof area's and so long as it is installed correctly it is a good system. Depending on which system is employed you can get extended warranties sometimes for the life of the system - anything up to 50 years, however, going by your description I would anticipate no more than a 10 year guarantee, however, not being installed by a certified company will probably mean that there is no guarantee!

You should find that the fibreglass system is breatheable up to a certain extent and can cope with a bit of sweating/interstitial condensation, but it is unlikely to cope with the level of condensation found where there is inadequate ventilation and/or no vapour barrier.

Regards