Newish fiberglass roof leak. Repairable?

[dobbslc]

I've got a 3 year old GRP flat roof that sprung a leak in last weeks rain. I've been up for a look but can't see any cracks or holes but it looks like a poor job with the GRP matting showing through the finish. Is that normal?
The leak is around one specific corner of a roof light so I'm thinking of adding some more resin or extra matting.
Thoughts?

 

[angellonewolf]

Is that white not primer coat ? When I had some at work the under coat was white the top coat gray also

How is the grp connected to the frame of the window looks to me as there is no way to stop the water going down the side of the window frame and inside of the grp ? Could just be the picture ?

 

[roofman]

Not enough gel coat on that job...can be patched by sanding back, clean with acetone, use resin and few layers of mat but must be bone dry and spotless clean. Not a big fan of f/g for roofing as it has no thermal movement.

 

[roofman]

Is that white not primer coat ? When I had some at work the under coat was white the top coat gray also

How is the grp connected to the frame of the window looks to me as there is no way to stop the water going down the side of the window frame and inside of the grp ? Could just be the picture ?

It's the way the latest roof widows are made these days, roofing 1st up and onto the upstand and flush fitting window sat on a bed of mastic 20 years ago when these type of lantern windows hit the streets they were sat on a welded four sided sill board that overhung the upstands,giving a good 75mm drip edge and weather protection.

 

[angellonewolf]

It's the way the latest roof widows are made these days, roofing 1st up and onto the upstand and flush fitting window sat on a bed of mastic 20 years ago when these type of lantern windows hit the streets they were sat on a welded four sided sill board that overhung the upstands,giving a good 75mm drip edge and weather protection.

yea had a new flat roof at work had 2 i say windows in it its only 2 pieces of glass with a bit of metal on it masticed in place


and one has a leak that just been noticed the builder is there at the moment so hes going to chase the window installer and roofer and see whats what

 

[Barking Mat]

Yeah, fixable, I've some questions to ask, I know grp, and water tightness, but I'm not familiar with this construction method.

Is that a very thin gel coat wash over the resined grp ?

 

[qwakers]

there should be a very thick gel coat over the whole thing, like a fiberglass boat. i did 2 coats of gel on my roof when i did it, mine is a lot older than the above roof and it doesnt leak....

 

[Barking Mat]

Should resemble a shower tray in my eyes, not the grand canyon ?

But, I'm not familiar with this roofing method.

Grind it back, fill it, numerous options, but I'm still not getting the gel coat wash ? I wouldn't be happy with that on a flat roof, where's @roofman ? When you need roofing advice ?

That needs repairing, and the whole surface properly gel coating, in my boating, not roofing experience.

I hate roofing incidentally.

 

[ajlelectronics]

In normal fibreglass work, the Gel coat is the first layer, normally that cured surface would be released from a mould. The gel coat goes hard without oxygen and the upper side stays slightly tacky to allow layup. Then the resin and mat is laid to the required thickness before Flowcoat /Topcoat resin is used as the finished surface. This goes hard in the presence of oxygen so it will not be sticky once cured.

I know nothing of roofing with it, but Brian would no doubt confirm or deny those notes.

 

[MattF]

where's @roofman ? When you need roofing advice ?

Erm...

Newish fiberglass roof leak. Repairable?

I've got a 3 year old GRP flat roof that sprung a leak in last weeks rain. I've been up for a look but can't see any cracks or holes but it looks like a poor job with the GRP matting showing through the finish. Is that normal? The leak is around one specific corner of a roof light so I'm...

www.mig-welding.co.uk

Newish fiberglass roof leak. Repairable?

I've got a 3 year old GRP flat roof that sprung a leak in last weeks rain. I've been up for a look but can't see any cracks or holes but it looks like a poor job with the GRP matting showing through the finish. Is that normal? The leak is around one specific corner of a roof light so I'm...

www.mig-welding.co.uk

 

[Barking Mat]

It's been a very long day.

 

[MattF]

It's been a very long day.

Aye, we'll go with that one.

 

[dobbslc]

Is that white not primer coat ? When I had some at work the under coat was white the top coat gray also

It's grey but not very thick.

It's the way the latest roof widows are made these days, roofing 1st up and onto the upstand and flush fitting window sat on a bed of mastic

@roofman thanks for getting involved I was hoping you would

I've also noticed a lot of condensation on the underside of the top glass but I'm not sure if I can lift the whole thing off and dry it out, it's got about 8 Tec screws in the sides that look like they hold it down. If it's held down with mastic will I damage it trying to lift it?

Yeah, fixable, I've some questions to ask, I know grp, and water tightness, but I'm not familiar with this construction method.

Is that a very thin gel coat wash over the resined grp ?

I don't know if it's a gel coat or just the resin, are they the same thing?
I didn't think there was enough of it whatever it is and you guys have confirmed that now

there should be a very thick gel coat over the whole thing, like a fiberglass boat. i did 2 coats of gel on my roof when i did it, mine is a lot older than the above roof and it doesnt leak....

Ok more stuff needed up there but what do I buy?

 

[Smallfry]

All the ones I have seen are smooth. Tosh another coat or resin over it after cleaning, or get the proper stuff. Make sure you start at the ladder, and finish at the highest corner with the Briar bush below.

Regarding cleaning, I spilt some polyester resin on the road while "repairing" a Mini at mums house in 1978. Its still there !

 

[Keith 66]

There are a lot of people doing grp roofs who have no idea of what makes the material work. A lot will be just a couple of layers of 450 gm mat if that which is light. Any movement & it will crack along joins etc also through expansion.
Polyester resin is a poor adhesive & will lift easily if damp gets underneath or if there is poor preparation.
You will need to grind the area back with a coarse sanding disc in a grinder, i use nothing finer than 24 grit discs, Clean with acetone & apply more mat & resin. Consolidate with a paddlewheel roller. Its gotta be dry or the new mat will suck up damp, you will see this as white spots or patches in the fibreglass that do not cure properly.
If you have a damp spot its permissible to dig it out & put some P38 (dont have to wait) filler in the crack to stop damp coming through while you glass over it! An infra red lamp is good for kicking the stuff off, As soon as the resin & mat has cured paint over with flowcoat which is gelcoat with wax in styrene mixed in. It dries with a smooth glossy finish.

 

[dobbslc]

Thanks for that.
I'll probably only do a patch around the upstand on this roof light if I get a dry day then the rest will have to wait until next spring.
So I need glass mat (I have a large roll left over from this roof that the roofer probably should have put on) resin and then flowcoat?

 

[ajlelectronics]

Ok more stuff needed up there but what do I buy?

Flowcoat or more commonly called Topcoat, unless you intend to add more fibreglass, in which case you need polyester resin (standard) too.

 

[dobbslc]

I'll put four 6" strips around the roof light upstands and re coat that to see if that fixes it.

 

[fizzy]

Why do they build them flat? I have never encountered a flat roof that doesn't leak

 

[Old Dog]

Don't forget the goggles. gloves and overhauls as fibre glass grinding is a total B*****D!! Course sanding disc's and grind back twice as far as you think. Hoover up all the dust and dry with a hot air gun. Degrease everything and I would G4 seal it first. then a few layers of chopped strand matting flattened down with the paddle roller, followed with the gel-cote. I get all my stuff from these people( Koi pond supplies ) and they have a few good videos on the site. https://www.fibreglassdirect.co.uk/fibreglass-pond-kit.html