Bad Roofing Job?

Kmurphy · 9 Apr 2018

Had our flat roof done. Nice looking fibreglass job, but it's been leaking in a spot roughly in the middle of the front wall (below the parapet)

I currently think it's a bad job and water is coming in the where the fibreglass meets the wall. Maybe no real trimming used??

Would like as many opinions as possible as to what the issue here might be.

They want to charge me £600 to fit flashings to resolve the problem, on a job I paid 2.5k on

Notch7 · 9 Apr 2018

Whats the sandy brown coloured line?

Flashings are not an extra, they are a necessary part of the job.

The 45 degree OSB edge trim is a bit weird to me.

GRP has 1 real disadvantage, its rigid when set. That means fibreglass should not be used to bond to abutments. The roof should have an upstand of about 100mm where it meets walls. The upstand is fitted to the roof not the wall. GRP is laid up the upstand. Then the lead flashing can be chased into wall and dressed down over the upstand. The result is a weathertight junction that allows movement.

Parapet walls can be a nightmare! Especially old ones.

Kmurphy · 9 Apr 2018

Notch7 said:
Whats the sandy brown coloured line?

I think that's a cement fillet he has used. Maybe instead of lead flashing...d

Notch7 · 9 Apr 2018

Kmurphy said:
I think that's a cement fillet he has used. Maybe instead of lead flashing...d

There should be no sand / cement mortar used on a GRP roof. Id have it taken off.

There are grp trims that can be used instead of flashing, although you cant beat the appearance of code 4 lead.

I suppose the abutment 45 degree detail is a bit similar to a grp trim you can get, but being done in osb that way looks bulky. We do a 100mm upstand with an arris rail, looks much neater.

Im not sure the board edges should be telegraphing through the top coat so clearly.

Did the roofers mention the building regs requirement of upgrading the insulation?

Kmurphy · 10 Apr 2018

No mention of building regs ??

Diver Fred · 10 Apr 2018

Why does one side look to have no Upstand? Is that where the leak is? Where is the drain?

Kmurphy · 10 Apr 2018

the roof is guttered on the edge with no upstand, it is very close to the neighbours house, but enough space for guttering. That was there before it was fibreglassed. The leak is under the centre front parapet wall

Diver Fred · 10 Apr 2018

Kmurphy said:
the roof is guttered on the edge with no upstand, it is very close to the neighbours house, but enough space for guttering. That was there before it was fibreglassed.

I'm surprised that the neighbours don't have a damp wall along there - how do you keep the gutters clear? (but that is a different matter.) To be honest I'd have spoken with the neighbours before you started and discussed having flashings into their wall with a drain off one end of the roof.

So on to the existing issue; OK - I'm not too experienced at this but it does look like the 'roofers' have ran the fibre glass above the line of tiles in the parapet wall - in my 'book' the flashing should be under those tiles. It looks like the original felt roofing was under those tiles (and possibly bonded into the mortar under the tiles).
Best way to put it right? First check to how good the pointing is on the parapet headers - you may get away with having the headers re-pointed... But that may only be tempory.
The way I'd do it is to have the headers removed, Code 4 flashing laid (in metre lenghts with 150mm overlaps*) over the tiles - from centre line of wall to about half way down the slope of the glass fibre roof and the hearders relaid. That should also be keyed into the ajoining wall(s)

* the overlap is to prevent the lead from cracking from expansion/contraction movement.

Kmurphy · 10 Apr 2018

wgt52 said:
Best way to put it right? First check to how good the pointing is on the parapet headers - you may get away with having the headers re-pointed... But that may only be tempory.
The way I'd do it is to have the headers removed, Code 4 flashing laid (in metre lenghts with 150mm overlaps*) over the tiles - from centre line of wall to about half way down the slope of the glass fibre roof and the hearders relaid. That should also be keyed into the ajoining wall(s)

That is what they and other roofers have suggested to fix it. The pointing on the parapet is pants they say and is where the leak is coming in. But, want to charge me. Seems to me like they didn't do the right job, but not being a roofer and my quote not saying ' lead flashings and fibre glass' seems to put me on the back foot (maybe)

Although one guy said to just get some thomson weather seal to have it sorted for ~5years and then pay for the flashings from a more reputable roofers

wgt52 said:
I'm surprised that the neighbours don't have a damp wall along there - how do you keep the gutters clear? (but that is a different matter.) To be honest I'd have spoken with the neighbours before you started and discussed having flashings into their wall with a drain off one end of the roof.

We clear the gutters every so often and although I asked the roofer about other potential solutions (I was open to pay for the best solution) what they've done is what I got offered...

Alastairreid · 10 Apr 2018

The job looks fine, its just not been finished properly.
Looks like they have done a like for like replacement and if they have not quoted for installing lead aprons theres not a lot you can do about it.

Kmurphy · 10 Apr 2018

It's not like for like, if previous roof was fitted under the drip of the parapet and the addition of the 45 degree OSB and the cement fillet below the drip, now means heavy rain fall will run over the cement and behind the OSB and then into my room...

catlad · 10 Apr 2018

Get rid of those roofers, They have skimped on materials.

Kmurphy · 16 Apr 2018

Anyone think I can do the lead work myself? It looks pretty straight forward to grind the pebbledash and cement off, chase into the brick and then put the flashing in and remortar + sealent + patination.

Even the parapet wall capping doesn't seem complicated, although the cost of the lead isnt much cheaper than paying someone

oldbutnotdead · 16 Apr 2018

That's a bodge (the 45 degree OSB upstands). As Notch7 detailed is the way to finish a GRP roof to a wall. Any warranty they've implied on the work (usual one is 'Materials guaranteed for 30 years') will not exist because they haven't installed to manufacturers' spec. Did they form a proper drip edge into the gutter?- if they didn't then that'll cause trouble in a few years. The trims needed to do the roof properly cost about £3 per metre, they've put a useless mortar fillet on cos lead costs about £10 per metre.

Yes installing cover flashing is pretty straightforward with an angle grinder plus diamond blade to rake out the mortar. Use the stainless steel clips to wedge the lead into the chase (rather than the old-school rolled up bits of lead)- the clips work fine & don't tend to lift the bricks! Don't be tempted to use fibreglass cover flashing (the price might appeal)- it is fine if your walls are flat and your chase is dead straight but otherwise is annoying to handle and will look a bit poo.

Kmurphy · 16 Apr 2018

Anyone know how to do a drain? Is it as simple as drilling out a hole in the back wall with some guttering and lead over the bottom?

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Bad Roofing Job?

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