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Is this GRP roof being done correctly?

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maneatchicken

from United Kingdom

Joined: 06 Mar 2012
Posts: 8
Location: London,
United Kingdom

PostPosted: Tue Mar 06, 2012 9:32 pm Reply with quote

We currently have an old Felt roof on our house which is dipping in places and decided to replace the roof with a GRP roof. We hired a roofer/builder who quoted to strip existing felt, re-fir, re-deck, and install GRP system to the entire flats roof.

When looking at the work done so far, I noticed the following:
1) The old felt was not completely removed but the firring/plywood was laid on top of the old felt (builder claims he removed the top layer)
2) We agreed to lay new firrings, the builder said the laid 4 inch of fall over approximately 10 meters (length of roof). Is this sufficient?
3) The plywood looks like ordinary plywood rather than Weather proof plywood or OSB - can this cause any issues with movement/moisture?
4) There is a noticeable dip in the middle of the roof which looks like there will be some puddling ... Is this normal/acceptable or can I assume there will be problems in the future?

Any thoughts? The builder has so far completed the decking and the first layer of resin...
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maneatchicken

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Location: London,
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PostPosted: Tue Mar 06, 2012 10:06 pm Reply with quote

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SurreyRoofingEstimator

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PostPosted: Wed Mar 07, 2012 9:35 am Reply with quote

As long as the existing roof deck is sound it is acceptable to board over the top of the existing felt but if you were quoted removal of deck it should be done or a reduction given.

The minimum design fall for a roof is 1:80 but better at 1:60 so the fall you have now is a little lower than it should be (1:100 based on your measurements)

One of our guys does a lot of GRP roofing and always uses T & G OSB3 as a deck, makes life easier as you don't have to bandage the joints but you can use plywood (can't tell you what's been laid there myself)

Pooling shouldn't actually cause any issue on a properly finished GRP roof but isn't desirable

Looking at the size of the roof there it looks over 50 sqm, if it is you should also have an expansion joint to allow movement
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maneatchicken

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Joined: 06 Mar 2012
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Location: London,
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PostPosted: Wed Mar 07, 2012 10:08 am Reply with quote

thanks surrey, the quote said to strip existing felt roof covering that is on the flat roof area which is covering the existing asphalt roof. so I assumed he would strip to joist. Or am i reading it wrong?

The quote also says to Lay furring pieces from front to rear elevation of the flat roof to give adequate fall to flat roof once re-boarded, with 18mm OSB i.e Smart Ply.

So he was going to re-board first meaning he was intending to strip right down, right?

This is the wood he is using - is this OSB then...

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SurreyRoofingEstimator

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PostPosted: Wed Mar 07, 2012 10:32 am Reply with quote

No, that's not OSB, follow link below which shows images of OSB

http://www.wickes.co.uk/sheet-materials/osb/icat/smosb/
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cotswoldbuilders

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PostPosted: Wed Mar 07, 2012 5:17 pm Reply with quote

OSB t&g is the more preferred board for glass fibre, and as SRE said, no need to bandage the joints when laid the correct way up as the small gap fills up with glue.
The board your roofers used is ply.
Are they fitting preformed trims around the edges and upstands.
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Nige F (8 Mar 2012)
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Zeberdee

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PostPosted: Thu Mar 08, 2012 7:11 pm Reply with quote

Sorry but looks a bit Micky Mouse to me.

Did you see any evidence of old felt being stripped off? Mess in a skip etc?
Taking off the top layer from an area that big would create quite abit of mess.

Plus you can still see the felt on the upstands around the parapit wall.

You may just have his word for it and that will have to do I'm afraid.
If it pools, I wouldn't worry to much if he's given you a gaurantee??
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maneatchicken

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Location: London,
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PostPosted: Thu Mar 08, 2012 8:16 pm Reply with quote

I know he didn't take much felt off - if at all- even though he said he took the top layer off because 2 hrs into the first day of work he started laying down furring...! I'm just worried that there might be cracks months down the line. Potentially due to movement as I have a roof on top of an old roof? Or am I worried about nothing?

I asked him why he didn't strip existing felt when I requested it, he said it didn't need stripping as the roof was sound. Shall I ask for a fee reduction for his short cut? It's 55m2 area, any suggestions on labour and waste disposal etc?
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dilly

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PostPosted: Thu Mar 08, 2012 9:09 pm Reply with quote

ok that is a bad job all trims should have been fitted b4 fibreglassing.
how is the detail going to be finished on parapet as old felt still on
He has run fibreglass onto felt this eats away at felt and will not stick
How long b4 topcoat?
more than 24hrs the topcoat will not adhere well unless he has washed down with acetone this revives laminate in order for a good adhesion.
have the boards got bba markings or is it cheap chinese ply that delaminates.
I think that is a typical bad job that gives grp roofs a bad name nothing to do with the product.Just very badly done.
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maneatchicken (9 Mar 2012)
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dilly

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PostPosted: Thu Mar 08, 2012 9:11 pm Reply with quote

ok that is a bad job all trims should have been fitted b4 fibreglassing.
how is the detail going to be finished on parapet as old felt still on
He has run fibreglass onto felt this eats away at felt and will not stick
How long b4 topcoat?
more than 24hrs the topcoat will not adhere well unless he has washed down with acetone this revives laminate in order for a good adhesion.
have the boards got bba markings or is it cheap chinese ply that delaminates.
I think that is a typical bad job that gives grp roofs a bad name nothing to do with the product.Just very badly done.
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maneatchicken

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Location: London,
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PostPosted: Thu Mar 08, 2012 10:40 pm Reply with quote

Thanks Dilly, this is how he is finishing the edgings off - yes the old felt all still there and... is it taped on and leaded across?? I'm really not sure what exactly has been done??

And the finishing for the roof windows - it seems that they covered over the existing felt.

Do these look ok to you guys?

(He wants full payment tomorrow...)

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maneatchicken

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PostPosted: Thu Mar 08, 2012 10:56 pm Reply with quote

here, another close up picture of the finishing beauty...

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...and 48 hrs between 2 resin applications (because one day was rainy - worrying as the edges were all unprotected and got very wet)
Also ordinary ply used..
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cotswoldbuilders

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PostPosted: Fri Mar 09, 2012 8:35 am Reply with quote

To be quite honest, thats not the best of jobs and I wouldnt put a gaurantee on that work, It looks like some who done it has been on a half day training course, or watched someone doing a glass fibre roof and thought that looks easy, I can do that.
Theres no thought been put into the prep work, ie all existing coverings removed, reason to check all existing timbers are sound.
I cant see from photos any fixings, the board looks like cheap chinese ply, the upstands should have been cut away so as the boards had a fine movement joint to edges.
As for boarding, I would have used T & G Osb, Im pretty sure the ply used will delaminate.
You could have had the chance to upgrade the roof insulation if roof was properly strip.
It doesnt look like the proper angle trims have been used to all perimeter edges and stuck straight to the felt, which is bad practice.
There should have been a lead flashing fitted under the coping stones and dress down over the upstands.
The lead work done around roof light isnt tidy.
In the last photo the felt has come away from the wall, Im pretty sure you will have delamination, the guys have saved a fortune on stripping in labour and skip hire, this is the hardest part of the job, the best part is re-boarding and glass fibre, but thats pointless on seeing how they have done it, perhaps when it leaks they are relying on the original roof underneath keeping out the water.
We renewed one similar to yours last year, the customer said it was renewed year previously, when we stripped the roof we found he had laid cheap boards over existing roof, no fixings, then 1 layer of torch on underlay with solar reflective paint to make it look like new.
Did you get several quotes, you may have gone with the cheapest, but it will cost more in the end.
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cotswoldbuilders

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PostPosted: Fri Mar 09, 2012 8:37 am Reply with quote

To be quite honest, thats not the best of jobs and I wouldnt put a gaurantee on that work, It looks like some who done it has been on a half day training course, or watched someone doing a glass fibre roof and thought that looks easy, I can do that.
Theres no thought been put into the prep work, ie all existing coverings removed, reason to check all existing timbers are sound.
I cant see from photos any fixings, the board looks like cheap chinese ply, the upstands should have been cut away so as the boards had a fine movement joint to edges.
As for boarding, I would have used T & G Osb, Im pretty sure the ply used will delaminate.
You could have had the chance to upgrade the roof insulation if roof was properly strip.
It doesnt look like the proper angle trims have been used to all perimeter edges and stuck straight to the felt, which is bad practice.
There should have been a lead flashing fitted under the coping stones and dress down over the upstands.
The lead work done around roof light isnt tidy.
In the last photo the felt has come away from the wall, Im pretty sure you will have delamination, the guys have saved a fortune on stripping in labour and skip hire, this is the hardest part of the job, the best part is re-boarding and glass fibre, but thats pointless on seeing how they have done it, perhaps when it leaks they are relying on the original roof underneath keeping out the water.
We renewed one similar to yours last year, the customer said it was renewed year previously, when we stripped the roof we found he had laid cheap boards over existing roof, no fixings, then 1 layer of torch on underlay with solar reflective paint to make it look like new.
Did you get several quotes, you may have gone with the cheapest, but it will cost more in the end.
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Zeberdee

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Posts: 159
Location: Birmingham,
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PostPosted: Fri Mar 09, 2012 1:41 pm Reply with quote

maneatchicken wrote:
I know he didn't take much felt off - if at all- even though he said he took the top layer off because 2 hrs into the first day of work he started laying down furring...! I'm just worried that there might be cracks months down the line. Potentially due to movement as I have a roof on top of an old roof? Or am I worried about nothing?

I asked him why he didn't strip existing felt when I requested it, he said it didn't need stripping as the roof was sound. Shall I ask for a fee reduction for his short cut? It's 55m2 area, any suggestions on labour and waste disposal etc?


Sorry but he said the roof was sound?? lol

Has he got x-ray vision??

You paid for the total strip off of felt and he hasn't done it simple.

Back to the pics you've posted..........I'm going to brutally honest here, And I hate slating other folks work but I have to speak up here... It looks a bodge job, Specially round the edges/upstands. coping stones should have came of with the grp going under the coping stones before they go back on or at least with a lead flashing dressed over the grp.

It looks like they wanted a quick IN AND OUT on that job, Just LAZY.
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