How to repair a leaking fibreglass roof

We appreciate your support via patreon www.patreon.com/BuildRepairandRestore This video shows how I repair a badly leaking fibreglass roof. I cut out the damaged section and replace the OSB boards and re apply new fibreglass matting with resin. I will coat the roof with topcoat in another video.
Thanks for watching and please subscribe for more videos.
You can contact me on 07580 512 409 for any roofing or building work in London

[@lutonbusdriver2315]

Just got to say firstly this was a really good, well presented video which explains everything clearly and concise. I also think that your work is brilliant and I really enjoyed watching how you solved this problem, step by step including all the merchandise that you purchased to carryout the job. Excellant 👍

[@mickjmcgregor4384]

Im a composite specialist , the first layer should be 450gm csm ane second layer should be 600gm the cut edge of the old grp should be sanded down to a feather edge and board gaps taped , the new matt should have the clean cut edge frayed wih both overlapping , the catalyst is 2% per 2 square meter 3kg polyester resin . NEVER do fiber glass if chance off rain water drops can cause pin hoes and water will ruin the emulsion in the matting I hope this helps

[@EC-ig8ts]

you're having such a kind and generous heart, spending extra time in video shooting and sharing these useful information to help people. Thank you very much.

[@gtd65]

Very enjoyable and informative video. Great basis for investigating my fiberglass balcony, which was hidden under paving slabs. The upper surface appears to have separated in layers under the slabs. I suspect the job wasn't done properly in the first place as UV really hasn't been an issue and the balcony is very rarely used.

[@anthonydavid1965]

Kudos to you for doing this video. It’s a lot of work and so helpful. Well done👍

[@diccoo32]

Thank you. You are a hero amongst us. I really appreciate these videos.

[@happyman9996]

Great video, hate it when it starts raining and your halfway through the job. I had a roofer in 2014 lay a fibreglass roof (GRP), he did a great job of tiling my roof, but a crap job of laying the GRP roof. It's leaked several times since and I've had to repair it. I've looked at GRP videos and learnt how to lay these roofs, doing one for my neighbour 6 years ago, without any problems since. To fix my roof I really need to rip it up, but have held off because of the expense and time. The so called roofer, didn't use wall fillets and no 18mm marine board underneath, only the thin ply that came attached to the insulation. I thought it wouldn't last, but didn't know much about theses roofs at the time. There are so many cowboys laying these types of roof out there. Thanks for the video, it's a nice refresh for me on how the job is done properly.

[@darrenthebuilder]

Sorry to hear about your problems. It is always good and satisfying if you can do it yourself. Atleast you know what has been done. Instead of marine ply, use 18mm OSB. It’s what’s recommended for GRP and is less likely to delaminate. Ply is too smooth. Good luck!

[@happyman9996]

Thanks for the info, don't stop the videos coming, cheers.

[@FloridaSummer2010]

Great video!! I have a fiberglass hightop camper. Your video just saved me lot's of $$$. Thanks again.

[@darrenthebuilder]

Amazing 👍🏾👍🏾 You’re welcome

[@noellakarl2087]

I love to watch you work.

[@lhfloors]

Good effort Darren so many problems with that roof your be back to replace it one day needs properly venting as well good luck

[@msives]

I've watched so many diy/builder videos on KZbin and yours are the best by a long way...you explain everything simply and clearly and make even tough jobs seem attainable for amateurs like me. My new favotite YT channel! 👍👍

[@darrenthebuilder]

Thanks Matthew really appreciate it

[@Danny-vx1wc]

Just about to repair mine, thanks for the pointers.👍🏻. Just need a dry day 🙄

[@stuartandrews4344]

Would wait a few months for the warmer weather, shouldn't lay grp below 5°C,it won't cure properly, but sadly many do & then have problems later.

[@mykalgb8643]

I really enjoyed watching your work on KZbin

[@AbdulGhaffar-ng7tg]

Best way to explain. Great work

[@hopewalker5764]

Another great video. Thank you so much for sharing your knowledge and experience. Don't give up. The subs will come.

[@darrenthebuilder]

You’re welcome and thanks 😊

[@sophloui276]

Hope to see part 2 with the final coat on the whole roof 👍

[@darrenthebuilder]

Soph Loui it should be uploaded later today

[@sevenodonata]

Seeing such good work was very satisfying 👍

[@amanda13244]

Haven’t caught up with your work in a while ... keep up with the work n information just watched a middle of this .

[@darrenthebuilder]

Thankyou 😊

[@jeremysmith7691]

You guys do some top notch work. 👌🏼👍🏼👍🏼👍🏼

[@darrenthebuilder]

Thankyou

[@bidders77]

Looks exactly what I was looking for. Top job that 👍🏼

[@lewisyarwood4381]

Amazing videos mate keep up the good work

[@yashswamy5833]

Very very clear thanks for the details provided.

[@happydays454]

Wow crazy roof i live in Albuquerque new Mexico USA and I've never heard of fiberglass roof they use to use tar and gravel, torch down and now every one uses tpo now

[@ukgardener973]

you make it look so easy! nice one!

[@darrenthebuilder]

Thanks

[@philacorbett]

Thank you I found this video really helpful.

[@HowToSandAFloor]

Great video, so much conflicting advice on this

[@barrie7777]

Great job 👍

[@robertferguson32]

Hi, really enjoying your videos, keep up the good work. Have you thought about getting a power sander or would it not work?

[@veritybarnes1506]

My fibreglass roof has been leaking and a roofer went up there and there are loads of pinholes in it so water has been penetrating. The contractor is still denying that anything is wrong. I wish you lived in my area and could come and fix it!

[@denisconor648]

Great stuff.

[@durhamsteven6930]

Great video

[@Jide80]

Hi Darren, your video always satisfying to watch. Please just a quick question. Let’s say when you went back the next day it leaked? Can you put another layer on that or scrap it and start again? Thank you in advance.

[@antonyporter5045]

great video cheers

[@leestanley8315]

I see it start raining as you was applying the fibber glass matting and resining? And that makes the roof have a reaction when dry like it becomes very hairy. If you read the tins or done the course you would know it can not rain at anytime of applying as when you are bridling the fibber you are mix’s water witch is a big no no. Just a little advice for the future. Also after applying to coat it’s best for the to have a 24 hour rain free time.

[@RicSeabergsUseful-Information]

Awesome job bruh

[@darrenthebuilder]

Thank you

[@Inglewhite1]

Hi, thanks for sharing your video. Would you say that a spongy roof is always a sign of the wood being rotten underneath or could it just be lifting and it’s air rather than water between substrate and grp and if not walked in may remain watertight? Mine is spongy in places but thought it may just be air beneath but that the GRP is still intact and waterproof as no sign of ingress in the room below. If water is getting through do you expect it would always show as a leak on the ceiling below?. I would have thought so? Welcome your thoughts thanks

[@uncled39]

Excellent

[@waterproofingdecksymas5853]

Good video

[@GeneLinetsky-GAL]

Hi - very useful video. I've had my GRP dormer roof spring a few leaks this winter just about 8 years after being done (nothing like the 25-30 years GRP "guarantee"). I suspect my contractor cut some corners back then... It only leaked two or three times (for the first time ever) last winter but I feel that an entire dormer roof deserves a new coat and repaint -- otherwise new leaks may appear elsewhere. I am quite unsure whether I should consider replacing the boards underneath -- unlike the house in this video, I have spec'ed WBP 18mm board there, and it only leaked a handful of times -- WBP is supposed to last a lot longer in case of water ingress. Your "step on the board to feel its springiness" test is very handy but not obvious to a non-professional.

[@darrenthebuilder]

Hi Gene, I would replace the boards. It will be impossible to remove the old Grp without taking the boards out and I wouldn’t recommend fibreglassing over the existing.

[@GeneLinetsky-GAL]

@@darrenthebuilder Thanks! ... that sounds like major work, pretty much a new GRP roof. I've had a look at the roof -- it looks like there are many pinholes in the areas where it leaks. Some websites I googled recommend sanding the affected areas down to the clear resin, "acetoning" those areas and then reapplying one (or two) resin layers with a new topcoat. Assuming that the plywood is not "springy" underneath, maybe that would fix it?? I don't mean to challenge your advice/expertise as you have to rely on the info I provided above... I am just trying to figure out the optimal (not the cheapest) solution here.

[@darrenthebuilder]

Hi Gene, you could try that. If the base isn’t damaged then as you said sand those areas and apply some mesh/resin over the suspect areas. Then see if your leaks stop. Look out for cracks as well. Cheers

[@darrenthebuilder]

Once repaired give the whole roof a run with 80 grit sand paper to provide a key and then paint with topcoat

[@GeneLinetsky-GAL]

@@darrenthebuilder OK let's see how I get on with this... Thank you for the tips!!!

[@SuperAna1954]

Great job, as usual

[@gurinderkular7209]

Great work and very informative, thank you. Instead of using the cure it topcoat would it be OK to use another product? I'm thinking of something like a liquid rubber or acrylic top coat. I find the fibreglass top coat let's the system down. For the price they charge its little more than a exterior paint and not helping the fibreglass.

[@darrenthebuilder]

Thanks. I’m not really sure about other products to be honest. And as I’m doing the work for someone I have to stay with what the manufacturers recommend to protect myself in case the product fails.

[@gurinderkular7209]

@@darrenthebuilder that makes sense. Thanks for the reply. Keep up the good work. When I need my loft roof which is grp replacing I'll let you know

[@darrenthebuilder]

gurinder kular thankyou 😊 Sure no problem

[@shelleyshell9441]

Nice job! I was just wondering if the customer considered replacing the whole roof? Since this was the second time you had to fix problem areas?

[@darrenthebuilder]

It would be very expensive (thousands) so it’s not economical but I think that should be the last of the issues now

[@Khristofu]

Great work. Liked and subbed. Had our roof fibreglassed last month but suspect it was done poorly. Alot of bumps on top and there is a strong smell of the resin inside the kitchen even after a month since it was laid. Likely not mixed properly? Do you think the bumps will be an issue?

[@darrenthebuilder]

Hi the bumps won’t necessarily be an issue, they may be cosmetically a problem more than anything. It’s hard to say if the mix is a problem but I wouldn’t expect to smell resin for more than a day. Do you know what product was used?

[@Khristofu]

@@darrenthebuilder they used cure it, first coat was done about 4 months ago, building work got put on hold, then they came back and done a 2nd coat. We did have some leaks in between that 12 week period i suspect due to it not being properly coated the first time.

[@neleempatel8182]

Only Pro's should be using the Grp system otherwise you end up with a very messy end product that proves to be brittle. Good repair job man

[@stuartandrews4344]

Known a few diyers do a excellent job with grp roofing, but a lot of problems is down to adding too much catalyst,& not enough wetting & consolidating the grp.

[@Hammers.grandad]

Good job. Is it possible to repair torch on felt roofs with fiberglass or is it better to stick with chipped felt?

[@MJ720]

You probably get asked this a lot, but how much does this sort of job cost? Or even how much would an entire roof cost to redo? Cheers

[@sureshmahatheva1732]

Hi brother very helpful video. Out roof is fibre glass roof. I noticed few leaks. Will Applying top coat stop leaks or I have repair with resin. Please help me

[@darrenthebuilder]

Topcoat won’t stop leads you need to glass it

[@kingkurtzig]

Nice job mate, what would you advise for cracks? Im looking at 'Alltimes PU Sealant'

[@darrenthebuilder]

Hi I haven’t use that product but with cracks I would sand it and apply resin and fibreglsss bandage then repair the repair with topcoat

[@shanewatson6562]

No air flow to

[@rfden]

Yes possibly roof sweating

[@stuartandrews4344]

@@rfden Definitely, air gap for cross flow ventilation,so important on a cold roof design...

[@teamosborneracing]

Great Video! One question: On average, how much would a repair such as this typically cost in supplies vs the cost of getting a "professional" trades person to do the job?

[@darrenthebuilder]

Thankyou I think the suppliers was about 250 and was 300 to do the repair From memory

[@superseven220]

@@darrenthebuilder very reasonable👍

[@thomassheridan4252]

@@darrenthebuilder way to cheep should have charged at least double that

[@itsallaboutme12345]

I need some repair work doing and I've tried some roofers which are refusing to come and rectify it. Excuse is the resin is of different types and what not. Just seemed as though to me they weren't interested in minor repair work...some expert advice would be appreciated

[@af6727]

Nice! What do you call the small roller you used to make sure the resin is spread out?

[@433elliot]

Consolidating roller or batten roller

[@JacobKnightRiderShop]

Wow here in the usa nobody does fiberglass roofs on the flat that I know of. I wonder why? Seems england does use it alot if they stock the resin.

[@nectafarious8842]

Differential expansion /contraction issues between the grp and the timber substrate, especially in hot climates. With no expansion gaps between the boards as well, they cup and lift at the edges, cracking the grp.

[@kung-fuhustle5755]

Great video buddy, just a quick question how much do u charge for a job like this, thx.

[@uncled39]

£895.00

[@c.m.303]

Too bad he didn't line up that last sheet of fiberglass. It should overlap yet it looks like there is almost no coverage on that back left corner.

[@uncled39]

Very bad. He'll be coming back to do that again and charging for it.

[@premiafeedermusic]

Ive watched a few of your videos. Get a your mask on when your rolling and cutting fibreglass. :)

[@JayG2K]

hi we had a fibre glass roof put on this year in a loft conversion dormer. Recently after painting there are 2 x damp stains close together around 50x50mm. there wasn't any sign of damp before interior painting was carried out. Do you think there is a leak or could it be with the cold weather and it condensation occur. I assume insulation was added in between the rafters but there could be a cold spot somewhere where builders left a gap.

[@The_Voice_of_Reason748]

Hi did you get to the bottom of this and did the roofer's fix it?

[@JayG2K]

It was for a customer o was working g at. The leak didnt reappear again so it is possible ot was condensation.

[@stuartandrews4344]

And those coax cables through grp roof ain't helping to keeping out mositure from getting to the decking, think owner should seriously consider it's time for a new roof, but that would cost thousands,so a rub down & new top coat.And it's a poorly constructed cold roof,no proper air gap for cross ventilation.Great work, & your subs should be far higher.

[@darrenthebuilder]

Thanks Stuart, you’re right it not built the greatest. I did give it a rub down and recoat aswell. Thanks for the sub.

[@Nellsta]

Aren’t you supposed to use bandage on the joints before the strand matting

[@adrianporter8403]

Looks like next doors has the same problem too!

[@arifismail.]

Just seen this video from start to finish..mate uve left all old wet osb debris and rubbish under the new osb boards..winds me up how some trades ppl cba to.work clean..wet timber is.open for moisture and wet rot over time

[@darrenthebuilder]

No I didn’t. Sorry that you’ve been wound up. Hope you can relax and unwind soon. Take care of yourself

[@seyhanwoodger6338]

Thank you so much for this video. Where can I get that cutter and the screwdriver ?

[@marcinlasota80]

Wow it's look like not correctly done how long is the roof done ?

[@moqureshi8279]

Why did it leak in 1st place . I have been told these roofs last 20 years and alot more ? Thanks !!

[@darrenthebuilder]

They should but it was laid poorly. The resin was too thin in places and no consolidated properly with a paddle roller so it had pin holes

[@moqureshi8279]

@@darrenthebuilder many thanks!!

[@fineaqua3279]

I heard that fibreglass is waterproof and weatherproof. If so, how did the water went inside?

[@darrenthebuilder]

It wasn’t installed well. If not done properly you can get tiny pin holes

[@samboswell8959]

Great job. Shame you are not based in the Midlands.

[@AjayDhatrak]

Which areas do you cover?

[@MrFlatroofer]

This is most "warm" GRP roofs end up after about 7-10 years. Just use a professional roofer using SBS polyester torch system, 30 year life at least.

[@kimburke575]

That will outlast the roof. 👌🏾

[@michaellack5139]

Acetone is good for dissolving polystyrene....little tip for you

[@subodhpatel4617]

Hi where are you based. Would you consider a similar repair in Bethnal Green?

[@entropydomain]

Can anyone suggest why this part has leaked but the rest of the roof is okay? If it was installed badly the whole roof will cause problems soon in my opinion as an unskilled non roofer 😂

[@Ms2Chill]

How long do these fiberglas roofs last?

[@mrflatroofer4089]

At least 3 years, 3 layer torch on with SBS polyester membranes, 30 years. and half the cost.

[@Dhanowaliboys]

Witch market you got this product can you tell me plz

[@JohnDuffell]

selco, it's trade only but you can just walk in and pay cash/card without an account

[@vaper106]

Can you remember how old was that roof .thx

[@darrenthebuilder]

Hi I don’t know sorry as I wasn’t the one who did the original roof

[@DanielPaprocki]

This is cold roof and it should have ventilation gap of 50mm above the insulation in order to work as intended. Unfortunately this roof doesn't have it so its going to keep failing regardless of any pinholes on the top. It's just bad design 🤷🏼‍♂️😄

[@augustinsuciu6697]

This is a cold roof and there need minimum 50mm gup for ventilation, I think this is the main problem with that roof

[@philstation335]

What store is that Dar cuz looks like it sells everything down here I go one place to get the osb another place to get all fiberglass stuff etc and ur forever driving arnd getting everything

[@darrenthebuilder]

Hi Phil, it’s Selco. We have loads in London. They’ve become the biggest now.

[@philstation335]

@@darrenthebuilder tell management to open one up here in Plymouth lol

[@darrenthebuilder]

Wow you’re all the way down there. I just checked and the nearest is Bournemouth lol a fair trek

[@philstation335]

lol yea I just checked are they public or just trade as I use totem timber which sells mainly just timber Sand cement but selco I've just looked practically everything u need all in one place

[@philstation335]

U wanna move to plymouth lots of work down here and a chilled out lifestyle my mate moved from London 10 yrs ago and cudnt believe how much slower the lifestyle was down here he's never been back since lol

[@rooftop8339]

You have totally mis diagnosed the problem. The only reason why the decking has failed is because it’s a cold deck roof installation without ventilation. The area you worked on is above the bathroom in the loft conversion. Yes you fixed it, but the problem will reoccur again.

[@darrenthebuilder]

It was due to pin holes. The bathroom is actually on the left hand side far from where the issue was.

[@vixsagoo3997]

Hi where are you based, i have a leak and i need someone to look at my roof.

[@radiogramgramophonetoons5802]

The mat is dry, bad laminating originally

[@TheKingsbridge]

you need to fix firings first under the osb ,that were rotten,& your find it’s more condensation problem also GRP👎🏻

[@darrenthebuilder]

Definately wasn’t condensation. There were pin holes in the OSB in that area. I think they are great once installed properly.

[@johnlerigo9703]

Should have bandaged the joints first, joints will crack when somebody walks near joints,

[@tinkletoesrus]

can you do that in the rain

[@darrenthebuilder]

No

[@barrymcmahon469]

Print side up on all OSB boards for correct tongue and groove fitment!!

[@darrenthebuilder]

Actually these boards are the opposite, print side down not up. I actually put the first one the wrong way. Mistakes happen but this won’t make any difference with one board and small patch. Cheers

[@spraduckjenkins5245]

I'd wear a mask with all that dust flying around, maybe some goggles too.

[@augustuspatrone6790]

Where are you based?

[@darrenthebuilder]

London

[@ar3919]

That's not good, in the city I live in, the new houses are using fiberglass and in front of my house they built 10 houses 5 years ago and they all have damaged roofs, one thing they are not using treated wood and they are using panels that They are not good for the roof because humidity rots them, otherwise the sun, rain and snow damage the fiberglass and that is the problem, it is better to continue using what has always been used, which lasts for many years without any problem and less expense.(Gaf Tri-Ply APP)

[@simonworsnop900]

That " cold roof " is built wrong and no amount of patches will repair it. Cold roofs rely on airflow between insulation and the roof covering ..in this case osb and fiberglass. That roof has noggins in restricting and creating dead zones in airflow and also insufficient air gap as stated above. Its suffering from sweating ( condensation) Wouldn't get this passed by our local building inspectors .....

[@SkillBuilder]

I agree, this is a classic case of sweating from the inside.

[@bbmirza24]

How can you tell it’s sweating and not a leaking roof? Is it the noggins? The spongy nature when he stands on it?

[@Paul-sk2dj]

Not really. It's a hybrid design.

[@sounduser]

​@@Paul-sk2dj Spot lights... And cold deck no vents....

[@patterdalezipsuzilil]

That roof should have lasted 1000 years the cost of them felt roofs all day with a silver bitch coating see it from space my roof I done my self 1986 none mineral and painted it every year last year was 5 years not painting it just forgot to through 2 gallons of cromopol on it fantastic stuff

[@darrenthebuilder]

If done right it will last long. Can you imagine trying to paint a roof on the top of a loft every year? Lol

[@patterdalezipsuzilil]

@@darrenthebuilder my roof is 9ft by 6ft I got a 25ltr tin for nothing on some site got all me stuff for nothing swopped it for sockets and cable😆😆 only took me half hour with a roller but this cromopol I used last year well 2 years ago feels like a fiberglass roof just ordered some more I can't be bothered stripping just built it up with this acrylic fibre stuff

[@Famous5s]

Am I the only one wincing about lack of gloves and mask... sure OK trainers, but that's not nice stuff you're handling? #feellikeahealthandsafetystickler Neat jump cut at 34:40 ;)

[@pierrechildress8875]

This is why I hate 'flat' roof jobs. Unless you use a moisture meter to find exactly where the water is coming from, you'll be doing another repair in a couple of years. I noticed the chimney may not have vent caps, and could use some tuck pointing in any case. It could be that rainwater is percolating thru the joinery cement finding its way beneath the sheathing. You really can't tell w/out an infrared camera, or at least taking many measurements w a moisture meter as mentioned before. These types of jobs are the worst.

[@garyengland5326]

You should have trimmed the existing laminate 50mm back from the perimeter so the first layer of matting bridged the cut line in the osb, then the second layer lapped onto the old laminate. That way the deck would be reinforced with two layers. That was also full of air, and in the rain 😳. Sorry, but that will fail again. My arse clenched when I saw there was no edge protection and 240v on a roof. Your life isn't worth saving a few quid - get some scaffolding up!

[@thomassheridan4252]

Must just be me but all wrong ,way to many things to go into,it's ok for a temporary repair job he didn't charge much for it ,but not correct and as for health and safety I hope the home owner had insurance.he needs to be trained correctly but hay ho if he's getting paid 👍

[@thomassheridan4252]

Forget to say enjoyed the video, seems like a very nice man.

[@TheNikkizoe]

get a belt man ;)

[@glassfibrespecialists.]

This video should be called "How to break all the rules whilst trying to repair a fibreglass flat roof"

[@darrenthebuilder]

I’ve got an even better idea. You’re free to make your own video showing all the rules. I’m sure you’ll get lots of views Cheers.

[@glassfibrespecialists.]

@@darrenthebuilder Sorry but your video shows how not to carry out a successful repair in a fibreglass roof.

[@darrenthebuilder]

You don’t need to apologise for anything as the repair is successful. As I said KZbin is free for everyone to make their own videos. People will profit from your better way. Everyone’s happy and you’ve contributed to society. 👍🏾

[@glassfibrespecialists.]

@@darrenthebuilder To be fair I recon your a nice chap, if you ever need any advice please give me a call.

[@darrenthebuilder]

I try to be. Thankyou 👍🏾 I think that’s the best approach for the trades.

[@johnlerigo9703]

You’ve left bad roofing in place, because you couldn’t be bothered to go to the front more, on front left near guttering, , that’s as bad as people who put roof on, take all bad arrears out, fella , you pushed down on it, saw it moved but left it and just left crap on top of insulation, people don’t no what a good job is until they have had one done, come on fella, when doing a job do it right, don’t pick fault with others if you don’t do it better

[@darrenthebuilder]

Where you on the roof? Or are you making these assumptions via a screen?

[@michaeloloughlin8184]

Seriously doubt there was even a leak, that was just the roof sweating, the same problem will reoccur not to mention the repair itself was questionable. get on some more courses, can never do enough!

[@darrenthebuilder]

There was a leak. Every time it rained. Quite badly. No problem since 👍🏾

[@andrewmilanovich5879]

Total waste of money all you have to do is add a piece of rubber and seam tape no reason for all this extra shit