Advice on replacing garage roof


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Hi,
I'm looking for some advice about replacing my garage roof. Currently it is constructed with several corrugated bitchumen sheets, centered with transparent plastic (I think PVC) sheets. These are supported with a few unequally spread wood beams. As you can see from the photos, over time there has been a build up of rainwater on several of the sheets which has caused them to badly bow to the point where the bitchumen is now torn and in desperate need to replacement. One of the sheets was replaced about 7/8 months ago and has already started to bow.
I had someone out today who recommended fibreglassing the roof and indicated that it would cost £2k+ for parts and labour, but this is quite a bit more than I was hoping to pay. I'm considering having ago myself. Would an option be to take off the existing sheets, put down some plywood/OSB3 sheets to strengthen the roof and then put down some new corrugated on top? Also does anyone have experience using EPDM rubber? I've read mixed reviews about this? Is this likely to be a difficult job?
Any help much appreciated!
Photos of garage roof: photos.app.goo.gl/LyityCt89JywzHf76
 
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Hi,

Welcome to the forum Rossy_87.

I would definitely advise against fiberglassing the roof. For £2,000 you could replace the entire roof doing the job yourself and possibly do a better job.

https://www.rubberflatroof.co.uk/product/epdm-rubber-roofing-membrane-1-2mm-rubberall/?gclid=Cj0KCQjw0YD4BRD2ARIsAHwmKVkmGGLBD5nTzUlOSHXka-W04a-L58hyg5V7_CFNPPi33HlOydOcPmoaArOCEALw_wcB

I'd install new joists at 16" on center covering with 18mm WBP plywood then you could choose the top covering. I've never used the rubber type roofing but 30 years ago my wife and I replaced our bungalow and two roomed extension roof taking two weeks of back breaking work but we did the job right first time. There will be many tutorial videos on YouTube to show how to do the job; do you need the roof lighting panels because these are always a problem; strip lights in the garage would allow you to make a top class job of sealing the roof once and for all. We used a product called Nuralite but this I think is a lot more difficult than using the rubber sheeting and more expensive?

All our neighbours have suffered years of roof problems each having "professional" roofers do the work;

104_1730.JPG


Here's our immediate neighbours roof having just had it installed by a professional roofer of 20 years experience? The job is simply appalling; a missing length of fascia and the roof is 1.5" too small all around because it doesn't overhang the single gutter; the gutter should be installed to two sides and back.

104_1744.JPG


In heavy rain there is a spectacular waterfall with the only water going down the drain being the water landing directly into it from the sky; the roofer is returning on Monday AGAIN.

May I suggest you do lots of research before jumping in; this is one job that is more manual than difficult; plan the job to the last detail and double or triple check all measurements then check again; anyone local to you with a wood burner will welcome the old timber. The job can be done from a ladder and once the first section of roofing is installed then this makes a good working platform; taking time and working safely are the way forward. Don't forget roof overhang for discharging rainwater into the gutters. Once you succeed with this roofing job it will give you immense satisfaction and very useful experience; the tools needed are few and a straightforward roof like this shouldn't take long to install.

When we installed our new roof we didn't have YouTube tutorials we bought a good book on the subject.

Up on the roof._0002.JPG


With zero roofing experience but desperately short of money and two ceilings already leaking I spent 18 months researching how to install a roof buying an excellent book on the subject whilst we worked flat out to save enough money to buy roofing materials; I worked on the roof and my wonderful wife worked just as hard skip filling and bagging up two ceilings. The main bungalow roof is in Marley Wessex tiles the two roomed rear extension covered in Nuralite sheets.


Up on the roof._0003.JPG


The Nuralite roof clearly shows the correct roof overhang in order to discharge water into the gutter; the stone archway I built over the kitchen window to replace a rusty lintel.


Up on the roof._0001.JPG


Here's the roof a few years ago when I had to replace the chimney stack adding a new chimney pot. All it takes is personal confidence and lots of research but never ever taking any risks regarding safety. Just because we're not roofers doesn't mean we can't learn; I wouldn't encourage anyone to go on a roof only to suffer an accident. I'm a mechanical engineer so I have plenty of skills I can transfer to any job.

Good luck.

Kind regards, Colin.
 
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You ask a question, and two Colins come along to reply!

As a trial, I had a small roof covered with fibreglass on an OSB3 base. The chap who did it for me is a master roofer and this was his first go at fibreglass. It was done free of charge for him to see how it lasted ..... we are friends and he has done many top class jobs for me.

Anyway, it lasted just over 4 years and then splits appeared around the edge that faces the morning sun. We checked that it had been correctly laid and bonded, and it had. So, he won't be using it again.

Now he has replaced it for free with new OSB3 and EPDM, that he has used many times in the past. Now we will see how that lasts.

Colin
 
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Hi,

I've never trusted OSB Colin so have never used it; I'd be interested to learn from others how reliable OSB is when used outdoors; I use WBP plywood.

Over 30 years ago whilst living in our previous house there was an alarming trend where stone flagged cottage roofs were being fiberglassed; they looked horrendous and I wonder how long this bodged repair would last; once applied the roof would then need completely replacing whereas doing the job right in the first place the flags could have been reused by simply turning them over; a roof needs to move with temperature changes and to breathe not be sealed like a plastic bag.

I'm an experienced glass fiber laminator; after a year I had to leave the job due to mild dermatitis in my hands; I left before the dermatitis became serious; I actually liked the job and we made all manner of products ranging from bath front panels to big roof sections for nuclear power stations; shop fronts were laid up on a huge plate glass table giving a mirror finish to the coloured gel coat; we used to catalyze 5 gallons of resin at a time applying it with long lambswool rollers. We were on bonus earning good money; we weren't supposed to lay up more than 4oz of mat at a time but we often laid 6oz and occasionally it would smoke as it cured. At the end of the day I would remove my boiler suit and wellingtons and stand them up they being one unit.

Anyone using Acetone please be warned Acetone can burst into flames just by gnashing your teeth; it's highly flammable; sunshine through a roof glass window had two open containers burst into flames; we used these for washing the tools out.

Glass fiber is expensive and over a period of years develops lots of crazing in the gel coat; I'd avoid using glass fiber if at all possible.

Kind regards, Colin.
 
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OSB3 (note the 3) is ideal for use outside, providing it has a waterproof covering, as in EPDM. The board itself is impregnated with a waterproof resin - hence the number 3 signifying that. As a test, I have a couple of bare offcuts stood in my garden with their edge facing the weather. 4 years so far, and no sign of mulching.

Colin
 

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