Greetings,

I have a number of leaks in a felt-roofed small flat roof extention.

It's been leaking for quite a while but I've been irresponsible and left it and now things have started to go mouldy!

It's about 1.8m x 4m rectangular apart from where a corner is missing where it joins the corner of the main house. So it's ' h' shaped essentially.


I've been recommended using EPDM roofing and I'm thinking of converting it from cold roof to warm roof at the same time.

I suspect joists have rotted and they've certainly been hacked about a lot for cables/piping (plus a guttering valley was cut into the joists- also leaking) so I think I'll remove the lot and start again and add furings(sp?) to give it some slope.


I know you can buy EPDM kits with all the trims and everything. There's loads of companies, any you'd particularly recommend?


Am I mad to be converting cold to warm roof? If I have to replace my joists anyway (or at least make significant repairs to what I have) it seems fairly easy to convert- I already have most of the selotex at least!

Any advice greatfully received- thank you!

James

I can't comment too much on what you're planning to do, but my shed roof started to leak and I decided to get rubber roofing from here (lots of useful info as well):

https://www.rubberroofingdirect.co.uk/

Next job is to fit it! Weather's much too hot to do this atm, so I'll wait for an overcast but dry day.

For a flat roof, EPDM seems to be good and they quote long life, but don't rule out fibreglass.

I fibreglassed our 6m x 2.5m flat roof over 20 years ago. Buying it all from Glasplies in Southport.

We have had one leak since then, but that turned out to be getting under the edge of the fibreglass, underneath the tiles of the pitched roof and was resolved with an extra piece of flashing.

IMHO if you've got to strip it back and replace rotten joists then I see it as worth converting from cold to warm roof. It'll make a noticeable improvement to the inside space all year round. Warmer (less heat loss/lower heating costs) in the colder months and cooler in the warmer months.

Around 15 years ago we added a glass roof conservatory to the back of our house. Nice to have the additional space, but freezing in the winter and boiling in the summer. A couple of years ago we had it re-roofed with a tiled system + Velux windows. Effectively changing it from a cold to warm roof. It's transformed it - usable all year round now and a pleasant place to be.

Can't advise on EPDM - never used/fitted it myself. It does seem recommended though.

I have just done my bike shed in EPDM. Very easy process and supposedly lasts for ages. Just as well because I had to replace the old bitumin roof every 3 or 4 years.

James,

I just replaced the roof on a double garage using epdm. Built up as a warm roof. I can’t see sense in doing it any other way.

It had an asbestos roof with basically no timber work left.

Put up new rafters, an osb deck, 100mm of Kingspan, another osb layer and then the epdm and finished with all the trim pieces.

A few gotchas along the way but worth it. The last epdm roof I did was cold and suffered from condensation inside as air was getting into the insulation.



Don’t underestimate the weight of the epdm. It was a mission getting an 80kg roll of material 2.5m up onto the roof!
Happy to email you a load of photos of my build If that helps.

[Edited on 22/7/21 by tegwin]

reroofed my large shed in EPDM last year after felt lasted less than a year and even when laid well it leaked due to being a shallow pitched pent shed.
Still looks good, was easy to lay and trim. Warm roof is better IMO, the venting of a cold roof is rarely adequate especially a flat one.

quote:

---

Originally posted by tegwin
James,

I just replaced the roof on a double garage using epdm. Built up as a warm roof. I can’t see sense in doing it any other way.

It had an asbestos roof with basically no timber work left.

Put up new rafters, an osb deck, 100mm of Kingspan, another osb layer and then the epdm and finished with all the trim pieces.

A few gotchas along the way but worth it. The last epdm roof I did was cold and suffered from condensation inside as air was getting into the insulation.



Don’t underestimate the weight of the epdm. It was a mission getting an 80kg roll of material 2.5m up onto the roof!
Happy to email you a load of photos of my build If that helps.

[Edited on 22/7/21 by tegwin]

---

Slope was built into the top of the wall. I then bolted a timber bearer into the top of the wall as it was a bit crumbly.

Rafters screwed into wall bearer. And add noggins.
Screw down osb to rafters
Plastic vapour barrier across whole lot.
Then kingspan on
Kingspan between joist ends. I added extra noggins inside as well.
Then top osb secured with ressessed cupped screws
Glue down epdm
Fascia boards on
Finish epdm edge with the correct trim strips.

trick is to get enough timber in to the ends of the rafters so you can nail your fascia boards and trim pieces to.

Yes height added is quite a bit but not really noticeable once it’s up.

Gain in headroom is fantastic as the insulation is above the deck.

I mentioned condensation as the last epdm roof I did was a cold roof with insulation pressed onto the spaces between rafters afterwards. Looked shit and leaked warm air onto the bottom of the cold deck.

U2u me an email address and il send you some photos if that helps

quote:

---

Originally posted by tegwin
Slope was built into the top of the wall. I then bolted a timber bearer into the top of the wall as it was a bit crumbly.

Rafters screwed into wall bearer. And add noggins.
Screw down osb to rafters
Plastic vapour barrier across whole lot.
Then kingspan on
Kingspan between joist ends. I added extra noggins inside as well.
Then top osb secured with ressessed cupped screws
Glue down epdm
Fascia boards on
Finish epdm edge with the correct trim strips.

trick is to get enough timber in to the ends of the rafters so you can nail your fascia boards and trim pieces to.

Yes height added is quite a bit but not really noticeable once it’s up.

Gain in headroom is fantastic as the insulation is above the deck.

I mentioned condensation as the last epdm roof I did was a cold roof with insulation pressed onto the spaces between rafters afterwards. Looked poo and leaked warm air onto the bottom of the cold deck.

U2u me an email address and il send you some photos if that helps

---

Thank you for all the advice folks.

Going to book a couple of days off week after next and give it a go then! What's the worst that can happen? The roof leaks!


Cheers,
James

I put EPDM on my shed roof today (2.5m x 2.8m) and it really wasn't too hard - a fair amount of physical effort, but not excessive. Getting the old roofing felt took more time than putting the new stuff on. The rubber sheet was VERY heavy to lift onto the roof though.

The water-based glue is bleedin' sticky, and gets everywhere! I kept finding my hands getting stuck to stepladders, the outside of my gloves, everything! And the paint roller I used is no longer fit for purpose...

Be sure to post some photos of the job.

I used rubber roofing direct and was pleased with their service. Beware though. A big roll of the stuff is heavy!

When we had our loft conversion done, the company wanted to do a felt roof. I insisted on EPDM. The boss was hesitant as his roofer was a traditionalist who more or less would only do slate or felt. The boss and one other guy went on an EPDM course and came back as an evangelist saying they would only ever do EPDM from then on. I think the instructor welting it with a sledge hammer until the plywood it was glued to broke but leaving no scar on the rubber is what did it for him.

We had a warm roof done, but only to maximise headroom. Birds on the roof are loud. I don't know if a cold roof gives more noise insulation.

Well 10 months later and it's still not bloody finished!

However, I ended up spending the last 6mths of 2021 clearing the garage, painting it, making the electrics resemble something safe and legal, putting in a work bench cut and shut from an ex-work one (Ayrton Senna's former Chief mechanic welded it up for me!) adding shelving... all so that I could actually empty my tools from the room that needs the new roof!

A new baby then appeared so I've been a bit occupied!

Anyway, roof well underway now.

All but the outermost old joists were actually ok so I've kept and that's saved me replacing the ceiling.
I built up around the outside of the roof with 6x2".
I've changed the direction of fall with new furrings.
Fitted 18mm T&G all over.
Primed the wall where the room joins the house and fitted Alutrix 600 vapour barrier over that.
150mm celotex (note- mixing brands and sizes so as to use donated off-cuts is a pain as they're not all the same thickness! ).

Next jobs this weekend:
18mm OSB top,
then fascia boards
Then I can finally fit the actual EPDM!
Then trims, then guttering.


It's been difficult only in so much as I've not done it before- if it was my 2nd or 3rd one I'd have been done much quicker.

The most astonishing thing has been... the cost! I've definitely spent ove £2750 and quite possibly closer to £3000. This is for a 5m x 2m (minus a bit) roof! So over £300 a square meter!

I've over bought on the OSB slightly and didn't need 1x 3m length of 6x2... but other than that I really don't know what more I could've done to save.


Still, it's been a fun project so far and we should get a decent utility room (you try drying enough clothes for 3 sons through winter without a tumble dryer! ) out of it at the end.

I've not taken many photos but have a few I can share when it's all done.

Cheers!!!
James