Garage Flat Roof Covering Options - Felt / GRP / EPDM?
Discussion
Hi Guys,
Apologies in advance for another 'which flat roof covering' thread!
We have an attached garage, approx 6m x 5m, on which the flat felt roof will need replacing soon - probably next year when the weather's a bit kinder. It's a simple rectangle with no 'protrusions': one of the 6m sides abuts the house wall, the other 6m is the gutter - leaving the two 5m sides as check edges.
The boards have been laid with inadequate fall, so they'll be getting replaced too.
So I've been weighing up the 'usual suspects': EPDM, GRP and good old felt - all of which seem to have their avid supporters (and anything else is rubbish!). This has left my head in a complete mess - possibly because I'm over-thinking it, as usual!
'Felt' seemed to go out of fashion, but appears to be making a bit of a comeback: some manufacturers now offer a 20-year 'materials' guarantee on their top-line SBS membranes - which would probably outlive me! A proper 3-layer torch-on application sounds good - but have those skills disappeared in the trade over the years?
GRP sounds okay in theory, but I've read a few horror stories about some installations. Quite a few temperature and resin setting times to consider, which makes for a bit of 'working against the clock'.
EPDM sounds the easiest of them all - particularly for a simple job like ours: just slap some adhesive down, fold out the sheet, roller into place, snip-snip to trim and fit the detailing. Bob's your auntie's brother.
But does the real difference lie in the quality of the installation - and are any of the options reasonably DIY-able?
Apologies in advance for another 'which flat roof covering' thread!
We have an attached garage, approx 6m x 5m, on which the flat felt roof will need replacing soon - probably next year when the weather's a bit kinder. It's a simple rectangle with no 'protrusions': one of the 6m sides abuts the house wall, the other 6m is the gutter - leaving the two 5m sides as check edges.
The boards have been laid with inadequate fall, so they'll be getting replaced too.
So I've been weighing up the 'usual suspects': EPDM, GRP and good old felt - all of which seem to have their avid supporters (and anything else is rubbish!). This has left my head in a complete mess - possibly because I'm over-thinking it, as usual!
'Felt' seemed to go out of fashion, but appears to be making a bit of a comeback: some manufacturers now offer a 20-year 'materials' guarantee on their top-line SBS membranes - which would probably outlive me! A proper 3-layer torch-on application sounds good - but have those skills disappeared in the trade over the years?
GRP sounds okay in theory, but I've read a few horror stories about some installations. Quite a few temperature and resin setting times to consider, which makes for a bit of 'working against the clock'.
EPDM sounds the easiest of them all - particularly for a simple job like ours: just slap some adhesive down, fold out the sheet, roller into place, snip-snip to trim and fit the detailing. Bob's your auntie's brother.
But does the real difference lie in the quality of the installation - and are any of the options reasonably DIY-able?
It's all about the workmanship.
GRP is probably DIY-able, but a 30sqm roof is a big project if you've not done GRP before.
A big job for one person IMHO.
GRP is tough and perhaps the best for surviving people walking on, putting ladders on the roof etc etc.
30sqm of rubber is a big heavy thing, needing several people to work with properly.
The flashing to the house wall needs to be right.
Felt is fine if done right.
There are other possibilities including insulated steel (and other?) profiles.
If you go for felt or rubber, then IMHO, you don't want to be making lots of holes for example to mount a load of solar panels.
Personally, I'd not want a black EPDM roof due to heating from the sun, unless loads of insulation was possible.
GRP is probably DIY-able, but a 30sqm roof is a big project if you've not done GRP before.
A big job for one person IMHO.
GRP is tough and perhaps the best for surviving people walking on, putting ladders on the roof etc etc.
30sqm of rubber is a big heavy thing, needing several people to work with properly.
The flashing to the house wall needs to be right.
Felt is fine if done right.
There are other possibilities including insulated steel (and other?) profiles.
If you go for felt or rubber, then IMHO, you don't want to be making lots of holes for example to mount a load of solar panels.
Personally, I'd not want a black EPDM roof due to heating from the sun, unless loads of insulation was possible.
Several years ago on the previous hoyse we had a flat felt roof over an attached garage/kitchen single storey extension. It needed renewal. We looked at options. One included a pitched tiled roof matching the main roof.
As an exercise we costed a full extra storey raising to create an extra bedroom above as the roof cost was already there. More complex with planning, regs etc but that's the route we took. Yes, extra cost but we were surprised at how relatively cheap for the extra work for a significant improvement. Back then finances were ok so it was a decent "investment". Maybe these days not so but worth investigating?
As an exercise we costed a full extra storey raising to create an extra bedroom above as the roof cost was already there. More complex with planning, regs etc but that's the route we took. Yes, extra cost but we were surprised at how relatively cheap for the extra work for a significant improvement. Back then finances were ok so it was a decent "investment". Maybe these days not so but worth investigating?
Thanks, OutIn for the helpful advice
It's one of those jobs that I *feel* I should be able to do myself, but do tend to dwell on the 'what could possibly go wrong'!
I'm swaying towards a quality 'felt' solution - even though it's often seen as 'old hat'. I'm tempted to buy a roll of torch-on to give it a try over a bit of the existing roof - purely to get a feel for the technique, particularly for the edge details (which seems to be the trickiest bit). Doing something for the first time 'for real' can be a daunting task - as in many areas of life
There are no plans for solar panels etc on the roof
ETA: thanks, sospan - I'll have a look at that option, but not sure if finances will permit it
It's one of those jobs that I *feel* I should be able to do myself, but do tend to dwell on the 'what could possibly go wrong'!
I'm swaying towards a quality 'felt' solution - even though it's often seen as 'old hat'. I'm tempted to buy a roll of torch-on to give it a try over a bit of the existing roof - purely to get a feel for the technique, particularly for the edge details (which seems to be the trickiest bit). Doing something for the first time 'for real' can be a daunting task - as in many areas of life
There are no plans for solar panels etc on the roof
ETA: thanks, sospan - I'll have a look at that option, but not sure if finances will permit it
Edited by Gaumon on Sunday 5th October 12:05
Gaumon said:
Thanks, OutIn for the helpful advice
It's one of those jobs that I *feel* I should be able to do myself, but do tend to dwell on the 'what could possibly go wrong'!
I'm swaying towards a quality 'felt' solution - even though it's often seen as 'old hat'. I'm tempted to buy a roll of torch-on to give it a try over a bit of the existing roof - purely to get a feel for the technique, particularly for the edge details (which seems to be the trickiest bit). Doing something for the first time 'for real' can be a daunting task - as in many areas of life
There are no plans for solar panels etc on the roof
ETA: thanks, sospan - I'll have a look at that option, but not sure if finances will permit it
Don't take it as 'advice' more like a rambling opinion that might help you do your own research!It's one of those jobs that I *feel* I should be able to do myself, but do tend to dwell on the 'what could possibly go wrong'!
I'm swaying towards a quality 'felt' solution - even though it's often seen as 'old hat'. I'm tempted to buy a roll of torch-on to give it a try over a bit of the existing roof - purely to get a feel for the technique, particularly for the edge details (which seems to be the trickiest bit). Doing something for the first time 'for real' can be a daunting task - as in many areas of life
There are no plans for solar panels etc on the roof
ETA: thanks, sospan - I'll have a look at that option, but not sure if finances will permit it
Edited by Gaumon on Sunday 5th October 12:05
I've never used torch-on felt.
It can't be that hard?
I did a shed roof in 'shed felt' with black gloopy adhesive and it seems to be OK after 10 years or so.
My parents had a felt flat roof dormer that needed re-doing after 20 years, then again after another 25.
On my old house we had a similar area of flat roof, this was replaced with EDPM, it went down quick and looked great. It had all 3 of the tricky bits, edges against a wall, against a ridged roof and the gutter side had several 90 degree bits, internal and external corners.
The 90s looked the hardest but there were patches over the cuts.
EPDM looks much easier to me, you only really need to worry about make good seals on the edges and around details. Not much else to go wrong.
The 90s looked the hardest but there were patches over the cuts.
EPDM looks much easier to me, you only really need to worry about make good seals on the edges and around details. Not much else to go wrong.
We just had our old felt roof over the garage ripped out and replaced at is was pooling constantly and leaking.
The builder put down new boards to create a better slope for drainage and than the new roof went on. Took about a 1 week in total 1-2 guys working on it most of the week, but the weather did cause some pauses. Total area is around 35sq metres, it already been tested well last few days. Zero pooling of water compared to the old felt roof. Total cost was £5k, absolutely zero chance I could have DIYed.
The builder put down new boards to create a better slope for drainage and than the new roof went on. Took about a 1 week in total 1-2 guys working on it most of the week, but the weather did cause some pauses. Total area is around 35sq metres, it already been tested well last few days. Zero pooling of water compared to the old felt roof. Total cost was £5k, absolutely zero chance I could have DIYed.
king heavy!Thanks for all the replies - it's much appreciated
For a bit of light entertainment, I found this instructional video on YouTube: https://www.youtube.com/watch?v=aNzsgvYTRTo
What could possibly go wrong....
For a bit of light entertainment, I found this instructional video on YouTube: https://www.youtube.com/watch?v=aNzsgvYTRTo
What could possibly go wrong....
Jeremy-75qq8 said:
My builder and I used to like GRP.
There are a number of issues
1. you can hear it move and crackle in the heat
2. It does crack when walked on and we had some leaks.
We now use EDPM which as long as welded up properly and bonded down works well.
The GRP deck on my boat is 34 years old and has no problems.There are a number of issues
1. you can hear it move and crackle in the heat
2. It does crack when walked on and we had some leaks.
We now use EDPM which as long as welded up properly and bonded down works well.
OTOH, I've watched a GRP flat roof peel off in a storm.
As well as the workmanship, there's the issue of what's under the skin.
I think any of it works well if done right?
I don't know the costs per sqm of the various materials. Trying to do GRP as cheaply as possible would be a mistake in my view.
Personally I'd regard that roof as too big to DIY, but I'd do say a balcony.
And if I wanted GRP work done, I'd be asking a boatbuilder not a general roofer or builder.
Where GRP might score is if you want feature like say a skylight or raised bits to bolt things to.
I DIYed my garage roof in GRP as it had a few tricky corners (it s a single with a narrower bit stuck on). Was easy enough using the Cure-it system but I can see lots of ways a builder (especially one willing to cut corners) could cock it up and get a poor result.
A big, simple roof and I d go for EPDM. I m planning a workshop/garden-room thing for next year and I ll probably use EPDM for that.
A big, simple roof and I d go for EPDM. I m planning a workshop/garden-room thing for next year and I ll probably use EPDM for that.
OutInTheShed said:
The GRP deck on my boat is 34 years old and has no problems.
OTOH, I've watched a GRP flat roof peel off in a storm.
As well as the workmanship, there's the issue of what's under the skin.
I think any of it works well if done right?
I don't know the costs per sqm of the various materials. Trying to do GRP as cheaply as possible would be a mistake in my view.
Personally I'd regard that roof as too big to DIY, but I'd do say a balcony.
And if I wanted GRP work done, I'd be asking a boatbuilder not a general roofer or builder.
Where GRP might score is if you want feature like say a skylight or raised bits to bolt things to.
I have a boat also. I wont get into a length competition. OTOH, I've watched a GRP flat roof peel off in a storm.
As well as the workmanship, there's the issue of what's under the skin.
I think any of it works well if done right?
I don't know the costs per sqm of the various materials. Trying to do GRP as cheaply as possible would be a mistake in my view.
Personally I'd regard that roof as too big to DIY, but I'd do say a balcony.
And if I wanted GRP work done, I'd be asking a boatbuilder not a general roofer or builder.
Where GRP might score is if you want feature like say a skylight or raised bits to bolt things to.
Bear in mind that a GRP boat whilst the same core material is far thicker and designed with ribs and stringers to give it strength. The material is also in the main bonding to itself so the expansion and contraction is the same.
GRP flat roofs work well when first installed but they do get multiple heat cycles and they are mounted on ply and against brickwork all of which is moving at differing rates. EDPM is flexible, in essence GRP is not.
GRP in a boat factory is also more consistently planned and installed.
Can it work? Yes - we had some that were fine we also had some that were not. I am sure that design and install had something to do with it but so did the overall environment. EDPM is a single large bit of movable rubber and in my view gives a more consistent outcome.
I DIY’d an EPDM roof this year for a new attached garage. 6.5 x 3.5m.
Did it comfortably in a day solo and bought the whole kit online (rubber/main deck adhesive/edge contact adhesive/trims). Kit was about £650 IIRC.
Very easy to do - plenty of decent tutorials on YouTube. Hardest bit will be getting the rubber up the ladder
Did it comfortably in a day solo and bought the whole kit online (rubber/main deck adhesive/edge contact adhesive/trims). Kit was about £650 IIRC.
Very easy to do - plenty of decent tutorials on YouTube. Hardest bit will be getting the rubber up the ladder
Just to throw another layer into the mix, what about a living roof over the top of whatever material you do choose?
Protects the felt/membrane from the sun/UV, can extend the life of the roof covering up to five times longer. Also great for water runoff, biodiversity reducgin C02 etc. Very low maintenance
Looks a lot nicer than a regular flat roof
Protects the felt/membrane from the sun/UV, can extend the life of the roof covering up to five times longer. Also great for water runoff, biodiversity reducgin C02 etc. Very low maintenance
Looks a lot nicer than a regular flat roof
ScottJB said:
I DIY d an EPDM roof this year for a new attached garage. 6.5 x 3.5m.
Did it comfortably in a day solo and bought the whole kit online (rubber/main deck adhesive/edge contact adhesive/trims). Kit was about £650 IIRC.
Very easy to do - plenty of decent tutorials on YouTube. Hardest bit will be getting the rubber up the ladder
A lot of problems with EPDM rooves can be traced back to abusing the material getting it 'up the ladder'.Did it comfortably in a day solo and bought the whole kit online (rubber/main deck adhesive/edge contact adhesive/trims). Kit was about £650 IIRC.
Very easy to do - plenty of decent tutorials on YouTube. Hardest bit will be getting the rubber up the ladder
It is not light!
Ryan80 said:
Just to throw another layer into the mix, what about a living roof over the top of whatever material you do choose?
Protects the felt/membrane from the sun/UV, can extend the life of the roof covering up to five times longer. Also great for water runoff, biodiversity reducgin C02 etc. Very low maintenance
Looks a lot nicer than a regular flat roof
I don't understand the living roof thing.Protects the felt/membrane from the sun/UV, can extend the life of the roof covering up to five times longer. Also great for water runoff, biodiversity reducgin C02 etc. Very low maintenance
Looks a lot nicer than a regular flat roof
Around here, if you pretend your roof is a field, you'll want a solar farm on it!
A flat roof that becomes a balcony is often a planning NO!, but it seems wrong not to use that flat space for something.
A lot of people seem to get excited about reducing the biodiversity of moss on their tiled roof...
rdjohn said:
I would be inclined to add standing seam solutions to the list.
Aargh - not more options 
Interesting, but it seems to look a bit too 'modern' for the rest of the house, though...Not really keen on the 'living' roof idea - although it might make a decent practice putting area
I'm thinking GRP is losing ground fairly rapidly, with EPDM coming up on the rails. Whilst EPDM has nice elasticity to accommodate movement, I still have (possibly unfounded) doubts about its 'real life' robustness.
Besides, torch-on felt looks far more 'Pistonheads' to install
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