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Default Flat roof question.

Recent rain has shown my flat roof is leaking. It's part of a conversion
built about 30 years ago. Very nicely built - the correct lie etc and
marine ply decking, and lead flashing. Think it is three layer. Size
approx 5x5 metres.

Any of the modern alternatives better? Membrane or fibreglass? And a rough
idea of relative costs would be nice too.

Access is easy, but it's never walked on etc except for any maintenance.

--
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Dave Plowman London SW
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Default Flat roof question.

On 26/07/2020 13:35:58, Dave Plowman (News) wrote:
Recent rain has shown my flat roof is leaking. It's part of a conversion
built about 30 years ago. Very nicely built - the correct lie etc and
marine ply decking, and lead flashing. Think it is three layer. Size
approx 5x5 metres.

Any of the modern alternatives better? Membrane or fibreglass? And a rough
idea of relative costs would be nice too.

Access is easy, but it's never walked on etc except for any maintenance.


EPDM seem all the rage.
https://en.wikipedia.org/wiki/Flat_roof#EPDM

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Default Flat roof question.

"Dave Plowman (News)" Wrote in message:
Recent rain has shown my flat roof is leaking. It's part of a conversion
built about 30 years ago. Very nicely built - the correct lie etc and
marine ply decking, and lead flashing. Think it is three layer. Size
approx 5x5 metres.

Any of the modern alternatives better? Membrane or fibreglass? And a rough
idea of relative costs would be nice too.

Access is easy, but it's never walked on etc except for any maintenance.


See what the little men say....
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Default Flat roof question.

In article ,
Jethro_uk wrote:
On Sun, 26 Jul 2020 13:35:58 +0100, Dave Plowman (News) wrote:


Recent rain has shown my flat roof is leaking. It's part of a
conversion built about 30 years ago. Very nicely built - the correct
lie etc and marine ply decking, and lead flashing. Think it is three
layer. Size approx 5x5 metres.

Any of the modern alternatives better? Membrane or fibreglass? And a
rough idea of relative costs would be nice too.

Access is easy, but it's never walked on etc except for any
maintenance.


I find it mildly curious that in the 21st century, no one has seen fit
to come up with something that can be poured, finds the crack and seals
it ...


It's already had that treatment. But same as paint, doesn't last forever.

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Dave Plowman London SW
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Default Flat roof question.

On Sun, 26 Jul 2020 14:07:41 +0100, Fredxx wrote:

EPDM seem all the rage.
https://en.wikipedia.org/wiki/Flat_roof#EPDM


Had ours fibre glassed about 10 years ago. New OSB boards, the old
torch-on felt had failed and knackered those boards. Took the
oportunity to fit 100 mm of celotext between the roof joists. The
fibre glass is still waterproof or at least if it is leaking it's not
getting to anywhere visible inside. But then there is a poly sheet on
the warm side of the insulation and up and over the joists...

--
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Default Flat roof question.

On Sun, 26 Jul 2020 13:35:58 +0100, "Dave Plowman (News)"
wrote:

Recent rain has shown my flat roof is leaking. It's part of a conversion
built about 30 years ago. Very nicely built - the correct lie etc and
marine ply decking, and lead flashing. Think it is three layer. Size
approx 5x5 metres.

Any of the modern alternatives better? Membrane or fibreglass? And a rough
idea of relative costs would be nice too.

Access is easy, but it's never walked on etc except for any maintenance.


Here you go, Dave. Don't say I never do anything for you:

https://polyroof.co.uk/
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Default Flat roof question.

In article l.net,
Dave Liquorice wrote:
On Sun, 26 Jul 2020 14:07:41 +0100, Fredxx wrote:


EPDM seem all the rage.
https://en.wikipedia.org/wiki/Flat_roof#EPDM


Had ours fibre glassed about 10 years ago. New OSB boards, the old
torch-on felt had failed and knackered those boards. Took the
oportunity to fit 100 mm of celotext between the roof joists. The
fibre glass is still waterproof or at least if it is leaking it's not
getting to anywhere visible inside. But then there is a poly sheet on
the warm side of the insulation and up and over the joists...


Big snag is actually knowing how long these 'new' methods do last. Plenty
claims, though. The decking is marine ply, so hoping it will still be
just fine. The chippie who did the work was very good indeed.

--
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Default Flat roof question.

On 26/07/2020 13:35, Dave Plowman (News) wrote:
Recent rain has shown my flat roof is leaking. It's part of a conversion
built about 30 years ago. Very nicely built - the correct lie etc and
marine ply decking, and lead flashing. Think it is three layer. Size
approx 5x5 metres.

Any of the modern alternatives better? Membrane or fibreglass? And a rough
idea of relative costs would be nice too.

Access is easy, but it's never walked on etc except for any maintenance.


Glassfibe will be quite a bit more expensive than EPDM. Probably best
to find a roofer who can provide quotes.

I don't think any special tools are needed to install EPDM, so it may be
suitable for DIY, though you may need several people to handle the
weight. It took 1 day to reroof a double garage with EPDM including
changing some boarding and maybe a joinst.

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Default Flat roof question.

On 26/07/2020 13:35, Dave Plowman (News) wrote:
Recent rain has shown my flat roof is leaking. It's part of a conversion
built about 30 years ago. Very nicely built - the correct lie etc and
marine ply decking, and lead flashing. Think it is three layer. Size
approx 5x5 metres.

Any of the modern alternatives better? Membrane or fibreglass? And a rough
idea of relative costs would be nice too.

Access is easy, but it's never walked on etc except for any maintenance.

How about old fashioned lead ?
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Default Flat roof question.

In article ,
Dave Plowman (News) wrote:
In article l.net,
Dave Liquorice wrote:
On Sun, 26 Jul 2020 14:07:41 +0100, Fredxx wrote:


EPDM seem all the rage.
https://en.wikipedia.org/wiki/Flat_roof#EPDM


Had ours fibre glassed about 10 years ago. New OSB boards, the old
torch-on felt had failed and knackered those boards. Took the
oportunity to fit 100 mm of celotext between the roof joists. The
fibre glass is still waterproof or at least if it is leaking it's not
getting to anywhere visible inside. But then there is a poly sheet on
the warm side of the insulation and up and over the joists...


Big snag is actually knowing how long these 'new' methods do last.


Sounds like the story of the salesman who turned up at Steinway pianos
saying "We've got this wonderful new material for piano hammers instead of
that old fashioned felt." Steinway said they try it out. "Ah, when should
I come back?" "In about 100 years."

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle


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Default Flat roof question.

In article ,
Robert wrote:
On 26/07/2020 13:35, Dave Plowman (News) wrote:
Recent rain has shown my flat roof is leaking. It's part of a conversion
built about 30 years ago. Very nicely built - the correct lie etc and
marine ply decking, and lead flashing. Think it is three layer. Size
approx 5x5 metres.

Any of the modern alternatives better? Membrane or fibreglass? And a
rough idea of relative costs would be nice too.

Access is easy, but it's never walked on etc except for any maintenance.

How about old fashioned lead ?


Doesn't help indoor FM radio reception.

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle
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Default Flat roof question.

Robert Wrote in message:
On 26/07/2020 13:35, Dave Plowman (News) wrote:
Recent rain has shown my flat roof is leaking. It's part of a conversion
built about 30 years ago. Very nicely built - the correct lie etc and
marine ply decking, and lead flashing. Think it is three layer. Size
approx 5x5 metres.

Any of the modern alternatives better? Membrane or fibreglass? And a rough
idea of relative costs would be nice too.

Access is easy, but it's never walked on etc except for any maintenance.

How about old fashioned lead ?


It is SW londun after all.....
--
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Default Flat roof question.

On 26/07/2020 19:18, charles wrote:
In article ,
Dave Plowman (News) wrote:
In article l.net,
Dave Liquorice wrote:
On Sun, 26 Jul 2020 14:07:41 +0100, Fredxx wrote:


EPDM seem all the rage.
https://en.wikipedia.org/wiki/Flat_roof#EPDM


Had ours fibre glassed about 10 years ago. New OSB boards, the old
torch-on felt had failed and knackered those boards. Took the
oportunity to fit 100 mm of celotext between the roof joists. The
fibre glass is still waterproof or at least if it is leaking it's not
getting to anywhere visible inside. But then there is a poly sheet on
the warm side of the insulation and up and over the joists...


Big snag is actually knowing how long these 'new' methods do last.


Sounds like the story of the salesman who turned up at Steinway pianos
saying "We've got this wonderful new material for piano hammers instead of
that old fashioned felt." Steinway said they try it out. "Ah, when should
I come back?" "In about 100 years."

Sometime in the 1970s I was involved in a submarine cable project.
Featuring Germanium transistors "Silicon hasn't been around long enough
to know they will last"

Asked my oncologist "what is the 15 years outlook for this
chemotherapy?" "Dunno: it's only been around just over a decade"



--
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"I don't."
"Don't what?"
"Think about Gay Marriage."

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Default Flat roof question.

On Sunday, 26 July 2020 13:36:08 UTC+1, Dave Plowman (News) wrote:

Recent rain has shown my flat roof is leaking. It's part of a conversion
built about 30 years ago. Very nicely built - the correct lie etc and
marine ply decking, and lead flashing. Think it is three layer. Size
approx 5x5 metres.

Any of the modern alternatives better? Membrane or fibreglass? And a rough
idea of relative costs would be nice too.

Access is easy, but it's never walked on etc except for any maintenance.


EPDM & fibreglass are both diyable. The issue we ran into with EPDM is that it's not compatible with bitumen, so every bit of boarding must be stripped off & renewed.

Lead is a foolish idea these days, even in apparently inaccessible places. Copper even more so. Many swear by steel, but it gets ugly in time.

In the end we left the old felt in place & used bedsheet, bitumen & sand. Crude for sure, but it was a very quick job costing almost £20 something and last time I looked was still in good nick years later. If/when it deteriorates, more cloth & bitumen is only another £20.


NT
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wrote in message
...
On Sunday, 26 July 2020 13:36:08 UTC+1, Dave Plowman (News) wrote:

Recent rain has shown my flat roof is leaking. It's part of a conversion
built about 30 years ago. Very nicely built - the correct lie etc and
marine ply decking, and lead flashing. Think it is three layer. Size
approx 5x5 metres.

Any of the modern alternatives better? Membrane or fibreglass? And a
rough
idea of relative costs would be nice too.

Access is easy, but it's never walked on etc except for any maintenance.


EPDM & fibreglass are both diyable. The issue we ran into with EPDM is
that it's not compatible with bitumen, so every bit of boarding must be
stripped off & renewed.

Lead is a foolish idea these days, even in apparently inaccessible places.
Copper even more so. Many swear by steel, but it gets ugly in time.


Not when heavily galvanised it doesnt.

And neither does aluminium.

In the end we left the old felt in place & used bedsheet, bitumen & sand.
Crude for sure, but it was a very quick job costing almost £20 something
and last time I looked was still in good nick years later. If/when it
deteriorates, more cloth & bitumen is only another £20.


NT




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Default Flat roof question.

I've been using EDPM,
went on a one day course to learn how to do the corners.

https://www.permaroof.co.uk/rubber-roof-videos



It's easy to repair with its special primer and glues and patches, like when i dropped a slate on it.

Made by firestone , Ultra violet resistant.

Normal shed roofing only lasts a few years.
Lead has to have gaps for expansion where nwater dirt and ice get in.

And while youre at it add loads of insulation under it.

I did OSB3, then kingspan attached with foam, then OSB3, then EDPM

George


On Sunday, July 26, 2020 at 1:36:08 PM UTC+1, Dave Plowman (News) wrote:
Recent rain has shown my flat roof is leaking. It's part of a conversion
built about 30 years ago. Very nicely built - the correct lie etc and
marine ply decking, and lead flashing. Think it is three layer. Size
approx 5x5 metres.

Any of the modern alternatives better? Membrane or fibreglass? And a rough
idea of relative costs would be nice too.

Access is easy, but it's never walked on etc except for any maintenance.

--
*I tried to catch some fog, but I mist.*

Dave Plowman London SW
To e-mail, change noise into sound.


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George Miles wrote:

I've been using EDPM,


Did my garage/kitchen/porch about 12 years ago.
I did OSB3, then kingspan attached with foam, then OSB3, then EDPM


Why two decks?

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On Monday, July 27, 2020 at 10:17:00 AM UTC+1, Andy Burns wrote:
George Miles wrote:

I've been using EDPM,


Did my garage/kitchen/porch about 12 years ago.
I did OSB3, then kingspan attached with foam, then OSB3, then EDPM


Why two decks?


First OSB3 was 18mm for the structure,
on top of beams.
Then a 2 layers of kingspan attached with foam
then thinnner osb3 foamed on it
(no screws or cold bridging,
and makes roof walkable)
then glued EDPM onto it.

[g]
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On 27/07/2020 10:04, George Miles wrote:
I've been using EDPM,
went on a one day course to learn how to do the corners.

https://www.permaroof.co.uk/rubber-roof-videos



It's easy to repair with its special primer and glues and patches, like when i dropped a slate on it.

Made by firestone , Ultra violet resistant.


I am glad that it is easy to repair as it looks like it might be easily
damaged.


--
Michael Chare


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In article ,
Robert wrote:
On 26/07/2020 13:35, Dave Plowman (News) wrote:
Recent rain has shown my flat roof is leaking. It's part of a
conversion built about 30 years ago. Very nicely built - the correct
lie etc and marine ply decking, and lead flashing. Think it is three
layer. Size approx 5x5 metres.

Any of the modern alternatives better? Membrane or fibreglass? And a
rough idea of relative costs would be nice too.

Access is easy, but it's never walked on etc except for any
maintenance.

How about old fashioned lead ?


Care to guess what that would cost? And likely to reinforce the roof which
wasn't designed for it?

Zinc would be cheaper. But noisy in the rain.

--
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Default Flat roof question.

In article ,
charles wrote:
In article ,
Robert wrote:
On 26/07/2020 13:35, Dave Plowman (News) wrote:
Recent rain has shown my flat roof is leaking. It's part of a conversion
built about 30 years ago. Very nicely built - the correct lie etc and
marine ply decking, and lead flashing. Think it is three layer. Size
approx 5x5 metres.

Any of the modern alternatives better? Membrane or fibreglass? And a
rough idea of relative costs would be nice too.

Access is easy, but it's never walked on etc except for any maintenance.

How about old fashioned lead ?


Doesn't help indoor FM radio reception.



Some of us have external aerials. ;-)

--
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Dave Plowman London SW
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Default Flat roof question.

In article ,
George Miles wrote:
I've been using EDPM,
went on a one day course to learn how to do the corners.


https://www.permaroof.co.uk/rubber-roof-videos




It's easy to repair with its special primer and glues and patches, like when i dropped a slate on it.


Made by firestone , Ultra violet resistant.


Normal shed roofing only lasts a few years.


Well, this has lasted 30. So you're not doing a good job of selling an
alternative. ;-)

--
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Dave Plowman London SW
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Default Flat roof question.

In article , Dave Plowman (News)
wrote:
In article , charles
wrote:
In article , Robert
wrote:
On 26/07/2020 13:35, Dave Plowman (News) wrote:
Recent rain has shown my flat roof is leaking. It's part of a
conversion built about 30 years ago. Very nicely built - the
correct lie etc and marine ply decking, and lead flashing. Think it
is three layer. Size approx 5x5 metres.

Any of the modern alternatives better? Membrane or fibreglass? And
a rough idea of relative costs would be nice too.

Access is easy, but it's never walked on etc except for any
maintenance.

How about old fashioned lead ?


Doesn't help indoor FM radio reception.



Some of us have external aerials. ;-)


which would ned to well above the new "earth"

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle
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Default Flat roof question.

On 26/07/2020 13:35, Dave Plowman (News) wrote:
Recent rain has shown my flat roof is leaking. It's part of a conversion
built about 30 years ago. Very nicely built - the correct lie etc and
marine ply decking, and lead flashing. Think it is three layer. Size
approx 5x5 metres.

Any of the modern alternatives better? Membrane or fibreglass? And a rough
idea of relative costs would be nice too.

Access is easy, but it's never walked on etc except for any maintenance.


For a flat roof on a double garage the quote was £2100+ vat for EPDM,
part of one joist and removal of old material.


--
Michael Chare


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On Monday, July 27, 2020 at 12:59:29 PM UTC+1, Michael Chare wrote:
On 27/07/2020 10:04, George Miles wrote:
I've been using EDPM,
went on a one day course to learn how to do the corners.

https://www.permaroof.co.uk/rubber-roof-videos



It's easy to repair with its special primer and glues and patches, like when i dropped a slate on it.

Made by firestone , Ultra violet resistant.


I am glad that it is easy to repair as it looks like it might be easily
damaged.


--
Michael Chare

EDPM stuck to OSB is tough stuff,
I broke mine by a slate sliding from high up the roof
and spearing it with a point

[g]

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On Monday, July 27, 2020 at 4:55:34 PM UTC+1, Michael Chare wrote:
On 26/07/2020 13:35, Dave Plowman (News) wrote:
Recent rain has shown my flat roof is leaking. It's part of a conversion
built about 30 years ago. Very nicely built - the correct lie etc and
marine ply decking, and lead flashing. Think it is three layer. Size
approx 5x5 metres.

Any of the modern alternatives better? Membrane or fibreglass? And a rough
idea of relative costs would be nice too.

Access is easy, but it's never walked on etc except for any maintenance..


For a flat roof on a double garage the quote was £2100+ vat for EPDM,
part of one joist and removal of old material.


--
Michael Chare


Check out the price of a kit from Permaroof if you do it yourself,
its not difficult.
And because it comes in a single sheet you dont have to do it all in one day,
you can drape the sheet over before gluing if it rains,
and stick one edge on day,
the rest another day.

It took me months to do parts of my house roof with it because so many corners

[g]
[g]
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Default Flat roof question.

"Dave Plowman (News)" wrote:
Any of the modern alternatives better? Membrane or fibreglass? And a rough
idea of relative costs would be nice too.


What would the team suggest for a 20 year old felt/bitumen flat roof that
has a small leak, but has some degree of sagging which causes ponding -
possibly due to movement of the underlying structure rather than softness of
the roof itself?

I see there's the equivalent of floor levelling compound for flat roofs, but
is it any good, especially on top of existing bitumen? How does it manage
to achieve a fall, rather than being a horizontal level?

Have quotes 2-3K for a strip and redo, but wondering if there's anything
less drastic?

Thanks
Theo
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Theo wrote:

some degree of sagging which causes ponding -
possibly due to movement of the underlying structure


Can you get any wedges/packers between the top of rafters and the
ply/osb/why?
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On Sun, 26 Jul 2020 18:20:35 +0100, Dave Plowman (News) wrote:

Had ours fibre glassed about 10 years ago.


Big snag is actually knowing how long these 'new' methods do last.


True enough, though glassfibre has been about for quite a number of
decades in other things like boats.

--
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Dave.





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Andy Burns wrote:
Theo wrote:

some degree of sagging which causes ponding -
possibly due to movement of the underlying structure


Can you get any wedges/packers between the top of rafters and the
ply/osb/why?


Possibly by taking the ceiling below out, but then I'm not sure that making
good the ceiling is going to be much less work than redoing the roof.
(There may be asbestos fibres in the ceiling, just for added excitement)

Theo
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On 28 Jul 2020 10:33:51 +0100 (BST), Theo
wrote:

"Dave Plowman (News)" wrote:
Any of the modern alternatives better? Membrane or fibreglass? And a rough
idea of relative costs would be nice too.


What would the team suggest for a 20 year old felt/bitumen flat roof that
has a small leak, but has some degree of sagging which causes ponding -
possibly due to movement of the underlying structure rather than softness of
the roof itself?

I see there's the equivalent of floor levelling compound for flat roofs, but
is it any good, especially on top of existing bitumen? How does it manage
to achieve a fall, rather than being a horizontal level?

Have quotes 2-3K for a strip and redo, but wondering if there's anything
less drastic?

Thanks
Theo



Just had our garage completely re-roofed. Cost about 900 GBP.
That ws after more than 25 years use and the old roof was very badly
installed, according to the roofer who stripped it off, whixh id why
it blew off.

I reckon if you've had 20 years out of it that's not bad and maybe
it's time for a completely new one.
- Mike
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Mike wrote:
Just had our garage completely re-roofed. Cost about 900 GBP.


Interesting. This is also a garage (conversion), let me guess about 6m x
3.5m. That sounds rather cheap!

(2-3K quotes did not include removing much woodwork assuming it to be
otherwise sound)

That ws after more than 25 years use and the old roof was very badly
installed, according to the roofer who stripped it off, whixh id why
it blew off.

I reckon if you've had 20 years out of it that's not bad and maybe
it's time for a completely new one.


That was the initial assumption. However it doesn't seem to have failed
completely, so wondering if there was something that could keep it going for
a bit longer (pending other things).

Theo
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On 26/07/2020 15:22, Chris Hogg wrote:
On Sun, 26 Jul 2020 13:42:50 -0000 (UTC), Jethro_uk
wrote:

On Sun, 26 Jul 2020 13:35:58 +0100, Dave Plowman (News) wrote:

Recent rain has shown my flat roof is leaking. It's part of a conversion
built about 30 years ago. Very nicely built - the correct lie etc and
marine ply decking, and lead flashing. Think it is three layer. Size
approx 5x5 metres.

Any of the modern alternatives better? Membrane or fibreglass? And a
rough idea of relative costs would be nice too.

Access is easy, but it's never walked on etc except for any maintenance.


I find it mildly curious that in the 21st century, no one has seen fit to
come up with something that can be poured, finds the crack and seals
it ...


I have done just that with Isoflex liquid rubber. Leaked at the
junction between my and my neighbour's garage roofs, bitumen felted.
Must have been quite a big crack as it took quite a lot, and at one
point appeared dribbling down the inside of the garage wall. Sealed
the leak though. https://tinyurl.com/y2fgfmzo

Joints in flat roofs are almost guaranteed to fail, especially
if both were originally built-up 3 -layer felt and one half has
been replaced with 2-layer torch-on felt. The heat of the sun,
and the dryness, especially the weather we have had this year will
soon make the joint fail.

IS the decking chipboard, plywood or OSB ?
The first will not like ingress of water.

If you are going to treat flat areas their special primer is well
worth using first.

I did my garage roof with an EPDM kit, but that involved redecking
with OSB3 first. 5.5 mtres by 2.8 metres. It was just on the limit
of my ability to get it up the ladder. A 5x5 sheet of epdm will need
2 people.

Flat roofs need replacing at least every 20-25 years. Some really
bad bodge jobs, like the garage roof of my first house was done in
2-layer felt in 1976, before the days of fibreglass reinforced
felt and every house had a leaking garage roof within 10 years.
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On 26/07/2020 16:32, Dave Plowman (News) wrote:
In article ,
Jethro_uk wrote:
On Sun, 26 Jul 2020 13:35:58 +0100, Dave Plowman (News) wrote:


Recent rain has shown my flat roof is leaking. It's part of a
conversion built about 30 years ago. Very nicely built - the correct
lie etc and marine ply decking, and lead flashing. Think it is three
layer. Size approx 5x5 metres.

Any of the modern alternatives better? Membrane or fibreglass? And a
rough idea of relative costs would be nice too.

Access is easy, but it's never walked on etc except for any
maintenance.


I find it mildly curious that in the 21st century, no one has seen fit
to come up with something that can be poured, finds the crack and seals
it ...


It's already had that treatment. But same as paint, doesn't last forever.


Isoflex, when used with its special primer should add about 8 years to
the life, provided it has no ponding or other problems.


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On 27/07/2020 12:59, Michael Chare wrote:
On 27/07/2020 10:04, George Miles wrote:
I've been using EDPM,
went on a one day course to learn how to do the corners.

https://www.permaroof.co.uk/rubber-roof-videos



It's easy to repair with its special primer and glues and patches,
like when i dropped a slate on it.

Made by firestone , Ultra violet resistant.


I am glad that it is easy to repair as it looks like it might be easily
damaged.



The 1.5 mm stuff is pretty tough. If it never or rarely gets walked
on then you would have to be very unlucky to damage it, unless
you have an arsewipe as a neighbour who chucks hydraulic oil and
or solvents on it.

It is glued onto OSB3/plywood using a water-based adhesive that
is rolled on with a decorating roller so as well as the EPDM
itself you have this layer of adhesive that seeps into the decking
and provides a 2nd level of protection.
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On 27/07/2020 14:20, Dave Plowman (News) wrote:
In article ,
George Miles wrote:
I've been using EDPM,
went on a one day course to learn how to do the corners.


https://www.permaroof.co.uk/rubber-roof-videos




It's easy to repair with its special primer and glues and patches, like when i dropped a slate on it.


Made by firestone , Ultra violet resistant.


Normal shed roofing only lasts a few years.


Well, this has lasted 30. So you're not doing a good job of selling an
alternative. ;-)


You said it had already been treated with something, so the actual
original probably lasted 20-25? years which is about right for a
built-up felted roof. Unless you want to reseal it with Isoflex
or whatever every 5 to 8 years thenyou might as well just get
it re-felted.

Avoid Acrypol if you have already using Isoflex, the two are
not compatible. DTDIGTTS.
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On 28/07/2020 10:54, Theo wrote:
Andy Burns wrote:
Theo wrote:

some degree of sagging which causes ponding -
possibly due to movement of the underlying structure


Can you get any wedges/packers between the top of rafters and the
ply/osb/why?


Possibly by taking the ceiling below out, but then I'm not sure that making
good the ceiling is going to be much less work than redoing the roof.
(There may be asbestos fibres in the ceiling, just for added excitement)

Theo


Sounds like it has already leaked allowing the decking to weaken and
sag, hence the ponding. Complete re-decking it the solution.

Be aware that part L means it will need to be insulated and too
many roofing people will insist on adding insulation on top of the
decking and then putting the felt over the insulation. If your flat
roof is a 'cold roof' (most are) , this is s complete waste of time
since the ventilaton will still allow cold air to circulate underneath
the insulation.

If the roof is redecked then adding 'celotex' between the joists and cut
to fit snugly, and the joints taped with silver foil tape with an air
gap above it is the way to go.
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On 28/07/2020 14:00, Theo wrote:
Mike wrote:
Just had our garage completely re-roofed. Cost about 900 GBP.


Interesting. This is also a garage (conversion), let me guess about 6m x
3.5m. That sounds rather cheap!

For redecking and felting, the going rate seems to be about £100 per
square metre.

I did my garage roof myself, 5.5 metres by 2.6 metres and is cost me
£700 just for materials, -

6 sheets OSB3 @ £21/sheet
4 new rafters to replace rotten ones
UPVC cladding over existing barge boards
EPDM kit, with adhesive, guttering and upstand trims
Screws and fixings. OSB3 must be screwed not nailed.


(2-3K quotes did not include removing much woodwork assuming it to be
otherwise sound)

That ws after more than 25 years use and the old roof was very badly
installed, according to the roofer who stripped it off, whixh id why
it blew off.

I reckon if you've had 20 years out of it that's not bad and maybe
it's time for a completely new one.


That was the initial assumption. However it doesn't seem to have failed
completely, so wondering if there was something that could keep it going for
a bit longer (pending other things).

Theo


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Andrew wrote:
Sounds like it has already leaked allowing the decking to weaken and
sag, hence the ponding. Complete re-decking it the solution.


That's what I suspected. Although I wondered if there was a say 5 year
shorter term fix?

Be aware that part L means it will need to be insulated and too
many roofing people will insist on adding insulation on top of the
decking and then putting the felt over the insulation. If your flat
roof is a 'cold roof' (most are) , this is s complete waste of time
since the ventilaton will still allow cold air to circulate underneath
the insulation.


This is a semi-integral garage, so I'm not sure part L applies? It's still
got a great big garage door, even if the internals are a bit nicer than a
normal garage. It isn't heated.

Quoters seemed to suggest stripping it back to add insulation would be much
more than a simple re-roof.

Trying to avoid 'and while you're doing that...' project creep.

Theo
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