Flat roof problems

We're in an old Victorian house. The lounge has a large bay window which
has a flat roof which is used as a balcony for the bedroom above. The
balcony is 4m wide at its maximum by 1.6m front to back.

The roof looks like it's been covered with glass fibre but it's leaking.
It was very bad but we've put some flashband in the area that was most
suspect and that has cured 90% of the problem but it still leaks slightly
we have had water dripping into the room below. We're in Weston-super-
Mare so the house benefits from all the wind and rain blowing up the
Bristol Channel. The leaks are much more pronounced when it strong
driving rain rather than just raining heavily.

The roof is sloping away towards one corner which is where the leaks
are. The roof also slopes towards the house rather than away from it as
there is a 100mm stone parapet on the outside.

I think I'm going to have to take the whole lot up and re-lay it while
the weather's still fine. Any suggestions on how to get it waterproof?
One final thing. We like sitting out there so quite high point loading
is going to occur. Pictures he-
http://i39.tinypic.com/156tk6o.jpg

Thanks,
Kit Jackson

On Tue, 20 Aug 2013 16:23:04 +0000, Kit Jackson wrote:

Flat roof problems

We're in an old Victorian house. The lounge has a large bay window
which has a flat roof which is used as a balcony for the bedroom above.
The balcony is 4m wide at its maximum by 1.6m front to back.

The roof looks like it's been covered with glass fibre but it's leaking.
It was very bad but we've put some flashband in the area that was most
suspect and that has cured 90% of the problem but it still leaks
slightly we have had water dripping into the room below. We're in
Weston-super- Mare so the house benefits from all the wind and rain
blowing up the Bristol Channel. The leaks are much more pronounced when
it strong driving rain rather than just raining heavily.

The roof is sloping away towards one corner which is where the leaks
are. The roof also slopes towards the house rather than away from it as
there is a 100mm stone parapet on the outside.

I think I'm going to have to take the whole lot up and re-lay it while
the weather's still fine. Any suggestions on how to get it waterproof?
One final thing. We like sitting out there so quite high point loading
is going to occur. Pictures he-
http://i39.tinypic.com/156tk6o.jpg

Thanks,
Kit Jackson

Firstly, that sounds like a decent size so do it up and enjoy :-)

Sound like the problem is the way the under parts of the balcony have been
constructed - wrong slope for drainage etc.

It may well be that the fibreglass has been a desperate attempt to fix a
hopeless roof.

Anyway, I would go for fibreglass but applied correctly to a properly
constructed roof/balcony.

At out last house we had a fibreglass balcony (somewhat bigger) at the
back over a sun room and that was fine, but it did have proper joists,
insulation, and a professionally applied deck.

Construction for something you walk and sit on should be much the same as
for an internal floor with regard to joist thickness and spacing. Someone
will be along with a calculator shortly :-)

If it has been leaking for some time you need to take the covering off
anyway to confirm that there is no rot underneath.

Straightforward to DIY - our pet builders have just done three recently
with no previous experience of fibreglass. One was a massive balcony, the
other two were flat roofs to sun rooms.

The main trick is getting the roof itself properly constructed and
insulated.

You can buy the fibreglass roofing kits off the Internet.

Cheers

Dave R

On 20 Aug 2013 17:23:22 GMT, David.WE.Roberts wrote:

Sound like the problem is the way the under parts of the balcony have
been constructed - wrong slope for drainage etc.

So you'd put the slope into the parapet wall? I think the OP wants to
sit out there not have a goldfish pond. B-)

Looking at the pictures the slope is right as, as it quite common,
the drainage point from the roof is between the end of the parapet
wall and the main house wall.

If the newer looking darker grey stuff is the recently applied
flashband that has nearly cured the problem I'd hazard a guess that
the upstand has fallen away and or failed in some way. Perhaps along
where it changes from horizontal to vertical. Have a good look around
and up the outside edge where the water drains out, gales can blow
considerable quanties of water through tiny holes.

The point loads from chair legs on almost any unprotected flat roof
material worries me. I'd be tempted to cover it with 300 mm slabs
spaced 1/2" or so apart to spread the loads, making sure there was
nothing underneath them to puncture the covering.

--
Cheers
Dave.

On Tue, 20 Aug 2013 20:01:54 +0100, Dave Liquorice wrote:

On 20 Aug 2013 17:23:22 GMT, David.WE.Roberts wrote:

Sound like the problem is the way the under parts of the balcony have
been constructed - wrong slope for drainage etc.

So you'd put the slope into the parapet wall? I think the OP wants to
sit out there not have a goldfish pond. B-)

Looking at the pictures the slope is right as, as it quite common, the
drainage point from the roof is between the end of the parapet wall and
the main house wall.

If the newer looking darker grey stuff is the recently applied flashband
that has nearly cured the problem I'd hazard a guess that the upstand
has fallen away and or failed in some way. Perhaps along where it
changes from horizontal to vertical. Have a good look around and up the
outside edge where the water drains out, gales can blow considerable
quanties of water through tiny holes.

The point loads from chair legs on almost any unprotected flat roof
material worries me. I'd be tempted to cover it with 300 mm slabs spaced
1/2" or so apart to spread the loads, making sure there was nothing
underneath them to puncture the covering.

Missed the pictures.

IMHO any design which slopes back to the house is ripe for problems - any
issues with drainage at the edges and you end up with a swimming pool with
the deep end by the house wall.

Joints between the wall and the deck are most likely to fail so it seems
sensible to have the water drain away from the house, not towards it.

However in this case that could be a major re-design.

With regards to point loads - I know you get shouted at if you wear
stilettos on a Yot but I don't recall any sailing or motor boat with flags
on the deck to protect the fibreglass.

We certainly didn't have any problems with garden furniture on our
fibreglass balcony.

Cheers

Dave R

On 20 Aug 2013 19:51:23 GMT, David.WE.Roberts wrote:

With regards to point loads - I know you get shouted at if you wear
stilettos on a Yot but I don't recall any sailing or motor boat with
flags on the deck to protect the fibreglass.

No but heavy traffic areas there will be duck boards and you wear
soft soled flat shoes...

We certainly didn't have any problems with garden furniture on our
fibreglass balcony.

Fibre glass bonded directly onto the decking is probably one of the
more substantial coverings but I wouldn't like to say you won't
induce micro cracks that will let the frost in and degrade it over
time.

--
Cheers
Dave.

On Tuesday 20 August 2013 21:11 Dave Liquorice wrote in uk.d-i-y:

On 20 Aug 2013 19:51:23 GMT, David.WE.Roberts wrote:

With regards to point loads - I know you get shouted at if you wear
stilettos on a Yot but I don't recall any sailing or motor boat with
flags on the deck to protect the fibreglass.

No but heavy traffic areas there will be duck boards and you wear
soft soled flat shoes...

We certainly didn't have any problems with garden furniture on our
fibreglass balcony.

Fibre glass bonded directly onto the decking is probably one of the
more substantial coverings but I wouldn't like to say you won't
induce micro cracks that will let the frost in and degrade it over
time.


My roofer was less impressed by GRP - said he had to felt over one that
cracked.

He had more time for butyl rubber but was still suspicous of how much it was
liable to tearing.


--
Tim Watts Personal Blog: http://squiddy.blog.dionic.net/

http://www.sensorly.com/ Crowd mapping of 2G/3G/4G mobile signal coverage

Reading this on the web? See:
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Kit Jackson wrote:

Flat roof problems

We're in an old Victorian house. The lounge has a large bay window which
has a flat roof which is used as a balcony for the bedroom above. The
balcony is 4m wide at its maximum by 1.6m front to back.

The roof looks like it's been covered with glass fibre but it's leaking.

I think I'm going to have to take the whole lot up and re-lay it while
the weather's still fine. Any suggestions on how to get it waterproof?


If you are going to be walking and putting chairs on a flat roof
you need to lay Promenade Tiles, over a waterproof base
http://www.castlecomposites.co.uk/

-

On Thu, 22 Aug 2013 00:10:01 +0100, Mark wrote:

Kit Jackson wrote:

Flat roof problems

We're in an old Victorian house. The lounge has a large bay window
which has a flat roof which is used as a balcony for the bedroom above.
The balcony is 4m wide at its maximum by 1.6m front to back.

The roof looks like it's been covered with glass fibre but it's
leaking.

I think I'm going to have to take the whole lot up and re-lay it while
the weather's still fine. Any suggestions on how to get it waterproof?


If you are going to be walking and putting chairs on a flat roof you
need to lay Promenade Tiles, over a waterproof base
http://www.castlecomposites.co.uk/

-

Thanks for that link. I've seen these tiles elsewhere and like the
rubber ones. Because of the point loading I was thinking I could build a
very shallow wooden deck on top of the roof to help spread the load.

I've still to decide on the best (easiest) method of getting a good seal
all over the roof. This site http://www.the-flat-roof.co.uk/Quality.html
provides a lot of useful information about different roof structures.
Can anyone comment of the different methods there?

I'm tempted to take everything up, lay waterproof ply on a continuous
slope with a 1" drop over the 4m width of roof, cover the whole lot in
hot bitumen (how many coats?) and put some sort of tiles (possibly these
rubber ones) on top. Good idea?

Kit Jackson

On 22 Aug 2013 07:34:23 GMT, Kit Jackson wrote:

Because of the point loading I was thinking I could build a
very shallow wooden deck on top of the roof to help spread the load.

The supporting "joists" will give linear "point loading", they would
also have to be along any fall so as not to obstruct drainage.

This site http://www.the-flat-roof.co.uk/Quality.html provides a lot of
useful information about different roof structures. Can anyone comment
of the different methods there?

Lots of what looks like good design information but as far as I could
see only refers to bitumen based coverings. Nothing about GRP or
butyl sheet.

I'm not overly keen on felt/bitumen based roofs, just had ours GRP'd.
Time will tell... Flat roofs are just a pain, full stop.

--
Cheers
Dave.

On Thursday, August 22, 2013 8:34:23 AM UTC+1, Kit Jackson wrote:


I'm tempted to take everything up

Essential

lay waterproof ply on a continuous slope with a 1" drop over the
4m width of roof,

That's only a 1:200 slope - I'd rather have a bit more if possible.
It shouldn't be essential to have the ply waterproof - it should
be dry under the top coat.

cover the whole lot in hot bitumen (how many coats?) and put
some sort of tiles (possibly these rubber ones) on top.

I think I'd be tempted to use butyl rubber as the waterproof layer
rather than hot bitumen. I've had some on the shed (under the
green roof) for about four years now, and it seems fine so far.

You certainly need something over the bitumen/rubber. Tiles,
decking, *something*

On Tue, 20 Aug 2013 21:29:34 +0100, Tim Watts
wrote:

On Tuesday 20 August 2013 21:11 Dave Liquorice wrote in uk.d-i-y:

Fibre glass bonded directly onto the decking is probably one of the
more substantial coverings but I wouldn't like to say you won't
induce micro cracks that will let the frost in and degrade it over
time.


My roofer was less impressed by GRP - said he had to felt over one that
cracked.

Roofers generally neither understand nor like fibreglass, mainly
because if properly done it lasts for many decades without needing
repair. Using felt on a flat roof a roofer is not only establishing a
job for life but one he can hand over to his son in due course
confident it will be a good earner for many years of leaking.

On Thursday 22 August 2013 17:37 Peter Parry wrote in uk.d-i-y:

On Tue, 20 Aug 2013 21:29:34 +0100, Tim Watts
wrote:

On Tuesday 20 August 2013 21:11 Dave Liquorice wrote in uk.d-i-y:

Fibre glass bonded directly onto the decking is probably one of the
more substantial coverings but I wouldn't like to say you won't
induce micro cracks that will let the frost in and degrade it over
time.


My roofer was less impressed by GRP - said he had to felt over one that
cracked.

Roofers generally neither understand nor like fibreglass, mainly
because if properly done it lasts for many decades without needing
repair. Using felt on a flat roof a roofer is not only establishing a
job for life but one he can hand over to his son in due course
confident it will be a good earner for many years of leaking.

Possibly.

I will reinvestigate that in 15 years or so.

At least now it has the correct decking (OSB, not chip) and the
soffits/edges are correctly profiled and vented. That was half the job.

--
Tim Watts Personal Blog: http://squiddy.blog.dionic.net/

http://www.sensorly.com/ Crowd mapping of 2G/3G/4G mobile signal coverage

Reading this on the web? See:
http://wiki.diyfaq.org.uk/index.php?title=Usenet

Dave Liquorice wrote:


I'm not overly keen on felt/bitumen based roofs, just had ours GRP'd.
Time will tell... Flat roofs are just a pain, full stop.


GRP is ok if it has been laid properly on a very solid base and is a
reasonable thickness otherwise it Will crack eventually and almost
immediately if you walk on it once its aged over 10 years

-