I've got a fairly large (4m by 3m) brick built garden 'shed' which has
a tiled roof. The slope on the roof is very shallow, so much so that
the tiles are practically horizontal.

The roof of the shed is now leaking (its been up there for maybe 15
years). The tiles look fine, so it looks like the leak is due to the
very shallow slope which doesn't allow the rain to run off properly.
There is a plastic sheet under the tiles, which has gone brittle,
which is where the water is probably getting in.

The question is which of the following options should I go for to
repair the roof:

1) Remove the tiles and battons underneath and replace the plastic
sheet above the rafters with a new one and then re-tile.

2) Replace the tiled roof with a felt or fibreglass roof.

Any opinions and does anyone have experience of fibreglass roofs?

"Zooologist" wrote in message
om...
I've got a fairly large (4m by 3m) brick built garden 'shed' which has
a tiled roof. The slope on the roof is very shallow, so much so that
the tiles are practically horizontal.

The roof of the shed is now leaking (its been up there for maybe 15
years). The tiles look fine, so it looks like the leak is due to the
very shallow slope which doesn't allow the rain to run off properly.
There is a plastic sheet under the tiles, which has gone brittle,
which is where the water is probably getting in.

The question is which of the following options should I go for to
repair the roof:

1) Remove the tiles and battons underneath and replace the plastic
sheet above the rafters with a new one and then re-tile.

2) Replace the tiled roof with a felt or fibreglass roof.

Any opinions and does anyone have experience of fibreglass roofs?


I'd personally go with your option one (1), but, using proper roofing felt
as the underlay, rather than just plastic sheet. The roofing felt should be
set as a good seal against the weather, or in other words, as a proper
roofing cover.

The tiles can then be placed back on battens, which are also sealed with
liquid felt to the underlay felt to stop the weather getting in, and also
give some more protection and comply with your local roofing style. The
battens should be screwed through to the roofing timbers with brass screws.
Done properly like this the roof should last a whole lot longer than just 15
years.

On Fri, 26 Nov 2004 17:14:53 GMT, BigWallop wrote:

I'd personally go with your option one (1), but, using proper
roofing felt as the underlay, rather than just plastic sheet.

Aye, or even one the more modern breathable membranes though for a
"shed" this is probably wasted.

The tiles can then be placed back on battens, which are also sealed
with liquid felt to the underlay felt to stop the weather getting
in,

You don't want to seal the horizontal battens to the felt or any water
that does get under will puddle at each batten and not run down and
out at the eaves.

--
Cheers
Dave. pam is missing e-mail

"Dave Liquorice" wrote in message
ll.com...
On Fri, 26 Nov 2004 17:14:53 GMT, BigWallop wrote:

I'd personally go with your option one (1), but, using proper
roofing felt as the underlay, rather than just plastic sheet.

Aye, or even one the more modern breathable membranes though for a
"shed" this is probably wasted.

The tiles can then be placed back on battens, which are also sealed
with liquid felt to the underlay felt to stop the weather getting
in,

You don't want to seal the horizontal battens to the felt or any water
that does get under will puddle at each batten and not run down and
out at the eaves.

Cheers
Dave. pam is missing e-mail


But the battens shouldn't be perfectly horizontal. They should always slope
slightly, either all to one end, or to both ends from the middle. This is
always normal practice to stop anything from gathering at the top edge of
the battens.

The slight run is never noticeable through the tiling.

(Zooologist) wrote in message . com...
I've got a fairly large (4m by 3m) brick built garden 'shed' which has
a tiled roof. The slope on the roof is very shallow, so much so that
the tiles are practically horizontal.

The roof of the shed is now leaking (its been up there for maybe 15
years). The tiles look fine, so it looks like the leak is due to the
very shallow slope which doesn't allow the rain to run off properly.
There is a plastic sheet under the tiles, which has gone brittle,
which is where the water is probably getting in.

The question is which of the following options should I go for to
repair the roof:

1) Remove the tiles and battons underneath and replace the plastic
sheet above the rafters with a new one and then re-tile.

2) Replace the tiled roof with a felt or fibreglass roof.

Any opinions and does anyone have experience of fibreglass roofs?

1 would be much better IF you use a decent quality membrane - not
plastic sheet. EDPM pond liner material would last well. Note the
majority of materials dont last well, as youve found.

The sheet under the tiles was always the real deal on that, tiles with
inadequate slope wont be at all watertight in themselves.

NT

Someone else has suggested re-tiling with a lower profile tile (as
well as replacing the felt underneath). Is this what low profile
tiles are designed for (ie specifically for roofs with a low angle)?

"Zooologist" wrote in message
om...
Someone else has suggested re-tiling with a lower profile tile (as
well as replacing the felt underneath). Is this what low profile
tiles are designed for (ie specifically for roofs with a low angle)?


Simple answer, no. Standard natural slate tiles are normally used for most
roofing designs if the area model demands it. Preformed concrete or
clayware tiles do come in profile formats, and also premoulded hybrid tile
systems that are made of ground up natural slate and concrete or clay
mixtures, so these do have different format patterns for differing roof
pitches or border styles.

I don't think anyone has asked what type of tiles you have on the roof, so a
low profile tile might help if you do have a preformed pattern tile system.
For standard natural slate though, it doesn't really matter. All natural
slate has the same sort of properties no matter what the roof angle.
Natural slate will only differ in the headlap required for different roof
angles. The headlap is the amount that the tiles overlap on each, and
slower slopes are normally set with tiles that are around half way over the
lower row. The headlap also helps in wind load strengths, and this is
usually worked out on the area of the country you're in and the rain fall
averages that are experience there.

The area you live in may also determine what material is actually used on
your roof covering and its design, so it might have been part of the shed
build permission to have a certain sort of tile on its roof. Aesthetically
pleasing for the area they call it, I think.

Thanks for the advice and comments. I spent a couple of hours this
afternoon lifting a few tiles on the roof in the area where the leak
is to see what sort of state it was in underneath. There were a few
pools of water, the battens were wet, but no obvious place where the
water could be getting in.

The existing tiles are around 1" thick (and 12" square) and are
corrugated with interlocking grooves on either side (left/right). The
slope on the roof is only about 8.5 degrees from the horizontal, the
lowest-profile tiles I have found specify 10 degrees minimum
(www.decra.co.uk). As such I don't think retiling will definitely
solve all the problems. What I'm thinking about now is fibreglassing
the roof, and then replacing the tiles on top of the new roof. That
way I get to keep the look of the original tiled roof, but should be
completely watertight and durable.