On Sat, 02 Aug 2003 22:25:06 +0100, Andrew McKay
wrote:

Repairs needed for a garden shed roof which is leaking.

What are the options for ensuring a waterproof covering? Roll of felt
from a DIY shed? Presumably there is some goo that can be bought to
seal the overlaps?

Andrew



I can give you a couple of ideas, one of which I've used, and the
second I am about to do.

1) For a shed that I built about 10 years ago, I boarded the roof with
18mm TGV timber (although that was not so important.

I then bought the heaviest felt system that I could find that didn't
require a torch to apply it. I believe it was made by Marley and was
several grades up from the cr*p they sell as shed felt.

http://www.marleywaterproofing.com/s...=waterproofing

I believe it is now sold as Rapidseal but can't remember what it was
then - it was certainly two layers.

I began by treating the boards with a good spirit based wood
preservative - three coats. Obviously if you have a roof that is
leaking, check for rot and fix.

There is then a bitumen primer, then the first layer goes on, followed
by joint sealer and the second. There are detailed instructions in
an application note on the web site.

There is a sealant in a gun cartridge as well which is used for
sealing corners etc.

The result has been very good and ten years later it's still looking
good. It does take a bit longer than simple felting but if you
follow the instructions and form drip pieces correctly it is worth it.

2) For a new timber cabin type shed that I am making I wanted
something a bit different than boring felt. I did think about tiles
but they didn't seem right and the pitch of the roof is very low at
about 20 degrees.

So I looked at cedar shingles and shakes. These are commonly used in
north America for roofing.

Shingles are created by taking sheets of cedar and sawing through at
an angle such that they are thicker at one end than the other.
They are then nailed through the thin ends to battens on the roof in
courses leaving a gap from side to side between them to allow for
expansion and contraction.
They are overlapped on successive courses such that gaps do not align
within three courses.

Shakes are similar, but generally are split by hand and so are rough
on one side and smooth on the other where they are sawn the same as
shingles. They go rough side up using a slightly different fitting
regime and give a more rustic appearance.

http://www.johnbrash.co.uk/shakes.shtml

http://www.cedarbureau.org/

I'm using a modified version of the method shown for low slope fixing.

The shed roof is boarded as before and treated. Then I have felted
it, but only with a regular heavy grade felt with overlaps.

I have then fitted wide pressure treated battens between the eaves and
the ridge using 450mm centres - i.e. perpendicular to the ridge.

On top of these are fitted pressure treated battens on 150mm centres
going parallel to the ridge and perpendicular to the first battens.

The reasoning behind this is that if any water should penetrate under
the shakes it will run down the felt on the roof boards.

The next step (probably tomorrow's job) is to attach the shakes by
nailing them to the horizontal battens using interlay felt between
layers. Silicon bronze or stainless steel nails are required, AIUI
due to tannins in the cedar which will eat other nail types.

The ridge will be completed with a pair of cedar board angled
appropriately and jointed.

Quite a bit of work, but I am pretty sure the end result will be worth
it.





..andy

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