Hi there Steve,

Bituminous Paint can be 'good' but it needs a lot of preparation
and 'good weather' whilst it cures to get it 'right'. It is also really
messy to
put on and, if windy, is a nightmare to keep off other things as it is quite
'thin'.

You might be better to try a 2-pack epoxy based paint (similar to
that used on Boat Hulls), if you are likely to encounter any severe weather
on you Observatory roof.

My local Observatory has used 'GlassGuard' brand paint and it lasts for many
years.

This is a 2-pack epoxy paint ('brilliant white') with glass fibres, which
are designed to reflect heat/light.

The last time we did our Observatory was around 10 years ago and it's still
going strong.

One word of caution - it is very expensive (around £100 for a set of 5L tins
which will cover
about 20 square meters of roof). Once mixed the paint takes about 6 hours to
'go off'.
You will have to sacrifice a few paint brushes as well as the paint doesn't
easily clean off your brushes!

It will keep as separate base and hardener for many years, just don't
contaminate one tin with the other
else you will end up with a tin of very solid paint.

Robert

"Steve - www.ukspeedtraps.co.uk" wrote in message
...
I am now at the stage where I want to weather proof my observatory roof.
Its
an octagon pyramid and I need to keep it as light as possible. Its made of
6mm exterior ply and I am looking for off the shelf suggestions to
weatherproof it. I don't want to use varnish.

I have been wondering if I could use some kind of bitumen paint with the
fibres in, not sure what its called but its used to coat or mend flat
roofs.

Any suggestions please
Thanks
Steve

--
The UK SpeedTrap Guide" @ www.ukspeedtraps.co.uk
The UK Weather Guide" @ www.ukstorms.com