Lightweight Roof

[Steve - www.ukspeedtraps.co.uk]

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

[Robert Williams]

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

[Maurice Gavin]

Ron Johnson's ply dome that I designed at

'weathered' with flexible epoxy paint and after two years is still perfect. It's much lighter than old fashioned bitumen.

[Steve - www.ukspeedtraps.co.uk]

I going to visit a chandlers next week and see what they offer.. I may take my camping chair as well so I can sit down just before they quote the price. Thanks Steve

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There is a " spray on " expanded PU foam which is insulating and water proof ( provided the skin is not broken ) Good for winter.

In Malaysia, we buy a corrugated zinc sheet which has this foam already applied. It's sound proof, weather proof and keeps cool.

Another alternative is to stick on sheet foam onto the plywood. Seal the seams with duct tape. Expanded polystyrene foam is cheap and good but will break and tear from itchy fingers of kids. Large sheets of bubble wrap also works well. Stick to plywood with contact adhesive or for expanded polystyrene a non solvent glue.

Do not use bitumen.....you'll regret it. Epoxy is good adhesive and waterproofing but so is normal paint ! Epoxy will cost 10 x more.

Have fun.

[Steve - www.ukspeedtraps.co.uk]

Thanks to all that offered suggestions, Special paint, .. close to £130 for a tin without primer.

Local glass fibre Co. came up trumps though, after a home visit to take a look and make suggestions he came up with £100 for all the matting and materials I need, and the guy even offered to visit when I was doing it to lend a had if needed for a few beers... I get him a crate and maybe he will let me take a back seat.

So glass fibre it is..

Thanks Steve

[Rick Dipper]

Proofex 3000.

Or Fibreglass, I woulf fibreglass.

Rick