Thread: Outdoor weather proof varnish

Any varnish, even the most expensive marine grade spar varnish full of nano-sized zinc oxide particles as UV protection, will do that over time.

I suggest you sand it off and either leave it bare (it is a durable timber, isn't it?) or roughly brush on something like boiled linseed oil or decking oil as a general finish. Just slop some more on every year - or even twice a year - and that should keep it reasonably healthy.

OR - if it really must be varnished:

Dissasemble and sand back to bare timber, coat with West Epoxy (ATL Composites in Qld are the Australian distributors but you won't find it at hardware stores - boat shops and speciality woodworker places stock it) paying plenty of attention to the end grain, scuff sand the epoxy and coat with a few coats of marine spar varnish. Repeat the scuff sand and varnish step every 3-5 years before the varnish film breaks down down and starts exposing timber to the elements.

Here's a how-to link.

Years ago I had a friend who used an exterior finish made by Sickens. It was UV stabalised and to my knowledge after some 15 years it still hasn't pealed or cracked. It has been recoated a couplew of times and each time the timber comes up looking like it was just out of the saw mill.

when I built my office I used Sikkens Cetol HLS as a base coat and covered it with Sikkens Super Natural on my cedar windows. That was 7 years ago and the windows on the North face have darkened and the surface is just starting to flake, very,very minor. On the South side they look the same as the interior just a bit darker than new but thats probably the cedar doing what it does.
Compared to the regular oil that my outdoor furniture requires this stuffs a dream.