I am in the process of constructing my new shed, when the rain allows !!

Most of the construction is made from recycled wood…just love wood….lovingly planed and sanded to show

the fantastic grains……anyway that has been yacht varnished !!

with regards to the roof….

I have placed 9mm exterior plyboard up there, sealed around all the edges and yacht varnished that to….

Now I'm thinking….yep looks great…same….lovely grain…………but will it last ?

Should I just do what everyone else does….felt it ?  Waterproof it ?

Any suggestions would be greatly rec'd.

Tracy

Tracy,

The main difference with exterior grade plywood is in the glue - typically it's better than that used for interior ply and will stand up to the ingress of water better. But 'better' just means longer and hence it will eventually start to de-laminate and you'll be replacing the roof unless you do other things to ensure that the water doesn't get in. You say you have sealed around the edges - what with? I would suggest a thinned down varnish - start with 1 part varnish to 2-4 parts thinner which should really get into the wood, then 1:1 Varnish:Thinner and finally on to a few non-thinned coats of exterior varnish. You should reapply a full coat of varnish once every couple of years as UV starts to break down the varnish over time - give the whole roof a wash with some mildly soapy water first to remove the clag, rinse & allow to dry, then a quick sand with some fine sandpaper and whack on a coat or two. With this kind of TLC your roof should last for years!

Cheers

Morgan