Bit off topic but still related to cars - just!
My brother has a car transporter trailer which was decked in plywood about 5 months ago.
It was treated with 3 layers of yaught varnish before it was fitted, but is already beginning to get damaged by the weather, ie.. seperating layers!

What should we do now???

Any suggestions appreciated,

Regards,

Mark

replace with waterproof ply, or checker plate ally

roughen up and coat with a layer of grp matting and resin.

Would be ideal to replace, but what are our options when leaving it on?

There must be some treatment out there that will extend its life for now.

Maybe some kind of thick varnish?

You need Marine Ply this comes in builders grade which is expensive or proper marine grade which is absolutely extortionate, the proper stuff has the edge stamped with a BS code number. You can also get BWP ply it is supposed to be waterproof but is not tough enough for serious outdoor use. It may just be cheaper to get steel sheet and run angle under where wheels go. with a coat of good anti rust zinc paint followed by chassis black this will do better than cheap ply.

Caber

Yes Marine Ply is the stuff you need. As caber says, expensive stuff. But it lasts forever and is designed to survive damp conditions (its not called marine ply for no reason!) We have had a few boats, all with marine ply bits on and all have stood up to years of salt water and rough treatment.

David

I recently went to my local building supplies to get some ply for my trailer and asked for exterior ply. They told me it was all suitable for outside so I bought normal 18mm stuff. I never got around to painting/varnishing it but it is still as new 5 years later. I also bought some 18mm ply from B&Q to make a tailgate and it delaminated and fell to bits within 2 months! Not much help but I like to tell storys!

if youre going to fibreglass it - dont use marine ply .

if youre going to fibreglass your existing floor , it will be extremely durable , i built a complete box trailer and fibreglassed it - the timber is especially good still .

trick is to re varnish with some G4(polyurethane varnish) - leave to go tacky/dry after 2/3 hours - then fibreglass it .

it all depends on what condition your timber is - and really needs a good dry out for assesment .

If your existing ply has 'blown' it's basically no good and needs replacing... marine ply should have been used.

cheers for the suggestions, fibreglassing seems interesting, would'nt have thought of that one. The ply isn't too bad yet, so hope we can sort something in time.

Regards,

Mark

18 mm birch or douglas fir shuttering ply is very good. It takes a pounding from wet concrete and lasts for yonks.
Alex

Or shuttering ply will both do the job but need coating with something or the veneer will come off.