Car Trailer - Replacing Ply, How Thick?

[Foresty Forest]

I have to replace the ply on my trailer. I think I should use marine ply for a longer life span. For this trailer would 12mm marine ply be adequate throughout? Or should I use 18mm for the floor? What would be the most cost effective way of preserving the ply. I'd like to use creosote (whatever they call it these days?), but that stinks - but it is cheap and effective. The trailer is about 6'x4'.

 

[Stivino]

The ply on the floor of my trailer was the floor from the caravan that is started out as. I used it to go to the pit and load it with loose coal. I used to pile it up with logs, too. It was never covered, it lived in the garden and the floor was never a problem.
I made another caravan into a trailer for a friend who was a stonemason, his trailer was treated the same as mine but, he used to chuck big lumps of stone into his and the floor somehow managed to withstand it.

 

[JohnD]

true creosote is carciogenic and not often found. You can get modern spirit-based wood preservers such as Cuprinol Clear that protect againt rot and worm (there are other own-brands but check the safety datasheets to confirm they contain plenty of toxic chemicals).

Over the preserver, you can get water-based breathing woodstains to keep the rain out, I find the ones sold for decking are most durable, they are very easy to reapply each year. You have to treat the edges of ply very thoroughly with multiple coats because if damp gets in the ply will delaminate.

If you use a paint, it prevents damp from drying out.

18mm or 22mm ply is what you use for floors, I think the trailer will need the same.

it's unlikely you will find true marine ply but there are WBP plies aplenty.

 

[Tigercubrider]

There is phenolic board, usually used for some truck floors/horse boxes and trailers.
You'd treat the edges.
Choose a decent one and it lasts an age.

Price up aluminium treadplate.

 

[Burnerman]

Another plus for the phenolic board, available in 12 or 18mm from the likes of Indespension.
Costs a bit but is nigh on indestructable......its used on trailers that carry mini diggers!
John

 

[Diver Fred]

12mm on frames for the sides. looking at the support available for the floor I'd be using 25mm ply.
Preserving - Underside paint with Bitumastic (a.k.a. Black Bitumen paint), 2 coats; allow to dry then a good spraying of Waxoyl. Sides and inside, wood preserver followed by fence treatment.

 

[ReganAndCarter]

Creocote from Tool Station.

https://www.toolstation.com/creocote-shed-fence-treatment-4l/p80210

 

[Foresty Forest]

Thanks.

Would Hammerite be acceptable for the chassis?

 

[Burnerman]

Yes, just don't expect it to do what it says on the tin, i.e kill rust because it doesn't......I now use a silver metal paint from Johnstones with an appropriate primer which I find much better.
You can shift a lot of the rust with a flap wheel and angle grinder if you choose.
John

 

[JohnD]

Hammerite is difficult to repaint, and rust can grow under the paint film. I prefer an anti-corrosion primer (even red oxide) and oil-based paint system

 

[Diver Fred]

Bitumastic is thicker than Crosote, and can be applied to both wood and metal as a preservative. The application of 'Waxoyl' adds to the thickness of the protection and also helps penetration into the timber. Did my trailer about 30 years ago, with a couple of resprays with Waxoyl in high wear areas and it's as good as new from the underside.

 

[Harry Bloomfield]

The ply on the floor of my trailer was the floor from the caravan that is started out as.

Modern caravans use a much thinner ply/insulation/ply makeup, rather than a solid ply sheet used in older caravans. It can be quite delicate even for walking on.

 

[Avocet]

Depends what sort of loads you're going to put in there. If you're just taking hedge cuttings down to the tip, I'd have thought 12mm for the floor and 9mm for the sides, otherwise you'll just reduce your payload. If you're going to be putting big "point loads" into it (like a car engine), I'd be inclined to go thicker. Phenolic coated ply is a good shout. Also, I've seen people put strips of wood (say, 38mm square) on the angle iron flanges round the edges (and down the middle) and then just screw decking planks to the wood. You lose a bit of space that way, but at least decking planks are cheap, usually pressure treated, and you can replace individual ones if they get damaged.

For the rust, my current preferred potion is 121 epoxy mastic.

https://www.rust.co.uk/product/cat/em-121-epoxy-rust-proofing-chassis-paint-7