What timber to repair my trailer?

[andymon]

Hello there

I need to repair my rotted wooden framed utility trailer . For the 4m square of timber required marine ply (18mm) will set me back £89.00 .
What are cheaper alternatives. The trailer is used for everything camping, building work the odd car boot sale etc.
The original wood was timber planking (untreated I think) and has lasted well over 10 years, so what are my alternatives for a trailer left out in the elements?

 

[xerxes]

WBP exterior ply should be suitable for this. It can delaminate so it's worth doing something to seal the edges.

 

[foxhole]

I'd spend the money well worth it if it lasts another 10 years.

 

[andymon]

Thanks people, good advice as always.