Hi,
we have a couple of these - one with pressure treated softwood, one with iroko - which have lasted 15+ years outside and are starting to look like they need replacing before too long.
My suggested options include:
- More pressure treated softwood;
- Oak or sweet chestnut (durable hardwoods, could be sourced within the UK easily enough);
- Larch or Douglas fir (durable softwoods, could be sourced from UK too)
- Tropical hardwood (e.g. Iroko, Sapele, Ipe)
or Accoya (if you want the timber to outlive you!)
All these will weather down to a nice greyish colour if left untreated/painted.
I'll probably choose oak (because I already have some), or Accoya if I'm feeling rich at the time.
Cheers, W2S