First of I'd just like to say hi and give you an idea of the project I have in the garden.
We are having a flower bed around the perimeter of the garden, raised about 32" and another in front of this one raised by 16".
There are 180 meters of wood needed if using 8"x3" for this project.
My question is, can I make these using 8x2 inch timber, and lined with some plastic sheet to prolong the life of the timber.
The costs saving between 8x3 and 8x2 is about £300..

Would it be strong enough?
What plastic lining would you recommend?

I appreciate your help and any other advice you have.

Many thanks