>>sounds more like a fence post with one edge rounded off
that's right. never thought of it like that. The flat edge would allow 2 to be stacked easily. Can it be bought in the ready planed form, or would I need to find someone who can do it.
>>Still recommend treating "treated" timber with some preservative.
I've got quite a bit of wood around the garden (mostly furniture) and have previously posted about what was the best thing to use on it. Other than some bizare advice about coating it with lindseed oil everyday for a year, there were no suggestions. Have you a name for a good preservative (clear and stained versions.)
>>unless you leave the wood dipped in oil and creosote for a long time, it won't last as an edging.
I thought the main area where it would get penetrating damp, would be from beneath (contact with soil) , so I planned to staple some thick plastic sheets underneath. Will that not help? What do people do with decking and sleepers? surely they last don't they?
Come to think of it, if both sides are planed, then it would have a flat top which, 1) wouldn't look as good and 2) leave a flat surface where water, frost etc. would settle.