Farm fencing - timber post and rail

I've done 300m post and rail in hardwood (messmate) with round pine posts (125 to 150mm)

I don't know specifically what are the general fencing requirements around treated pine rails and so the following may not be any assistance for your specific situation.

The round pine posts were hammered in by the fencer with his tractor at 2.4m apart. This is a standard distance for hardwood rails to stop/minimise bowing which is usually side to side when looking down the length of the rail.
If more than 1 rail, then the joints on the post are staggard. Generally, these days its hard to get 6m lengths in hardwood and so they come in 5.4m which are better anyways given the posts are 2.4m spacing (less waste)

The hardwood rails (125x45 or 150x45) are all pre drilled clamped in place on the posts and fixed to the post with GAL 100mm bugle head screws for the middle and 125mm for the ends.
Some of my rails have been up for 8+ years and no issues.

Just recently completed a back yard with 1 top rail and dog mesh similar to what you describe.


None of my treated pine posts have had any additional treatment although by the sounds of it with 150x150 square posts, all your holes will be pre-dug and concreted in??....so I guess any additional treatment applied will be a bonus.
If concreted in, based on what I've read with wood posts, make sure the post is sitting on dirt or crushed rock so the post doesnt sit in a bowl (the concrete encasing) of moisture/water over time.
If your doing any end assemblies to take the strain of your fence mesh (assuming its roll out mesh and not mesh panels??), make sure the strain post rail is at the same height as your pine rail so it blends in.


EDIT: Just looked at your link, is it mortice construction for the rail??