Thread: 280x25 to go into ground for letterbox-preservative??

I believe the old wooden lamposts used creosote to keep the pests away and to act as a preservative.

Thanks for that. I thought there must be something I could use.
Cheers

Old timers charred the butt end of fence posts and house stumps to dissuade termites.Some of the posts that look as though they have been creosoted may well have been charred.
Remember also, you can't paint over creosote.

creosote is carcinogenic

280x25 is a unusual size to use to mount a letter box on, any particular reason to use that size,a piece 100x75,100x50 or 75x75 would hold most letter boxes.if you do use creosote be carefull it will burn sensitive skin easily,it was used for many years to stop termites. lloyd.

Mike, I thought creosote is banned for inground in most states, similar to sump oil and other residual treatments which don't breakdown, hence the bug industry now have to use organic sprays which have a much shorter life.

Why not just use a durability 1 (Ironbark, messmate, grey gum etc) species? Also good practice rule of thumb, is a minimum 450mm in ground or 1/3 in ground and 2/3 above ground whichever is greatest.

280x25mm board might be used so the mailbox can be cut into the timber and still have meat around the face of the mailbox to kind of picture frame it? or 'cause Mike has it handy?

Not sure you can buy creosote these days. I did a job for my daughter that involved posts in the ground. I asked SOL to buy some creosote to paint the bottoms of the posts and he brought home a container of a substitute, He was told that you cannot buy creosote now, I have not ckecked the veracity of this.

Chippy 71

AKA Colin.

Thanks again for the assistance. I will check the local Bunnings and see what is available.

The timber is to be H3 treated pine and the isze is due to the box being one designed for a fence/ wall etc but I intend to frame it with 2 posts on the sides and a top - reckon it will be a bit different and look OK once painted up.

Cheers

You won't need to use anything on H3 pine. A note on your design though. There are a couple of letterboxes like that in the neighbourhood and differential movement between the posts has torn one letterbox apart (it maybe near trees though from memory). I'd be tempted to run a bit of booker rod under the letterbox if there's roots nearby.

Cheers
Michael

Originally Posted by echnidna

creosote is carcinogenic

That's probably why the termites won't go near it!

Originally Posted by bluegum30

280x25 is a unusual size to use to mount a letter box on, any particular reason to use that size,a piece 100x75,100x50 or 75x75 would hold most letter boxes.if you do use creosote be carefull it will burn sensitive skin easily,it was used for many years to stop termites. lloyd.

Quite right about the unusual size. The post will be very stiff in the 280 direction, very flexible in the 25 direction, so take care with anything attached to it. The usual practise here is more like 90x90 (4x4 nominal Imperial) where free-standing. Also more common is about 600mm embedment vs 300.

For best longevity, I suggest about 150mm crushed rock below the post, and crushed rock rammed encasement in a 150mm diameter hole (for 90x90 post). This is to allow water to drain away from the post.

Treated timber should be satisfactory. For additional insurance, see if Bunnings has liquid wood preservative. A product here contains copper naphthenate at about 9%. The label contains text, "... violation of Federal law ...," so YMMV for sure.

Cheers,
Joe