When you put in a new gate post, durability is a must have, and many people, myself included, have not been satisfied with regular pressure treated or tanalised spruce posts. They rot quickly at the interface between the ground and the air, which is where fungus and insects thrive, having both moisture and oxygen. This video describes three attempts to counteract short-lived timber posts (as well as some chainsaw milling tips).

1. Choose the species of timber

There are many naturally durable kinds of timber. In this instance we are chainsaw milling White Oak. Other long lasting timbers include Black Locust, Osage Orange, Cedar, Hawthorn, Chestnut, etc. Using a durable timber species will mean the treatment of the wood can be a lot less toxic.

In general, even on these species, the sapwood is much less durable, and along with the bark, is worth removing.

Manoeuvring about with timber this size can be quite challenging. Levers are handy!

For the first time we also experimented with an exceptionally primitive DIY Vertical CS Mill jig. Surprisingly it worked quite well!

In terms of actually transporting the cut posts, 8ft long sections of 8″x8″ and 9″ x 8″ oak heartwood, we used the quad and trailer, as the ground is too boggy to use much else. So despite spending a reasonable amount of time on the fixer-upper JCB (more on that another time), we couldn’t use that in this instance.

No more than two at a time seemed prudent!

2. Treatment (FIRE!)

The kind of treatment tested here is one that has been used for centuries. It involves charring the timber, creating a protective torrefied layer, that is harder than the un-charred wood (which is incidentally similar to the way our Palaeolithic ancestors hardened their sharpened sticks to make spear-like weapons). Outside this hardened torrefied layer is the carbonized char, which should also be unappealing to fungus and insects.

We used the experimental rocket stove to do the charring, supporting the posts on a roller attached to a small scaffolding tower… It worked well.

The process exists in many cultures, but is probably most well known in Japan, where ancient wooden temples, with the treatment, still exist today. In Japan, the treatment is known as ‘shou-sugi-ban’.

It’s worth noting that this is an experiment – some posts we charred and some we didn’t – let’s see in 20 years how things are going…

Update: There has been an interesting study published 2021 suggesting that there are NO durability benefits to charring in most wood species (see here https://www.mdpi.com/1999-4907/12/9/1262).

We scraped away the very outermost layer of char on our posts. Why? Well for the explanation and the other details, like how deep to char etc. just watch the video :)

3. Installing the Gate Posts & Moisture Management

The last step to getting a strong, long lasting post, is to put it in right! Depending on the local ground conditions the tends to mean ‘rocking’ it solid. That is digging a hole big enough to fit the post, and a surrounding layer of compacted stones, that will provide excellent drainage.

Again to see our method on this, just watch the vid, but basically it involves some rather vigorous compacting of rocks round the post. adding another layer, compacting again, etc. etc. The rocks come slightly proud of ground level and slant away from the post to cast water away…

Finishing Touches

We added a little copper hat as we had some scraps knocking about anyway, but anything that will protect the exposed end grain on top and send water off will help. That could be as simple as cutting a chamfer on top, or nailing on a small wooden board…

Anywhere metal is in contact with the oak, such as the gate hinges and closure, it’s a nice idea to insulate with some thin plastic – this prevents it reacting with the tannins in the oak and corroding faster (and making unsightly black stains down the oak).

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Posted: 10|26|20 at 1:14 pm. Categorically squeezed into: Woodplay.
Tags: Chainsaw Mill, charring, Gate post, Oak Post, Preserving wood
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