buying new fence posts
First things first as I like to say lol, you have to choose which fence posts to buy and where from. For this, you need to find your local builder's merchant or sometimes the bigger DIY stores but generally, the merchants or even farmers suppliers will have what you're looking for.
The typical fence post timber is usually spruce or larch from our own forestry sites, harvested sustainably, where the ground is then replanted with new trees. Most timber comes certified as coming from a sustainable source and it's important that your timber comes via that route. Imported timber is a bit of an unknown quantity in that regard, so just be aware of what your buying is my best advice. Even if it doesn't matter all that much to you, your client, if you're selling your services, well they might not be happy if you're using non-sustainably sourced material, so just consider that before you decide.
Now you don't always get a choice in the timber yards, but if you've been in the business a while then you've probably worked up a bit of a relationship with the staff and the yard boss at the merchants or the sawmill. My own personal preference for my posts was to choose larch if I could get it in a reasonable timescale. You only have to ask if there's any in stock or coming through the mill anytime soon, and the guys will let you know and set it aside for you if you ask them to. Otherwise, just go with what's there, and that will probably be spruce. I do prefer larch though, because it's tough as old boots and I like that about it. Choices are probably going to start widening in the future as the forestry planters are being directed to plant native mixes of trees now, so that's going to be interesting to see over the next few years.
I usually go for 100mm square posts because I don't see the point in using 75's unless it's a really low fence. I stick with my tried and tested 4x4's but it's up to you.
For length of fence post, here's my choice. For a 3ft high fence, a 5ft long post will do. I dig down 45cm, or a foot and a half, then smash the pointy end in 6 inches with the post rammer to hold it steady whilst the concrete sets.
For a 4ft high fence or 1.2m, a 6ft post will do. Again, dig down a foot and a half or 450mm, put the post in line with the string line and level it up, then smash it down 6 inches to the string line and set your concrete around it.
For a 5ft high fence I choose an 8ft post for extra strength and for a 6ft fence I choose 9ft long or 2.7m 4x4's with points on them.
Now I'll say this, some will say an 8ft post is adequate for a 6ft fence. Even the Institute of Civil Engineering states to dig down 600mm (2ft) and set concrete around the post. I don't agree with that, and I'll tell you why. I've made about half of my living replacing fences which didn't stand up to the wind in a storm, precisely because the posts were too short to handle the leverage placed on them by a high wind. My rule of thumb comes from way back, the old school, however high your fence is, half it, and that's how deep your post should go. Following that rule has never let me down, and in turn, none of my clients have ever been let down by me, and that means a lot to me personally.
That's the sizes covered, so now just check on the treatment certification too. For timber which is going to be used outdoors, it's all now generally treated with chemical at the sawmill before it's sent to the yards for sale, and each batch comes with a treatment certificate so you know it's fit for purpose.
In the old days, the treatment chemical was a close cousin of creosote or often it was just creosote, but those days are gone. You can still buy creosote, but only if you're a farmer or a trade professional and even then there are new rules. Creosote is no longer allowed to be used in domestic gardens for health and safety reasons. It's quite nasty stuff at the end of the day, and you don't want it on your skin or leeching into the ground.
The modern outdoor timber treatment is called incised treated and it comes with a UC4 tag or classification. UC4 stands for usage class 4 and means the timber is suitable for use in contact with the ground outdoors. The incised bit means that the timber was processed with lots of tiny cuts or incisions before it was chemically treated, and that means the chemical was able to penetrate deep into the grain of the timber. The firms which supply this UC4 incised timber will normally give it all a 15 year guarantee against rot, so these labels and certifications are worth checking before you buy.
If you only have one supplier near you and they don't have UC4 fence posts, they can probably order them in for you, or you can find another supplier who will usually deliver, and often that's free if the order is big enough.
So there you go. You can go and buy with some degree of confidence. And one other tip I would give you; if you find some yard boss who says none of that certification or classification is important, just walk away. There's some timber out there and no-one knows where it came from or what treatment, if any, it has, so just don't risk it. Cheap timber is cheap for a reason and the last thing you want is to go to all this time, trouble, hard work and expense for the new fence to fall down after a few years, or months because the timber was old, untreated firewood, as I call it. There is black-market timber out there, coming off boats from all around the world, cheap and nasty and God only knows what bugs it's infested with too. You just steer well clear of it and your fence will stand the test of time.
Next up, you've got your posts and it's time to dig the post holes and start setting the new fence posts into place. See you on the next page. Digging post holes.