Timber
Post and rail, and other types of wooden fencing are costly in materials and time-consuming to erect. Only good quality timber, either naturally durable or treated with preservative, should be used. Information on choice of timber and suitable preservative treatments is given in Chapter 4 – Fencing materials.
Traditionally, wooden fences were built out of oak or sweet chestnut, which are the most durable of the locally available timbers. Sweet chestnut is not native, but is long naturalised, having been introduced by the Romans. The traditional method of splitting or cleaving the timber to produce posts, rails and pales (thin, narrow boards) gives the most durable product, because the timber cells are not cut through, as with sawn timber. Wood split this way absorbs less water than sawn timber, and is more resistant to weathering.
After a period of decline, cleft or riven hardwood fencing is making a comeback, as it is a sustainable product which does not require the use of chemicals for preservation. It can be locally produced where suitable timber and skills exist. See here for further details.
Fittings
Always use galvanised nails and screws in fencing. Non-galvanised fittings will wear loose as they rust. Nail length should be 21/2 to 3 times the thickness of the timber held, nailed to a post of sufficient thickness that the nail does not protrude.
The main problem with using nails is that the wood is liable to split. This occurs particularly when nailing close to the end of a rail.
Splitting can be lessened by:
- Blunting the point of the nail by tapping it with a hammer. This causes the nail to cut through the fibre of the wood, rather than splitting it.
- Pre-drilling a hole through the rail.
- Using longer nails, driven at an angle as shown.
The traditional method of mortising rails without additional nailing (see below) avoids this problem.
The usual size of nails for post and rail fencing is 4mm x 100mm (to BS 1722 Part 7). The plans in chapter 1 give the sizes of nails required for different designs of wooden fencing. Numbers per kg of common sizes are given below.
Table 7a Plain round head nails, galvanised
| Length (mm) | Gauge (mm) | Number per kg |
|---|---|---|
| 150 | 6.0 | 31 |
| 125 | 5.6 | 42 |
| 125 | 5.0 | 51 |
| 100 | 5.0 | 66 |
| 100 | 4.5 | 79 |
| 100 | 4.0 | 101 |
| 75 | 4.0 | 128 |
| 75 | 3.75 | 145 |
| 75 | 3.35 | 187 |
| 50 | 3.35 | 284 |
| 50 | 3.0 | 342 |
Some designs of fence require bolts, for example to secure rails for attaching vertical boards on screening or security fencing. Bolts give a much stronger join than using nails or screws. Coach bolts are the most secure, because they have a square collar which locks in the wood as the nut is tightened.
The length of the bolt should be equivalent to the thickness of the timbers, two washers and a nut, plus 5mm. For a neater finish, a shorter bolt can be used, with the nut countersunk into the wood. Bolts with a diameter of 6 or 8mm should be sufficient. Preferably obtain galvanised bolts.
Brackets for attaching fencing panels to posts are available from the manufacturers of fencing panels. These are described here.
‘Metposts’ are metal spikes which are driven into the ground to hold wooden posts, mainly for panel fencing. They are quick to use and durable, but more expensive than the length of post and concrete which they replace. They are useful for fence repair. Bolt-down Metposts are available for use on concrete or wood foundations.
