How to Build a Timber Fence

What you need

Fence panels, posts, concrete, gravel, a post-hole digger or spade, a string line and pegs, a spirit level, a tape measure and a wheelbarrow. Buy pressure-treated timber for the posts — they sit in the ground and untreated posts rot in a few years. Gravel boards for the bottom of the run are worth buying too: they keep the panels off the ground so they do not rot.

Step 1 — Set out the line

Run a string line between pegs along the boundary and check it is straight — a fence that wanders looks wrong from the first panel. Make sure the fence sits on your side of the boundary: check your deeds if you are unsure, and talk to your neighbour before you start, because a fence in the wrong place is a dispute, not a DIY job. Check your local rules on fence height too — limits vary by area.

Step 2 — Work out the materials

Measure the run and divide by the panel width, rounding up: that is the number of panels, and you need one more post than panels — one at each end and one between every two panels. The fence calculator does this and gives you the rails too (two per panel). Order a spare panel and post: timber varies, and a damaged board on delivery day should not stop the job.

Step 3 — Dig and set the posts

Before you dig, check for underground cables and pipes — in the US call 811, in the UK use LinesearchbeforeUdig, and anywhere else ask your local utility. Dig each hole about 600 mm (2 ft) deep and 300 mm (1 ft) square — roughly a third of the post goes in the ground. Set the first and last posts first, run the string line between them, then set the rest to the line, checking each one is plumb with the spirit level. Concrete the posts in and brace them while the concrete sets; do not hang panels on green concrete.

Step 4 — Fix the panels and finish

Once the concrete has set, slide the panels between the posts and fix them with clips or screws, checking each one is level. Fit gravel boards along the bottom so the panels sit clear of the ground, and treat any cut ends with preservative — cut timber is where rot starts. Step back and sight along the run: a straight fence reads as one line, and any post out of line shows immediately.

Worked example

A run 100 ft long with 8 ft panels needs ⌈100 ÷ 8⌉ = 13 panels, 13 + 1 = 14 posts and 13 × 2 = 26 rails. The concrete for the posts — 14 holes, each 1 ft square and 2 ft deep — is 28 ft³ in total; with 10% wastage that is 30.8 ft³ (1.14 yd³), or 52 bags of 80 lb. Those are exactly the numbers the fence calculator and the concrete calculator give you.

Common mistakes

• Posts too shallow. A post with only a foot in the ground leans in the first strong wind. About a third of the post belongs underground.
• No gravel board. Panels sitting on wet ground rot from the bottom up. A gravel board keeps them clear of the soil.
• Hanging panels on green concrete. Concrete that has not set moves under load. Wait until it has set before you hang anything.

Safety

Check for underground utilities before you dig — hitting a cable or gas pipe is dangerous and expensive. Concrete burns skin and eyes: wear gloves, eye protection and boots, and wash splashes off straight away. Posts and panels are heavy and awkward — lift with your knees and work in pairs. Check your local rules on fence height and boundaries before you build.

Try these calculators

• Fence Calculator — panels, posts and rails for any run.
• Concrete Calculator — volume and bags for the post holes.
• Gravel Calculator — volume and weight for a gravel base.