A fence is only as reliable as the posts holding it up. Knowing how to install fence posts properly prevents common problems like leaning panels, gates that don't close properly, and a boundary fence that looks decidedly wobbly after just one wet winter. The key is not simply putting a timber or concrete post in a hole - it is choosing the right post and digging a vertical hole that is the correct depth and in line with every other post,
Whether you are replacing a single damaged post or building a full run of closeboard fencing, good preparation saves time, materials and potentially a great deal of frustration. Ground and site location, fence height, and the type of fence all affect the method, so no single depth or fixing method suits every garden.
Plan the fence line before digging
Start by confirming where the boundary sits. Do not assume an old fence is exactly on the legal boundary, particularly where neighbouring gardens have changed hands or fences have been replaced over the years. If there is any doubt, check your property deeds, and if there is a discrepancy, agree the fence line with your neighbour(s) before you do anything else. Many a good friendship has been ruined by accidentally moving a line an inch or two.
Mark the proposed line with a taut builder's string line. This gives you a clear reference for setting posts straight and helps reveal awkward level changes. Measure the total length, then mark out your post centres based on the type of fence you are installing.
Before digging, consider buried services. Water pipes, electric cables, drainage runs and telecommunications cables can all be close to the surface in established gardens. If you are unsure, use service plans where available and take particular care near buildings, driveways and utility entry points.
Choose posts that suit the job
For a typical garden panel fence, pressure-treated timber posts provide a traditional appearance and are straightforward to work with. Choose posts rated for ground contact, rather than using ordinary treated timber intended for above-ground work. The section size matters too: a 75mm x 75mm post may suit a light, sheltered boundary, while 100mm x 100mm posts offer more strength for taller fencing or exposed sites.
Concrete posts are a practical choice where long service life and low maintenance are priorities. They do not rot and are particularly useful for featheredge fencing, heavy panels or damp ground. Their weight makes handling more demanding, however, and they need careful positioning before the concrete sets.
Metal post systems like DuraPost Classic are much lighter than concrete posts; they are rot-proof, strong, and can last in excess of 20 years.
Post length should allow for the finished fence height plus the section buried below ground. As a working rule, aim to set around one quarter to one third of the total post length into the ground. For many 1.8m garden fences, this means using 2.7m posts with approximately 750mm below ground. Taller fences, loose soil, and exposed coastal or hilltop locations will require deeper holes and stronger posts. For most fences below 1.5m, the minimum depth is 600mm.
Tools and materials for installing fence posts
It is a good idea to get everything ready before commencing work. You will normally need a tape measure, hammer, string line, spirit level, saw, spare battens to use as post props, and an old tarpaulin or similar to stop the spoil from ruining your lawn, together with suitable screws or nails. To dig the holes, you will need a post hole digger (sometimes called Double Shovels) and/or a fencer's graft, a narrow, strong, long-handled spade developed for digging small, deep post holes. If you are digging a lot of holes, get a graft and double shovels as they will save you loads of time. For just one or two post holes, you can get away with a standard spade and a trowel combined with your arm. A shovel and wheelbarrow to help clear spoil is useful, and the wheelbarrow is excellent for mixing dry-mix concrete.
For each post, allow enough concrete or post-setting mix for the hole size. Keep a few treated timber packing pieces or temporary braces to hand. These make it far easier to hold a post plumb while it is being set. Wear gloves, safety footwear and eye protection when cutting or mixing materials.
How to install fence posts step by step
Begin with an end or corner post, as this establishes the line for the rest of the fence. Dig the hole wide enough to be able to work around the post when it is stood in the hole- roughly 200 to 300mm wide is common for a standard garden post, although larger posts will need more room. Dig to the planned depth, keeping the sides reasonably neat and vertical.
Place the post in the hole and align with the string line. Check it for plumb on two adjacent faces with a spirit level, then brace it temporarily. Do not rely on checking only one face: a post can look upright from the garden yet lean along the fence line.
If using traditional drymix concrete, place a small amount around the post base, compact it carefully and recheck the level. Continue adding the drymix concrete in layers, tamping each layer really well to remove voids. A piece of 3"x 2" or 4" x 2", about 5ft long, makes a great tamper. As you fill the hole around the post, check several times to make sure the post is still vertical. If it is slightly off, adjust by tamping harder on one side of the post to bring it back into line. Finish the concrete just below ground level and slope the top away from the post. This sheds rainwater rather than allowing it to sit against the timber. The drymix will absorb moisture from the ground and set hard, usually within a couple of days. If the post has been tamped up good and hard, then the post is usually solid enough to have panels attached straight away.
For more information on drymix concrete and mixing tips, see the Installation Tips section of our 20mm Ballast bags.
Postmix offers an easier option for some jobs. Attach two or three battens to the post to hold it in position. Follow the product instructions closely, as water quantities and setting times vary, particularly in cold weather. The convenience is useful, but do not rush the alignment stage. Once the mix starts to set, you can't correct a misaligned post. Do not be tempted to wiggle the post to see if the mix has set. Instead, tap the top surface of the post mix gently to check if it is hard.
With the first post secure, set the second end post and run a string line between them at the intended face of the fence. Install intermediate posts to that line, checking the spacing as you go. Measure between post centres and also test-fit a panel, rail or gravel board to check your measurements. Do not be tempted to dig all the holes first, as this very rarely works out.
On sloping ground, decide whether the fence will follow the slope or be stepped. A raked fence follows the gradient and suits closeboard or rail systems. Panels need to be stepped to remain level and rise or fall in clear stages. Set this out before fixing anything permanently, especially for stepping panels, as post heights will need to be adjusted for the steps.
Allow the posts to set before loading them
Concrete gains strength over time. Although a rapid-setting mix or drymix may hold a post in place quickly, it is sensible to avoid hanging gates until the material has cured as instructed. A gate puts repeated sideways force on its hinge post, so use a suitably substantial post, deeper footing and strong galvanised fittings.
Once the posts are firm, fit wooden post caps and finials, or metal post caps, to timber posts if required. A cap protects the end grain from rain and gives the fence a cleaner finish. When attaching panels or rails, use galvanised or stainless-steel fixings to reduce staining and corrosion.
Common mistakes that shorten a fence's life
The most common issue is using undersized posts or setting posts too shallow. It may look secure on installation day, but wind pressure and saturated soil gradually work a shallow post loose. Thin posts and shallow holes are common mistakes.
Another mistake is allowing timber to sit in standing water. A well-shaped concrete collar and sensible drainage around the fence line help, but no timber post lasts forever in permanently wet ground. In very damp gardens, using rotproof concrete posts or metal DuraPost may be the more economical choice over the life of the fence.
For homeowners and trade installers alike, the best fence starts with fence posts matched to the site, not the cheapest available post. Take time over each post, keep the string line tight and allow the concrete time to do its job. The result is a boundary that looks straight on day one and remains straight through the seasons.
