How to build a garden arbour

Video by Toolstation. This guide is based on the "How to build & treat a garden Arbour with Toolstation products" video from the official Toolstation UK channel. It covers the build from post setting through to the timber treatment stage, with practical notes on fixings and finish. Well worth a watch before you order your materials.

1. Choose the right spot and prepare the ground

Think about where the arbour will get the most use. A sunny corner with some shelter from the prevailing wind is usually the sweet spot. Check there are no underground cables or pipes below your post positions before you dig.

Mark out the footprint with pegs and string. Clear any turf or vegetation in the area and, if you are setting posts directly into the ground, compact the base. Soft, waterlogged ground will not hold posts well — it is worth addressing that before you start.

2. Set the posts plumb and level

Dig post holes at least 600 mm deep for a standard garden arbour — deeper if the soil is loose or sandy. A post hole borer makes this faster than a spade alone.

Use fence post spikes if you want to avoid concrete. Drive them in, check they are plumb with a spirit level, then drop the posts in. That said, concrete is more permanent and worth the extra effort for a structure you plan to train heavy climbers up.

Pack concrete around the posts, check for plumb again before it sets, and leave it to cure for 24 hours before building on top.

3. Build the side frames

Cut the horizontal rails to length and fix them between the posts at the required height. Galvanised screws or coach bolts give the best strength. Coach bolts look cleaner from the outside if the arbour will be in a prominent spot.

Add any trellis or lattice panels to the sides at this stage. Fix them to the inner face of the frame so they sit neatly and are protected from the worst of the weather by the post and rail.

4. Construct the roof frame

The roof is usually the trickiest part, but only because it needs to be square and properly supported. Cut the ridge beam and fix it between the two front and rear top rails. Then add the roof joists at regular intervals — 300–400 mm spacing works well for a standard sized arbour.

Use joist hangers or angle brackets to fix each joist to the ridge and side rails. It takes longer than just toe-screwing, but the joint is stronger and will not work loose over winter.

5. Fit the roof slats

Roof slats give shade and somewhere for climbers to grip without completely blocking the light. Space them evenly — around 50–75 mm apart gives a good balance. Fix each one with two screws per joist.

Pre-drill to avoid splitting the timber, especially near the ends of the slats. It takes a few extra minutes but saves a cracked board that then needs replacing before the structure has even been up a season.

6. Sand any rough edges and apply timber treatment

Sand down any rough cut edges and splinters before applying treatment. You will handle this structure regularly — a splinter from a roof joist is irritating enough to be worth five minutes with 80-grit paper.

Apply a quality exterior wood preservative or fence stain, working into all the end grain carefully. End grain soaks up moisture fastest and is where rot tends to start. Give the whole structure two coats, allowing the first to dry fully before the second goes on.

7. Anchor the finished structure and add climbers

Check the whole structure is stable by pushing it gently from different angles. If it rocks, add diagonal cross-bracing between a post and the adjacent rail. Better to sort it now than after you have planted a rose up it.

Plant climbers — roses, clematis, honeysuckle — at the base of each post and tie them in to the trellis or slats as they grow. Give them a cane to start with so they head in the right direction.

When to call a handyman

Call Richard if the ground is rocky or waterlogged, the proposed site has buried services, the design is larger or more structural than a standard garden arbour, or if you are not confident working with concrete footings. Getting the posts right at the start is the part that makes the difference between an arbour that is rock solid and one that leans a bit more each year.