Install a custom trellis.

Custom trellis on top of a fence or as a standalone garden divider typically costs £40–£140 per metre supplied and fitted in the UK, depending on whether you're using ready-made panels or bespoke joinery. A typical 6 m back-garden fence-top trellis run is £250–£700 fitted.

Trellis serves three jobs: extending fence height for privacy without needing planning permission, supporting climbing plants, and providing visual interest in itself. The best installs combine all three.

Typical UK costs

Common installations

• Fence-top trellis — adds 30–60 cm of height to an existing 1.8 m fence, taking total height to 2.0–2.4 m. The "trellis" qualification matters legally — see "planning permission" below.
• Standalone garden divider — separating zones (vegetable patch from lawn, lounging area from utility) with a freestanding trellis screen. Usually 1.6–2.0 m tall, set in concrete posts.
• Wall-mounted trellis — fixed to a house or garden wall to support climbers. Spacers behind the trellis are essential to allow plant tendrils to wrap.
• Pergola-attached trellis — vertical panels between pergola posts, creating a partial wall while keeping the open structure.

The planning trick — fence height vs trellis

UK garden fence height for permitted development: 2 m to a back boundary (without facing a highway). Anything above needs planning permission. Trellis on top of a fence is treated as part of the fence height for planning purposes — so a 1.8 m fence with 60 cm trellis still totals 2.4 m and exceeds permitted development.

The exception: trellis with adequate gaps that genuinely allows light and visibility to pass through is sometimes treated more leniently by some councils, but always check before installing. A cooperative neighbour and a polite chat is the safest route.

Choosing the right design

• Square diamond pattern — classic, dense, good privacy. Suits formal gardens.
• Larger square pattern (50–100 mm) — more open, better for climbers, less privacy.
• Vertical battens — modern look, more screening than open trellis but lighter than solid fence.
• Shaped tops (arched, scalloped, convex) — period and decorative gardens; raises the visual impact.

Things people often miss

• Wind loading — trellis catches wind. The supporting posts must be deep enough (600 mm minimum, 750 mm for tall designs) and the existing fence posts strong enough. Adding 60 cm of trellis to a fence with rotted posts will pull the whole fence over in a gale.
• Climbing plant weight — mature wisteria, climbing roses, or ivy can add 30–50 kg to a 2 m run of trellis. Heavier-duty trellis and posts pay back over time.
• Spacers for wall trellis — fixing trellis flat to a wall traps moisture and damages the wall finish. Use 25–40 mm spacers so air can circulate behind.
• Treatment — even pre-treated softwood needs re-treating every 2–4 years to prevent rot. Hardwood (oak, iroko) needs less but isn't maintenance-free.
• Neighbour conversations — adding height to your side of a shared fence affects their daylight too. A polite chat first avoids planning complaints later.

Frequently asked questions

Want a local pro to handle this? A fence specialist or carpenter will fit trellis to existing fences, check post strength, and advise on the right design. Bespoke joinery costs more but lasts longer and looks better than chain-store panels.