Summary
Composite fencing has moved from a niche premium product to a mainstream option over the last decade, largely following the same market path as composite decking. The appeal for homeowners is straightforward: no annual re-staining or preservative treatment, resistance to rot and insect damage, and a consistent factory finish that doesn't silver, warp or split the way timber does over a 10–15 year period. For tradespeople, the appeal is a lower callback rate and a product that photographs well for portfolio work — but it comes with a materially different fixing method, different tooling considerations (cutting produces plastic-laden dust, not clean sawdust), and a price point that needs to be sold on lifetime value, not upfront cost.
The core material is wood-plastic composite (WPC): reclaimed or virgin wood fibre, typically 50–70% by weight, bonded with recycled or virgin HDPE (high-density polyethylene) under heat and pressure, then extruded into board profiles. Better products are "capped" — co-extruded with a thin protective outer shell of pure polymer that resists UV fade, staining and mould far more effectively than uncapped composite, which behaves more like a slightly better-than-timber material rather than a genuinely low-maintenance one. The distinction between capped and uncapped is the single most important spec decision on a composite fencing job, and it's the one many customers don't know to ask about.
This article covers board and post specification, the installation method (which differs meaningfully from timber panel or close board fencing), the planning and boundary rules that apply, and how to have the cost conversation with a customer comparing composite against timber on price alone.
Key Facts
- Material composition — wood-plastic composite (WPC): typically 50–70% recycled wood fibre, remainder recycled or virgin HDPE, plus bonding agents and UV stabilisers
- Capped vs uncapped — capped composite has a co-extruded protective outer layer resisting UV fade, mould and staining; uncapped composite fades and can absorb moisture at cut edges over time — always specify capped for fencing exposed to weather
- Standard board dimensions — typically 150mm–180mm wide × 20–30mm thick, tongue-and-groove or slot-fit profile, supplied in lengths matching standard panel widths (1.83m/6ft most common)
- Standard fence heights — built up from individual boards: six boards at ~300mm each commonly reaches 1.8m; also available in 0.9m, 1.2m, 1.5m and 2.0m configurations depending on board count
- Post types — aluminium-cored composite post (100mm × 100mm), full recycled-plastic post, or timber post with a composite sleeve — aluminium-cored posts give the best long-term straightness and resistance to warping
- Post spacing — typically 1.8m–2.0m centres, product-specific; always follow the manufacturer's span table rather than assuming timber spacing applies
- Fixing system — boards slot into a U-channel or H-channel groove on each post rather than being face-nailed; end boards are secured with concealed clips or colour-matched screws
- Fixings specification — stainless steel or A2-grade screws recommended; standard galvanised fixings can cause staining on light-coloured composite boards over time, unlike on timber
- Expansion gaps — composite expands and contracts with temperature more than timber; manufacturers typically specify a 5–10mm gap at board ends and between board and post channel — check the specific product datasheet
- Ground clearance — despite being rot-resistant, composite boards should still sit clear of soil (minimum 50mm, ideally on a gravel board) to prevent algae staining and water pooling at the base
- Post foundation — set in concrete to the same depth guidance as timber: 600mm for a 1.8m fence, 750mm for 2.0m+, per BS 8500 concrete specification — see fence post installation depth
- Manufacturer warranty — typically 15–25 years structural, often 10 years against colour fade on capped products; uncapped products usually carry shorter fade warranties
- Service life — 25–30+ years typical for capped composite versus 15–25 years for pressure-treated timber close board
- Fire performance — composite fencing is not subject to the same Euroclass fire classification scrutiny applied to composite decking/cladding on buildings post-Grenfell, but flammability varies significantly by product and manufacturer certification should be checked for any installation close to a building or boundary with a neighbour's structure
- Cutting and waste — composite offcuts and dust are plastic-wood composite, not clean timber — cannot be burned on site (unlike treated timber offcuts, which shouldn't be burned either due to preservative content) and should go to general construction waste; cutting produces fine dust that benefits from an FFP2/FFP3 mask and dust extraction
- No dedicated BS 1722 equivalent — timber fencing follows BS 1722 (various parts by fence type); precast concrete fence posts are covered by BS EN 12839 (Precast concrete products — Elements for fences), not BS 1722-3, which is sometimes cited for this in trade literature but actually specifies strained wire fences; composite fencing has no directly equivalent British Standard for the finished product, though board material is commonly tested to BS EN 15534-6 (wood-polymer composites — specifications for fencing profiles and elements)
Quick Reference Table
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Try squote free →| Feature | Composite fencing | Timber close board (comparison) |
|---|---|---|
| Typical supply cost per linear metre (1.8m height) | £150–£300 | £85–£140 |
| Typical labour cost per linear metre | £35–£65 (slightly higher — post channel setup) | £35–£60 |
| Maintenance | None required — occasional wash down | Re-treat/stain every 2–3 years |
| Service life | 25–30+ years (capped product) | 15–25 years |
| Colour options | Fixed at manufacture — cannot be repainted effectively | Can be re-stained any colour |
| Warping/splitting risk | Very low with aluminium-cored posts | Moderate over 10+ years, especially in wet ground |
| Fixing method | Slot into post channel, concealed/colour-matched fixings | Nailed/screwed to arris rails |
| Post foundation | Same as timber — concrete-set, 600mm+ depth | Concrete-set, 600mm+ depth |
| Cutting on site | Produces plastic-composite dust, needs PPE | Standard timber sawdust |
| Standard board width | 150–180mm | 100mm (feather edge pale) |
| Planning permission threshold | Same as any fence — 2m (1m near highway) | Same as any fence — 2m (1m near highway) |
Detailed Guidance
Choosing between capped and uncapped composite
Capped composite carries a co-extruded outer polymer skin that does almost all of the weathering work — it's what gives the "never needs treating" claim its real substance. Uncapped composite is a step up from timber in rot resistance but will still fade unevenly, can develop surface mould in damp, shaded gardens, and is more prone to moisture ingress at cut ends where the wood fibre is exposed. For any job being sold on low-maintenance value, specify capped boards and check the manufacturer's technical datasheet confirms this explicitly — "composite" alone is not a reliable spec description, since budget ranges vary hugely in wood-fibre content and cap quality.
Post system and setting
Aluminium-cored composite posts are the preferred specification for straight, long-term-stable runs — solid composite or plastic posts can flex or bow over long spans, particularly in exposed or windy sites. Post setting follows the same principle as timber: one-third of the above-ground height set into concrete, with 600mm minimum depth for a standard 1.8m fence and 750mm for 2.0m. See fence post installation depth for the full depth and concrete specification.
The key installation difference from timber is the fixing method — boards do not get nailed through their face. Instead, each post has a routed channel (or a bolt-on U-channel bracket system for retrofits and timber-hybrid posts) that the board tongue slides into. This means:
- Set and concrete posts first, exactly as for a timber fence, checking each post is plumb and level to the string line before the concrete sets.
- Allow the full concrete cure time specified by the manufacturer (typically 24–48 hours minimum for postcrete, longer for standard concrete mix) before loading the posts with boards.
- Starting from the base, slide the first board into the post channels on both sides, checking it sits level.
- Continue board by board up the run, checking for the specified expansion gap at each post junction.
- Fit the top capping rail or trim (if the system includes one) and secure end boards with the manufacturer's concealed clip or colour-matched screw system.
Ground clearance and gravel boards
Even though composite doesn't rot, it should not sit in direct soil contact. Continuous ground contact traps moisture against the board and encourages algae and green staining on the lower courses — a cosmetic but very visible fault that generates complaints even though it isn't a structural failure. Fit a gravel board (composite or concrete) at the base, giving 50mm+ clearance between the lowest composite board and the ground, exactly as recommended for timber. See concrete post gravel boards for gravel board specification.
Expansion and contraction
Composite material moves more than timber with temperature change — boards fitted tight to a post channel in cold weather can bind or bow in summer heat if the manufacturer's expansion gap isn't respected. This shows up months after installation as boards that won't sit flush or that creak audibly in warm weather. Always check the specific product's datasheet for gap tolerances rather than assuming a universal figure — this varies meaningfully between manufacturers and board profiles.
Fixing hardware — avoid galvanised on light colours
Standard galvanised screws and clips can leach a grey-black stain onto lighter composite boards (grey, sand, driftwood tones) over a few years as the zinc coating weathers — a fault that's invisible at handover and appears 12–24 months later. Specify stainless steel (A2 minimum) or the manufacturer's own colour-matched fixing kit for any visible fixing point.
Selling composite over timber — the cost conversation
Composite loses on upfront material cost every time — typically 1.5–2.5x the supply cost of comparable timber close board. The case for it is entirely on total cost of ownership: no re-staining labour every 2–3 years (typically £8–£15 per linear metre per treatment in materials plus labour), a longer base service life before replacement, and a consistent appearance that doesn't need ongoing customer effort. For customers planning to stay in the property 10+ years, or who have explicitly said they don't want a maintenance task, the total-cost argument is genuinely strong. For customers on a tight budget or planning to sell within a few years, timber close board remains the more sensible spec — don't oversell composite where it doesn't fit the customer's situation.
Frequently Asked Questions
Does composite fencing need any treatment or maintenance?
No preservative treatment, staining or painting is required — this is the core selling point. Manufacturers typically recommend an occasional wash down with water and a mild detergent (not a pressure washer at close range, which can damage the surface finish) to remove surface dirt or algae, particularly on boards near ground level or in shaded, damp positions.
Can composite fencing be repainted if the colour fades or the customer wants a different colour later?
Not effectively. Colour in composite boards is integral to the material (mixed through the extrusion, or as part of the capping layer), not a surface coating, so conventional paint or stain doesn't bond well and looks patchy. If a colour change is wanted, board replacement is the realistic option, not repainting — worth flagging to customers who might want to change the look later, since this is a genuine limitation compared to timber.
Is composite fencing more fire-resistant than timber?
Not necessarily, and this varies significantly by product — composite decking and cladding products used on buildings have faced serious fire-performance scrutiny post-Grenfell, and garden fencing composite is not automatically exempt from similar concerns depending on the wood-fibre and plastic content. Check the specific manufacturer's fire test certification for any job where fire spread risk is a factor (close to a building, in a high-risk location) rather than assuming composite is inherently safer than treated timber.
Does composite fencing need planning permission?
The same rules apply as for any garden fence — under Schedule 2 Part 2 Class A of the Town and Country Planning (General Permitted Development) (England) Order 2015, fences, walls and gates up to 2m above ground level (non-highway boundary) or 1m where adjacent to a highway used by vehicles or its footpath do not need planning permission. See planning permission fences walls for the full breakdown including Listed Buildings, Conservation Areas and Article 4 direction exceptions.
How does the installation time compare to timber close board?
Broadly similar for the post-setting stage (identical concrete-and-cure process), but slightly slower for board fitting on some systems where each board needs individual alignment into a channel rather than being nailed in a continuous run — budget a similar or marginally higher labour allowance than timber close board of the same run length.
Regulations & Standards
Town and Country Planning (General Permitted Development) (England) Order 2015, Schedule 2 Part 2 Class A — governs permitted height without planning permission for fences, walls and gates
BS EN 15534 — Composites made from cellulose-based materials and thermoplastics (wood-polymer composites); a multi-part series — Part 1 covers general test methods, Part 6 covers specifications for fencing profiles and elements specifically; check which part a manufacturer's datasheet references
BS 8500 — Concrete specification, applicable to post foundation concrete mix regardless of post material
BS 1722 series — the equivalent British Standard suite for timber fencing by type; precast concrete fence elements (posts, gravel boards) are covered separately by BS EN 12839, not by BS 1722-3 (which specifies strained wire fences); composite fencing is not directly covered by BS 1722 but is often benchmarked against it in manufacturer literature
Building Regulations — generally do not apply to garden fences and walls; a structural retaining wall over 1.5m may fall under Building Control, but this is rare for a standard boundary fence installation
Permitted development rights for householders — Planning Portal / gov.uk
Town and Country Planning (General Permitted Development) (England) Order 2015 — legislation.gov.uk
WRAP: Timber and composite waste guidance — WRAP (waste and recycling guidance relevant to composite offcuts)
timber close board fencing — the traditional timber alternative, useful for direct cost/spec comparison
concrete post gravel boards — post and gravel board specification shared between composite and timber systems
fence post installation depth — foundation depth and concrete specification, identical requirement for composite posts
planning permission fences walls — height limits and permitted development rules applying equally to composite fencing
fencing installation pricing guide — general fencing pricing benchmark for cost comparison