Composite Decking Boards UK: Specs, Sizes & Wholesale 2026

For contractors pricing jobs, merchants building a composite range, or developers specifying materials for a housing scheme, knowing the precise board dimensions, construction grades, and ordering minimums matters far more than marketing language. This guide covers everything a UK trade buyer needs to know about WPC composite decking boards in 2026 — from raw dimensions and fixing systems through to subframe requirements and wholesale container volumes. If you are new to composite as a material category, our composite decking UK guide covers the broader buying decision, and our 2026 UK composite decking price guide covers cost comparisons with timber and PVC in detail.

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Composite Decking Board Sizes and Profiles

BOHAI's current catalogue contains six decking profiles. Use the profile code on the quotation, sample, test report and packing list; a generic label such as “standard composite decking board” is not enough to confirm the section being supplied.

Available lengths

Discuss 2.9 m, 3.6 m, 4.0 m and 5.8 m lengths against the selected profile and current production plan. Choose the length from a project cut plan, vehicle and rack limits, access to the site and the container plan—not from a generic “most popular” claim. Use the deck material calculator to compare board counts and waste before fixing the order.

Surface textures

The catalogue shows H1 Straight Grain plus H2, H3 and H5 Wood Grain surfaces. Ask for a physical sample with the profile code and colour written on it. A surface name does not prove that every profile, cap construction and colour is available in the same combination.

Installation gaps

BOHAI's installation guide specifies 5–7 mm between the sides of adjacent boards, about 5 mm between a capped board and a wall, and 3–5 mm at butt joints. Every butt joint sits on double joists so each board end has its own support. Do not derive a gap from a generic thermal-expansion formula when the written installation value is available.

Hollow vs Solid Composite Deck Boards

Hollow boards contain longitudinal chambers; solid boards carry material across the full cross-section. Geometry changes board weight, handling, stiffness, sound and cost, but “solid” is not automatically best for every deck. Compare the named profile, support spacing, project loading, finish and document scope.

Our confirmed formulation is approximately 60% wood powder, 30% HDPE and 10% additives. The material can be recycled and reused at end of life. That is not the same as claiming that every input is recycled, so we do not describe the feedstock that way without separate evidence.

When hollow profiles make sense

Hollow composite decking boards reduce material and handling weight. They can suit residential terraces, balconies and distributor stock where the selected profile and support layout meet the project requirement. Keep chamber ends, drainage and trim details visible on the drawing rather than assuming that every hollow section behaves the same.

When solid profiles make sense

Solid profiles can be considered where the project values a denser cross-section, different acoustic feel or a particular loading detail. Concentrated loads such as planters, hot tubs, stair landings and wheeled equipment still require specific support; a solid board is not a substitute for a designed subframe.

For the six catalogue profiles above, use 350 mm as the maximum joist centre for a straight lay unless the written profile-specific instruction is tighter. Reduce the spacing for diagonal layouts and add local support under concentrated loads.

Grooved Edge vs Square Edge Profiles

Composite decking boards are available with two edge profiles: grooved and square edge. The profile determines the fixing method and has direct implications for installation time, finished appearance, and ease of board replacement.

Hidden Fixing Systems for Grooved Boards

Grooved edge boards have a continuous channel machined into both long edges. Fixings are concealed using T-clip fasteners that engage the channel at every joist crossing point. One clip is placed per joist crossing per board edge — a 4.0m board laid at the 350mm maximum needs 12 spans, so 13 joists at an actual 333mm centre, which works out at 13 clips per board per edge, or 26 clips per board total.

Hidden fixing systems produce a clean, fastener-free surface with no screw heads to rust or cause trip hazards. The clips simultaneously provide consistent drainage gaps and accommodate thermal expansion. For the full installation process including subframe layout and clip positioning, see our guide on how to install WPC decking. The installation process with T-clips is slightly slower than face-fixing but the finished result is visually superior and easier to maintain long-term.

Face-Fix Systems for Square Edge Boards

Square edge boards are fixed by driving screws through the face into the joist below. Pre-drilling is recommended to prevent surface cracking, and stainless steel or decking-grade coated screws should be used to avoid rust staining. Countersinking creates a flush finish, though screw heads remain visible.

Face-fixing is faster and familiar to any carpenter. Square edge boards are easier to replace mid-run — removing a board requires only unscrewing, rather than carefully disassembling from one end as with clipped boards. Square edge profiles are also the correct choice for fascia boards, stair risers, and all decorative trim applications where the fixing edge is not accessible for clip installation.

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Classic, 3D Embossed and Capped Composite Decking

Classic and 3D embossed boards expose the WPC surface; capped or co-extruded boards add a polymer shield around the WPC core. The shield is the wearing layer. Compare the number of capped sides, profile, surface, colour and scoped test report instead of relying on “premium” as a specification.

What co-extrusion changes

A capped surface is designed to improve stain resistance, cleaning and colour retention compared with an uncapped surface. BOHAI does not publish one universal cap thickness for every profile, so ask for the section and written specification of the board being quoted.

Profile ZSGJ138H23A has a scoped R10 result under AS 4586-2013 Appendix D, measured by Intertek report 230625005SHF-001. This is a shod wet-ramp result. It is not a barefoot pool classification and it should not be moved to another profile without evidence. We do not currently hold a BS 7976 pendulum value, DIN 51097 barefoot classification or EN 13501-1 reaction-to-fire classification for these decking grades.

Warranty scope

Capped co-extrusion products carry a 15-year limited stepped schedule and classic uncapped products a 10-year limited stepped schedule. “Stepped” means the covered value reduces in bands over time. Ask for the written schedule for the actual product; warranty length is not a service-life promise.

Use the UK composite decking cost guide and calculator to compare the whole system—boards, joists, clips, trim, waste and installation—rather than relying on an unsupported price per square metre in a specification article.

Composite Decking Colours by Product Family

Colour availability belongs to the product family, not to one universal six-colour chart. The current catalogue shows:

Request candidate colours together and review full-board samples in the project light. Order spare boards with the same batch because a later production run of the same named colour is not guaranteed to be visually identical. Darker surfaces generally absorb more solar heat, so colour belongs in the barefoot-use and exposure discussion.

Subframe, Joist Spacing and Accessories

The maximum joist centre for the listed BOHAI composite decking boards is 350 mm for a straight lay. Tighten the spacing for diagonal layouts or concentrated loads. Do not carry across the 400 or 500 mm spacing sometimes used in generic decking guides.

Butt joints and drainage

Every butt joint uses double joists: each board end sits on its own joist. Keep 3–5 mm between the two ends, 5–7 mm between board sides and about 5 mm from a capped board to a wall. Form a drainage path or gutter at the base so water leaves the assembly rather than ponding under it.

Compatible joist materials

The installation system can use aluminium, stainless-steel or WPC joists. Current accessory dimensions include a 40 × 30 × 3000 mm WPC joist and a 40 × 25 × 2900 mm aluminium joist. Note that the aluminium length is 2900 mm, not 3000 mm, when taking off quantities.

Clips and trim

Boards fix with stainless-steel or plastic clips, with stainless starter clips at the first and last edge. L-shaped corner trim is 50 × 50 × 3000 mm. Match clips, screws, joists and trim to the named board profile and exposure; the board alone is not a complete decking system.

For the complete sequence, see how to install composite decking.

Composite Decking Wholesale and MOQ

BOHAI manufactures WPC products at Guangdong Bangying New Material Co., Ltd. in Sihui, Zhaoqing, Guangdong. The minimum order for decking is 70 m². A first order therefore does not have to be a full container.

Samples before an order

Samples are free; the buyer pays the courier and that cost is credited against the first order. Request the candidate colour, surface and a sawn cross-section so the profile geometry and cap coverage can be checked before the commercial order.

What a useful quotation includes

Send the profile code, surface, colour, board length, quantity, accessories, destination, required date and Incoterm. The quotation should state the unit, packing basis, port, production schedule and document scope. Freight and lead time are live commercial inputs, so they must come from the current quotation rather than a permanent promise on a web page.

Documents stay attached to the profile

CE/CPR, slip and other reports name their scope. Ask for the document against the exact board being quoted and treat a missing method as a gap—not as permission to copy a result from another profile. ISO 9001 and ISO 14001 management-system certificates are valid to April 2027, but they are not product performance tests.

For broader sourcing questions, read the UK composite decking supplier guide, then send the full specification through the form on this page.

Composite Decking Boards UK: FAQ

What composite decking board sizes does BOHAI supply?

The current catalogue lists six profiles: 138 × 23 mm (two hollow variants), 138 × 25 mm hollow, 140 × 23 mm solid, 140 × 25 mm solid and 145 × 30 mm solid. Discuss 2.9 m, 3.6 m, 4.0 m and 5.8 m lengths against the selected profile and production plan.

What is the difference between hollow and solid composite decking?

Hollow boards contain longitudinal chambers, while solid boards carry material across the cross-section. That changes weight, handling, stiffness and sound. Select by the named profile, support layout, loading and document scope rather than assuming one geometry is universally better.

Which is better: grooved or square-edge composite decking?

Grooved boards accept hidden clips along the long edges. Square-edge boards are useful where an exposed edge, fascia or face-fixed detail is required. Many decks use grooved field boards with square-edge finishing pieces.

What joist spacing should I use for BOHAI composite decking?

Use a maximum of 350 mm centres for a straight lay on the listed profiles, and tighter spacing for diagonal layouts or concentrated loads. Every butt joint sits on double joists so each board end has its own support.

What gaps should installers leave?

Use 5–7 mm between board sides, about 5 mm between a capped board and a wall, and 3–5 mm at butt joints. Keep drainage paths open and follow any tighter profile-specific instruction supplied with the order.

What is the minimum wholesale order?

The decking MOQ is 70 m². Samples are free; the buyer pays the courier and the cost is credited against the first order. Send the profile, colour, length, quantity, accessories, destination and required date for a per-unit quotation.

Which colours are available?

Co-extrusion, classic and 3D-embossed ranges have different colour cards. Request the colour card and full-board samples for the product family being quoted; do not assume every colour is available on every construction and profile.

Ready to Get Started?

Download our full composite decking specification sheet or request a wholesale quote at /pages/contact