Boardwalk Decking: Specifying Composite Boards for Lakeside and Riverside Walkways
A boardwalk is a public walkway that happens to be made of deck boards. The surface is walked in shoes, usually wet, often by people who did not choose to be there and cannot easily go around — and it is maintained on a public budget by someone who will still be responsible for it in fifteen years.
That changes which properties matter. This page covers what the water does to the build-up, what the board can and cannot be asked to do, and where our evidence stops — including the structural question, which is not ours to answer.
👟
R10, shod wet
The condition a boardwalk is actually walked in
🧴
No coating cycle
No sanding, staining or closure for re-coating
⚖️
22.4 kg/m²
Boards only, for elevated structures
📏
350 mm max
Joist centres for 140 × 23 mm
🛡️
15-year warranty
Stepped, co-extruded boards
What Changes When the Walkway Is Public and Near Water
A garden deck and a boardwalk use the same boards and almost none of the same reasoning. These are the differences that decide a specification.
| Private garden deck | Public boardwalk near water | |
|---|---|---|
| Who maintains it | The owner, who can choose to skip a year | An asset team on a budget, for the life of the structure |
| What closure costs | An inconvenience | Lost access on a route people rely on, plus signage and traffic management |
| How it is walked | In shoes, mostly dry, by people who chose to be there | In shoes, frequently wet, by anyone — including wheelchairs and pushchairs |
| What is underneath | Prepared ground | Often an elevated structure over water, reed bed or soft ground |
| What water does | Drains through the gaps and away | Rises and falls, may submerge the structure, carries silt and encourages growth |
| What gets specified | A board | A whole build-up, usually with a structural engineer involved |
The Argument That Actually Wins a Boardwalk
It is not the board. It is what the board does not need over fifteen years.
Timber boardwalks are priced on the day and paid for annually
A treated timber walkway needs cleaning, sanding and re-coating on a cycle, and each cycle means closing the route, mobilising a team, and doing it again in a few years. Over the life of a public asset that recurring cost usually exceeds the difference in material price at purchase.
Composite removes the coating cycle, not the maintenance
Our boards need washing down; they do not need sanding, staining or sealing, and there is no re-coating closure to programme. Be clear about the distinction when you present it: no coating cycle is not the same as no maintenance. Silt, leaf litter and algae still need clearing, and on a shaded waterside route they need clearing more often than on an open deck.
Where the saving is easiest to evidence
Ask the asset team what a single re-coating cycle costs them, including closure and traffic management, and how often it falls due. That figure, multiplied across the design life, is the comparison that matters — and it is a number they already have, which makes it far more persuasive than anything a supplier can assert.
Estimate Boards and Compare Offcut
Walkways are long and narrow, so the run length usually decides the waste rather than the area. Quantity is calculated from the 145 mm effective coverage width, not the nominal board width.
Six Things Water Does to a Walkway
None of these appear on a garden deck away from water. All six should be settled before the build-up is specified.
🌊
The level moves
Design flood level, not today's water level, sets the soffit height. A structure that is occasionally submerged is a different specification from one that never is.
🪵
Silt arrives and stays
Flood water leaves fine sediment in the board gaps. Gaps that suit a garden deck can blind over on a waterside route, so plan how they will be cleared.
🦠
Shade plus damp grows algae
A route under trees beside water stays damp. Algae is the usual cause of a slip complaint on a boardwalk, and it is a cleaning-frequency question rather than a board question.
👟
It is walked wet, in shoes
This is the condition the shod ramp test represents, which is why our R10 figure is relevant here in a way it is not for a barefoot pool surround.
🏗️
It is usually elevated
Posts, bearers and foundations in or beside water are a structural and environmental design, not a decking selection. Get that designed before choosing boards.
🌱
It may be in a protected site
Conservation areas often restrict what can be introduced near water. Ask early what the consenting body requires in writing; see the evidence section below.
Boards and Substructure for a Walkway
Colour, variants and the full specification are on each product page.
Co-extrusion Decking Board
23 × 138 mm · 15-year cover
Capped on four sides including back and edges. The profile our R10 shod-wet slip result was tested on.
View product →
Co-extrusion Wide Board
23 × 148 mm · 15-year cover
Wider face, fewer joint lines along a long run. Same build-up height as the 138 mm board.
View product →
Zinc Plated Steel Keel
Substructure
Set out at 350 mm centres or tighter. Material selection near water is a corrosion question for your engineer.
View product →
Aluminium Keel
Substructure
Alternative section where the corrosion behaviour or the lighter weight is preferred.
View product →
Sequence for a Waterside Walkway
The first three steps are consenting and engineering. The board is chosen after them, not before.
Establish the design flood level and the consenting requirements
From the authority or the environmental regulator. This sets the soffit height and often restricts what may be placed in or near the water. Nothing downstream can be fixed until it is written down.
Have the structure designed
Posts, foundations, bearers and any handrail or edge protection are a structural design for the specific site. We supply boards and substructure sections; we do not design the walkway.
Settle the width, falls and accessibility requirements
Width and gradient are usually set by the access standard the route has to meet. Confirm which one applies before setting out.
Set the joists at 350 mm centres or tighter
That is the maximum for the 140 × 23 mm board. Narrow the centres where the route carries wheeled traffic or concentrated loads.
Lay boards with the specified clips and expansion allowances
Leave the side, end and perimeter allowances for the profile and the local temperature range. A long straight run moves most at its ends, which is where the allowance has to be.
Write the clearing regime into the handover
Say how often the gaps and surface should be cleared, and record it. On a shaded waterside route this is the single maintenance task that actually matters.
Have the flood level and the structural design already?
Send the walkway length and width, the design flood level, the substructure material and the destination port. We will come back with a board quantity, the clip and keel list and the build-up weight.
Slip on a Boardwalk: Why Our Figure Is Relevant Here
This is one of the two places where the test we hold matches the way the surface is actually used. It is worth being precise about why.
The test and the use match
A boardwalk is walked in shoes, and the condition that matters is wet. That is what the shod ramp test represents. Our co-extruded decking board, profile ZSGJ138H23A, is classified R10 — Intertek report 230625005SHF-001, AS 4586-2013 Appendix D, measured at 15°, which sits mid-band in the 10–19° R10 range. AS 4586 Appendix D and DIN 51130 share the same R scale.
What it does not cover
The result belongs to that one profile. It does not extend to the wide board, the tiles, the classic range or any fencing product. We hold no BS 7976 pendulum value, which is the method most UK specifiers and the HSE prefer, and no DIN 51097 barefoot classification. If your consenting body names a method, ask us against that method rather than against the rating we happen to have.
The honest caveat about algae
A slip classification is measured on a clean surface. On a shaded waterside route the real variable is biological growth, and no rating survives a neglected surface. Specify the clearing regime alongside the board — it will do more for the safety record than the difference between one classification and the next.
Three Things We Cannot Evidence for a Waterside Project
Stated now rather than at approval, because all three tend to surface late.
Structural performance of an elevated walkway
The only bending data we hold is in-house testing to GB/T 24508-2009, carried out on fencing profiles, not by a third-party laboratory and not on decking. We quote it as in-house QC and nothing more. The structural design of a walkway, its posts and its foundations belongs to the engineer for that project.
Leaching and behaviour in water
We hold a REACH declaration of conformity — EC 1907/2006, Article 33 SVHC below 0.1%, Article 67 Annex XVII. Two things to be clear about: it is a manufacturer's declaration, not a third-party certification, and it was issued for the fencing profiles T180H24 and T90H24, not for decking. We have no immersion or leaching testing for a board in standing or flowing water. For a conservation site, ask the consenting body what evidence it requires and tell us early.
Fire classification
We do not hold EN 13501-1. Public realm projects in the EU frequently ask for a reaction-to-fire class, and we cannot provide one today. An Australian test to AS ISO 9239.1 exists but is a different framework and should not be offered as a substitute.
What we do when the answer is no
Testing can be arranged on the specific profile a project intends to use, with the cost paid up front and credited in full against the order. On a public scheme the programme usually allows for it if it is raised at design stage rather than at approval.
Boardwalk Decking: Common Questions
Specification
What joist spacing should a boardwalk use?
350 mm maximum centres for the 140 × 23 mm board. Narrow them where the route carries wheeled traffic, at changes of direction, and anywhere a concentrated load is expected. The spacing of the supporting structure beneath the joists is a structural design question, not a board question.
What do the boards weigh?
22.4 kg/m² for the 140 × 23 mm board, about 0.22 kN/m², derived from 3.25 kg per linear metre at a 145 mm effective coverage width. That is boards only. On an elevated walkway the engineer will want the whole build-up, including joists and fixings.
What lengths are available?
2.9, 3.6, 4.0 and 5.8 m. A walkway is usually one long run, so check how your run divides into those lengths before estimating — the calculator above compares offcut across all four.
Can the boards be submerged?
We have no immersion testing, so we cannot give you a supported answer for a board that is periodically underwater. Establish the design flood level first and tell us what the structure will actually experience; if the project needs evidence for immersion, it has to be tested.
Safety and maintenance
Are the boards slip resistant enough for a public walkway?
The co-extruded decking board, profile ZSGJ138H23A, is classified R10 under AS 4586-2013 Appendix D — the shod, wet ramp test, measured at 15°. That is the condition a boardwalk is walked in, which is why the figure is relevant here. Whether R10 satisfies your consenting body is their decision, and if they specify a pendulum PTV instead we do not hold one.
What about algae?
It is the usual cause of slip complaints on shaded waterside routes, and it is a cleaning question rather than a material question. A slip classification is measured on a clean surface; no board rating survives a surface that is not cleared. Write the clearing frequency into the maintenance regime at handover.
What maintenance does composite actually need?
Washing down, and clearing silt and leaf litter from the gaps. There is no sanding, staining or sealing cycle and therefore no closure for re-coating. That is the lifecycle argument — but it is no coating cycle, not no maintenance.
Evidence and supply
Do you have structural certification for a boardwalk?
No. Our only bending data is in-house testing to GB/T 24508-2009 on fencing profiles — not third party, not on decking. We do not design walkways and we do not provide structural certification for them. That belongs to the engineer for the project.
Is the material safe to use over water or in a conservation area?
We hold a REACH manufacturer's declaration — SVHC below 0.1%, Annex XVII — but it is a declaration rather than a third-party certificate, and it was issued for the fencing profiles rather than for decking. We hold no immersion or leaching data. Ask the consenting body what it requires in writing and raise it with us at design stage.
Do you have a fire classification for public realm work?
Not one an EU project will normally accept. We do not hold EN 13501-1. An Australian test to AS ISO 9239.1 exists but is a different framework and we do not offer it as a substitute.
What is the lead time, and can we see the boards?
20 days production for standard catalogue sections. Samples are free — you cover the courier, and we credit it against your first order. Sending a sample for independent testing is a reasonable step on a public scheme.
Send the walkway details
Length and width, design flood level, substructure material, the access standard the route must meet, and the destination port. We come back with a board quantity, the clip and keel list, the build-up weight, and a plain statement of which evidence we can and cannot supply.
Start from the flood level and the consent, not the board
Send the walkway dimensions and what the consenting body requires. We will confirm the board, the substructure list and the quantity — and tell you plainly where our evidence stops.