Decking Boards Technical Data

Decking Boards Description

UK Composite decking boards are made from a mixture of hardwood fibres (approximately 55%) and high density polyethylene with the addition of certain additives to improve physical, weathering and processing properties. The polyethylene used in our decking boards is a high quality, recycled material made up of mainly bottle, film and pipe materials.

The hardwood fibres are also a recovered material which are processed to FSC standards, filtered and dried before being compounded with the polyethylene. The resulting product is 90-96% recycled and 100% recyclable.

UK Composite Decking Boards®has many useful properties when used as decking, these include:

  • Low moisture absorption
  • No rotting, splintering or splitting
  • In-built termite and UV resistance
  • Excellent dimensional stability
  • Slip resistant surface in the wet and dry  (tested to HSE standards)
  • No toxic materials to leach into the soil
  • Easy as wood to work with

Decking Boards Application Data

UK Composite Decking boards® AT21 profiles are well suited for use as decking, fencing, pool sides, marinas and other similar applications. They may also be used as a replacement for wood in many other areas where a non-load bearing support or structure is required.

The other profiles in the range can be used for fencing, railings, cladding, garden edging and post & rail projects to name but a few. UK Composite Decking® profiles are best suited for outdoor applications where the product’s inherent advantages over wood can be exploited as fully as possible.

UK Composite Decking® Installation Instructions:

More detailed instruction is included in our ‘Quick Installation Guide for Installers – Data Sheet 1’ available on request.

It is vital that you read this data sheet before commencing any decking boards installation.

Decking Boards Installation Tools

You can use the same tools used for timber to fabricate and install UK Composite Decking boards. With the 25mm x 136mm deck boards, support frame joists must be spaced on maximum centres of 455mm (18”) or less for residential decks, 405mm (16”) or less for commercial applications.

When laying the timbers at 45 degrees to the support frame the joists should be spaced on centres of 330mm (13”) or less (300mm or less for commercial applications). Boards should not overhang the joists by more than 40mm.

(If using the 24mm x 95mm deckboard, joist centres should be 355mm (14”) max and  255mm (10”) if fitting diagonally.)

When butting boards end to end, this must be done over a double width bearer to ensure both boards are sufficiently fastened down. Screw holes must be pre-drilled (to prevent splitting) at least 20mm, and not more than 40mm in from the cut edge. Deck boards must span at least 3 bearers in order to give the board the load bearing properties stated in our literature and to eliminate the possibility of sagging over time.

For optimum water drainage and to allow for proper ventilation, a gap of 5mm must be left in-between the boards and a minimum 5mm gap at the cut ends of the boards (for hot, humid or damp areas, a 10mm gap is required between the cut end of the board and any walls).

Failure to do so will promote the growth of mildew and prevent moisture evaporation, these gaps will also allow for material expansion in hot weather.
Good airflow under the deck is vital to prevent moisture remaining for long periods on the underside of the boards, poor airflow will invalidate the warranty.

Composite Boards Fixings

Only use screws designed for composite decking boards, normal timber decking screws are not strong enough and will invalidate the warranty. We supply a stainless screw specifically designed for Ecodek decking boards®.  It is available in a range of colours to match the decking.  Use 2 screws per joist/bearer (if using 50mm screws, then 3 screws per joist).  Always pre-drill before screwing down the board, we recommend using a SMART-BIT® for fast & easy drilling (available from UK Composite Decking®).

Never leave the end of the board unrestrained, it must  be pre-drilled & screwed down within 20-40mm of the cut end. The screw head should sit flush with the bottom of the groove (or decking surface if using a smooth board). Do not use fasteners within 18 mm of the side of the board. (The rule of thumb is to screw into the second groove on each side of the board if using the grooved side.)

NB: If using the 38mm x 88mm sub-structure profile (i.e. as a joist), it must be noted that it needs more support than with a softwood equivalent. We recommend either laying the substructure profile directly on the surface to be built upon, or supporting it on posts but with a maximum span of 1 metre between post supports, secondly, there must never be more than 100mm overhang at the end of the substructure profile.

It must also be noted that when screwing composite to composite, the screw pilot holes must be 3.5mm diameter and at least 90% of the depth of the screw, this is because composite is very tough and if the pilot hole is not deep or wide enough, the screw can shear off during installation.

decking boards screws

Slip Resistance Decking Boards

Ecodek composite decking boards have been extensively tested for its Slip Resistance Value (SRV or PTV). Under normal conditions, they meet the HSE’s standard for a flooring that they describe as ‘Low Potential for Slip’.

In order to maintain your decking board as a slip resistant surface, it is imperative that you regularly wash the deck to remove dirt/algae and other foreign bodies as these will have a negative effect on the SRV.

It is also important to maintain any drainage channels or gaps that you have in your deck so that standing water is kept to a minimum. SRV’s are as tested on a level  surface. If UK Composite Decking® is to be used on an incline (such as an access ramp) then the SRV will reduce accordingly and we strongly recommend the use of anti-slip treads (see datasheet 19).

It is the responsibility of the purchaser to ensure that the product remains ‘fit for purpose’ for whatever gradient the decking is used on. Consideration must be given to the method of construction of the ramp so as to maintain optimum levels of grip (i.e. direction of boards, angle of incline, amount of foot traffic etc). UK Composite Decking® can help specify various non-slip products specific to any particular application. (Enquire for further details.)

Care and Maintenance

Because of the combination of natural hardwood fibres and recycled high density polyethylene in UK Composite boards, you may experience slight colour variation between boards as you lay them, this variation will weather to a slightly lighter, but much more even hue during the first few months but may take much longer in shaded areas.

Note: Fading is significant on the lighter colours and if colour fade is an important factor for you, we advise choosing a darker colour such as Dark Brown, Slate Grey or Black for your deck. “Slight colour variations are natural within any composite deck product. These variations are not a product defect and thus are not covered by the product warranty.”

Do not allow leaves and other debris to lie on the deck surface as this will cause staining and promote mildew growth. When using a barbecue or similar, it is recommended that a plastic sheet or other suitable material is placed around the area to protect the deck from oil/grease splashes.

Most heavy stains, dirt and mildew can be washed off using a power washer and a deck cleaner. We recommend ‘Our Composite Deck Cleaner & Revive’ (available from most hardware stores or direct from us). Oil and grease stains may require the use of a de-greasing cleaner and light rubbing with a soft brush or sponge to remove the stain.

Keeping the deck clean, free of debris and  maintaining drainage and ventilation gaps are essential basic maintenance  requirements. Regular washing of your deck with a proprietary grade of deck cleaner containing anti-fungal additives will keep dirt and algae at bay and also allow your deck to maintain an optimum level of slip resistance. Not cleaning your deck may allow fungal growth to spread which will invalidate your warranty.

Sizes & Colours

Currently available in 5 standard colours, 2 shades of brown, 2 shades of grey and black. Other colours and lengths can be manufactured upon request. (See the profile range literature for a more comprehensive and detailed list.)

Profile sizes (approx):

21mm x 136mm reversible deck board in 2.4m, 3.6m and 4.8m lengths
19mm x 136mm cladding board in 3.15m lengths
38mm x 88mm (sub-structure) heavy duty solid profile in various lengths
24mm x 95mm & 25mm x 136mm  smooth decking profiles – various lengths

Handling & Storage

UK Composite Decking is heavier and more flexible than wood and this needs to be considered when transporting boards. Boards should always be stored on a flat surface or on a close boarded, full length pallet with bearer centres of 900mm or less for up to 1350 kilos full pallet weight and 600mm centres or less up to a maximum of 2500 kilos full pallet weight.

Warranty Details

UK Composite Decking boards come with a limited 25 year warranty against structural failure caused by  termites, fungal decay, splitting and splintering. It must be noted however, that for this warranty to be upheld, the product must have been installed and maintained to the guidelines as set out in our literature. Please read our warranty (available from our website) for further information.

Trouble-Shooting Guide:


Colour variation after Installation

Colour variation after weathering

Water puddles / warped boards

Ice or snow build up

Oil/grease stains

Heavily soiled area


Rust marks

Probable Cause

This is to be expected prior to natural weathering

Darker areas may be exposed to less weathering


An un-even support structure, inadequate gapping, poor ventilation or clogged gaps between boards

Water puddles followed by below-freezing conditions

Oil stains, barbecues, food etc.

Foot traffic, airborne dust, pets etc.

Can appear in poorly drained or heavily shaded areas and under deck furniture

Low quality fasteners, ferrous objects such as garden furniture

Action(s) Required

 Once the material has been exposed to the elements for a few months, the colour should even out.

Wet the darker areas with water to accelerate the weathering effect. If the area suffers from constant shade, use a proprietary deck cleaner (treat as a heavily soiled area) to accelerate the process.

Drainage slots may need to be cut into inadequately spaced boards. Install adequate ventilation gaps.  For clogged gaps, use a flat tool to remove the debris.

You can use rock salt, although it may scratch the decking. Other ice-melt products may leave a slippery residue (consult with product manufacturers).

Remove oil/grease stains with a household or automotive de-greasing product as soon as possible.

Use a power washer and Our Composite Deck Cleaner & Revive. (See datasheet 8 available on website.)

Use ‘Simply Gone’ mould & mildew cleaner, available from UK Composite Decking. (See datasheet 16 available on website.)

Use Our Composite Deck Cleaner & Revive and a soft brush or sponge on the marks.

UK Composite Decking Physical Properties

Mechanical Properties

Tensile Strength
Flexural Modulus
Flexural Strength
Impact Notched
Impact un-notched
Water Absorption
Coefficient of Expansion
Screw Retention (composite decking screw)
Nail Retention (5mm ring shank)
Specific Gravity
Slip Resistance (Grooved/Dry)
Slip Resistance (Grooved/Wet)
Hot Nut Test
2.7kN Mid Span Point Load
4.5kN Mid Span Point Load

Test Method

 BS2782: Part3, method 320C 1
ISO 178 Span 150mm
ISO 178 Span 150mm
BS2782: Part3, method 359
BS2782: Part3, method 359
ASTM D1037
Across length
 Compared to Red Cedar
Compared to Red Cedar

BS 7976-2:2002
BS 7976-2:2002
BS 4790:1987
BS 1195:1998
BS 1195:1998


 1.3 Mpa 2.1% Elongation
4181 Mpa
31.5 Mpa
8.4 KJ/m²
11.1 KJ/m²
0.08 mm/m/°C
76% greater
18% greater
1.1    ± 0.05
PTV=58 (Low potential for slip)
PTV=37 (Low potential for slip)
16mm (Approved for domestic & contract use)
455mm bearer centres
405mm bearer centres