TerraBase™ Composite Decking Joists

TerraBase™ Composite Decking Joists – A Strong Foundation for Long-Life Composite Decking

A great deck is not only about the boards you see. What sits underneath them is just as important.

TerraBase™ Hollow Composite Decking Joists by Green Plank are developed to provide a durable, practical and low-maintenance substructure for modern composite decking systems.

Manufactured with approximately 65–70% beech hardwood fibre, selected European-sourced recycled HDPE (rHDPE) and functional additives sourced from Europe and/or the USA, TerraBase™ combines a high natural-fibre content with modern composite technology.

The declared raw materials offer 100% traceability, giving distributors, contractors, installers, architects and professional project buyers greater transparency regarding the materials used in the product.

With a 70 × 45 mm hollow profile, TerraBase™ Composite Decking Joists are designed to provide a stable supporting base for appropriately engineered decking systems while using material efficiently.

TerraBase™ normally requires no routine painting, staining or oiling, making it particularly suitable for a component that becomes difficult to access once the finished decking has been installed.

A Long-Life Deck Starts Below the Surface

When people choose a new deck, most attention naturally goes to the visible surface – colour, texture, profile and overall appearance. But the long-term performance of the decking system also depends heavily on what is underneath it.

The substructure is the foundation of the entire deck.

Properly designed Composite Decking Joists support the decking boards, establish the required spacing, provide a suitable base for clips and screws, and create the necessary space for ventilation and drainage.

That is why choosing the right Composite Decking Joists should be considered an important part of the complete decking system rather than simply a hidden component.

70 × 45 mm Hollow Composite Decking Joists

TerraBase™ has a profile dimension of 70 × 45 mm with a hollow internal construction.

The profile is designed to provide a stable foundation for suitable decking systems, while its hollow geometry helps reduce unnecessary material use and profile weight compared with an equivalent solid cross-section where a solid profile is not technically required.

For professional Composite Decking Joists, however, external dimensions alone do not determine structural performance. Wall thickness, chamber geometry, material formulation, support spacing, temperature, fixing arrangement and expected loading all influence the final performance of the installed system.

Installation & Spacing Guidance for TerraBase™

Correct spacing is essential for the performance of any composite decking substructure. There are two different spacing dimensions that must be considered when designing a TerraBase™ installation:

1. Joist spacing: the centre-to-centre distance between adjacent TerraBase™ Composite Decking Joists.
2. Support spacing: the distance between the structural support points underneath each TerraBase™ joist.

These dimensions should not be confused. The allowable spacing between TerraBase™ Composite Decking Joists is primarily determined by the decking board installed above them, while the allowable support spacing underneath TerraBase™ depends on the structural performance of the 70 × 45 mm hollow joist itself.

Typical Joist Spacing for Composite Decking

TerraBase™ Composite Decking Joists should be positioned according to the installation requirements of the selected decking profile.

Depending on the Green Plank decking product, application and expected loading, typical joist centres may fall within approximately 300–400 mm c/c for many conventional decking applications, while selected specially engineered systems may permit greater spacing when specifically documented.

The installation instructions for the selected decking board always take priority. If a decking profile requires 300 mm c/c, TerraBase™ must be installed accordingly even if another decking profile can be supported at a wider spacing.

Support Spacing Beneath the 70 × 45 mm TerraBase™ Joist

The distance between pedestals, concrete supports, beams or other load-bearing support points underneath the TerraBase™ profile must be treated separately from the decking-board joist spacing.

Because TerraBase™ is a 70 × 45 mm hollow composite profile, a universal maximum unsupported span should not be assumed from its external dimensions alone.

The permitted support spacing depends on:

• Profile wall thickness and internal chamber geometry
• Material formulation
• Decking dead load
• Expected pedestrian and imposed loads
• Point loads
• Temperature and long-term creep behaviour
• Number and position of supports
• Fixing arrangement
• Residential or commercial use
• Required safety factors

The maximum support spacing for TerraBase™ should therefore be confirmed by Green Plank technical documentation, mechanical testing and/or engineering calculations for the applicable installation.

Supports should be positioned on a stable, load-bearing base and arranged so that the joist is continuously supported according to the approved system design. TerraBase™ should not be installed as an unrestricted structural spanning member unless that particular span and loading condition has been technically verified.

Keep All Joists Level and Properly Supported

All TerraBase™ Composite Decking Joists should be installed on a stable and properly prepared base. Support points should be level and arranged to prevent unwanted movement or excessive deflection.

Do not attempt to correct significant variations in the underlying surface simply by forcing the Composite Decking Joists into position. The supporting base should first be properly levelled or adjusted using an approved support system.

Allow for Drainage and Ventilation

Composite decking requires proper drainage and ventilation beneath the finished surface.

TerraBase™ should therefore not be installed in a way that permanently traps water around or inside the substructure. The supporting surface should allow water to drain away, and adequate airflow should be maintained beneath the decking.

Where the project requires a fall for drainage, the complete substructure should be constructed according to the specified drainage design and the installation requirements of the selected decking system.

Decking Board Ends and Joints Need Proper Support

Board ends and butt joints require particular attention. Each decking-board end must have adequate support in accordance with the installation instructions for the selected profile.

Where required by the decking system, double joists or separate adjacent TerraBase™ joists should be installed at butt joints so that each board end can be independently and correctly fixed while maintaining the required expansion gap.

Board ends should not be left unsupported between Composite Decking Joists.

Diagonal Installation Requires Closer Joist Spacing

If decking boards are installed diagonally rather than perpendicular to the TerraBase™ Composite Decking Joists, the effective distance between support points beneath the decking board increases.

For this reason, closer joist spacing is normally required for diagonal installations. The exact spacing should follow the installation requirements for the selected Green Plank decking profile and installation angle.

Perimeter, Steps and High-Load Areas

Additional Composite Decking Joists or blocking may be required around:

• Deck perimeters
• Stairs and steps
• Board ends
• Butt joints
• Changes in decking direction
• Heavy planters or fixed equipment
• Commercial access areas
• Other concentrated-load locations

These areas should be considered during the design stage rather than after the decking installation has started.

Quick Installation Guidance

Designed for Reliable Screw Holding

TerraBase™ is developed with a focus on reliable screw holding when the correct fixing system and installation method are used.

Composite materials behave differently from conventional structural timber when screws are installed. Correct installation practice is therefore important.

Where specified in the installation instructions, a small pilot hole should be drilled before inserting a conventional screw. Pre-drilling can make installation easier, reduce local stress around the fixing point and help position the screw correctly.

Alternatively, a suitable special-purpose screw with an integrated drilling point can be used where it has been specified or approved for the applicable TerraBase™ system.

Recommended Fixing Principle

1. Mark the correct fixing position.
2. Use the specified screw type and dimensions.
3. Pre-drill an appropriately sized pilot hole where required.
4. Alternatively, use a suitable drill-point screw where approved.
5. Drive the screw using controlled torque.
6. Avoid overtightening.
7. Check that the fixing has achieved correct engagement with the Composite Decking Joist.

Exact pilot-hole diameter, screw dimensions, edge distances and tightening requirements should always follow the latest TerraBase™ technical documentation.

European-Made Screws

For applicable TerraBase™ systems, European-made screws can be supplied or specified as part of the fixing solution.

This allows the Composite Decking Joists and compatible fixing components to be considered together as part of a complete system.

65–70% Beech Hardwood Fibre & European Recycled HDPE

TerraBase™ Composite Decking Joists are manufactured with approximately 65–70% beech hardwood fibre, selected European-sourced recycled HDPE and functional additives from Europe and/or the USA.

Performance depends on the balance between wood fibre, polymer, coupling technology, stabilisation, functional additives, profile geometry and manufacturing process.

TerraBase™ is therefore developed as an integrated material and profile system rather than simply a mixture of wood and plastic.

100% Traceability of Declared Raw Materials

TerraBase™ Composite Decking Joists provide 100% traceability of the declared raw materials for the applicable product specification.

This provides distributors, contractors, architects, building-material merchants and professional buyers with greater transparency regarding the origin of the materials used.

No Routine Painting, Staining or Oiling

TerraBase™ Composite Decking Joists are designed for use without routine painting, staining or oiling.

This is particularly valuable for a substructure because the joists become less accessible once the decking boards have been installed.

The complete decking system should nevertheless be inspected periodically to ensure that drainage, ventilation, fixings and support points remain in suitable condition.

Developed with Nordic Conditions in Mind

Outdoor substructures in northern European climates can experience significant seasonal variations in temperature and moisture.

TerraBase™ Composite Decking Joists are developed with demanding Nordic outdoor conditions in mind.

Correct construction remains essential. Good drainage, adequate ventilation and appropriate spacing should always form part of the installation design.

Up to 30-Year Warranty

Selected TerraBase™ products and systems can be offered with a warranty of up to 30 years, subject to the applicable product specification, application, installation requirements and current Green Plank warranty terms.

One Standard Colour

TerraBase™ is primarily a technical substructure product and is available in one standard colour.

Because Composite Decking Joists are normally concealed beneath the decking, priority is placed on material quality, functionality, fixing performance and long-term service rather than an extensive colour range.

Focus on a Lower CO₂ Footprint

TerraBase™ is developed with a focus on natural fibre, recycled polymer, efficient material use, long service life and a lower CO₂ footprint.

The hollow construction can contribute to more efficient material use and lower profile weight compared with an equivalent solid cross-section where a solid profile is unnecessary.

Specific CO₂ figures or comparative environmental claims should be supported by applicable product-specific LCA, EPD or equivalent environmental documentation.

TerraBase™ Composite Decking Joists – Technical Overview

For Distributors, Contractors & Professional Project Buyers

TerraBase™ is more than an individual joist. It is developed as part of a complete composite decking concept.

For distributors, building-material merchants, decking specialists, installers, contractors, architects and project developers, TerraBase™ provides the opportunity to combine the visible decking with a compatible Composite Decking Joists solution.

For larger projects, Green Plank can support the evaluation of joist spacing, support spacing, profile selection, clips, screws, material quantities and overall system configuration based on project-specific technical requirements.

Request TerraBase™ Pricing, Samples or a Project Proposal

Are you a distributor, importer, building-material merchant, decking specialist, contractor, architect or project developer? Talk to Green Plank about adding TerraBase™ Composite Decking Joists to your product range or specifying them for an upcoming project.

Send us your project area, selected decking profile, proposed joist spacing, TerraBase™ support arrangement, substrate, expected loading and required quantity. Green Plank can then help evaluate an appropriate system configuration and estimate the required quantities of Composite Decking Joists and compatible fixing components.

For distributors and merchants: Ask about samples, technical documentation, volume pricing, commercial terms and opportunities for long-term cooperation.

For contractors and project buyers: Send your drawings or project specification for a project-based quotation and technical system recommendation.

Do not let the hidden substructure become the weakest part of a long-life composite deck. Build from the ground up with TerraBase™ Composite Decking Joists and contact Green Plank for a quotation, sample, technical evaluation or project-specific proposal.

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