Engineered Joists

Omni Co’s Engineered Timber Division design and manufacture precision-designed metal-web joists, also known as Posi-Joists, offering a modern, efficient and sustainable solution for floors and roofs.

By combining timber flanges with a galvanized steel web, these joists achieve excellent strength-to-weight ratios, longer spans, and allow simple integration of services such as plumbing, electrics and ventilation.

The open metal web joists provide clear and distinct advantages in comparison to standard solid timber joists or I-joists.

What are Posi joists?

Posi-Joists (metal-web joists) are structural members made from parallel timber chords connected by an open metal web. This hybrid structure provides the stability and load-carrying capacity of traditional solid joists but with the added advantage of open webbing, enabling services to pass through easily without drilling or notching.

The result is a lightweight, dimensionally stable and factory-engineered system that saves on-site time, reduces waste and improves build quality.

Key Features and Benefits

Longer Spans

Fewer internal load-bearing walls are required, allowing greater design flexibility and open-plan layouts.

Service Integration

Open web design enables HVAC ducts, plumbing and electrical services to be installed easily within the floor zone.

Lightweight Handling

The joists are easy to lift, manoeuvre and install, reducing manual handling time and equipment requirements.

Precision Engineering

Manufactured in controlled factory environments for consistent quality, straightness and tolerance.

Material Efficiency

Optimal use of timber and steel for high performance with less material waste.

Acoustic and Fire Compatibility

Can be integrated with acoustic layers, resilient bars and fire protection systems as per the Structural Timber Association (STA) Pattern Book.

Sustainibility

Timber is sourced from certified sustainable forests (FSC/PEFC), reducing embodied carbon and aligning with Modern Methods of Construction (MMC) objectives.

Indicative Posi Joist Span Table

Joist Depth	Joist Centres	Max Span	Typical Uses
304mm	400mm / 600mm	4.0m - 6.5m	Large spans, commercial floors
253mm	400mm / 600mm	3.5m - 5.0m	Mezzanines and larger floors
225mm	400mm / 600mm	3.0m - 4.5m	Long domestic spans
202mm	400mm / 600mm	2.6m - 3.8m	Domestic and light commercial

(To be used for early design planning — not for structural design. Final spans must be verified by a qualified engineer or manufacturer software.)

Posi Joist Sectional Sizes

Posi Type	Depth	Flange Depths	Clearance between flanges
PS16	421mm	47mm / 47mm	327mm
PS14	373mm	47mm / 47mm	279mm
PS12	304mm	47mm / 47mm	210mm
PS10	253mm	47mm / 47mm	159mm
PS9	225mm	47mm / 47mm	131mm
PS8	202mm	47mm / 47mm	108mm

(To be used for early design planning — not for structural design. Final sizes must be verified by a qualified engineer or manufacturer software.)

Fire Performance and Compliance

Omni Co’s Posi-Joists are designed and detailed in accordance with the Structural Timber Association Pattern Book, ensuring compliance with recognised fire performance standards for structural timber systems.

All systems are engineered to meet current Building Regulations and can be supplied with third-party certification and test data where required.

Chipboard Flooring and Decking

22mm Floor Decking - Moisture Resistant P5 2400mm x 600mm - Omni-Co. - Floor Joists, Engin

22mm Chipboard Decking

Our metal web joists are typically decked using structural tongue-and-groove chipboard or OSB panels. The wide top flange provides ample fixing area for flooring materials, ensuring a solid feel underfoot and reducing squeaks. Combined with D4 glue it creates a structurally stable floor that is simple to install.

It is made from P5 flooring grade chipboard with a durable, weather resistant and anti-slip surface layer. This surface is bonded to both sides of the board, which creates a product that is protected from moisture.