A new technical guide on metal web joists is being issued to housebuilders in the UK to showcase the flexibility and benefits of the product for both house and commercial applications.
Metal web joists are made from strength graded softwood chords joined with high strength engineered steel webs. They are structural components which can create floors, roofs and walls. Their open structure makes them lighter to handle and allows for services to pass through easily. Joists can be assembled onsite or a fully assembled floor or roof cassette can be manufactured offsite, helping to support the industry’s move towards modern methods of construction (MMC).
Published by the Trussed Rafter Association (TRA), the Metal Web Joist Buyers’ Guide provides information, illustrations, guidance and handy checklists covering all aspects of floor design and loading, and fixings between the joists and beams within the floor zone. The guide also covers the manufacture of metal web joists, the role of the design team in customizing solutions, and the provision of structural calculations for building control. In addition, it includes detailed information on floor joists and roof trusses as part of its comprehensive coverage.
Nick Boulton, TRA chief executive, said:
“We have developed the Metal Web Joist Buyers’ Guide to help housebuilders and designers understand all the benefits and flexibility of this product. With increasing interest in MMC, metal web joists are ideal components to help speed up and improve the build process. Floor and roof cassettes also decrease the amount of time spent working at height therefore improving safety.
“The guide offers information on design responsibilities, structural considerations, and the metal work required. There is also information for contractors to explain how to store and install once onsite and of course advice on staying safe when working with metal web joists. The guide provides best practices for how joists should be installed and warns against having them drilled or notched without proper consultation.”
For further information or to download a free copy of the guide please visit the TRA website.
1. Introduction
Metal web joists, often referred to as posi joists, have transformed the way modern buildings are designed and constructed. By combining robust timber chords with pressed metal webs, these innovative joists create an open web structure that delivers exceptional flexibility for architects and builders. This unique design not only streamlines the construction process but also helps reduce labour costs, making metal web joists a popular choice for a wide range of projects. In this article, we explore the technology behind metal web joists, their key benefits, and how they are shaping the future of construction.
2. What Are Metal Web Joists?
Metal web joists are engineered structural components that feature a combination of timber and a metal web, resulting in a lightweight yet strong joist suitable for both floor and roof applications. Unlike traditional solid joist alternatives, metal web joists can span greater distances, allowing for more open and flexible building layouts. Their open web design makes it easy to install essential services such as plumbing, electrical cabling, and ductwork, all while minimizing the need for drilling or notching. This not only speeds up installation but also reduces site wastage, supporting environmentally sustainable construction practices. Whether used in residential or commercial projects, metal web joists offer a practical solution for modern building needs.
3. Key Benefits for Housebuilders
For housebuilders, metal web joists offer a host of advantages that can streamline the construction process and reduce overall costs. The open web structure simplifies the installation of services, such as pipes and cables, eliminating the need for time-consuming drilling and making it easier to accommodate changes in internal room layouts. This flexibility allows for creative design solutions without compromising structural performance. Additionally, metal web joists require less timber than traditional solid joists, resulting in lower material costs and a more sustainable approach to building. The straightforward installation process also means reduced labour costs, helping projects stay on budget and on schedule.
4. Understanding the Latest Metal Web Technology
Recent advancements in metal web technology have led to the development of posi joists with enhanced span capability and efficiency. Thanks to their unique open web design, these joists can span far greater distances than alternative timber products, making them suitable for a diverse range of building types, from domestic homes to industrial and commercial spaces. Manufacturers’ design teams can customize end details, overhangs, and web configurations to meet the specific requirements of each project, ensuring optimal performance and fit. This adaptability, combined with reduced site wastage and the ability to tailor solutions for any application, makes metal web joists a versatile and future-proof choice for construction professionals.
5. Integrating Mechanical Ventilation Systems
The open web structure of metal web joists makes them particularly well-suited for integrating mechanical ventilation systems, including advanced heat recovery solutions. With easy access for the installation of services such as cabling, pipes, and ductwork, builders can seamlessly incorporate energy-efficient ventilation into their designs without compromising the building’s structural integrity. This not only supports environmentally sustainable construction but also enhances indoor air quality and comfort for occupants. By choosing metal web joists, architects and builders can create buildings that are healthier, more energy-efficient, and ready to meet the demands of modern living.
