A Guide to Different Types Of Wooden Floor Joists

When it comes to constructing a building, the choice of floor joists plays a crucial role in determining its structural integrity and overall functionality. There are three distinct types of wooden floor joists, each with its unique advantages. In this guide, we’ll break down the main differences between these three types of floor joists and discuss their installation requirements, helping you make an informed decision for your construction project.

1. Traditional Solid Timber Floor Joists

Traditional solid timber floor joists are exactly as the name suggests – they consist of solid pieces of timber. While you can easily source these from your local builders’ merchants, it’s essential to note that the timber supplied is typically of C24 or C16 grade, which is a slightly lower grade than what we use at Minera Roof Trusses. Here are some key points to consider:

• Shorter Spans: Traditional timber joists have limitations in terms of the span they can achieve due to the use of lesser-grade timber.
• Longer Installation Times: The nature of onsite alterations required during installation can extend the project timeline.
• Increased Labour Costs: Skilled professionals are often required for on-site alterations, leading to higher labour costs.
• Increased Costs: You might need additional specifications from an engineer, potentially causing delays due to high demand.

2. Timber I-Joists

Timber I-joists are engineered wood products designed with top and bottom timber flanges and a specialised strand board (OSB) in the middle, forming an ‘I’ shape when viewed from the side. In the UK, two main suppliers of timber I-joists are James Jones JJI Joists and Steico.

James Jones JJI Joists:

• These are a prefabricated version of a joist that eliminates some of the shortcomings of traditional solid timber joists.
• The manufacturer can design and cut I-joists as needed from pre-made stock lengths.
• These joists can span greater distances while being lighter to handle on-site.
• JJI joists allow for on-site alterations in limited positions, such as for cabling and pipework installation.
• PAS 2050 Accredited which means they properly measure all the carbon locked up in their timber products and report on this.
• A composition that resists shrinking and warping.

If a customer chooses to opt for an I joist approach to their floor or roof then they must ensure that the designers know where the pipework is to be positioned before commencing design. The necessity for pipework to be predetermined in some cases can be complex which is where an open metal web joist solution comes into its own.

The extra design considerations needed prior to manufacture do mean that they can potentially provide a more economical solution to open metal web joists but lack where metal web joists allow more freedom during installation and service fit-out.

James Jones JJI joists are stocked in various depths, from 220 to 450mm, with 4 width options (47mm, 63mm, 72mm and 97mm). These all come in 10, 12 or 14 metre stock lengths which can be cut down before being delivered to suit your needs on site.

Steico I-joists:

Steico’s I-joists have top and bottom flanges made from laminated veneer lumber (LVL).The process of softwood being bonded together results in greater strengths for extreme load bearing capabilities.

• Due to its increased strength, the laminated timber is 48% slimmer than the C24 timber used in standard I-joists.
• Lower swelling and shrinkage rates due to a production moisture rate of approximately 9%.
• Easy material to work with, as it doesn’t require pre-drilled fastening due to the nature of softwood.
• Reduced thermal bridging due to lower material usage.

3. Open Metal Web Joists

Open metal web joists, also known as posi joists or easi joists, supplied by Minera Roof Trusses, offer a unique set of benefits, catering to the modern demands of construction. Here’s what sets them apart from the alternatives:

• Sustainability and Efficiency:
  Fabricated using steel, an environmentally friendly and recyclable material, open metal web joists have a minimal carbon footprint.
• Exceptional Span Capabilities:
  They can provide clear spans across large areas without the need for intermediate columns or supports, creating open and flexible spaces.
• Customisation and Versatility:
  Engineers and architects can tailor them to specific project requirements, accommodating various loads and applications.
• Ease of Installation:
  They are lightweight, standardised, and easy to install, reducing construction timelines and labour costs.
• Fire Resistance:
  Steel construction offers excellent fire resistance, a crucial safety feature.
• Reduced Material Waste:
  Precision manufacturing results in minimal material waste, saving resources and reducing disposal costs.
• Lower Maintenance Needs:
  Steel components are durable and long-lasting, reducing the need for maintenance over time.
• Design Freedom:
  The open web design allows for easy routing of utilities, reducing the need for complex planning and alterations.
• Compatibility with Modern Construction Methods:
  Open metal web joists work well with modern construction materials and methods, enhancing their versatility.

Choose Minera for your next floor joist project

In summary, open metal web joists provide a sustainable, efficient, and versatile solution for modern construction projects. Their ability to span large areas, accommodate custom requirements, and offer excellent fire resistance makes them a valuable choice for architects, engineers, and builders looking to optimise structural integrity and environmental impact. Consider your project’s specific needs and choose the floor joists that best align with your goals for a successful construction venture.

If you’re looking to start your next project and require high-quality, sustainable floor joists, get in touch today for a free, no-obligation quote.