Why is correct Joist spacing important?

In this newsletter we explore joist spacing and the considerations before installing Teckwood’s composite decking. But before we get onto that we need to explain why you need to plan your decking with the right joist spacing.

It’s essential to plan your joist spans and joist spacing correctly as this will ensure that any decking that you build is safe and structurally sound, for you, your family and your friends.

Teckwood as a responsible supplier of composite decking puts its decking material through in-depth independent testing to find the correct joist spacing.

More important than all that, though, joist spacing and span requirements are based on tried and true industry standards, they are in place to make sure your decking is safe and structurally sound for you, your family, and your friends.

But why does joist spacing matter? The durability of your decking relies on the strength and success of its framework, joists included. If a builder installs deck joists too far apart, the decking will sag and will ultimately fail.

What is joist spacing?

Joists play a vital part in the framework of a decked area. The horizontal members that run the length of the project support the decking itself. Joists must supply the strength necessary to hold up the decking that rests on them.

Joist spacing refers to the distance between joists and is measured in centimetres or inches. If you draw a line down the centre of two joists and measure the distance between them as 600mm or 24 inches, then the joist spacing is 600mm or 24 inches centre to centre.

Joists often consist of wood or steel, because composite or plastic joists usually lack the strength needed to support the weight of decking. However, Teckwood’s steel reinforced composite joist can be used to support decking.

How far apart should my joists be for Composite Decking?

Teckwood recommend a maximum joist spacing of 350mm or 14 inches centre to centre or less. For decking installed at a 45-degree angle, Teckwood recommend 300mm or 12 inches centre to centre.

What is the correct joist spacing for Teckwood’s composite decking?

Hallmark Composite Decking	350mm
Harmony Composite Decking	350mm
Pyrodeck (Fire Rated to Class B) Composite Decking	350mm
Vintage Composite Decking	350mm

Frequently asked questions

What is Composite Decking?

Composite decking is an alternative to traditional wood decking that contains both wood and plastic ingredients.

What does centre to centre mean?

Millimetres or inches at centre to centre means the distance from the centre of one decking joist to the centre of the next joist. For example, the distance between the centre of one joist to the centre of the next measures 350mm or 14 inches. The joist spacing is 350mm or 14 inches centre to centre.

What are the best joists for Composite Decking?

Decking framework, including decking joists, are the backbone of your flooring construction. To get the most of your composite decking, you want to create the best foundation possible. To do this, you will need to find the best joists to use. 

• Materials: You can build decking frameworks from different materials. The usual type of material used for joists is wood, especially in residential settings.
• C16 Timber: C16 is the most commonly used form of timber. It can be used in many different applications and is the most cost effective option. C16 timbers are kiln dried to minimise the amount of moisture in the wood. This grade of timber which is commonly used in internal construction such as floors, walls and roof joists is not only cost effective, it has the strength and other properties such as bending, compression and density which are required for construction. As strong, versatile and cost effective this grade of timber might be, it does have some defects, such as grain deviations which may affect the strength of the timber as well as some cosmetic defects such as sap stains and sometimes and an uneven surface.

• C24 Timber: C24 timber is the superior cousin of C16. This grade is also kiln dried and used in construction products and is especially suited for outdoor uses. It is more superior in terms of its properties such as strength, resilience and appearance with very few defects if any. C24 timber costs slightly more than C16.
• Steel: Using steel to build your subframe is probably the least cost effective deck framing option. Steel joists and bearers can span longer distances than a wood deck frame, however at the expense of ease of construction. Steel deck frames are very heavy to handle and require anti rust protection treatments applied to the components each time they are cut to avoid corrosion. Steel joists are also very time consuming to install.
• Steel reinforced composite joist: Teckwood’s wood plastic composite joist is a simple and elegant solution that can be laid directly onto your finished surface. The steel reinforced composite joist option is an ideal high performance structural solution when using pedestals, especially on those difficult balconies. When placed on a level base, the steel reinforced joist provides a reliable alternative to traditional substructures.
• Aluminium: Lightweight, marine-grade structural aluminium features the same long span and high load decking framework as steel. Aluminium joists will not be damaged by water. They offer a long life solution to fitting decks. Even in extreme weather or temperatures, aluminium joists will not distort or rot away.

Summary

No matter what kind of material is used for the outdoor deck. A strong and durable decking support frame set at the right centres is more important than the decking that you choose. A good decking frame can make your outdoor decking last longer.

For further information on how to construct your new decking and what options are available contact our knowledgeable sales team on 0800 799 9082 or email to info@teckwood.co.uk. 

Teckwood your composite jost spacing and more specialist!