Joist bridging

The term 'bridging' refers to a brace, or an arrangement of braces, that is fixed between floor or roof joists to keep them in place, prevent joist rotation, and distributing loads over more than one joist. Other, similar terms include 'nogging' and 'dwang'.

Bridging can help strengthen a floor and stop it from bouncing when occupants walk across it. By bridging, each joist shares load with the one/s next to it, which can help reduce deflection by as much as half.

There are a number of different bridging techniques that can be used. Solid bridging involves joist-depth timber being installed perpendicular to and between the joists. Cross-bridging involves an ‘X’ being formed between joists by pairs by braces (also known as herringbone struts).

If a floor has bridging running down the centre already, it can be stiffened further by adding additional rows on either side. The bridging that is already in place should be fastened tightly using additional nails or screws. A good rule-of-thumb is that the span of the joists should be measured and then divided by three, with rows of bridging then placed at both of the one-third points.

[edit] Related articles on Designing Buildings Wiki

• Batten.
• Brander.
• Dwang.
• Floor definition.
• Flooring defects.
• Herringbone strut.
• Joist.
• Nogging.
• Types of floor.