- Project plans
- Project activities
- Legislation and standards
- Industry context
- Specialist wikis
Last edited 28 Sep 2020
Herringbone struts can be made of timber or pre-galvanised mild steel. They are sometimes used as an alternative to solid block bridging (or noggins/dwangs), particularly for long-span domestic floors. They are generally installed at the centre of a span when floor joists exceed 2.5 m. Spans exceeding 4.5 m may require two rows spaced at 1/3 and 2/3 span.
They may be the preferred option if there is a lot of pipework or cabling to accommodate between joists, as they reduce the amount of drilling that would be required through solid noggings, which would weaken the floor.
A common problem in older dwellings is that floors feel ‘springy’. This can, in part, be because the herringbone struts have been removed in order to run services. Their re-introduction, or the reintroduction of regular noggings can help reduce the problem as the floor is encouraged to behave more as a 'slab' rather than a series of individual joists.
Alternatively, and perhaps more reliably, the floor can be strengthened, by 'sistering' steel, timber or ply reinforcing joists to the side of the existing joists, although, perversely, the installation of reinforcement can be made more difficult by the presence of herringbone struts or noggings.
 Find out more
 Related articles on Designing Buildings Wiki
Featured articles and news
Helping communities preserve and enhance historic environments.
Creating comfortable climates despite extreme temperatures.
Study examines how adjustable arrangements can succeed.
Government announces plans to improve accessibility.
Resource addresses pandemic-related NEC4 contract issues.
Incorporating EDI into the provision of fair access.
Government announces global innovation strategy.
An architectural biography. Book review.
The house where the future king of France lived.
The teacher, architectural technologist and mum offers her insights.
Careful planning needed as supply chain issues continue.
The sensitive conversion of a neglected Cornwall structure.