- Project plans
- Project activities
- Legislation and standards
- Industry context
Last edited 05 Apr 2018
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
The world heritage list has evolved to embrace built, cultural and natural heritage.
The Ocean Cleanup project
The various types of bond and when they are used.
It's vital the industry responds to proposals for reform of the safety regulatory system.
RSHP's Merano wins RIBA accolade.
How to differentiate between partial possession and early use.
Ofwat proposes £12 billion additional investment and £50 bill reductions.
Avoiding 'winner's curse' and other useful info.
Developing test methods for video flame/smoke detectors
Waiting for a new deal ...but will funding materialise?