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.
 Related articles on Designing Buildings Wiki
Featured articles and news
RSHP unveil their involvement in a boundary crossing which will provide a new entry point into Hong Kong.
With PFI currently under the spotlight due to Carillion, this introductory article explains what they are.
Estimates suggest that up to 30,000 small firms could be at risk of non-payment as a result of Carillion's collapse.
Sir Oliver Letwin to lead an independent review into the delays in the delivery of housing.
As Carillion collapses, read our article explaining insolvency in the construction industry.
43,000 jobs at risk as Carillion declares insolvency..
1961 saw the publication of three important books about urban design that remain relevant today.
Next week the planning fee increases by 20% and new fees are introduced.
How the transformative power of BIM and other digital technologies can be used to gain a competitive edge.
Relevant events and relevant matters are terms used in some contracts, but knowing the differences is important.
Government release statistics showing how many people are now on the property ladder due to Help to Buy schemes.