- Project plans
- Project activities
- Legislation and standards
- Industry context
- Specialist wikis
Last edited 24 Sep 2020
A firring is a thin strip of timber (or ‘batten’) that has been cut along its length diagonally so that it tapers, with one end deeper than the other. Firrings are used in the construction of flat roofs to create a fall, ensuring that water runs to the lower side. Typically they are designed to a fall of 1:40, which given on-site inaccuracies should result in a minimum fall of 1:80 in the finished construction.
They are manufactured by cutting at an angle along the length of a timber batten. As this requires specialist cutting equipment, firrings are often manufactured off site. Commonly available sizes have a maximum cross section of 47mm x 50mm, 47mm x 75mm and 47 x 100mm
Firrings are cut in pairs, with the pieces on both sides of the cut line being used so as to minimise waste. They can be cut in identical pairs or folding pairs. Identical pairs are the same when cut, whereas a folding pair are cut to form a continuous fall when placed end to end.
NB: The term metal furring system or MF System refers to a technique for creating a seamless plaster internal finish with a void behind for the installation of services. Plasterboard is fixed directly to the concealed metal furrings. This can be used as an alternative to traditional timber batten construction for walls and ceilings.
 Find out more
 Related articles on Designing Buildings Wiki
Featured articles and news
One of England's grandest country houses.
Take just two minutes to provide your feedback.
An update of standards and regulations are under consideration.
Exploring the key to the adoption of this abundant energy source.
His clients have ranged from Liberace to St Nick to world-class athletes.
These tactical structures can be permanent or temporary.
Organisation recognises milestones of the project's next phase.
Welding and metalworking businesses must manage respiratory risks.
New report explores how regulations are being put into action.
The golden thread and BS 8644-1.
Bitumen binder may delay road surface deterioration.
A varied portfolio of internationally recognised buildings.
Threatened by housing and expanding universities.
Getting "boots on the ground" to make things happen.