Noggins between floor joists are a form of solid strutting used to improve rigidity and help distribute loads through the floor structure. NHBC gives a simple minimum layout for solid timber joists.
Under 2.5m span: no intermediate strutting is normally needed
For joists spanning less than 2.5m, NHBC's minimum provision does not require an intermediate row of strutting.
2.5m to 4.5m span: use one row at mid-span
Install one row of strutting at the centre of the span.
Over 4.5m span: use two equally spaced rows
For longer spans, provide two rows at equal spacing along the joists.
Solid noggins should be at least 38mm thick and 75% of the joist depth
NHBC permits herringbone strutting in 38 × 38mm timber or solid blocking at least 38mm thick and at least 0.75 times the joist depth. Strutting should not project above or below the joists and should be installed before the floor deck.
Noggins improve rigidity; they do not replace correct joist sizing
If a floor is springy because the joists are undersized, damaged or overloaded, adding blocks alone does not correct the underlying structural problem. Check the joist design and condition first.
For the timber itself, browse structural timber. For connections and supporting hardware, see joist hangers & timber connectors.
