6.4.15 Strutting
Strutting shall be provided where required, in accordance with the design, to distribute loads and ensure adequate rigidity of the floor structure.
Strutting should:
- not project beyond the top and bottom edges of joists
- be firmly blocked to the wall at the end of each run
- be provided before the deck is laid.
Proprietary metal strutting should comply with Technical Requirement R3.
Strutting should be provided along the length of joists at intervals recommended in Table 4 or 5. These should be provided in addition to those required at support, depending on the type of support. The following are minimum provisions.
Solid timber I-joists
Strutting to solid timber I-joists should be:
- provided in accordance with Table 4
- herringbone (38mm x 38mm timber) or solid blocking (minimum 38mm thick and 0.75 x the depth of the joist).
Table 4: Strutting for solid timber and I-joists
| Joist span (m) | Rows of strutting |
|---|---|
| Under 2.5 | None needed |
| 2.5-4.5 | 1 (at centre of span) |
| Over 4.5 | 2 (at equal spacing) |
I-joists
Strutting to I-joists should be:
- provided in accordance with Table 4, where required.
Metal web joists
Strutting to metal web joists should be:
- provided in accordance with Table 5
- solid timber ‘strongback’ bracing (see Figure 33).
Table 5: Strutting for metal web joists
| Joist span (m) | Rows of strutting |
|---|---|
| 4-8 | 1 (at centre of span) |
| Over 8 | 2 (at equal spacing) |
Last updated: 2nd January 2025