Issue 28 – June 2011
When selecting subfloor metal components in zones B and C, you need to first determine the amount of subfloor ventilation that is being provided, as this will affect the choice of material that can be used. For sheltered subfloor spaces in corrosion zones B and C, hot-dip galvanised components and fixings (complying with the requirements of Table 4.2) can be used provided they are more than 600 mm above the ground. Grade 304 stainless steel components and fixings are required for:
- zone D, whether sheltered or exposed
- any fixing into timber that is within 600 mm of the ground in any zone
- for use with ACQ and CuAZ treated timber in exposed or sheltered locations (Table 4.3 also allows the use of silicon bronze for fixing cladding) – when using ACQ or CuAZ in closed areas hot-dip galvanising is required for fixings and fasteners.
Table 4.1 gives the required weight of galvanising for steel components. To meet the requirements of Table 4.1, fabricated (specifically designed) steel items need to be manufactured from a minimum of 5 mm steel (see note 6) to allow sufficient galvanising to be deposited during the corrosion protection process.
Information supplied by BRANZ