Issue 45 – December 2012
- New Standards for efficient compact fluorescent lamps lighting
- Subfloor braces
- Where stainless steel components must be used
- Cantilevered joists for decks
Electricians and lighting retailers are being advised that compact fluorescent lamps (CFLs) imported for sale in New Zealand must now meet minimum energy performance Standards (MEPS). The new Standards mean all CFLs must perform to defined criteria including guaranteed minimum lifespan, maximum start-up time, maximum run-up time to reach 60% full brightness and limits on mercury content.
All packaging for CFLs must also feature information on lumens, wattage lifetime, and mercury content.
CFLs may also qualify for ENERGY STAR, which sets a higher bar than MEPS. If a product carries the blue ENERGY STAR mark, it means it is one of the most efficient, high-performing products on the market.
Subfloor braces as required by Section 6 in NZS 3604:2011 Timber-framed buildings must be 100 x 100 mm for braces up to 5 m long or 100 x 75 mm for braces up to 3 m long. Clause 18.104.22.168 says that: 'A diagonal timber subfloor brace shall consist of one continuous length of timber.'
Clause 22.214.171.124 does not exclude the use of built-up members (say 2 x 100 x 50 mm members to give the 100 x 100 mm member) for diagonal subfloor braces. However, when two or three built-up members are used, they must be fixed together with:
- nails spaced at not more than six times the thickness of the thinnest framing member along its length – so for a 50 mm thick member, nails at 300 mm maximum centres
- nails must have a penetration into the adjacent framing member of three-quarters of its depth – for a 50 mm member, the required penetration is 37 mm and the nails shall be driven alternatively from each side
- for members 140 mm or wider, there shall be a minimum of two nails at the centres given above.
→ The minimum timber grade for subfloor braces is SG8, and the minimum treatment required can be found in B2/AS1 Amendment 7 Table 1A, which is available free on the Building section of the MBIE website (http://branz.us4.list-manage.com/track/click?u=827ea0dfc4037c85a8cdaa0aa&id=d114e71836&e=20c3d9ef22)
Note 4 to Table 4.3 of NZS 3604:2011 Timber-framed buildings requires that grade 304 (or grade 316) stainless steel fixings are used when in contact with exterior timber, timber piles, or subfloor framing treated with either copper azole (CuAz – preservative code 58) or alkaline copper quaternary (ACQ – preservative code 90) where the timber is in sheltered or exposed locations.
BRANZ considers it good practice to specify stainless steel fixings for all external timber treated with a copper-based treatment if the timber will be damp in service.
Table 4.1 of NZS 3604, covering fixings and fastenings except screws and nails, allows the use of galvanised fixings in a limited number of circumstances such as:
- sheltered subfloors with less than 7000 mm2 clear area of ventilation for fixings connecting to treated piles and all other fixings more than 600 mm from the ground for Corrosion Zones B and C
- nail plates and wire dogs in closed and roof spaces in all corrosion zones
- structural fixings except fabricated brackets that are a minimum of 5 mm thick in a sheltered environment in Corrosion Zones B and C.
Table 4.3, covering nails and screws, allows the use of unprotected galvanised fixings in Corrosion Zones B and C for:
- framing in sheltered areas
- framing in exposed areas
- fixing a non-structural cladding
- fixing a cladding that acts as bracing.
Unprotected galvanised fixings may also be used to fix a non-structural cladding in corrosion zone D unless the cladding is CuAZ or ACQ-treated timber, cedar or redwood.
Some cladding suppliers may require stainless steel fixings as a component of their cladding system, especially when used as bracing.
The maximum cantilever length for deck joists that project beyond a support such as a bearer should be determined using Section 7.5.1 of NZS 3604:2011 Timber-framed buildings. The amount of cantilever permitted is determined using Table 7.2 (far right column) for members that will be wet in service. Note that 90 mm and 140 mm deep joists have insufficient depth where a cantilevered balustrade is required (for example, a fall distance of more than 1 m from the finished deck surface).
→ More detail is given in Figure 2 of the Build article Cantilevered joists(http://branz.us4.list-manage1.com/track/click?u=827ea0dfc4037c85a8cdaa0aa&id=a6927a45ea&e=20c3d9ef22) (Build 127 December 2011/January 2012, pages 21–22).
This construction is different from the lapped and bolted cantilevered balcony joists in Figure 7.6 of NZS 3604:2011.
Summarised from BRANZ Guideline, November 2012.