You may have recently received a blog from QBCC regarding the inappropriate use of gun nails in framing anchors and straps.
QBCC received a great deal of response from industry practitioners and associations.
To provide further detail and clarity about the QBCC’s requirements, the QBCC convened a forum on 16 December 2015 consisting of leading connector manufacturers (MiTek, Multinail, Pryda), truss suppliers, Building Certifiers and industry associations such as the Housing Industry Association, Master Builders Association and Timber Queensland.
It was accepted by the forum participants, that despite the best intentions of practitioners when using gun nails, the ability to accurately install these fixings to very stringent and specific instructions (which was an alternative previously allowed by some connector manufacturers) was virtually impossible to achieve on the job site in practice with some types of connectors.
Following consideration of all the issues the forum agreed upon the need for the following specific fixing methods for various connectors:
Triple Grips, Multi Grips and Universal Grips:
Due to the physical dimensions of these connectors, the fixings must be hand driven, using only the proprietary connector nails specified by the connector manufacturer.
Note: Gun nails are unsuitable for use with the abover connectors.
Cyclone Ties, Tie-down Straps, Creeper Connectors:
Due to the additional length of these connectors which can potentially allow for nails to be more accurately located, when installed, strictly in accordance with manufacturers recommendations, gun-nailing can be an acceptable alternative to hand nailing providing:
- the specific brand, type, number and size of gun nail as recommended by the connector manufacturer is used to achieve the required design strength capacity for that connector; and
- gun nail fixings are located in compliance with the following diagram which indicates minimum acceptable critical distances for fixings.
Note: AS 1684 requires metal straps to be nailed with 30 x 2.8 dia. nails. Where 2.5 dia. gun nails are used in lieu, 20% additional nails to those given in AS 1684 are required to be installed to achieve the same capacities.
Masonry Bond Beam Ties (pre-punched or un-punched):
Where tested and supported by the manufacturer, gun- nailing is acceptable where:
- the nails used are the specific brand, type and size as recommended by the manufacturer; and
- the nails are installed in the location and nailing pattern as recommended by the manufacturer
In conclusion if practitioners comply with the above requirements when using these connectors, you will ensure a worry free and compliant installation that not only meets all regulatory requirements including performance, but is backed by the resources and warranties of the leading connector manufacturers.