Bracing FAQs

In the along direction the provisions in NZS3604:2011 for hip-ends and mono-pitch roofs are very conservative and not consistent with specific engineering principles. From a wind loading perspective there is no difference between a traditional equal sided triangular gable end and a triangular mono-pitch with the same roof above eaves height. In the across direction the NZS3604:2011 tables suggest only a very small difference between conventional and mono-pitch roofs up to 5 or 10 BU/m for low roof heights above eaves. Given engineering principles and the variety of roof shapes in actual construction it has been decided not to include the additional complexity of hip-ends and mono-pitch roof slopes in the GIB EzyBrace® software. This is consistent with the approach Winstone Wallboards has adopted in previous versions of the software.

The NZS3604:2011 tables give requirements for rounded building dimensions, e.g. 7.0 building height, 2.0 roof height above eaves, etc., and in addition the NZS3604:2011 tables have underlying assumptions relating to dimensions such as floor height above ground. The GIB EzyBrace® 2011 software does not read the tables but is based on ‘first principles engineering’ and permits entry of accurate building dimensions. Differences can also occur because the ‘multiplication factors’ used with the NZS3604:2011 tables have been rounded and more accurate seismic coefficients are used in the GIB EzyBrace® 2011 software. Another common reason for differences is where NZS3604:2011 assumes the same dimensions for both storeys in a two storey building whereas the GIB EzyBrace® 2011 software permits entry of different dimensions for lower and upper floor. It is important to note that the GIB EzyBrace® 2011 software has been written based on first principles engineering, has been independently peer reviewed, and independently appraised as complying with NZS3604:2011.

Houses designed in accordance with NZS3604 have an assumed minimum life of 50 years and need to be designed for a 1/500 year earthquake exceedence probability (the default). However, some home owners wish to build a more robust and durable home and wish to design for a 1/1000 exceedence probability which equates to a life expectancy of 100 years. Other buildings (such as schools or medical facilities) can often be designed and constructed in accordance with NZS3604 but sometimes have to meet a different earthquake exceedence probability. This selection is now available to designers using the GIB EzyBrace® 2011 software by selecting the ‘Annual Exceedance probability’ button on the ‘Demand’ calculation sheet.

A password is not required to operate the software. If a password warning comes up you are trying to modify a locked cell. The workbook now contains a separate ‘Custom Elements’ tab. Here you can enter custom elements and these will now be available for use on all resistance sheets.

The changes have been made due to the updated New Zealand Standard NZS 3604:2011.

Winstone Wallboards reviewed all GIB EzyBrace® systems, due to the changes to the NZS 3604:2011, and decided to make some additional changes to the systems to deliver easy and efficient systems.

(1) New GIB EzyBrace® software, that is compliant with NZS 3604:2011. (2) Slightly modified single fastener pattern (50/50/50/75/75/150). (3) Larger-headed GIB Braceline® screws no longer required when installing BL systems. (4) Increased allowance for use of the new GIB® Standard in ceiling diaphragms. (5) Responsibly conservative bracing methodology.

The Department of Building and Housing (DBH) has cited NZS 3604:2011 as of 1st August 2011. The DBH has stated that NZS3604:1999 will still be valid until January 2012, at that time any consented plans will have a two year completion period. Any new consent applications from February 2012 will have to use NZS 3604:2011. Our recommendation is that designers should move to using GIB EzyBrace® 2011 immediately now that the DBH has cited NZS 3604:2011. The new installation requirements for GIB EzyBrace® 2011 should only be installed on plans specified with GIB EzyBrace® 2011 systems. If the plans are still specified with GIB EzyBrace® 2009 systems they should be installed using the 2009 systems.

To make identification easier the new GIB EzyBrace® 2011 systems have a suffix added to the system identifier, either an "N" or an "H". For example, GIB® Standard plasterboard one side is referred to in the 2011 Systems as GS1-N. For further information refer to the downloadable PDF attachment.

The ‘N’ identifies the system does not have hold-downs, the ‘H’ indicates the requirement of hold-downs in the system

Winstone Wallboards recommend that systems should be installed as specified. However, if the design follows the WWB recommendation of resistance being 10% greater than demand, then the 2011 systems, with minimum GIB® Grabber® 32mm x 6g, can be used as long as all GS and BL elements are installed using the new fastener pattern.

Yes, but the plan will need to be re-complied by the Building Consent Authority (BCA).

As with the 2006 and 2009 GIB EzyBrace® systems, GIB® Grabber® screws are the only brand of screw used in the Winstone Wallboards testing and hence make up the full system appraised. These are the only screw brand that Winstone Wallboards monitors the quality of and can confidently confirm the consistency of performance and that Winstone Wallboards can stand behind.

As only GIB® Grabber® screws have been tested and approved for use in GIB EzyBrace® systems a producer statement from the alternate supplier covering the use may be required to gain compliance.

The minimum line total requirements in NZS3604:2011 have changed to 50% of D/n, 15 x L for external walls, and no less than 100 bracing units on any line. Most often the requirement to exceed 50% of Demand divided by the number of bracing lines governs. This check has been automatically incorporated in the software, as well as the absolute minimum of 100 bracing units. The designer still needs to do a 'manual check' for 15 x L on external lines, however, this will rarely be critical once the other conditions are complied with. Note that the line totals give a minimum shortfall when the requirements have not yet been met and a positive total once they are achieved.