When does a Fonzie flat become a Class 2? It's a costly difference!
Collaborative construction or what is often called ‘integrated project management’ can be a powerful tool in most new construction projects, but not often afforded in ‘smaller’ projects. Small is sometimes seen as easy and ‘standard’ as was the case in a 2 storey housing project.
Throw in a remote architect, pre-sold homes, a project builder keen to finish, and lack of sub trade collaboration, and your 2 storey project can blowout easily by $10,000 to $15,000, and that’s PER HOUSE! Whether it’s 1 or several houses (as it was), that’s your margin gone!
Background
Following on from our recent warehouse case study which required two systems to be selected, today’s involves much more, and five various systems to resolve all issues.
Several houses designed as dual living, upstairs, and downstairs as separate homes, with a unit on top of the garage, master bedroom, ensuite, and hallway. What apparently was a Class 1 building now became Class 2 due to a portion of the upper unit overlapping the living areas of the unit below, so not only were the boundary walls now requiring 90 minute fire rating, there were many other fire rating considerations not originally taken into account for the dual living.
Typically the ‘Fonzie Flat’ clause in the BCA determines what is still Class 1a where above a garage, however in this case the flat was above the living area also.
In collaboration with the building certifier, the fire rating requirements of the change were determined and included:
Timber floors separating the storeys or above motor vehicles are to have an FRL of 30/30/30 or have a fire protective covering on the underside
Internal separating walls must have FRL 60/60/60 of -60/60 for non-loadbearing walls
External loadbearing walls for distance to fire source feature less than 1.5m external wall may be timber framed with the outer wall having FRL 90/90/90
Internal loadbearing columns and walls supporting upper storeys have FRL 30/30/30
The debate over the correct classification – Class 1a or 1b or 2, and therefore consideration of these challenges PRIOR to design was obviously problematic, but then the project team starting the works again compounded the problem. Once we became engaged – without collaboration in the pre-build stage – there were already a number of issues onsite prior to the certifier inspections.
Considerations included:
Class 1 boundary wall requires 60-minute fire rating for 900mm or less from boundary wall, however, the Class 2 boundary wall requires 90-minute fire rating for 1500mm or less from the boundary wall
The construction was of timber frame with 70mm studs, therefore ‘usual’ providers of fire rated walls were limited as many only use 90mm studs
The garage bounding wall was constructed out of Loxo panel and finished to the underside of the floor joint creating a cavity between the dwellings in the ceiling space
Loxo panel also didn’t finish to the upper roof eave so compartmentation was not met. Above the roof, a system had to be installed to continue the party wall line – which now became a boundary wall
Fire rated ceilings couldn’t pass over the top of the internal walls as stud framing was installed first
Load bearing studs holding structural timber beams for the upstairs floor joist required fire rating
Internal vertical and horizontal corners needed blocks replaced with full timber stud in corners as per Wood Solutions to maintain compartmentation
Penetrations passing between units require fire rating so a number of fire stopping systems were selected
We provided marked up plans with the new fire rated systems selected, and the creating of the installation manuals to ensure ALL of these issues were addressed on site, for compliance.
The issue in the garage, separation between the two garages are not met.
Issue: The load bearing wall requires fire rating as it’s holding up the LVL and floor joint for the upper level
Summary
Mistakes do happen, but for the small amount it may be to add a passive fire expert in at the design stage or at least before the build starts, can prove extremely valuable in savings during the build.
Credit goes to this builder who wasn’t entirely certain and so engaged us to:
Review the designs and plan the fire rating systems
Assist along the way to ensure the correct installation
Inspect and certify the works
Our engagement ensured the buildings did not get completed, painted, and ready for handover before the problems were identified. That would have involved tens of $,000’s to rectify EACH completed building.
But if things just don’t add up when the build starts, erring on the side of caution is usually a very good start!
For advice on your next project call our certification team on 1800 PASSIVE or email plus@plus.systems
Please note: This is general awareness only and had been provided as a guide derived from the experience and training of the Plus team. For project specific advice, consult to your Building Certifier/ Surveyor.