Building extensions and a granny flat: SIPS system

  • Creation Date: Wednesday, 19 June 2019


I am considering building a office (perhaps future live in flat) above my garage; can I use a SIPS system to do this?  Can you advise on the requirements for the office floor/garage roof (i.e. the platform on which to build upwards upon).  The existing garage is a single building compiled of an older portion (that was a lone single garage approximately 6 m x 5 m) to which an additional newer portion (double garage floor area approximately 7.5 m x 10 m) had been added.  It has the double brick outside walls and an internal double brick wall (the old single garage‚Äôs one outside wall) and the roof is currently a flat roof.

 At the same time I will probably also need to erect a two bedroomed granny flat on my property for my in-laws to come and live in.  The available space to build is restrictive and thus the typical standard designs of the SIPS will probably not be completely suitable, can a non-standard design of building be obtained instead? If it can be done what would the typical cost implications be?


The first issue that you would need to consider is the distance from the boundary to the wall of the existing garage. If it is your intention to convert any of the existing garage space into an office or living area then, under the new Zoning regulations there is a 2m side building line restriction if the property is over 400sqm and 1m if the property is less than 400sqm. Only garages and store rooms can be built, with neighbour permission, over that line. Any Title Deed restrictions that are greater than the above would override the Zoning Regulations and would apply unless you have them removed from the Title Deed. The new Zoning Regulations permit the construction of a free standing (or connected) second dwelling with full kitchen of up to 120sqm. A further issue is that at least 2 on site parking bays must be provided for properties over 400sqm.

As far as SIPS buildings go, there is no restriction to what can be designed or built and a building can be designed to suit your available space and application. There may be a restriction on the clear span for the floor of the upper story but nothing, I am sure, that a structural engineer would not be able to sort out. You can have either a concrete or timber floor construction depending on budget, lifestyle choices or the construction of the existing buildings. As mentioned, the building line restrictions will dictate most of your options.

 Any floor between a garage and a dwelling above it must have a 1-hour fire rating.

When it comes to cost, you can budget on a standard brick building and you will most certainly make a saving on the cost of the walls and on time as the construction time is greatly reduced. Pricing any building without a drawing will unfortunately not be possible.