How to Design Granny Flat Conversions with Fire Rated Walls

Granny Flat Conversions and Fire-Rated-Walls: Why and How to solve the problem

We’ve just completed our first few Granny Flat Conversions Pricing and Process Page. It sets out how to begin your Granny Conversions for approval and we thought we’d share some of the processes and potential pitfalls in converting Sheds or Garages into Living Spaces, Studios or Granny Flats in Sydney.

1.The first difference between a normal granny flat approval and garage conversions is that you might need a Fire-Rated-Wall if one of the following exists:

(a) The converted structure is within 1.8 meters of the main dwelling, measured from wall-to-wall.

(b) The converted structure is within 0.9 metres of the side or rear boundary.

2. The second difference is the BASIX (Energy Efficiency) Requirements for the conversion need to be brought up to standard. This means even if the existing structure has been partially or fully renovated, it still needs to have all of the insulation, hot-water and drainage systems in place to be approved.

3. The third area of importance is that the existing wet-areas (bathroom and shower) need to also be certified by a licensed ‘Water-Proofer’ as being up to standard.

4.  The final notable difference to a normal granny flat is the need to have a Structural Engineer Certify the Existing Slab and Frame.

Below, we show an example where a granny flat conversion needed a fire-rated-wall, due to being too close to the main dwelling:

granny flats and fire rated walls

fire-rated-wall shown on Site Plan

Most of the preceding requirements are Building Code of Australia and BASIX requirements. The good news is that here at Granny Flats Sydney (NSW) Pty. Ltd. we are the experts in granny flat conversions and we posess the  know- how to save you the most amount of time and money when it comes to converting your existing shed or garage into a legally habitable building.

Feel free to check out our Process and Pricing Page (linked above) or give us a call and we’ll asses the suitability of your structure for conversion.

Warm Regards,

Serge Panayi

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34 replies on How to Design Granny Flat Conversions with Fire Rated Walls

  • Brian D Ward says:

    If I wanted to build a granny flat underneath our existing house, what sort of fire rating would I have to achieve for the ceiling and external walls?

  • Serge Panayi says:

    Hi Brian,

    You’d need fire-rating to any wall or ceiling which adjoins the main dwelling. This means a fire-rated product or masonry etc to that wall or ceiling to 60/60/60. This must penetrate through the frame as well.

    For example, the fire-rated-wall must completely seal the 2 sections in all three dimensions from each other. I hope that makes sense.

    Feel free to call me if you need further clarification. Ph: (02) 9785 2781

  • says:

    One wall of my detached garage is within 900 mm of the boundary. Whilst the wall itself should be ok from a fire rating perspective (brick veneer construction, nil openings facing the boundary) how can fire rating of the eave and roof be achieved? (Metal skillion roof with timber fascia and frame exposed, eave protrudes approx 200mm from wall towards boundary)

  • Serge Panayi says:

    Hi Dominic,

    This is a good question. You’re right that the brick wall is fire-rated since it has no openings on that boundary side. Incidentally, if a building adjoins a Public Reserve (road, park, walkway etc) it doesnt need fire rating.

    With the Eaves/Fascia, if it’s not within 450 mm of the legal boundary it also doesn’t need to be fire-rated. Otherwise, a colorbond fascia and fibro eaves sheet is fine. The gutter of course must not be plastic.

    The frame being exposed is not good. The building frame MUST be sealed. This can be achieved via a number of ways including fire-proof sheeting or other cladding.

  • Geoff says:

    I’d like to ask about a garage conversion to a granny flat on a heritage listed property. The garage is to the rear of the property. Is it worth while trying or is it a waste of time?

  • Serge Panayi says:

    Hi Geoff,

    It depends on what your Section-10.7 Certificate says. You’ll need to get this from your Local Council or look in your Contract if its less than 1 year old. Otherwise you can buy one from Council for exactly $53. It’s called a Section 10.7 (Part 2).

    Usually on Page-5, the Certificate will state whether or not the property can have Complying Development under ‘The General Housing Code’. If it says ‘yes’, you may be able to; otherwise probably not. Your local Council are unlikely to support a granny flat conversion in a heritage or conservation area.


  • Robert says:

    Hi Serge

    Currently thinking of a garage conversion,
    I have one wall adjacent to nieghbour which is less then 900mm everything else is okay.
    Does this need to be fire rated (instead of bringing the wall in)

  • Serge Panayi says:

    Hi Robert,

    Yes you’ll need to fire rate it, unless:
    1. The wall is brick or other masonry
    2. The adjoining land is a public reserve, road etc

  • Ken says:

    I have a brick garage whose rear is 2.8m and side is 0.45m from the boundaries.The side has no windows, but concern is that rear wall of garage has 2 windows.

    (1) I understand I don’t need to fire-rated the walls since its brick walls. However do I need to seal off the windows at the rear?

    (2) Because of setback constraints for the rear and side, can I still get approval CDC approval via a private certifier in 10 days, assuming no other constraints?

    • Serge Panayi says:

      Hi Ken,

      The 0.45 metre side can never have any window or door openings.
      The 2.8m rear is fine for openings since it’s greater than the BCA requirement of 0.9 metres.

      You can still get approval for a granny flat conversion as long as the structure being converted is ‘existing’. i.e. Not a new footprint on the property. Any new extension must meet the 0.9m side and 3m rear setback requirement.


      Serge Panayi.

  • Dave says:

    Doing a garage conversion to granny flat.
    Timber frmaed double garage. less than .9 metres from the main house. (House has brick wall). The full length of GF is alongside the main house. I believe I’ll need to fire rate the external GF wall. Other than Brick is there a cost effective solution eg Villaboard?
    Trying to keep the ocsts down.
    Thanks for your advice/thoughts.

    PS. I’m in Blacktown Council but can’t find a good set of clear guidlines.

    • Serge Panayi says:

      Hi Dave,

      There are a number of non-masonry solutions to achieve compliant Fire Rating to what the BCA calls 60/60/60. This is if wall-to-wall is less than 1800mm
      Boral and James Hardie sell a ‘fire-rated-wall-system’ which can be applied externally and/or internally depending on your preferred solution.
      The key is to also remember that any fascia, eaves or gutter must also be fire proofed if within 900mm of each other.
      Gutter and fascia can be Colorbond.
      Eaves can be fibre cement. All apertures must be sealed and any surface (including roofing) which is less than the specified must be fire rated.
      You’re effectively sealing the 2 structures from each other as though they are neighbouring dwellings with an imaginary fence between them at 900mm from each wall face and 450mm from each fascia.

      I hope this helps.
      Serge Panayi
      Granny Flats Sydney NSW Pty Ltd

  • Arry says:

    Hi Serge,

    I have a rear extension just one year old designed for storage and laundry. The overall land is 240sqm (in Mascot) and The rear extension for storage is about 24sqm. It was made by bricks and has final occupation certificate. The boundary to the neighbour’s fence is less than 300mm.
    The final occupation certificate contains:
    Description of Development: construction of detached outbuilding to accommodate storage and laundry.
    Commencement of building work, footings prior to pouring of concrete, timber frame prior to lining, waterproofing of wet areas, storm water pipes prior to backfilling, final inspection – issue of Occupation Certificate are satisfactory.
    It has own window and door, I just want to convert this storage into studio which has own bathroom and simple kitchenette. Do I need any permission? or what I should do to get any permission and how likely it can get. Sorry I am just wanting to keep cost down and dont want to build I regret later.

    • Serge Panayi says:

      Hi Arry,

      You’ll need permission for this conversion, yes.
      A ‘studio’ is defined as a detached ancillary structure, so this can’t be a studio because it’s attached to the primary dwelling. If it is going to have it’s own kitchen it will need to be approved as a granny flat and a Fire-Rated-Wall installed. It will need it’s own separate entry form the outside of the dwelling. Read our Conversion guides here:


      • Arry says:

        Hi Serge, sorry I was not really clear. The storage is in its own, i.e., separate from the house (not attached) and it locates at the rear. It has access from driveway. It is completely made by bricks. I reckon I will not fit a kitchen but rather just a simply sink. It will however has own bathroom.
        If I engage your company, how likely the permission can be granted?


  • Paul Bergin says:

    Hi Serge,

    I have to fire rate my side wall as its less than the 900mm offset. It is currently a corrugated (custom orb) colourbond wall. Is there a product that I can use on the outside – ie. unscrew the colourbond and replace with another product. Do I only have to fire rate the external wall, or do I also have to the the internal wall.

    Thanks Paul

    • Serge Panayi says:

      Hi Paul,

      There are various products made by Boral and James Hardie which work. Some are applied externally, some internally and some on both sides of the wall.

  • Soraya says:

    Im hoping you can help me, I am thinking of buying a house with extension that was advertised as a granny flat but has now been called a teenage retreat. This apparently means the kitchen is not approved. Is it possible to have someone come out and get it approved?

  • Mamunur says:

    Hi Serge
    I have a 32 square meter brick double garrage in the front of the property which is attached with the main dwelling. .One side is 1 m from the boundary. Land size is 534 square meter and land is 12.5 m wide.

    Can I built a one bed room granny flat? How do I proceed?

    Thank you.

    • Serge Panayi says:

      Hi Mamun,

      It should be ok as long as the wall and roof separating the 2x dwellings is fire rated.
      Please feel free to give me a call and we’ll take a closer look at it.


  • Dave says:

    I have garage fit out with ceiling height as written below:
    bed room =2200mm
    Launge room = 2200mm
    kitchen = 2100mm
    Bath room = 2100
    other requirements looks Ok.
    is it possible to get approval for granny flat. Can you get the approval from penrith city council

    Thanking you in anticipation

    • Serge Panayi says:

      Hi Dave,

      bed room =2200mm NON-COMPLIANT
      Launge room = 2200mm NON-COMPLIANT
      kitchen = 2100mm COMPLIANT
      Bath room = 2100 COMPLIANT

      Minimum wall-heights are an Australian Building Code requirement so the Council area is irrelevant, sorry.


  • Petar says:

    Hello Serge,

    I have a home and want to convert the rear games room and bedroom & ensuite to a secondary dwelling. There is an existing hollow twin brick wall (from slab to underside of non-combustible roof) with a doorway separating it from the rest of the home. I need a Fire Engineer or consultant to help with the CDC plans to council for the separating wall. Can you help.

  • Tofiq says:

    Hi, can we make a granny beside the principal home(attached) facing primary road. Got good frontage. Total block 600m2. Want to make it beside not at back of the block. Do we need to keep gap if we built granny beside the primary home facing to street? Thank you.

    • Serge Panayi says:

      Hi Tofiq,

      You can indeed build to the side of the primary (main) dwelling as long as you follow these guidelines:
      – If detached from the dwelling, the granny flat must not be further forward than the average of the nearest two adjoining dwellings facing the same street.
      – If detached, must be minimum 900 mm from the main dwelling, otherwise a fire-rated-wall will be needed on that side of the granny flat.
      – The side setback must be minimum 900 mm, otherwise a fire-rated-wall will be needed on that side of the granny flat.

      We have approved/built quite a number of granny flats to the side of the main dwelling and this can be a fantastic (if not the very best) arrangement, so you’re very fortunate.



  • ryan says:

    great site and information,

    I am consider to convert a garage and part of ground floor 2 rooms into a grannny flat, but the first floor was originally a timber extention above, I am wondering solution to fireproof the granny flat on the groundfloor, what is the cost per meter square??

    • Serge Panayi says:

      Hi Ryan,

      Thanks for your kind feedback.
      I cant specify a price to install a fire rated wall or floor/roof. The cost can vary greatly depending on access for a builder.
      It’s honestly best to get a quote from someone and go from there. Needless to say it can be as simple as a covering over an existing covering or major surgery with associated structural work.
      The total Conversion Approval price is fixed with us as listed here:


  • Anne Flint says:

    Have a 2 bedroom, one bathroom, living area (no kitchen) space underneath the house that I would like to convert to a compliant 2bd self contained separate dwelling. (Approx 108 mts square). I understand it would need to be fire separated too. Is there someone who can give advice/ do conversion work?

    • Serge Panayi says:

      Hi Anne,

      The maximum size is 60 sq m.
      There are strict fire-separation (fire-rated-wall) requirements that can be critical in any decision but is doable on paper.
      Give us a call and we’ll look at it for you.



  • Amy says:

    Hi Serge

    I was hoping to build a brick veneer two story granny flat in the location of my existing double garage. (Will knock down the existing garage to do this). Land size is 715msq. The side boundary to the proposed granny flat footprint (and existing garage) is a minimum of 900mm (at the front corner of the granny flat to the side boundary) and 2400mm setback from the rear corner of granny flat to the side boundary. Both corners are on the same elevation facing this side boundary, which is a common driveway leading to two battleaxe properties at the rear of my property. Although the ground floor dose not encroach on the specified minimum 900mm setback to side boundary, a small portion the first floor front corner of the granny flat (a triangular shape 0.468mm sq) does encroach on the 1550mm side setback required for a 2 story granny flat. If this wall is fire rated, without any openings, can I still submit the plans as a complying development? Using the Side setback formular .9m + [.25 x 2.6(height >3.8m)]
    = .9 + .65
    I would need a 1550mm setback to the side boundary for a two story granny flat.

    • Serge Panayi says:

      Hi Amy,

      The quick answer is no, you can’t breach the ‘new’ granny flat setback requirements in this scenario. This is because you’re not carrying out a Conversion. It’s a knock down and rebuild.

      A Conversion as Conplying Development cannot result in any change to the existing footprint nor the existing heights. This is the only way to preserve the existing (reduced) setbacks. I.e. there must be no change to the existing garage’s size externally.

      You’re spot on about the minimum side setback required in your measurements and it must apply to the entire building. Remember the rear setback would also have to be a minimum of 8 mtrs at this height.

      You could apply for a DA instead but there are no guarantees as there is with the SEPP.

      I hope this helps.


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