Mortlake 2137 · City of Canada Bay
Granny Flat Builders in Mortlake: When the Ground Has a Past
Before you dig in Mortlake, find out what used to be here.
Mortlake is a riverside pocket of old cottages and mid-century brick on blocks of 400 to 800 square metres, right next to Breakfast Point, which was once an industrial site. Most lots are fine. Some carry a contamination note. That changes how a granny flat gets approved.
Short answer
Will a contamination note stop a granny flat in Mortlake?
Usually not. Start with the planning certificate, then a preliminary site investigation by a consultant. Most lots come back clean or need only targeted remediation, though any soil leaving site needs a waste classification first, which shapes the slab design and cost. Canada Bay DAs take 11 to 15 weeks, and flats near the Mortlake ferry rent for about $550 to $850 a week.
Written and reviewed by Oliver Alameri
Licensed builder, NSW Contractor Licence 487805C · Founder, Buildana
Fact-checked
Read the certificate for one line in particular
Canada Bay's controls flag industrial-legacy contamination in parts of Rhodes and Mortlake. The section 10.7 planning certificate for your lot will say whether council holds information about contamination or a previous use that could have caused it.
If it does, state planning law says whoever approves the work must weigh up contamination first. In practice? Usually a DA rather than a certifier's quick sign-off, and council will want proof the land is suitable.
Clean certificate, lot above 450 square metres? Then the normal code path usually applies.
One line on the planning certificate decides whether this is a six-week or a six-month project.
How site investigation works
Contamination assessment in NSW follows a staged process set by the EPA's guidelines, run by an environmental consultant.
Stage one is a preliminary site investigation: a desktop review of the land's history, a site walkover, and often a few soil samples. Plenty of residential lots stop right there. Clean. If something turns up, a detailed site investigation follows with more sampling, and where remediation is needed a remedial action plan sets out how, with a validation report at the end confirming it's been done properly.
For a granny flat, the footprint is small, so the investigation is usually targeted at where you'll dig and where the garden will be.
- Preliminary site investigation: history, walkover, initial sampling
- Detailed site investigation, only if needed
- Remedial action plan, if contamination must be dealt with
- Validation report once remediation is complete
Is there a note on your certificate?
Forward the Mortlake address, or the 10.7 certificate if you have it. I'll read the contamination and heritage notes and tell you which approval path you're on before any design money goes out.
0476 300 300What it means for the build
Excavated soil from a flagged lot has to be classified before it leaves the site, and some classes cost far more to dispose of. Slab design can reduce the amount of soil that needs to go.
A house DA in Canada Bay generally takes eleven to fifteen weeks, and the consultant's report adds to that. Heritage conservation areas cover some Mortlake streets too. One more referral.
With Canada Bay's 0.95 factor, the Rawlinsons Sydney rate puts mid-spec construction around $2,090 to $2,520 a square metre. Investigation, soil disposal and any remediation are priced separately once the consultant has reported.
Demolition and the old outbuildings
Demolition queries come up a lot in Mortlake. Before a granny flat goes in, old sheds, garages and carports often come out, and in a 1900s to 60s suburb those can contain asbestos. Test before anyone touches them.
With the ground understood and the old sheds gone, the build itself is straightforward on Mortlake's shale.
Mortlake granny flat checklist
Six checks that set the approval route and budget.
- 01
Contamination notes on the section 10.7 planning certificate
- 02
The lot's previous uses, if known
- 03
Heritage conservation area status for your street
- 04
Asbestos in old sheds, garages or carports
- 05
Lot size against the 450m² code threshold
- 06
Where the flat can sit to minimise excavation
Mortlake granny flat questions
What does a contamination note on my planning certificate mean?
Council holds information suggesting the land may have been used for something that could cause contamination. It doesn't mean the land is contaminated, but it triggers an assessment before new development is approved.
What is a preliminary site investigation?
The first stage of contamination assessment: a review of the site's history, a walkover and usually some soil sampling by an environmental consultant.
Can I still build a granny flat on flagged land?
Usually, yes. It typically means a DA and a consultant's report showing the land is suitable, with any remediation done first.
Is Mortlake in Canada Bay Council?
Yes. Mortlake, postcode 2137, is in the City of Canada Bay, beside Breakfast Point and Cabarita.
Sources and references
Costs are from the Rawlinsons handbook with the local cost index applied; rules and timeframes are checked against the sources below.
- City of Canada Bay
- Rawlinsons Australian Construction Handbook, Rawlhouse Publishing
- Environmental Planning and Assessment Act 1979 (NSW)
- State Environmental Planning Policy (Housing) 2021
- Asbestos, SafeWork NSW
- Search heritage databases, NSW Environment and Heritage
- NSW Planning Portal Spatial Viewer (zoning, FSR and hazard maps)
Understand the ground. Then build on it.
A Mortlake granny flat that starts with the land's history, not a surprise at the excavation stage.