Lot size and Floor space ratio question

DeeAu · May 03, 2024 10:37 pm

Hi,

Sorry I am a newbie.

I have a question regarding the lot size to house size ratio/percentage.

My lot size is 480 sqm. I have drawn up a plan (double story) with the total house size of 375 sqm (78%).

My Architect thinks it may not be approved because the lot to house size exceeds the ratio. The land is in Blacktown city council.

On a side note, I have seen house and land packages from reputed builders where the Lot to house size ratio exceeds than my case. For instance there was a package where the lot size is 312sqm and house size is 294sqm (i.e. the house size is 94% of the lot size).

Any advice would be greatly appreciated.

Many thanks

chippy · May 04, 2024 1:34 am

It's not the size of the house in M² it's the actual footprint of the house. So your 375m² design may be 225m² downstairs and 150m² up stairs.
The plot ratio is based on the 225m² and not the combined total.
The fact that your architect doesn't know this is a bit of a worry.

DeeAu · May 04, 2024 10:36 am

Hi Chippy,

Really appreciate you taking time to answer my question.

To be exact my ground floor is 194sqm and the first is floor 184sqm = Total area 378m2. So it is very comforting to know my plans are compliant in NSW. Thank you.

If it's ok, can I ask another question please.

Is there another calculation/ratio where you consider both floors and calculate the staircase and void spaces once, calculate only 1 car space in a double car garage, exclude storage areas, etc. (I have seen this somewhere).

Once again, I really appreciate your help.

Many thanks

P.S. Any recommendation for an Architect in the Sydney North West area, please?

chippy · May 04, 2024 11:54 am

Hi Dee
I'm in WA but from what I have seen the whole plot ratio calculation is similar everywhere, but I'd encourage you to have a chat to someone in your local area that is across the planning requirements.
There are a few things that need to be considered when designing a house. Setbacks from the front and the other boundaries (including openings), over looking of second storey windows and finally the plot ratio.
In WA our zoning is expressed as open space, so the percentage of the block that is still open or unbuilt after construction. Different zoning types have different amounts required.
The calculation uses the entire footprint of the house not including eaves, so basically external walls. In WA if your alfresco is open on 3 sides you can get a provision back for a certain amount but not all of it and porticos are similar I think.
Garages and voids are all included with no provision for them.
You absolutely need to get help from someone who understands the planning requirements for your area. Having said that you sound like you are only sitting about 40% coverage as described so I'm sure you are good.

DeeAu · May 04, 2024 12:54 pm

Thanks a million Chippy.
Really appreciate your generous advice.

dotty · May 06, 2024 10:26 am

DeeAu

I have a question regarding the lot size to house size ratio/percentage.

My lot size is 480 sqm. I have drawn up a plan (double story) with the total house size of 375 sqm (78%).

Depends on your residential zone and Blacktown's allowable GFA. If your architect doesn't know, I would also be worried as that's the point of an architect to design based on the requirement of the council and you.

I would call the duty planner at Blacktown council and ask.

DeeAu · May 06, 2024 10:28 am

Many thanks for your advise Dotty

Mattms · May 06, 2024 12:53 pm

chippy

It's not the size of the house in M² it's the actual footprint of the house. So your 375m² design may be 225m² downstairs and 150m² up stairs.
The plot ratio is based on the 225m² and not the combined total.
The fact that your architect doesn't know this is a bit of a worry.

It's unfortunate that many salespeople even client often overlook this detail. Nowadays, many land estates impose additional restrictions, such as allowing only 40% of the plot land to be used for building the first floor in a double-storey house.

DeeAu · May 06, 2024 12:57 pm

Many thanks Mattms