Building A Duplex For Beginners

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Hi everyone

I have just joined the site and have read through many of the passed threads about building duplexes however, I thought it would be an idea to start a new thread about building a duplex from scratch for the beginner so I can clearly understand the steps involved.

I am at the very beginning stage where I am ready to search for suitable land on which to build a duplex. So the first step I'd like to discuss is how to search for suitable land.

I realise each council sets the rules for what will be accepted and I have read the info available on the council websites but some of it is 'double dutch' and unclear.

I am open to buying in different areas. One area I have been looking in is the Sutherland Shire Sydney. From What I understand the council rules are min. block size of 600m2 which would allow for strata subdivision or 800m2 to allow for torrens title subdivision. All with a min. frontage of 18 metres.

Anyone build duplexes in the Sutherland Shire? Is the above correct or have I got it wrong?

I have also looked in the northern suburbs Sydney. But the council seems to have a higher min. block size of 700m2.

Does anyone have any hints or tips with regards to buying suitable land? For eg. How do I find suitable land? Or how do I know if a block of land I have found will be suitable? There are some blocks I have found that I think might be suitable but do not know the next step of how to confirm this. I dont want to buy a block then find out I cant build a duplex!

I'm eager to get started and it seems your site has a lot of people on it willing to help.

Her's a start Duel,

Maybe others can add on to the list.

DIY Site Analysis

• Check zoning
• Contour survey – ask vendor if they have one available
• Soil test (geotechnical report) to determine engineering requirement for foundations - ask vendor if they have one available
• Determine whether dwelling can be built on slab or needs to be bearer and joist.
• Can the stormwater be drained to the street? If not, is there inter allotment drainage to tap into?
• Retaining walls needed? Can cost between $150-$300 per sqm.
• Check to see if stormwater retention is required (council).
• Existing vegetation to be removed?

Study the Council Development Control Plan and the Local Environment Plan to assess the requirements for:
• Boundary setbacks
• density control
• private open space
• absorption areas
• building height planes
• car parking
• impact on adjacent development
• character of design
• energy efficiency (BASIX)
• landscaping
• stormwater management system.

Thanks for the info rockstar. I have found a few sites already that seem suitable. I read on another post that employing a project builder is far cheaper than building with an architect.

I am going to go to Homeworld in Kellyville soon to have a look at what is available. Even though these are off the shelf designs I think they will suit my purpose.

Does anyone have any advice when it comes to choosing a site to build a project home on?

For eg. I'm assuming that if I can fit the floor plans onto the block (including council setback rules, density and checking whether there is any easements) then there should be no problem.

So far the idea of this seems very simple - a matter of picking a site on which the house will fit and then going to pick a duplex to build from Kellyville. Then six months later you have a duplex.

Can neighbours stop a duplex from going ahead?

Also from my calculations if I build them and they are not going to sell for a much as I want then renting them out will cover interest.

Also I was wondering if you are able to get feedback from a project builder like Masterton on what is possible to put on a block of land BEFORE you purchase it. Has anyone done this before?
Great topic .. looking to start my first one too but struggling to find a good step-by-step guide.

The closest thing to a guide I found is this book ( but its not written very well with a beginner in mind.

Jumps a bit over the place and not organised as a step by step book.

If someone here is willing to write a good guide I will definitely pay $$ to buy it ! .. hint hint .. :)
Also I was wondering if you are able to get feedback from a project builder like Masterton on what is possible to put on a block of land BEFORE you purchase it. Has anyone done this before?

Much easier to get the council development guidelines and check yourself what is required. Most builders wont give you a guaranteed "this will work" and will think you are wasting their time.

Check the guidelines for minimum lot size, open space requirements (and how they measure them), set backs. Then get some basic plans you like and see if it will work on your specific block.

Much cheaper generally to use a project builder unless the block is a bit unusual in shape and the project builders will struggle to get "regular" plans onto the site.

Do your due dillegance properly. Work out what they are ACTUALLY selling for when complete and make sure you have a decent margin (min 30% is what most people go by) in the deal as budgets always blow out a bit. Don't just say that if you can't make a profit you will just rent them out. You may as well in, in that case, just buy the finished product and save the stress, risk and holding costs.

Befriend someone with RPData and do your research properly and start first at the council and work out the blocks you should be trying to buy and not the other way around.

Good luck with it.
Yesterday, I rang up REA (principal partner in agency) and organised time for him to drive hubby around to look at duplex blocks ideally we would like a block that a slab could be put on - but we wanted to look at all blocks available.

Plus what is coming onto the market...

Last night I spent hours going through and I looked at every block available for sale in the post code I want.

Previous to this I have been looking periodically eg. every week I look at latest listed + read newspapers and REA advertising papers.

Today we drove around for an hour and half and looked at blocks from 235K downwards.

Hubby and I had already decided on block and value.

As we got out of car - I discussed putting in an offer I said 138K REA had previously said he thought 139K would be the price.

He suggested he start negotiations at 135K which he did and 10 minutes after dropping us off 135K was offered and rejected so we put in an offer of 140K (as another block which is worse has gone to contract at 140K).

I asked for a copy of soil report (geotechnical report) and a contour plan if available as this is not a flat block of land. Plus if offer accepted I want a 60 day settlement.

We are in the process of organising finance with a morgage broker and saw our accountant today as well.

Generally - I think I know what I am doing in my own patch. If you are starting out then you need to talk to someone who has brought and built duplexes a few times in your own patch or do your first build with an experienced builder.

BUT you must make your decisions and be responsible for your own actions. You can use a project manager BUT you will not make much profit (if any) and you don't learn the steps.

One thing you should do - is read all the information on your council website relating to building duplexes.

Ring the council building inspector and ask what you need to read, the are generally quiet helpful.

Where are you getting blocks of duplex size for 140k? I am also picking up a duplex block next month, but in the 450k range. Granted, it is within 10km from the CBD in a decent built up area. Are these cheap sites out in the mountains?
Where are you getting blocks of duplex size for 140k? I am also picking up a duplex block next month, but in the 450k range. Granted, it is within 10km from the CBD in a decent built up area. Are these cheap sites out in the mountains?

North Coast of NSW (not on coast 30 minutes inland.

Of course I could have brought an approved duplex block for $235K but I believe value is made at initial purchase price.

ahh ok...definitely agree with you that profit comes from purchase price...which is why i wouldn't mind picking up a duplex block in the city, but that's not possible. Mind you, the finished product is worth more eventually I guess.
Hi Duel,

I'm building a duplex right now in Sutherland Shire Council.
Bought the property about 2 years ago and only just getting ready to go to council now.
Has taken alot longer than I thought to prepare everything.
Going through a project home builder.
Lucky we are renting the current house out.
Anyway, this first one is just a learning experience for me, don't care if I don't make any instant growth out of it, even a slight financial loss.
But still hoping for a good result.
Block is 665sqm.
That was the only thing I enquired about with council before deciding to buy the place, knowing I wanted to knock down and build a duplex.
Also, a massive abt 20m high tree right in the middle of the front yard.
It's a Camphor Laurel, so no permit required to chop that beast down.
Basically, just went into this project blind.
I don't like doing too much research and get into analysis paralysis.
I like to just jump in and get things going.
It's kind of exciting going through the process for the first time, not knowing what will happen.
I have some building experience, worked on 2 houses from start to finish before and know my way around a building site, so not totally inexperienced.
Only inexperienced from the planning and preparation part from start to DA approval, but that has changed now and it will be much easier on the next one.

I have learnt so much already, and these lessons will definately pay off in the future.

Let me know if you have any questions and I can let you know my experiences so far.