Congratulations – you’ve decided to build your dream home!

You review your architect’s concept floorplan, “House A” (above), and really like it, but decide it would be even better if you moved a wall or two to make it look like “House B“.

Since they both have the same floor area, there won’t be any difference in building costs, right?

House Build Cost Saving: Design for Roofline

Moving walls on a floorplan is as simple as changing lines on paper.

Unfortunately, paper is 2 dimensional – your new home isn’t!

Changing Walls = Changing Rooflines

And rooflines are one area that can contribute significantly to home building costs.

The diagram below shows the roofline consequences of the floorplan change from “House A” to “House B”:

Compared to House A, House B’s roof will add hundreds, possibly thousands, in extra home building costs in the form of:

• An extra roof hip
• An extra roof valley
• Extra roof trusses and members
• Added complexity with tiles and guttering
• Additional labour and time on site

Keep in mind, this is an oversimplified example – real life examples are usually far more complex (what does your current roofline look like?)

House Build Cost Savings: Conclusion

Moving one wall on a floorplan can unknowingly add hundreds, possibly thousands of extra dollars in additional roofwork.

And walls are only one aspect of an entire house.

When seeking a residential architecture/design firm, be sure to look for a firm who understands the design AND building consequences of their design decisions made.

Otherwise you may find it is the builder informing you of the ramifications of your design decisions – months later when it comes time to hand them their very handsome paycheck.

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So your project has finally completed the rigorous design & planning permit process and your architect has sent your Building Permit Documentation Package out to tender.

The only problem is you’ve received back three wildly differing tender responses from separate builders.

How can one builder’s tender offer come in at almost twice as much as the other builders? Which builder should you choose?

This article will outline the construction tender process so you can make a more informed decision.

Construction tender evaluation

Much of the variation in tender offers comes down to one factor: Sub-Contractors.

Sub-contractors are the many carpenters, plumbers, bricklayers, electricians, painters and other specialised trades that work together to make a building. As suggested by the name, sub-contractors are the tradespeople subordinate in law to the building contractor (the Builder). For the most part sub-contractors work on a “piece rate”, that is to say they quote to carry out the works and deliver as they see fit as long as it fulfils the contract.

The construction industry relies on the sub-contract system that works by supply and demand. A sub-contract bricklaying gang might work for say half a dozen builders, and the communication between the builders and the sub-contractors determines the scheduling.

Sub-contractors are rarely available “next week” but they are almost always available “next month”. If you want them next week, it’s probably going to cost more than getting them next month.

So planning and scheduling are important in getting the best outcome when scheduling sub-contractors.

When is a builder not a builder?

In selecting a builder, a client is actually engaging a collection of sub-contractors to complete the building works under the supervision and instruction of the head contractor (the builder). That contractor must warrant the work of each and every one of those sub-contractors.

Ideally a builder should get at least three quotes for each of the different sub-contractors for each project. These quotes will almost always vary wildly because of:

1. A lack of understanding. In this case a sub-contractor is likely to overestimate for some part of the works they don’t understand or that is ambiguous.
2. Demand. If a sub-contractor with machines and a gang of trades is otherwise sitting idle, they will work for less than when their book is full and their gang is busy.
3. Opportunity. Most sub-contractors will consider shunting another job if their “I’m really busy but I’ll do it if they accept my outrageous quote” submission wins the job.

The builder will then factor all of these quotes for every subcontractor into his final construction tender offer for your job.

Conclusion

When evaluating construction tenders, there are three reasons why builders will provide wildly varying quotes:

1. Lack of understanding
2. Demand
3. Opportunity

Of these three reasons, the last is outside of your control.

The moral of the story is to ensure your architect does all that they can to address the first two reasons:

1. Lack of understanding. The more detail you can provide in your Building Permit Documentation Package, the less each subcontractor needs to guess (and thus overestimate), and
2. Demand. The earlier your builder is involved in understanding your design, the more lead time he can give to his subcontractors so that they can schedule a full book of work.

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How much would it cost to build my home?”

This is possibly the number one question builders get asked. Although there are several ways this question can be answered, there are 3 critical underlying factors that any answer must depend on.

The Size-Finish-Cost Triangle

When asked the inevitable question “How much would it cost to build my home?”, we find it helpful explaining the concept of the “Size-Finish-Cost Triangle”.

The Size-Finish-Cost Triangle dictates that when building any home, only two of the three elements of Size, Finish and Cost can be fixed – the third element must ‘float’ (ie. this third element is dependent on the other two).

Size refers to the total number of square meters of the home that is to be built – not just the building footprint. As an example, a house with a ground storey of 120 m2 and a second storey of 80 m2 would have a building size of 200 m2. Size is often a constraint dictated by the site where the home is to be built.

Finish refers to the level of finish in $/m2 that is appropriate to spend given the location and demographic of where the home is to be built. For example, an architecturally designed island villa would have a very different level of finish to a suburban multi-unit development.

Cost refers to the total budget a client can set aside for their project (don’t forget to include GST). Also be sure to keep in mind any allowances for architecture and design fees.

The concept of the Size-Finish-Cost Triangle is an early warning system. It is a simple check to see if the outcomes that are being requested are unreasonable or are within the ballpark.

Size-Finish-Cost Triangle Example #1

A client brief determined that the Cost and Size of their home must be fixed. This automatically determines the Level of Finish that can be applied to their home:

• Cost fixed at $300k (excluding GST)
• Size fixed at 240 m2

Therefore Level of Finish = $1,250 / m2  ($300k / 240 m2)

Size-Finish-Cost Triangle Example #2

A client brief determined that the Size and Level of Finish of their home must be fixed. This automatically determines the Cost of the project.

• Size fixed at 240 m2
• Level of Finish fixed at $1,800 / m2

Therefore Cost = $432,000 (240 m2 x $1,800 / m2)

Interpreting the Size-Finish-Cost Triangle

In example #1, above, the client may realise that the Level of Finish is far too low for the target market. In this case, either the Cost (budget) will need to be increased or the Size of the built area will need to be decreased.

In example #2, the client may realise that Cost is far too high for the target market. In this case, either the Size or the Level of Finish will need to be decreased.

Be wary if a developer, architect or builder tells you that they can fix all three elements the way that you want it – this is simply not possible and will most probably lead to surprises later in the build process.

Where can I get Level of Finish information?

Level of Finish rates can be found from several sources:

• You could ask any Builder or Quantity Surveyor/Building Estimator for the rates they use.
• Rawlinsons and Cordells (now known as Reed Construction Data) are also two national quantity surveying firms who publish industry construction estimates, updated quarterly. These are very detailed and can be expensive to purchase – although once again, your builder or quantity surveyor will most probably have access to these guides.
• If you wanted to do your own groundwork, you might also find quantity surveyor BMT & Associate’s online construction cost calculator to be a useful guide. BMT also produce a regular newsletter with updated Level of Finish rates for specific building types (although the data published is for Sydney and will need varying depending on your region):
  http://www.bmtqs.com.au/construction_cost_calculator.htm

Conclusion

The concept of the Size-Finish-Cost Triangle is an early warning system that is helpful in answering the question: “How much would it cost to build my home?”.

It is not intended to be used to fix contract prices at the commencement of a project but is a simple check to:

• See if the outcomes being requested are unreasonable or are within acceptable ranges
• Define which two elements are the most important priorities for the client
• Decide on any adjustments that may need to be made early in the project

Related Links

• Rawlinsons Publishing Construction Cost Handbook
• Reed Construction Data (Cordell’s) Housing Building Cost Guide
• BMT & Associates Construction Cost Calculator

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The 2009 bushfires that spread through Kinglake and surrounding townships, causing massive loss of life and property, has been said to be Australia’s worst ever natural disaster.  In response to this tragedy, in March Victoria adopted a new Australian Standard AS 3959-2009. The aim of this new standard is to improve the ability of buildings to withstand attack from bushfires. This article will provide an overview of the new standard and it means for your next build project.

Bushfire Attack Levels (BALs)

The AS 3959-2009 standard defines new construction requirements based on six, defined “Bushfire Attack Levels (BALs)“. The BAL that your property falls in is determined by a number of factors and is essentially the amount of risk that your property is at in the event of a bushfire attack. The six BALs are a sliding scale of risk starting from BAL-LOW (insufficient risk to warrant specific construction requirements) through to BAL-FZ (Direct exposure to flames from fire front in addition to heat flux and ember attack).

It is important to note that these BALs apply to every new building in Victoria that now must meet the associated BAL construction requirements – this is not just for regional/bushfire affected areas. In majority of inner city and inner suburban areas however, the BAL will most probably be classified as ‘BAL-LOW’.

How are BALs for each property assessed?

There are two methods for assessing a property’s BAL:

1) Simplified method

The Simplified method is a six step site assessment process that can be made by an owner, architect, building surveyor or builder:

• Step one Determine the Fire Danger Index (FDI)
• Step two Determine the site’s vegetation types
• Step three Determine the distance from the site to the vegetation
• Step four Determine the slope of the land under the vegetation
• Step five Determine the BAL
• Step six Apply the construction requirements set out in Australian Standard AS 3959-2009

2) Detailed method

The Detailed method is necessary when the down slope of the subject property is greater than 20 degrees. In this case a qualified Fire Safety Engineer must be engaged to do the assessment.

At what point does BAL compliance get checked?

BAL construction requirements form part of the Building Permit. The BAL assessment and relevant compliant construction methods must be included in the working drawings and associated building permit documentation.

The building surveyor confirms that the BAL assessment is accurate for your property then checks that the appropriate BAL requirements are satisfied in your building permit documentation.

How do the BALs affect build costs?

The higher the BAL, the higher the level of compliance costs. The lowest two BALs may potentially not incur any additional construction costs however for homes being built in the highest BAL-FZ, be prepared to incur anywhere from $30,000 and more in extra build costs.

How do the BALs affect Developers?

It is important to note that because BALs affect individual properties, developers who are building multi-unit residential estates may find that due to the specific location of each dwelling, some dwellings may actually have a higher BAL (& therefore added construction costs) than other dwellings in the same estate. In other words, there is no one BAL for an entire estate.

Useful links

• Building Commission of Victoria’s Guide to assessing your property’s Bushfire Attack Level
• Purchase Australian Standards’ AS 3959-2009 incorporating BALs
• Victorian Bushfire Reconstruction & Recovery Authority Bushfire Rebuilding Frequently Asked Questions
• Housing Industry of Australia (HIA) media release of the new AS 3959-2009 incorporating BALs

About Simone Schenkel

Simone Schenkel is the lead Sustainability Architect with Brutal Art Design + Build. She is part of the 2009 Victorian BAL volunteer program and has been conducting voluntary BAL site assessments in Kinglake, Kinglake West, Whittlesea and Humevale.

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1. Bushfire Attack Level (BAL) Assessments