Many people contemplating home renovations under estimate the cost of the works. This may be due to a lack of knowledge of current construction costs, a false sense of the savings that may be made by being an owner builder or failure to consider necessary repairs or upgrades to the existing home.

This indicator has been prepared by Caulfield Krivanek Architecture with Rodney Vapp and Associates Quantity Surveyor and is a guide to help prospective renovators estimate the likely value of intended renovations.

This guide should be read in conjunction with the DIY Home Improvement Guide prepared by Caulfield Krivanek Architecture.

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Renovation Calculation Guidelines

Renovation and extension costs can be estimated by the following process:

  1. Calculate the structural cost of new construction on a square metre basis.
  2. Calculate the fitout cost of kitchen, bathrooms and laundries and add these to the structural cost.
  3. Calculate the cost of upgrades required to the existing part of the home. Typically rewiring, re plumbing and new guttering may be required. It is important to know the condition of your home so you can allow for all necessary repairs. Your Architect can assist you with a professional assessment here.
  4. Calculate the cost of decks, verandas, garages, carports, etc.
  5. Calculate GST and Professional Fees

Structural Costs of new construction (per sq m) 

Standard Home: Typical brick veneer or timber extension.
Under 30m²  $1,890 – $2,840 / m²
Over 30m²     $1,260 – $1,890 / m²

Quality Home: Timber or brick veneer extension with design feature walls, bay windows.
Under 30m²   $2,520 – $3,500 / m²
Over 30m²      $1,680 – $2,540 / m²

Luxury Home: Timber or brick veneer extension with high ceilings, quality wall and floor finishes.
Under 30m²   $3,800 – $4,520 / m²
Over 30m²      $2,730 – $4,100 / m²

Fitout Costs


Standard Kitchen:    $10,840 – $14,910
Quality Kitchen:        $17,120 – $26,880
Luxury Kitchen:        $24,680 – $38,430

Bathroom & Ensuite:

Standard Bathroom: $10,610 – $17,220
Quality Bathroom :   $15,590 – $24,260
Luxury Bathroom:    $24,150 – $38,010

Standard Ensuite:     $6,410 – $9,870
Quality Ensuite:        $11,340 – $16,070
Luxury Ensuite:        $17,010 – $25,730


Standard – Luxury    $4,520 – $17,120

Powder Room:

Standard – Luxury:   $4,940 – $16,280

Existing House Upgrades 150sq.m to 240sq.m

New Guttering:  $3,150 – $4,410
Rewiring:            $6,620 – $9,980
Re-Plumbing:    $8,610 – $17,120

Concrete tiles:     $9,960 – $16,170
Terracotta tiles:  $11,970 – $17,330
Colorbond:           $7,980 – $12,290
Slate:                     $19,220 – $52,500

External re-Painting
Poor condition:   $4,095 – $5,780
Good condition:  $2,940 – $3,990

Internal re-Painting:  $1,000 – $1,370 (per room)

Window replacement: $650 – $1,470 (2 sq.m window)

Rising damp repair: $1,580 – $5,250

Underpinning cracked brick walls: $900 – $1,790 (per m)

Construction Add Ons

Calculate the approximate cost of carports, garages, verandas

Carports & Garages

Single carport (15m²):   $6,300
Double carport (35m²): $14,000
Single garage (15m²):     $13,200
Double garage (35m²):   $29,400

External works and services 

On a relatively flat site with good soil add the following percentage allowance for external works and services to cover fencing, paths, driveways, landscaping, drainage and water supply, electrical and gas connections. Adjustments will have to be made to the below percentages depending on site conditions such as soil condition, slope of site and accessibility to the work site. Your Architect can help estimate these costs.

Works up to $150K:  Add 20% – 25%
Works from $150K to $500K:  Add 15% – 20%
Works over $500K:  Add 10% – 20%

GST & Professional Fees

You will need to add 10% GST to your estimate. You may be able to claim some of this back depending on your personal taxation structure and the nature of your renovation. Your accountant or taxation consultant can advise you of this.

You will also need to make an allowance for architects, structural engineers and possibly other design consultants fees. New building works require planning and building permits, as well as council approvals, and in some cases zoning approval. Speak with your Council, as they should be able to provide you with estimates of costs, as well as expected approval time frames. These would typically be a total of 15% to 20% of the construction cost, and generally need to be paid in the early stages of the project.

Regional Differences

Construction prices vary from city to city and are generally more expensive in rural areas. Using Sydney construction prices as a base, capital city adjustments are approximately as follows:

  • Melbourne -1%
  • Brisbane +4%
  • Adelaide 0%
  • Perth +5%
  • Hobart 0%
  • Rural areas +5% to 15% depending on distance from major cities

Total Cost Structure 

The approximate cost structure of new homes and renovations is as follows:

  • Materials 40%
  • Labour 30%
  • GST, taxes, fees, permits 20%
  • Builders profit margin 10%

Owner Builders

For people considering being owner builders, savings may be made in labour costs and builders’ profit margin, although plumbing and electrical work must always be done by licensed contractors.

Owner builders may not obtain the same trade discounts as builders, so a premium of 5% to 10% on materials may apply.

Home Safety

Homesafe Group is committed to making all Australian homes safer by design. Refer to the Home Improvement checklist at The items listed in the Home Safety Design part of this checklist will add little or no cost to your home improvement project, but they will make your home far safer for your family, visitors, tradespeople, and future owners of your home.

A successful home improvement or renovation should provide owners with a tax-free capital investment over time, as well as an appealing, safe, energy efficient and functional home to be enjoyed for many years. If you are considering renovating your home, contact the team at Caulfield Krivanek Architecture to discuss your project.

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