Construction Finance
Estimating Construction Costs
5 min read- Finance Guide
- Updated 2026
Quick answer
Typical contingency allowance
5% 15%
depending on project complexity and what is already fixed in contract pricing
- Core cost source Builder contract or quote
- Lender focus Total project budget
- Common missed costs Site works and variations
1300 421 044
1300 421 044
Detailed explanation
A strong construction cost estimate starts with the building contract or detailed quote, then adds every cost the contract does not fully cover. That includes site preparation, engineering, permits, utility work, retaining, drainage, landscaping, driveways, upgrades, fixtures outside contract scope and a sensible contingency for unknowns.
What should be in the cost estimate
A lender ready budget normally includes these components
- 01Building contract or builder quote
- 02Site works and foundations
- 03Approvals and consultant fees
- 04Utility connections and external works
- 05Owner supplied or excluded items
- 06Contingency allowance
When building the budget, check that:
the contract price matches the plans and specifications- every excluded item is listed elsewhere in the budget
- site conditions and authority costs are not underestimated
- there is enough buffer for variations and price movement
Cost categories lenders look for
A complete estimate often includes:
-
fixed price building contract or clearly itemised quote with inclusions and exclusions
-
site costs such as excavation, piering, drainage, retaining or difficult access if relevant
-
professional and authority costs including plans, engineering, permits and certification where applicable
-
extras not inside the building contract such as driveways, fencing, landscaping, blinds or appliances if borrower is funding them
-
contingency for variations, unknown ground conditions or contract gaps so the finance structure is realistic
Contingency guide
-
Low complexity
5%
-
Typical project
10%
-
Higher risk build
15%+
How lenders assess the budget
Lenders review
fixed price building contract or acceptable cost schedule- plans, specifications and inclusions
- quotes for items outside the builder contract
- site cost allowances and whether they look realistic
- completed value compared with total project cost
- borrower contribution, equity and contingency position
- whether the total budget supports smooth progress draws
Typical focus points
-
Main contract price
Must align with plans and inclusions
-
Excluded items
Need separate funding or clear allowances
-
Site and authority costs
Often underestimated if not checked early
-
Contingency
Helps absorb surprises without immediate funding stress
Need Help with your Project?
Common problems
Construction budgets often fail because the number looks neat on paper but does not include every real project cost the lender and builder will eventually expose.
Site costs are underestimated
Ground conditions, slope, retaining, drainage or access issues can make the real build cost materially higher than the first estimate.
Possible solutions include:
obtain detailed site assessments early- allow realistic provisional sums or extra cash buffer
- question unusually low site allowances
- recheck the budget before applying for finance
Items outside the contract are missed
Driveways, landscaping, fencing, window coverings, appliances or utility work may not be in the builder contract but still need funding.
Possible solutions include:
- compare inclusions against the full project wish list
- obtain quotes for excluded items
- separate must have and optional upgrades
- make sure lender knows what is borrower funded
No realistic contingency
A budget with no buffer can become stressed quickly when variations, authority costs or material changes arise during the build.
Possible solutions include:
- include a sensible contingency from the start
- keep extra cash outside the loan where possible
- avoid spending the buffer on upgrades too early
- review the budget again before signing the contract
Steps to get Finance
Step
01
Prepare plans, specifications and a draft scope of works.
Step
02
Obtain builder pricing and identify all exclusions and site costs.
Step
03
Add approvals, consultants, utilities and owner supplied items.
Step
04
Set a realistic contingency and confirm your equity contribution.
Step
05
Submit the full budget package with the finance application.
Step
06
Refine the budget if valuation, contract changes or lender conditions require it.
Speak with a Property Finance Specialist
Construction cost estimation can vary significantly depending on the design, site, contract structure and which items are included or excluded from the builder price.
A specialist can review the project budget and help identify gaps, likely lender concerns and where extra contingency or equity may be needed.
Speak with a finance specialist about your construction budget
Submit the short form below and a finance specialist can review your project costs, likely lender requirements and whether the budget looks complete.
Contact Form
Your enquiry is confidential
Prefer to speak with someone directly ?
Call us to discuss your construction cost questions
Additional Questions
You may also find these questions helpful
