A valuation cannot be ordered on a rough sketch. The valuer needs council-approved or near-final plans, the specification list with inclusions, the signed or near-signed fixed price contract, and site details. They compare the finished home to recent sales of similar new or near-new homes in the same area. If there are no comparable new homes nearby, valuers become conservative.
The valuer's job is to say what the house would sell for, not what it costs to build. High-end inclusions, custom architecture, pools and landscaping typically cost more than they add. A $900,000 build on a $700,000 block is $1,600,000 of cost; if the suburb ceiling for new homes is $1,450,000, the valuation lands there and the loan is sized on $1,450,000. You fund the $150,000 gap.
This is why specialists ask for the plans and contract before the loan application goes anywhere. A desktop opinion early can save you from committing to a build the lender will not fully fund.
Some lenders also report the land value with the house removed, because that is the lender's security in the weeks between demolition and frame stage. If the existing mortgage is high relative to the bare land value, the lender may require you to reduce it or fund the demolition and early stages yourself before the loan settles.

A knock down rebuild is a construction loan wrapped around an existing mortgage, so lender choice, valuation approach and progress payment handling matter more than the headline rate. We connect you with a finance specialist who handles knock down rebuild deals.
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Property Finance Help is a lead generation service, not a lender, broker, or financial adviser. All information on this website is general in nature and does not take into account your personal objectives, financial situation, or needs. Consider seeking independent professional advice before making any financial decision.
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Disclaimer: Property Finance Help Australia provides general information and referral support only. We are not a lender, broker or credit provider and do not provide personal credit advice. Property Finance Help is a lead generation service and not a lender, broker, or financial adviser. We do not provide loans or credit decisions. We connect users with third-party finance professionals who may assist with their enquiry. All information on this website is general in nature and does not take into account your personal objectives, financial situation, or needs. Before making any financial decisions, you should consider seeking independent professional advice. By submitting your details, you consent to being contacted by third-party providers.