Above 80% the lender is exposed to a build that is not finished on a site where the old house has been removed. The lenders that accept this want to see a mainstream builder with a strong track record, a standard fixed price contract, genuine savings history or clear equity, no credit issues and comfortable serviceability with rent included. Investment purpose knock down rebuilds above 80% are harder again.
LMI on a construction loan is based on the total approved amount at the peak, which includes the refinanced mortgage. On a $1,000,000 loan at 90% LVR the premium can be $20,000 to $30,000 depending on the insurer, capitalised into the loan so you pay interest on it for the life of the loan. Interest rates for high LVR construction loans are also typically higher than the lender's standard rate.
Reduce the build scope, contribute cash from savings or a family gift, use a guarantor security if a parent has equity and the lender accepts it on construction, or wait until the existing mortgage is lower. A specialist will usually run all four against your numbers before recommending an LMI path, because the premium plus the higher rate over 30 years is significant money.

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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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.