Most people increase their existing mortgage, either with their current lender or by refinancing with a new one. Your renovation loan plus your existing mortgage balance can usually be up to 80% of your home’s estimated value once the project is finished. You’ll need a registered valuer to provide this estimate. If your construction contract has a schedule of payments due at set completion stages, your lender will arrange for these amounts to be drawn down as required. That way you don’t have to borrow and pay interest on the full amount from the very beginning.