Construction Loans in NZ: How Building Finance Actually Works

Why a construction loan is not just a mortgage

If you are building rather than buying an existing house, the bank is not handing over a lump sum on settlement day. It is funding a project that does not exist yet, and it manages that risk by releasing money in stages. That single difference drives almost everything else: how the loan is structured, what deposit you need, and why your repayments can move around during the build.

A typical construction loan in New Zealand is a floating-rate facility, usually interest-only during construction, which is then fixed once the house is complete and a Code Compliance Certificate is issued. You draw down in agreed amounts as each stage is finished and signed off by your builder and, in most cases, by a registered valuer. Common stages are slab or foundation, framing, roof and closed-in, interior linings, and practical completion. Christchurch and Auckland builders tend to run to these same stages, though the dollar split varies with the build contract.

The practical consequence is that you pay interest only on the money actually drawn. If your first draw is $180,000 of a $650,000 build, that is all you are charged on until the next stage is certified. It keeps holding costs lower early on, but it also means your final repayment figure is not locked in until the last invoice is paid.

Deposits, land, and what the banks actually assess

Most lenders want at least 20 percent equity across the whole package, land plus build. If you already own the section outright, that equity usually does the job, which is why people often ask how to borrow money from home equity to fund a build on land they already hold. A registered valuation on the section, plus the fixed-price build contract, forms the basis of the application.

How to borrow money from equity in your existing home works much the same way, except the bank takes a mortgage over both properties until the new build is finished and the loans can be restructured. Lenders generally cap total lending at 80 percent of the combined end value, and some will go further if you are using a Kainga Ora first home loan, which allows a 5 percent deposit for eligible buyers and has income caps that change from time to time. Check the current thresholds before you assume you qualify.

The documents that trip people up are rarely the loan forms. They are the build contract, the builder's timeline, and the insurance. Banks want a fixed-price agreement with a licensed building practitioner, a consented plan, and confirmation that the builder carries contract works insurance. A turnkey contract with a well-known group home builder is the easiest to finance. A labour-only arrangement with a mate who is a builder is close to unfinanceable.

What happens when the build runs over

Cost overruns are the classic construction loan problem. If the build goes 8 percent over contract, you need to cover that gap from savings, a variation to the loan, or a pause while you renegotiate. Lenders do not automatically top up mid-build, and a fresh application at that point goes through full servicing again.

Take a couple in Hamilton with a $220,000 section and a $580,000 fixed-price build. They borrow $640,000, keeping 20 percent equity in the finished property. Their fixed-rate home loan rates on the existing house are already committed, so the construction portion sits on floating, around 1.5 to 2 percentage points above the best one-year fixed rate. On a nine-month build that costs them roughly $4,000 to $6,000 in extra interest, which is the price of flexibility.

Delays also hit your insurance. A policy that covers a house under construction needs to be in place before the slab is poured, and cover can lapse if the build site is left unattended for more than 60 days. Tell your insurer when stages slip.

Comparing offers before you commit

Rates on a construction facility are negotiable in a way that standard home loans are not, because fewer lenders write them and each one prices the risk differently. Bring competing offers to the table. A 0.2 percent difference on $600,000 is $1,200 a year, and cash contributions toward legal fees are common when you are also moving your everyday banking across.

Use a home loan affordability calculator with the completed build value, not the contract price, and run the numbers at two percentage points above the advertised rate. That is the realistic stress test once the loan converts to principal and interest over 25 or 30 years. A mortgage loan broker near you who writes construction deals regularly will know which lenders are currently approving them and which have quietly tightened up.

Read the loan agreement for the drawdown schedule and the conditions attached to each payment. Some lenders release funds only after a valuer inspects; others accept the builder's written confirmation. Knowing which applies to you prevents the awkward week where the framing is finished and the invoice is due but the money has not moved.