How much does a loft conversion or second-storey addition cost in New Zealand?

Since loft conversions and second-storey additions in New Zealand vary markedly in cost, providing a blanket estimate for these projects isn’t very helpful. Instead, by identifying the elements of the renovation that have the greatest budget impact, we can paint a clearer picture of what these projects may cost you.

Utilising your unused attic space or building another storey are great options to increase your home’s living space if your property doesn't allow for a lateral extension. However, these projects come at a premium. A loft conversion or second-storey addition can start at $250,000* and easily exceed $400,000*. 
Understanding the main budget drivers - structural considerations, weatherproofing, existing roof and joinery, and access - will help you anticipate the potential cost of your loft conversion or second-storey addition. Having executed thousands of renovations, we’ve come to recognise patterns amongst similar projects: these four budget drivers have the biggest impact on the costs of an upper level transformation.
In this article, we’ll explore exactly how these factors affect a project’s final cost. Our goal is to help you understand what’s involved with the costs behind loft conversions and second-storey additions, but for a better idea of what you might pay for your specific project, it’s best to work with a Refresh Renovation Consultant** who can assess your goals and provide an accurate estimate. Both building and resource consents can also be involved if you are changing the roofline or roofing materials, or infringing height-to-boundary requirements.

Main budget drivers

  • Structural considerations
  • Weatherproofing
  • Existing roof and joinery
  • Access

Read on to find out how much your loft conversion or second-storey addition may cost depending on the changes you are looking to make.

Structural considerations

Loft conversions and second-storey additions typically require structural and foundational adjustments, as the original house was not built to bear the extra weight of additional living space. In many cases, load-bearing steel or timber beams must be installed as well as underpinning to the existing flooring to reinforce the structure. Architects and engineers will need to come on board to ensure everything is properly constructed and, as you can imagine, these services come at a premium. Limiting the number of steel beams and using timber for strengthening where possible will help keep costs down. 


A costly and often overlooked aspect of building a second-storey addition is ensuring that the worksite is weatherproof. Removing the roof on your property exposes your home and its interior to the elements, so proper weatherproofing keeps your property and its contents safe and allows the crew to work uninterrupted.
Full scaffolding that can be covered in plastic shrink wrap is a good option that provides watertightness. While scaffolding rental is an additional expense (but essential for on-site health and safety requirements) it allows your project to remain on track and avoid weather-related delays that can be even more expensive in terms of time and money.

Existing roof and joinery

Consider the starting point and finished result of your project. Is your existing roof tall enough to accommodate a new living space? Does your vision of the finished loft include any new windows or skylights? Needing to address either of these factors will increase the final figure on the docket.
Generally speaking, the steeper your roof’s pitch, the more likely it is that your roof will accommodate a new living space. Not having to alter the roof itself will keep your costs down, as you will only need to install skylights or dormer windows into the pitch of the roof to provide natural light. For flat roofs and skyward additions, anticipate extra expenses. A contingency budget also helps if old leaks or rot are uncovered during the build.  


Access points may already exist if you’re simply converting your space; however, if you’re executing an addition, you’ll need to consider how you’re going to reach it and enter the space. Traditional stairwells are the easiest to build and install, so they’re the most cost-effective option. The layout of your home could impede a straight set of stairs so you may need to seek alternative options, such as a spiral staircase or a ladder.

Want to discuss the cost of levelling up your property?

Our 5-step process includes a thorough costing phase which assesses the scope of your project and a corresponding fixed quote. But first things first; to get started, get in touch with a local Renovation Consultant** and arrange a free no-obligation consultation.
*Costs are shown as an indicative guide of what previous projects have cost. The costs of renovating a home increase each year as material and labour costs rise. For an estimate/quote on your specific project, please consult your local Refresh Renovations specialist to find out more about our planning, design and build process.
**All Refresh Renovations franchises are independently owned and operated.

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All Refresh Renovations franchises are independently owned and operated.

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