Blending Modern Design with an Existing Home: Two-Storey Addition with PIR Panels and Solar Integration
- ziliamagdeeva
- Sep 4
- 2 min read
Updated: Sep 10
Adding a new structure on top of an existing home is never straightforward. This architecturally designed project involved the construction of a new two-storey addition over part of the existing dwelling. The result is a striking contrast between the modern new form and the character of the original house.
When you add a new storey above an existing
home, the challenge isn’t just structural, it’s about finding the right approach: how to add strength without unnecessary complexity.
Do you weigh down the old structure and risk major strengthening work, or do you find a smarter way forward?
The Structural Challenge
The key question from the outset was clear:
How do you safely support a two-storey structure without relying on old foundations?
The main challenge with this project from a structural perspective was building over the part of the existing house without the need for significant strengthening of the existing structure. Building above an existing home often means strengthening walls, floors, and foundations - costly work that can snowball quickly.
At the same time, the site presented additional engineering considerations:
Wind: Very high wind zone, requiring careful bracing and robust connections
Earthquake: Rock at shallow depths, but still a seismic design case to meet NZ standards
Load demands: Ensuring beams, joists, and bracing met both gravity and lateral force requirements
Our Approach
Working alongside Tennent Brown Architects, we developed structural solutions that supported the architectural intent without overloading the existing structure. The addition was designed to avoid loading the existing foundations, with new supports bypassing the existing wall framing and carrying the load directly down to new piles.
Structural Model
Architectural Model
Real
Key elements of the design included:
New foundation piles and bearers aligned with the architectural layout, designed to resist both vertical and lateral loads
Targeted bracing: new linings and anchor piles added only where required to meet seismic and wind demand
Efficient midfloor design: beams and joists checked for vibration, serviceability, and ultimate limit states
Careful integration of the existing roof connections with the new framing, ensuring seamless structural performance
This philosophy kept the design light on the old, strong on the new.
Structural Model
Architectural Model
Real
Using PIR panels on the roof
Another interesting aspect of this project was the use of PIR roof panels, which is becoming increasingly common to achieve the new insulation requirements. These panels were supporting solar panels, so we had to design the fixings of the panels to ensure their structural adequacy.
The Result: Old Meets New
The finished project showcases how smart structural design can bring ambitious architectural concepts to life without compromising safety or efficiency. The contrast between old and new creates a distinctive home that is both functional and future-ready.
Structural Model
Architectural Model
Real
Key Takeaway:
With the right approach, it’s possible to add bold new spaces above existing homes, without the heavy cost of reworking foundations.
Modern design needs modern engineering.
Whether it’s solar-ready roofs, high-performance insulation, or ambitious new additions, our team can help you achieve your vision with confidence. At DTCE, we specialise in creating structural solutions that keep costs under control while delivering safe, future-ready homes.
Get in touch to see how we can help bring your next project to life.
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