Narrow properties in inner-city sites present a unique challenge when it comes to lateral stability. A building must be structurally stable without relying on any structures outside of the site boundary. The ability of a building to resist wind and earthquake loads that are applied horizontally comes from its lateral stability system. However, the challenge with narrow properties is that the simplest solution for this system is the use of return walls. These walls protrude into the space, making the property even narrower. This compromises the goal of taking full advantage of the property's width.
The original architectural vision for the Annandale House only included brick walls running the full length of the property along the boundaries, without any return walls protruding into the space. To provide lateral stability, a series of rigid, fully welded steel portal frames were initially proposed throughout the length of the building. This is a common solution to this challenge. And a design decision that closely aligns with the architectural requirements. But this is not the simplest solution. It is expensive, complicated and often architecturally challenging to incorporate: it disrupts the continuity of the brick walls. A simpler solution is return walls that protrude inside the space. But who wants this? It is making a narrow property even narrower.
So at the initial workshop for this project, I presented the idea of the portal frames. David’s response was one of shock. “Really?” he said.
“There are other options,” I said, “but I’m not sure you will like them?”
I jokingly threw around a few ideas, almost whimsically, knowing well that David would not bite at them. One option I offered was the idea of return walls cutting into the space. I never thought David would run with it. This was also part of a larger discussion, including the options about the construction materials generally. In particular, we were discussing the advantages and disadvantages of a timber framed building and concrete framed building. There was a potential move away from the timber solution and move to concrete. With the the additional challenges of using brick for stability, blockwork become an obvious contender to present as an option for these stability walls.
But with the move to concrete, David was making another connection that I didn't initially pick up on. The combination of block and off-form concrete seemed like the perfect partnership. I could see the architectural connections formulating in his head as we discussed it further.
Blockwork used for lateral stability and presented as an architectural feature.
Of course, we had no idea at the time that all of these seemingly tiny decisions would end up culminating into an award winning project.
The initial architectural brief with no return walls in the space. The intial solution consisting of a series of structure steel portal frames, maintaining the original architectural vision. The final solution with a series of reinforced blockwork return walls which became architectural features of the house.
Annandale House is a multi-award winning project that showcases the harmony between structural engineering and architecture. The narrow, original weatherboard cottage has been retained and restored, and the new extension features a concrete structure with minimal cladding, allowing the materials and structure to be the architecture. The house features an indoor/outdoor space, a green roof garden, and a small living area defined by reinforced block walls that provide lateral stability. The collaborative approach between architect and structural engineer led to a successful project that won the top residential architectural prize in NSW, the Hugh And Eva Buhrich Award For Residential Architecture.
