Seaforth House | JLA

A few days after moving into his home, I asked Michael if he was happy with the choice to use a structural steel frame. After all, all nine of the other engineers told him to use concrete. His response was blunt. “If I had used concrete, I would still be building. In fact, I would probably only be up to level 3. That decision saved me at least 18 months of rent, and that is just the start of my cost savings.”

I didn’t know it when we started the structural engineering for this single residence house in Seaforth, but the client, Michael, had discussed the project with nine other engineers before he engaged us. Apparently all nine had suggested the building be constructed using concrete.

All nine engineers suggested the building be constructed using concrete.

The first question he asked us during our first conversation was “how would you suggest we build it?” And my response was simple. I didn’t know, yet. Most clients expect me to instantly know the best way to build a building. After all, I'm an expert. But I have learned by experience that instantly knowing a structural solution is rare. And if I do think I know the solution, I now know it is almost certainly based on my own personal bias. And bias is not what you want or need here. Clients often get annoyed when I suggest a “discovery stage” to a project. In frustration, I had one client even burst out, “Why do we need to explore options, just do what is right!” But Michael didn't see it this way. He was curious.

“Why wouldn’t you use concrete?” he asked.

“That is definitely an option,” I said, “but that is not the only option. Why don’t we have a quick review of other options and see if there is anything better?”

Through the course of a few conversations over a couple of days, I started to develop the complex layers of narrative around Michael, his family requirements, his ideal solution, the project itself and what success looked like to him. Through this discovery process, there was perhaps one key element that got me thinking differently - and moving away from concrete. Michael was going to be owner-builder, and he wasn’t an experienced builder.

Having been on a construction site hammering pieces of timbers together, I knew that one of the most challenging and time consuming parts to a build is the laborious, time consuming and risky task of simply setting out the building. I know how important it was to do correctly, and how devastating it can be if you get it wrong. With timber stick framing, you are essentially setting out the building with every stud, joist and rafter you install. Every piece of structure requires a measurement, based on the setout of the building. And I will never forget: measure twice, cut once. Every time. Concrete is similar: every piece of formwork, requires a measurement that defines the setout of the building. Measure twice, cut once.

I identified a key matrix for success: we needed to sort out the complex process of the building setout. Prefab was the obvious answer.

I said to Michael, what we want is the setout to be done by someone else. We essential want to prefabricate, off site, as much as we can. Then when you are on site, doing all the other parts of the build, you don’t have to worry about the setout. The prefabrication was done off site, on a computer, and then in a factory. We explored a few options for prefabrication including precast concrete, prefabricated timber and CLT. Due to limited site constraints and balancing risk, we chose steel.

Architectural Typologies

Seaforth House was a steel framed single residence house on a property that was torrens title. It was going to be built by an inexperienced owner builder. What is very unusual about Seaforth House, is that it is essentially eight storeys high. In this way it is an usual architectural typology. I knew this. It is why I knew the discovery stage of the project was essential for defining the success matrix. Importantly, Michael was also onboard with the importance of this exploration.

Architectural-Structural Pairs

Building types can be divided into architectural typologies. There are numerous architectural typologies, but there are three special architectural typologies. What is special about these three is that they have standard matching structural solutions. I call them the architectural-structural pairs. What is more, these pairings are universal seen across the globe.

The first architectural typology that has a matching structural solution is the timber stick framed house. The timber stick framed house is a prevalent architectural typology characterized by a structural framework constructed from wooden vertical members called studs and horizontal members. It is widely used in residential construction across the globe.

The second architectural typology that has a matching structural solution is a single-level warehouse which is a specific building form generally designed for industrial or commercial purposes. It is characterized by a structural system primarily constructed using steel members and is typically utilized for storage, distribution, manufacturing, or logistical operations. Again, this solution is widely used across the globe.

The third architectural typology that has a matching structural solution is a concrete framed high-rise building which traditionally refers to a building form that utilizes concrete as the primary structural material as the vertical and lateral support elements and the floor plates.

So there we have it, three architectural typologies with matching structural solutions. The architectural-structural pairs.

Surprising Global Adoption

As I mentioned, these three is that the matching structural solutions are almost universal in their adoption. Almost anywhere in the world you will find these architectural-structural pairings. How can that be? It is surprising, even bizarre.

I find it surprising for two reasons. Despite different regions, climates, supply chains, local skills, histories, politics, education systems and cultures, these pairings are common. I also find it surprising because, when you look through the lens of the success of a project, these pairings often don’t necessarily make sense in todays world. These pairs exist simply from legacy. A legacy when materials were expensive and labour was not. And a legacy based on a deep history, including education and training programs that are engrained in our thinking and our doing.

Seaforth House is a great example of this. Despite being a residence, which is usually one or two storeys and might fall into that architectural-structural pairing of a timber framed building, it is an eight storey building. And how is an eight storey building traditionally constructed - anywhere in the world? The architectural-structural pair of the high rise building - a concrete frame.

Success

The reality is that Michael could have constructed his house in concrete. And when he moved in, he would quite reasonably would have rated it as a success. After all, he had nine professionals, expert advisors, telling him that is how he should build it. It was only because we did something different, something better, that he actually has a way to compare.

Michael could have constructed his house in concrete, and when it was complete, he probably would have rated it a success. After all, he had nine expert advisors recommending it.

This is what is so unusual about the construction industry. Each building is only built once. As many have said before me, every building is a prototype. It is almost always impossible to do a realistic comparison of two different methods of construction. And when the method you chose, particularly if it an architectural-structural pair doesn’t pan out the way you expect, you justify it by saying that the unexpected is normal. And surprisingly, some unpredictable event happens on most projects. The unexpected is is to be expected. We stick to what we know, despite knowing there are faults, because we justify our decision by simply saying that any other way of doing it would be worse, even when we don’t know. We are balancing risk, and what we know is perceived as less risky, even when it goes off the rails.

I am going to talk about what we need to do when a building doesn't fit into these known pairs, but before I do that I am going to explore the idea that we may need to think again about these pairs.

Think Again

Just because a building may fall into a standard architectural-structural pair, does not mean that the structural solution has to be predetermined. I am simply saying that these are standard solutions. This gives us a place to start. Deviations from this pairing is common and often preferred. Seaforth House is exactly this deviation. We focused on the success matrix, not the standard pairing.

What the standard pairing does is allow you to skip the discovery stage of the project, and jump straight to the execution stage. This can be done when the team doesn't consider it appropriate to deviate from the architectural-structural pairing, or the team isn't skilled in going through the discovery process.

Beyond the Architectural-Structural Pairs

I want you to turn your mind now to other architectural typologies that exist. There are lots of them. For each of these typologies, determine if there are matching structural solutions that exist for these typologies. In other words, where there is a standard structural solution that is used on greater than, say, 90% of all these buildings globally. Can you think of any? I have struggled to find any.

Let's focus on one missing pairing in particular. In Australia we call it the three storey walk-up. It is primarily a residential development, but may also be a mixed use development that might consist of car parking, perhaps some commercial space on the ground level and then multiple units on the upper two levels. It is part of the "missing middle" in residential development. We are having trouble building them fast enough, and economically, to keep up with demand.

We are struggling to find an architectural-structural pairing for the multiple architectural typologies used for medium density multiunit residential development. Without this pairing we will struggle to meet our global housing needs.

A few decades ago, it was common for these to be constructed using hand over hand brickwork and suspended concrete slabs, but this form of construction is generally being abandoned. With labour being expensive, it no longer makes any economic sense to build like this. With advancements in earthquake prediction, brick is rarely being used as a structural material. With changing fire regulations, certain materials are challenging to use. Timber could be seen as a viable option, but with different fire regulations around the world, there is no universally accepted timber alternative. So, at the moment we do not see a universally adopted alternative form of construction.

(There are many other architectural typologies that we could discuss but I want to make a special mention to my favourite. That is the humble car port. It is my favourite to talk about because it is my least favourite. Surprisingly we engineer car ports all the time. The reason it is my least favourite is because it does not fit into an architectural-structural pair, but tell that to an architect, and you will get a blank stare. Surely it is simple. Surely it is just a timber framed structure. Well it isn’t. Can you guess why? I will save that discussion for another time.)

What do we do when an architectural solution doesn't fall into an architectural-structural pairing or when we want to explore something different? The team must undertake a process of discovery. A process that determines what the structural solution will be. I save that discussion for another time.

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