Conversations With an Architect: Concrete vs Timber Upper Floors, Which is Better for Luxury Homes?
Updated: 5 minutes ago
In this week’s “Conversations with an Architect”, we chose to discuss a subject that comes up often when designing homes for our clients: the choice between concrete and structural timber for upper floors. Because the choice affects construction timelines, comfort, and a home's character, I asked Mel Gawi to explain his preference and why comparing the two should go beyond price.
Many people assume timber is both cheaper and faster than concrete. Is this correct?
“No. For a simple rectangular floor with standard spans, timber may be quick and economical, but when constructing a large mansion, the choice between the two needs a different assessment altogether.” He then elaborates, “There are many things that add complexity to the project: long spans, openings, multiple bathrooms and wet areas, changes in level and finishes. When selecting timber, it can often add to labour time because it needs to be coordinated and installed properly. Other factors add to the cost, such as supporting beams, connection details, acoustic treatment, and wet-area finishes. These include joists and flooring sheets, for instance. All this adds to time. Having said that, timber can perform well, but the savings it offers should be clearly demonstrated; don’t assume they will, as they depend on the variables.”
You mentioned that a larger home needs a different assessment. Do you favour concrete in larger homes?
“What I value is the solidity underfoot, the stiffness, and sense of permanence. Choosing concrete can also provide a good base for larger tiles or stone, often used in substantial high-end bathrooms. The mass in concrete helps with the airborne sound reduction. Footsteps and other impact noise still need underlays and appropriate finishes and ceiling details to manage how the noise travels, but regardless of which option you choose, timber or concrete, neither delivers good acoustics unless you consider the whole assembly. These qualities are part of the experience that the clients we design homes for are paying for.”
How much should the scale and budget influence the decision?
“I’d encourage each client to ask themselves if they want a comfortable everyday home, or a mansion with a different level of finish that offers solidity and presence. Everyone who has stepped into a home with concrete floors will feel the difference in how it feels – the sound and the solidity. For example, a Ferrari and an everyday car both provide transport, but the experience and investment differ. Another example: a $2,000 stove and a $350,000 cooking range both cook the same meal, but their appearance, craftsmanship, and experience differ. Likewise, a $50 speaker and one costing $5,000 or more both play the same music, but it’s what you value that helps determine what you invest. When people say “you get what you pay for,” there’s truth in that; however, spending more doesn't automatically mean better quality. I’d put things into context and look at the overall cost. If the construction cost is $10 million and a concrete upper floor adds $200,000, that is 2% of the budget. I’d say, if it delivers the feel and performance you want, consider that a modest investment. These figures I’ve thrown in here are illustrative, as the actual difference needs to be priced accurately per project. The important question is not simply what the concrete floor costs, but what additional cost it represents over a fully compliant timber alternative, and what the client receives in return.”
In terms of the overall construction, where would you prioritise spending?
“In the parts that are difficult to replace. I would not reduce the quality of the structure to spend more on technology. You can upgrade things like speakers, appliances, and control systems, but replacing an upper floor is a major structural undertaking. So, I’d say get the bones of the home right first, then choose technology to suit the budget. Concrete is an integral part, as it is a structural element. I’d prioritise getting the structural elements right.”
How about external walls – would you prioritise them in the same way?
“Yes. Wherever practical, I prefer brick external walls, and I would avoid foam-based cladding and fibre-cement sheets. I always lean towards solid construction because I value its feel and durability, but this is a preference. I’m not saying that all lightweight cladding cannot perform well, because it can. What I’m saying is that any wall system still needs proper design and installation.”
I’ve heard a lot about Bondek lately. How do conventional suspended concrete and Bondek compare?
“So, a conventional suspended slab uses temporary formwork, and the slab, beams and reinforcement are designed by the engineer as a whole. Bondek uses profiled steel decking as permanent formwork and becomes part of the slab as the slab’s structural system. It can reduce formwork and reinforcement requirements, but the complete floor is not automatically cheaper once you include the decking, concrete, reinforcement, propping, and supporting structure. Where structural steel is used, fabrication, connections, cranes and installation can significantly add to the cost. With conventional concrete, more of the expenditure may sit in formwork, reinforcement, and concrete beams. With Bondek, costs shift to decking and steelwork. I’d recommend always comparing the totals.”
To get an accurate estimate of cost, what should a proper cost comparison include?
“First of all, price the same design, finishes and performance requirements across all options. Make sure to include everything. If you want the price for conventional concrete, make sure to include the formwork, propping, reinforcement, the concrete pumping, all labour and supports. For Bondek option, include all the concrete associated with decking, reinforcement, supports and installation. When comparing timber prices, always check that the price includes framing, beams, connections, flooring, acoustics, wet-area construction, and preparation for finishes. I’d be cautious with industry square-metre rates. They can serve as an early guide; however, inclusions and exclusions matter a lot. For a complex mansion, they serve as a guide only, but you need project-specific quotations that cover all the inclusions I mentioned.”
Have you noticed any commonly overlooked methods that can add to the cost?
“Yes. Wet areas. As an example, you can’t allow for standard Yellow Tongue throughout and assume the bathrooms are resolved. Wherever compressed fibre-cement flooring is specified, make sure that you include its material cost, handling, supports, and installation cost. Those sheets are not cheap. The substrate, waterproofing, falls and finishes must work together. Another thing to remember is that concrete needs appropriate waterproofing, as its stiffness does not eliminate cracks or the need to detail junctions and penetrations.”
Have you seen anticipated timber savings disappear?
“Oh yes. I recently asked a builder who had recommended timber floor structure against my recommendation for concrete, “Was it worth going with timber?” I wasn’t surprised when he whispered in my ear, “It was almost cost neutral.” The builder explained that the timber floor had taken longer to complete, and by the time the subfloor was upgraded throughout to Hebel panels, the overall cost was almost the same as concrete. And we all know that time is money. Additional labour, site overheads, and delays before the next trade starts can turn a saving into a cost instead. In this instance, the client ultimately received a different floor system with little cost difference and a longer construction time and replacing it with concrete later would be a major structural undertaking. Having that experience only reinforced my view. Early on, I’d ask if the savings are worthwhile before changing the structure.”
What has your experience been with construction speed using the different methods?
“On a recent large mansion project, we completed three levels of concrete floors within seven months. Given its size and complexity, I consider that extremely fast! In my view, reaching the same stage in timber would not necessarily have been any quicker, particularly at the standard we wanted. That is my assessment of that particular project, not saying that concrete is the solution every single time. Sometimes timber prefabrication can be fast, and Bondek can speed up parts of the formwork process. Conventional concrete requires formwork, reinforcement, inspections, pouring and then appropriate curing and support periods. So in summary, the whole programme matters, including when the floor is ready for the trades that follow.”
Can using concrete benefit the construction programme? I’m thinking about the project timeline, assuming it can allow multiple trades to work together.
“Well, on a recent project, a suspended concrete floor remained exposed to the weather, yet we found the basement below stayed dry. We had used a Xypex admixture in a substantial portion of the slab to improve resistance to water penetration, and it allowed us to proceed with basement fit-off before the upper levels were enclosed. With timber, I would have expected additional weather protection before confidently progressing that work, so yes, it can. It was, again, our experience on that project, not saying that it’s a norm, as joints, cracks, penetrations and openings still need attention, and conditions must be checked before moisture-sensitive finishes are installed and so forth. But progressing downstairs while work continues above can benefit the programme, for sure.”
What role do workmanship and inspections play?
“A major one. Hugely important. Every system needs coordinated drawings, competent trades and appropriate inspections. Concrete reinforcement and embedded items must be ready before pouring. Timber framing, connections and bracing must match the engineering. There’s a lot to coordinate, check, and review. Rectification costs time regardless of material. In terms of competent trades, Australia also benefits from tradespeople bringing experience from Europe and other regions with strong concrete and masonry traditions. Skilled formworkers, steel fixers and concreters expand what we can achieve on complex homes. Ultimately, the quality reflects training, experience, care and supervision.”
What about fire safety and concrete?
“Concrete is non-combustible, but fire performance depends on the complete construction. I mean the supports, reinforcement cover, connections and penetrations. But timber systems can also meet the requirements. No floor should simply be called “fireproof.” Because concrete is heavier, it needs suitable foundations and supports. Services and openings require early coordination because changes after pouring can be very expensive. Access, pumping, cranage, propping and curing also affect the programme. “
When would you choose timber?
“Where it suits the project. It could be for a lightweight addition, due to particular access constraints, in a straightforward layout, or a properly priced design that meets the client’s expectations with a meaningful saving. I’d say my preference for concrete doesn’t replace a fair evaluation of both systems, as they both have their pros and cons.”
Say a builder recommends timber as a construction method; what important questions should the clients ask?
“I’d ask how many mansions or homes of comparable scale or complexity to the one they’re pricing have they built? Why is timber better for this design? What is the complete saving? The effect on the timeline, these sorts of questions? I would also request a comparison covering engineering, supports, acoustics, wet areas, finishes and programme, including any changes to floor depth, ceiling heights or services. A builder’s experience is valuable, but do not follow the recommendation blindly. I’d ask for the reasoning and figures, then decide with your architect and structural engineer.”
What’s your approach to design when you think about durability and construction methods?
“I like to think we are designing homes that could stand for more than 500 years, serving many generations. It's become our motto, and although it’s something we strive towards, not a guarantee, it changes how you approach a building; it makes you think beyond the first owner. That’s also where structure, materials, workmanship, and the ability to maintain the home become important. How can it adapt to future changes, and so on? These considerations strongly influence the construction methods you choose and how you build the house. No home lasts for centuries without care, but if you begin with durability in mind, you make different decisions about where to invest and where to save. For me, good architecture should give future generations something worth keeping, looking after, and making their own.”
Any final advice?
“It would be to be clear about your budget and the home you want to experience. I’d compare total costs, construction time and long-term performance. My views are shaped by recent, hands-on construction experience, seeing what things actually cost, how long they take and how they perform on site. We bring that practical knowledge to our clients as added value alongside our architectural design services, helping them assess proposed savings and understand the consequences of their decisions. Always ask what you actually save, and if that saving will give you the home you set out to build.”
Mel Gawi is the Principal Architect and Manager of Architeria Architects, designing quality homes with longevity and timelessness as its trademark.
Interior Design Director
Comments