Think of a good kitchen knife. The blade is hard steel because it needs to hold an edge. The handle is timber because it needs to be comfortable and grippy. Nobody argues the whole knife should be steel. Buildings work the same way: each material does the job it's best at.
Yet timber projects often get framed as all or nothing. "Can we do it in CLT?" is the question we hear most. The more useful question is "where does timber earn its place in this building?"
Five hybrids that work
1. CLT floors on timber frame walls. The floor is the hardest-working element in a mid-rise building: it spans, it carries people, it separates fire compartments and it has to stop footsteps being heard below. CLT is very good at all of that. Walls, on the other hand, mostly carry load straight down, and timber studs do that with a fraction of the timber. Put them together and you get a solid, quiet floor on an efficient wall. It's often the simplest fire compliance pathway too, because the CLT floor protects the walls below.
2. Glulam frame with CLT floors. The classic office combination. Glulam columns and beams carry the load to a few points, and CLT spans between the beams. It gives open, flexible floors and lets the structure be the ceiling finish.
3. Timber over a concrete podium. Ground floors carry car parks, retail, plant rooms and wet areas, and they're the floors that get wet during construction. Concrete makes sense there. Above the podium, where the plan repeats, timber takes over. This is the most common hybrid in Australia, and for good reason.
4. Concrete or steel cores with timber everywhere else. Lift and stair cores are sometimes kept in concrete for stability, lift supplier requirements or fire strategy. It works well, with one condition: timber moves with moisture and concrete doesn't. The connections between them need to allow for that movement, floor by floor.
5. Timber-concrete composite floors. A thin concrete topping bonded to timber beams or panels. The concrete adds mass for acoustics and stiffness for vibration, and the timber does the spanning. It's heavier and slower than a dry timber floor, but it can unlock longer spans.
Where hybrids go wrong
Mixing materials isn't free. Every interface between systems is a place where things can go wrong, and the problems are almost always in the gaps between trades:
- Movement. Timber shrinks across the grain as it dries. Over six storeys of timber frame, that can add up to tens of millimetres if it isn't detailed for. Concrete cores, lift rails, risers and façades fixed to the concrete don't move with it. Plan for it on day one.
- Fire and acoustic details. Each system has its own tested details. Where two systems meet, the detail often has to be engineered, not looked up.
- Procurement. Two suppliers means two sets of shop drawings, two programs and a builder who has to coordinate them. Someone needs to own the interface.
- Tolerances. Steel is built to millimetres, concrete to a centimetre or two, timber somewhere in between. Connections have to absorb the difference.
None of these are deal-breakers. They just need to be designed rather than discovered on site.
Why suppliers rarely propose hybrids
Ask a CLT supplier for a concept and you'll get a CLT building. Ask a frame fabricator and you'll get a framed building. That's not bad faith. It's what they make. The hybrid that suits your building is often split across two or three suppliers, and nobody in that chain is paid to suggest it.
That's exactly the gap we set up Timber Concept to fill. We have no product to sell, so the question is only ever what works best for the building.
A practical starting point
When we look at a new project, we sort each part of the building by the job it does:
| Element | Main job | Often best in |
|---|---|---|
| Floors | Span, separate, stay quiet | CLT, cassettes or composite |
| Loadbearing walls | Carry load down | Timber frame or CLT |
| Long spans and open areas | Span far, stay shallow | Glulam beams |
| Ground floor and wet areas | Resist water and wear | Concrete |
| Cores | Stability, lifts, fire | CLT or concrete |
Then we check the supply chain can actually deliver that mix where the building is. If it can, a hybrid is usually the best-value timber building you can get.
Got a project that doesn't fit one system? Send it through and we'll show you which mix makes sense.