Choosing a timber system is a bit like choosing a car. A ute, a hatchback and a people mover will all get you to work. The right one depends on what you're carrying, how far you're going and what you can afford to run. Timber is the same. CLT, glulam and timber frame will all hold a building up. The question is which one suits your building.
Here's how we work through it on a typical 3 to 7 storey project.
Start with the plan, not the product
Before talking about any system, we look at three things on the architect's drawings:
- Repetition. Do the floors stack? Rooms that sit directly on top of each other mean walls can carry load straight down, with no transfers.
- Spans. How far apart are the walls or columns? Apartment and aged care plans often have walls 3.5 to 4.5 m apart. Offices and community spaces want 7 to 9 m of open floor.
- Height. Every extra storey adds load to the walls at the bottom, and more demand on fire and stability.
Those three answers narrow the field quickly.
Loadbearing CLT: stacked rooms, fast install
Cross-laminated timber walls and floors suit buildings with lots of repeating rooms: apartments, student housing, aged care, hotels. The walls between rooms do double duty as structure and as the fire and acoustic separation.
The upsides are speed and simplicity. Panels arrive cut to size, with openings already formed, and a small crew can stand up a floor in days. One supplier provides walls and floors, so there's less to coordinate.
The catch is timber volume. CLT walls use a lot of fibre, and on a 5-storey scheme we typically see 120 to 140 mm walls carrying the load comfortably. That's more timber than the walls strictly need at the top of the building, which is where cost creeps in.
Glulam post and beam: open floors
Glulam columns and beams with CLT or cassette floors suit offices, schools and community buildings, anywhere the plan needs to stay open. Timber goes only where the load is, so material efficiency is high, and internal walls can be lightweight partitions that move later.
The trade-offs are depth and coordination. Beams sit below the floor, which eats into ceiling height or pushes up the floor-to-floor. Services need to be planned around them from the start.
Timber frame: the underrated option
Timber frame is what most Australian houses are built from, and people forget it scales. The NCC has allowed timber buildings up to 25 m effective height (roughly eight storeys) under its deemed-to-satisfy provisions since 2016, and framed buildings at four and five storeys are common overseas.
At the lower levels of a mid-rise building, the studs work harder. On a recent 5-storey scheme we sized 170x45 LVL studs at 300 mm centres for the lower floors, stepping down to 150x45 at 400 centres higher up. That's still far less timber than a CLT wall. And framed walls are easier to prefabricate with insulation, windows and cladding already fitted.
The catch is the supply chain. Prefabricated frame at mid-rise scale needs a fabricator with the capacity and the engineering support to deliver it, and in some regions there's only one or two.
The quick filter
| If your building has… | Start by looking at |
|---|---|
| Repeating rooms, spans under about 5 m, 3–7 storeys | Loadbearing CLT, or timber frame walls with CLT floors |
| Open floors, spans 7–9 m | Glulam post and beam with CLT or cassette floors |
| 1–4 storeys, budget-driven, strong local frame supply | Prefabricated timber frame and cassettes |
| A mix of the above | A hybrid (see our note on mixing materials) |
The honest answer
Most buildings don't sit neatly in one row of that table. The ground floor is retail, the upper floors are apartments, and there's a lift core in the middle that someone wants in concrete. That's normal. It's also why we compare three to five systems on every concept rather than starting with one.
If you're weighing up systems for a project right now, send it to us. We'll tell you within 48 hours which ones are worth a proper look.