Steel and timber framing
What they share
Section titled “What they share”Both are framed technologies: a relatively sparse load-bearing frame, insulation between the members, linings inside and out. The logic of the build-up, vapour control, the service cavity and acoustics are similar too.
So much of the building physics described in this knowledge base applies to both.
Where steel is stronger
Section titled “Where steel is stronger”Dimensional stability
Section titled “Dimensional stability”It does not take up moisture, does not swell, warp or shrink. Dimensional stability.
Non-combustible material
Section titled “Non-combustible material”Steel does not contribute to the fire. Even so the structure’s fire resistance has to be verified, because the thin section heats up quickly.
Accuracy and repeatability
Section titled “Accuracy and repeatability”Machine production gives millimetre accuracy and identical quality in series.
Biological attack
Section titled “Biological attack”It does not rot, insects do not eat it, and the material itself does not go mouldy.
Material cycle
Section titled “Material cycle”Steel is recyclable to a high degree, and the structure is screwed, therefore demountable.
Where timber is stronger
Section titled “Where timber is stronger”Thermal conductivity
Section titled “Thermal conductivity”Timber conducts heat orders of magnitude worse, so the thermal bridge from the frame is far smaller. With steel this has to be compensated by detailing. Thermal bridging in steel.
Renewable raw material
Section titled “Renewable raw material”The origin of the material and the embodied carbon question favour timber, if the source is sustainable.
Working by hand
Section titled “Working by hand”On a smaller project, with a simpler tool set, shaping timber on site is easier.
Where the difference is to be managed, not claimed as an advantage
Section titled “Where the difference is to be managed, not claimed as an advantage”Steel does not burn but loses strength when hot. Timber burns but the charring layer protects its core, and its design accounts for this. Both have to be calculated for fire — just by different logic.
Moisture
Section titled “Moisture”Timber is damaged when wet, steel corrodes. For both, the answer is a dry structure, not the choice of material.
When to choose which
Section titled “When to choose which”It depends on the project: span, number of storeys, fire requirements, manufacturing background, local labour and client preference all play a part. Vertical extensions and structures needing high accuracy in series are typically steel’s ground.
The point
Section titled “The point”The question is not which material is better, but whose weakness we can manage better on this project. Both technologies are good designed well and bad designed badly.