Steel vs timber frame

Both work; the right choice depends on span, cost, speed and site.

Steel handles long clear spans and heavy loads in slim sections - ideal for openings, portal frames, mezzanines and where you want maximum clear space.

Timber / oak / SIPs is fast to erect, warm, sustainable and well-suited to garden rooms, extensions and self-builds where spans are moderate.

Many projects use both - a steel frame or beam carrying a timber structure. I draw either, so the advice here is neutral: the engineer's design decides sizes; I detail whatever it calls for.