Steel or timber: choosing the right beam

What decides it

Span, load, available depth and access. A short span under modest load is often perfectly served by timber. A long span under a masonry wall almost always needs steel. The choice is an engineering outcome, not a preference.

Where steel wins

Steel carries more load in less depth. Where headroom is tight, where the span is long, or where a wall above is being carried, steel usually becomes the only sensible answer. A universal beam of modest depth can carry what would need an impractically deep timber section.

Where timber is the better answer

Shorter spans, lighter loads, and situations where getting a steel beam into the building is genuinely difficult. Timber is easier to handle, easier to fix to, and does not need the same attention to bearing detail or corrosion protection.

Flitch beams sit in between

A flitch beam sandwiches a steel plate between timber members, giving more capacity than timber alone while remaining easier to handle and fix to than a steel section. It is a useful answer for awkward access.

What people underestimate

The bearing. A beam is only as good as what it lands on. Padstones spread the concentrated load into the masonry below, and an undersized padstone crushes the wall regardless of how well the beam itself was calculated. This is one of the commonest omissions we see in previously altered properties.

Deflection, not just strength

A beam can be strong enough and still deflect enough to crack the finishes above it. Deflection limits are usually what governs the size on domestic work, particularly under masonry.