A timber member cannot be selected by matching the outside dimensions or an invented “equivalent capacity” of a steel beam. Earlier numeric equivalence, span and carbon tables on this page have been removed because they lacked a documented comparison basis.
Compare the same function
Give the designer the same opening, loading, support conditions and movement requirements for each option. Ask how the proposal affects structural depth, connections, fire protection, moisture exposure and construction access. A material-only comparison misses these parts of the installed design.
Engineered timber products require their own manufacturer data and design assumptions. Our UB dataset and steel deflection tools cannot analyse them by substituting a new section name. For broader technical context, see SCI P449 on steel-timber hybrid construction; it is not a domestic substitution table.
Compare cost and environmental evidence
Obtain quotes for the complete installed scope. For environmental comparisons, identify the actual products, quantities and life-cycle boundaries in their declarations. Do not treat a generic emissions factor or a claim that one material is always greener as a project assessment.
Document the final design and its supporting evidence before ordering. Changes between timber, steel or a hybrid arrangement require the designer’s review and the applicable approvals.
Structural work must be designed by a chartered structural engineer and receive the applicable Building Control approval. This article is educational and has not received an independent engineering review.