When carbon fibre is the cheaper answer

A column that is 20% short on capacity has two answers. Demolish and rebuild it, or bond carbon fibre to what is already there. The first is understood by every contractor in the country. The second is faster, quieter, adds no dead load, and on most jobs is cheaper — but only once you count the things nobody puts in the bill of quantities.

Rebuilding a column means propping the floors above it, cutting out sound concrete, exposing the reinforcement, and pouring against an existing structure. It means the building is out of use for weeks. On a working factory that downtime is usually the largest number in the exercise, and it does not appear in the structural estimate at all.

Where the cost lines cross

CFRP is applied to the outside of the member. Preparation, primer, saturant, fabric, topcoat — millimetres of added thickness, no props for the fabric itself, and the space is back in use once the resin has cured.

• Downtime, priced honestly, is usually decisive — not the cost of materials
• Added dead load is effectively zero, which matters on transfer slabs and old foundations
• The bond is the whole system: preparation and workmanship carry the design, not the fabric

Where CFRP loses is against fire without protection, against very large capacity increases, and on a substrate too degraded to bond to. The honest answer on a chloride-contaminated column is repair first, strengthen second — which is why the repair trade sits next to the strengthening one.