What a 60-unit scheme now carries before a single brick is laid

Statutory and planning costs have been accumulating one at a time, each announced separately and each absorbed separately. Added together they are no longer a line in the appraisal. They are a category.

Count what a mid-sized residential scheme is now expected to carry before construction begins. Community Infrastructure Levy where it is charged. Section 106 obligations. Biodiversity net gain. And from 1 October, the Building Safety Levy. Each was introduced on its own terms and each is usually appraised on its own terms.

The stack

• CIL. Charged per square metre at rates set by the charging authority, with wide variation and its own reliefs and instalment policies.

• Section 106. Scheme specific and negotiated, so it resists benchmarking, but it is rarely the smallest item on the list.

• Biodiversity net gain. Off-site units, on-site works, and thirty years of management and monitoring. Three costs in different places in the appraisal.

• Building Safety Levy. Chargeable floorspace multiplied by a published local rate, halved on previously developed land. On a 5,000 square metre scheme in Wiltshire, around £158,000.

Only one of those four is a construction cost. The others are land and appraisal costs, which is precisely why they end up misplaced, and a misplaced cost in a residual appraisal does not just sit in the wrong row. It changes the answer.

We do not negotiate section 106, administer CIL or buy biodiversity units. That work sits with the project manager or the planning consultant. What we do is make sure each of the four lands in the appraisal on the right basis, in the right row, and at the point in the cashflow where it is actually paid. That is where they are most often got wrong.

Why a single percentage will not do

The tempting shortcut is to carry the lot as a percentage of build cost. It fails for a simple reason: none of the four is driven by build cost. CIL and the levy are driven by floorspace. Net gain is driven by site area and habitat. Section 106 is driven by what the authority asked for. A percentage of construction cost is a proxy for none of them, and it will be wrong by a different amount on every scheme.

It also hides the sensitivities. A change in the previously developed land position halves the levy. A change in the habitat baseline moves net gain materially. Neither of those is visible once everything has been rolled into one number.

How we set it out

Four lines, each with its own basis stated, each placed at the point in the cashflow where it is actually paid. CIL on its instalment policy, section 106 on its trigger points, net gain split between the build cost and the appraisal, the levy before the final certificate.

It takes longer than a percentage. It is also the only version a funder can interrogate, which tends to matter at exactly the moment you need it to.

What this means for your scheme

• Four separate lines, four separate bases. Not one allowance.

• None of the four is driven by build cost, so a percentage of build cost will be wrong.

• Place each at its real payment point. Front-loading them distorts the facility requirement.

• Test the two that move most: previously developed land status and the habitat baseline.

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Sources. Building Safety Levy regulations and published local authority rates. Biodiversity gain condition amendments, August 2026. CIL and section 106 positions vary by authority and should be confirmed locally.