UK · Updated 2026 · Explainer

Part Z Embodied Carbon Explained for UK Builders

Part Z is the proposed amendment to UK Building Regs mandating whole-life carbon assessments on major projects. Whether or not it becomes statutory in 2027, most tier-1 contractors already require the reporting. Reclaimed materials are the single biggest lever.

What Part Z actually mandates

  • Whole-life carbon assessment (A1–C4)
  • Reporting against RICS PS 1st Ed. methodology
  • Embodied carbon limits set by building type
  • Sequestration accounting for bio-based and reclaimed materials

Why reclaimed materials matter

Reclaimed brick carries 5% of the embodied carbon of new brick. Reclaimed steel: 4%. Reclaimed timber: 10%. A single tonne of reclaimed brick in a wall saves 90kg CO₂e vs new.

Frequently asked questions

+Is Part Z law yet?

Not as of April 2026. It's a coalition-led amendment with strong industry backing, expected to become mandatory in 2027 or 2028.

+How do I evidence reclaimed content?

Keep the SurplusBuilder receipt and the seller's source description. Most auditors accept this as evidence of A1–A3 avoidance.

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