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Renovation of thermal elements

You need to apply for¬†Building Regulations before you start any work on renovation of a thermal element.

What is a thermal element?

A thermal element is something that separates a heated or air-conditioned space from the outside. This could be a wall, floor or roof (but doesn't include windows, doors or roof-lights).

If 25% or more of a thermal element is being replaced or renovated, you will be expected to improve the thermal performance of that element.  This will usually be achieved by adding insulation.

Examples of the renovation of a thermal element.

  • Renewal of pitched or flat roof coverings - e.g. re-tiling, re-slating of pitched roofs or replacing of flat roofs.
  • Renewal or replacement of ceilings under a roof space or flat roof (with or without the renewal of the supporting structure).
  • Renewal of cladding to external walls or dormer cheeks.
  • Renewal of a finish or cladding to an external wall area or elevation (render or other cladding) or applying a finish or cladding for the first time.
  • Renewal of internal wall finishes to an external wall (excluding decoration) or where you are applying a finish for the first time e.g. re-plastering or dry lining of walls.
  • Renovation or replacement of a solid or suspended floor, involving the replacement of screed or a timber floor deck.

If you need help or advice please contact Powys Building Control using the contact details on this page.

Your local builders' merchant may also be able to give you advice on the most economical solutions.

If you don't have your work authorised by Building Control, this may cause problems when the property is sold. In some cases, it could lead to prosecution.



  • Email:
  • Phone: 01874 612290
  • Address: 
    • Brecon Office - Neuadd Brycheiniog, Cambrian Way, Brecon, Powys, LD3 7HR
    • Llandrindod Wells Office - County Hall Llandrindod Wells LD1 5LG
    • Welshpool Office - Neuadd Maldwyn, Severn Rd, Welshpool SY21 7AS
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