Use Welsh approved documents and the relevant building control authority. Planning use, HMO licensing and building regulations are separate checks. The new Welsh building control regime has transitional arrangements from 1 July 2026.
Describe the proposed work accurately
Give building control a clear scope, floor plan and intended use. The approval route can depend on the building and the type of alteration.
- Identify structural work, fire precautions, drainage, insulation, ventilation and any conversion into separate homes. A project described only as refurbishment may conceal controlled work.
- Check planning permission, conservation or listed-building constraints separately. A planning decision does not approve the building-regulations detail.
- Establish the applicable Welsh building control regime and transitional position, including the changes beginning on 1 July 2026 where relevant.
Agree the route before starting
Confirm the application or notice, responsible people, information needed and inspection stages with the appropriate building control body.
- Keep drawings, specifications and structural calculations under version control. Give the contractor the approved or agreed version.
- Arrange inspections before work is covered up, including structural connections, drainage, insulation and fire stopping where relevant.
- Ask what approval is needed for a change during the work. Do not let a contractor replace a specified detail without checking its effect.
Obtain completion evidence
Practical completion and building control completion are different records.
- Keep inspection findings and resolve outstanding items. Obtain the relevant completion or final documentation and retain it with the property.
- Collect electrical, gas, fire and other specialist certificates appropriate to the work. Confirm they identify the correct dwelling and scope.
- If historic work lacks approval, discuss the available regularisation or other route with the council before describing it as compliant. Opening up or further work may be needed.
Example: a house is divided into flats
A fictional owner proposes two self-contained flats. Check planning, the material change of use, fire and sound separation, services and the Welsh building control route before work. A new council-tax entry for each flat is not evidence of building-regulations approval.
What to do
- Describe the proposed use and physical work to building control.
- Check planning, licensing and any freeholder consent independently.
- Keep approved plans, inspection records and completion documents.
Evidence to keep
- Written approval and applicable regime
- Plans, inspections and completion evidence
Sources and guidance
- Converting a house into flats or bedsitsWelsh Government · checked 20 October 2026
- New building control regime: transitional arrangementsWelsh Government · checked 20 October 2026
- Building regulations circularsWelsh Government · checked 20 October 2026
Related guides
- Check asbestos before disturbing building materials
- Separate Welsh fire design from building safety duties
- Manage your responsibilities when commissioning works
- Check the address, occupation and proposed works with the council
- Distinguish current duties from future reform
- Check a loft before letting it as a bedroom