Mandatory SuDS approval in Wales

In Wales, you must obtain SuDS (Sustainable Drainage Systems) approval before starting construction if your development has a construction area of 100 square metres or more, or involves more than one dwelling. This is a legal requirement under Schedule 3 of the Flood and Water Management Act 2010, which has been commenced in Wales but not in England.

Starting construction without SuDS approval exposes you to SAB enforcement action, including temporary stop notices, stop notices and enforcement notices. Failing to comply with a notice is a criminal offence carrying an unlimited fine. This guide explains who needs approval, how to apply, and what to expect from the process.

When SuDS approval is needed

You need SuDS approval from your local authority's SuDS Approval Body (SAB) if either of the following applies:

• The construction area is 100 square metres or more
• The development involves more than one dwelling

This applies to all types of construction, not just housing. Commercial, industrial, and mixed-use developments are all within scope if they meet the threshold.

SuDS approval is separate from planning permission. You may need both. Even if your development has permitted development rights (and does not require a planning application), you still need SAB approval if it meets the threshold. You can submit a combined application to the local planning authority and SAB, or apply to the SAB separately.

What happens after approval

Once your SuDS system is built in accordance with the approved design, the SAB normally adopts it. This means the local authority takes on long-term responsibility for maintaining the drainage system. This is a significant benefit compared to private drainage, which would remain your responsibility indefinitely.

The adoption duty has exceptions: the SAB is not required to adopt a system that serves a single property or single curtilage (owned, managed and controlled by one person, or by persons together), or any part of a drainage system that is or becomes a publicly-maintained road. If your scheme falls within these exceptions, plan for private maintenance arrangements.

If you build your SuDS system but it does not match the approved design, the SAB may refuse to adopt it. You may also face enforcement action if the deviation is significant. A non-performance bond may be required as security to ensure the drainage system is completed as approved.

If your application is refused

You can appeal a SAB decision to Welsh Ministers under the Sustainable Drainage (Appeals) (Wales) Regulations 2018. You cannot begin construction while the appeal is pending — building without approval still exposes you to SAB stop and enforcement notices regardless of appeal status.