SiteKiln gives you plain-English information, not legal, planning, or engineering advice. If you're designing drainage for a project in Wales, you'll need a drainage engineer familiar with the Welsh National SuDS Standards.
# SAB and SuDS in Wales, The Extra Gate England Doesn't Have
You've basically got an extra approval to pass through in Wales before you dig, and it's all about how you deal with rainwater.
1. What SAB approval is and who needs it
Since 7 January 2019, Schedule 3 of the Flood and Water Management Act 2010 is fully commenced in Wales.
Every local authority in Wales now acts as a SuDS Approving Body (SAB).
The SAB must approve surface water drainage for certain new developments before construction starts. This is a separate approval from planning permission, you need both.
You normally need SAB approval if the work:
- Is a new development of more than 1 dwelling, or
- Has a construction area of 100m² or more and has drainage implications (i.e., will change how surface water runs off the site)
Common exemptions (always check with the local SAB):
- A single new dwelling where the total construction area is under 100m²
- Other construction work where the total area is under 100m²
- Conversions that don't increase the footprint beyond the threshold
- Some agricultural buildings (varies by SAB)
In practice: two new semis, a terrace of three, a commercial unit over 100m², a car park extension, or a new housing estate in Wales will almost certainly trigger SAB approval.
2. How Wales differs from England
This is the critical bit for anyone working cross-border.
| Wales | England | |
|---|---|---|
| Schedule 3 commenced? | Yes: fully live since January 2019 | No, not yet commenced |
| Mandatory SuDS? | Yes · for qualifying developments | No mandatory requirement (encouraged through planning policy) |
| Separate approval body? | Yes · SAB at each local authority | No SAB · drainage handled through planning and LLFA consultation |
| Legal requirement? | Yes · must have SAB approval before starting | No separate legal approval for drainage |
| Enforcement? | Yes · stop-work notices, fines | Through planning enforcement only |
If you're used to English jobs, the big practical change in Wales is: drainage is its own formal approval with its own paperwork, drawings, fees, and decision timeline. It's not just a planning condition, it's a separate legal consent.
The government has indicated it plans to commence Schedule 3 in England too, but as of April 2026, this hasn't happened. When it does, the Welsh system will likely be the model.
3. The SAB application process
Each Welsh council runs its own SAB, but they all follow the same national framework.
Step 1: Pre-application advice (strongly recommended)
SABs offer a chargeable pre-application service where you can discuss:
- Whether your project actually needs SAB approval
- What SuDS features they'll expect for your site
- Any site-specific constraints (ground conditions, proximity to watercourses, contamination)
Pre-application fees are typically around 30% of the full application fee.
This is where you take a drainage engineer's sketch or layout and get early feedback, far cheaper than designing something, submitting it, and being told to start again.
Step 2: Full SAB application
Submit to the local SAB, usually through the council's website or planning portal.
You'll need to provide:
- Site location plan with the construction area boundary clearly marked
- Drainage layout showing all SuDS components and connections
- Calculations demonstrating compliance with the Welsh National Statutory SuDS Standards (S1-S6)
- Construction details · how each SuDS feature will be built
- Operation and maintenance details · who maintains what, and how, for the lifetime of the development
- The correct application fee based on site area
Step 3: SAB decision
The SAB must normally decide within:
- 7 weeks for most applications
- 12 weeks if an Environmental Impact Assessment (EIA) is needed
They can approve, approve with conditions, or refuse. If refused, you can appeal or amend and resubmit.
SAB approval must be obtained before construction starts. Not before completion, before you break ground.
4. What SuDS features they usually want
The Welsh Government's National Statutory SuDS Standards require drainage that meets six standards:
| Standard | What it means |
|---|---|
| S1: Destination | Runoff goes to the right place (infiltration first, then watercourse, then sewer, in that priority order) |
| S2: Hydraulic control | Flow rates and volumes are managed so flooding doesn't get worse |
| S3: Water quality | Pollution is treated before water leaves the site |
| S4: Amenity | The drainage adds something positive to the development (green space, visual quality) |
| S5: Biodiversity | The drainage supports wildlife and ecology where possible |
| S6: Design | The system is robust, maintainable, and will last the lifetime of the development |
Typical features you'll see on Welsh sites:
- Permeable paving on driveways and parking bays · water soaks through the surface instead of running off
- Rain gardens and planted basins · landscaped areas that collect and filter roof and hardstanding runoff
- Swales and grassed channels · shallow vegetated ditches that carry water slowly instead of pipes
- Attenuation · ponds, oversized pipes, tanks, or crates that hold water back during storms and release it slowly
- Soakaways and infiltration trenches · where ground conditions allow water to soak into the soil
- Green roofs · on flat-roofed buildings, to absorb and slow rainfall
The SAB will assess your design against all six standards. Getting S4 (amenity) and S5 (biodiversity) is where most designs need tweaking, it's not enough to just manage the water; you need to show it creates something positive.
5. Fees and timescales
Fees are set by Welsh regulations and scale with site size.
Typical fee structure (based on published council schedules):
| Site area | Approximate application fee |
|---|---|
| Up to 0.5 hectares | £350 base + £70 per 0.1 ha |
| 0.5 to 1 hectare | Base + £50 per 0.1 ha above 0.5 ha |
| Above 1 hectare | Scaled further, up to a maximum of £7,500 |
| Pre-application advice | Typically ~30% of the full application fee |
Example: a 0.3 ha residential site might pay roughly £350 + (3 × £70) = £560 for the SAB application, plus ~£170 for pre-application advice.
Decision timescales (from validation):
- 7 weeks · standard applications
- 12 weeks · applications requiring EIA
Build the SAB timeline into your programme. This is not a "couple of days" turnaround, and if the application needs amendments, add more time.
6. What happens if you start without SAB approval
If a development that needs SAB approval starts without it, the SAB has enforcement powers.
Under Schedule 3 and the Sustainable Drainage (Enforcement) (Wales) Order 2018:
- The SAB can inspect sites and issue enforcement notices requiring work to stop or drainage to be altered
- Non-compliance with an enforcement notice is a criminal offence · punishable by fines
- The SAB can carry out remedial work itself and recover the costs from the developer
For you on the ground, that means:
- Work halted until drainage is approved and compliant
- Re-doing driveways, car parks, and drainage that don't meet SuDS standards · at your cost or the developer's
- Programme delays while redesign and resubmission happen
- Arguments over who pays · usually landing with the developer or main contractor, but the delays hit everyone on the job
No SAB approval = real risk of stop-work orders and costly rework.
7. Practical advice if you're crossing the border from England
If you're an English firm, subcontractor, or gang doing jobs in Wales:
Before you start groundworks:
- Ask: "Has this job got SAB approval?" If nobody can answer, that's a red flag.
- Get the SAB approval reference number and conditions from the main contractor or client · read the conditions, because they affect how you build.
When pricing work in Wales:
- SuDS features cost more than a bit of tarmac and a gully. Permeable paving, rain gardens, swales, attenuation tanks · these all need allowing for in your price.
- Factor in SAB application fees and any pre-application costs if you're the developer.
- Factor in the maintenance obligation · SABs require a maintenance plan and may adopt the SuDS (meaning the council maintains them), but adoption comes with conditions.
On small projects:
- Single dwellings under 100m² or extensions under the threshold may be exempt · but still consider basic SuDS (permeable surfacing, soakaways) because planners and SABs appreciate consistency and it avoids arguments.
Golden rule: treat SAB sign-off like planning permission. If the job doesn't have it and it needs it, don't start.
What to do next
- If you're pricing a job in Wales: ask the client or main contractor whether SAB approval is in place or needed
- If you're a developer in Wales: contact the local SAB for pre-application advice before designing the drainage
- If you're doing groundworks: get a copy of the SAB approval and conditions before you dig
- If you work cross-border: understand that Wales has mandatory SuDS and England doesn't · yet. Price accordingly.
Sources
- Flood and Water Management Act 2010, Schedule 3 · legislation.gov.uk/ukpga/2010/29/schedule/3
- Sustainable Drainage (Enforcement) (Wales) Order 2018 · legislation.gov.uk/wsi/2018/1145
- Sustainable Drainage (Approval and Adoption Procedure) (Wales) Order 2018 · legislation.gov.uk/wsi/2018/557
- Welsh Ministers' Standards for Sustainable Drainage Systems · gov.wales
- Natural Resources Wales, SuDS guidance · naturalresources.wales
- CIRIA, The SuDS Manual (C753) · ciria.org (industry standard reference)
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