Do building control and planning talk to each other? Drainage, SuDS and the gap between them

A building control officer tells you the simplest thing to do is run the surface water into the sewer. Your planning condition says infiltration first, greenfield runoff rates, attenuation for a one-in-100-year storm. Both cannot be right, and only one of them can be enforced against you. So, do building control check planning permission? They do not — and that single fact is where a great many drainage disputes on small and medium sites begin.

Planning and building control are separate consent regimes with different statutory purposes, different people reading the drawings, and, on drainage, very different tests. This article sets out where they diverge, why the sewer keeps winning, which consent actually binds you, and what has shifted in 2026.

A building regulations completion certificate proves your drains meet a technical standard. It is not proof that you have built what your planning permission told you to build.

Do building control check planning permission?

No. Building control do not check whether you have met your planning conditions, and a building control sign-off is not evidence that you have. The two systems answer different questions and neither one audits the other.

Planning decides whether something can be built and on what terms. It weighs flood risk, drainage, design and the impact on neighbours, and it fixes the terms in conditions attached to your permission. Building control, under the Building Regulations 2010, checks how the thing is built against a technical standard — structure, fire safety and, for our purposes, whether the drains are adequate. At the end of it a building control body issues a completion certificate confirming the work meets the Building Regulations. It says nothing at all about your planning conditions.

• Planning asks: should this development happen here, and on what terms? The answer arrives as a permission with conditions attached.
• Building control asks: does the built work meet the technical standard in the Building Regulations? The answer arrives as a completion certificate.
• Neither asks: whether the other has been satisfied. There is no duty on a building control body to read your decision notice, and no duty on a planning officer to look at your Part H drawings.

So you can hold a valid completion certificate and still be in breach of your planning permission. The two run in parallel, and you have to satisfy both.

What is the difference between planning permission and building control on drainage?

On drainage the split is stark. Planning looks at the whole site and the wider catchment over the lifetime of the development; building control looks at the pipes. A scheme can be entirely compliant with one and nowhere near the other.

A planning drainage condition typically asks you to restrict how fast water leaves the site, often to greenfield runoff rates, to store the difference in attenuation, to design for a one-in-100-year storm with an allowance for climate change, and to show water quality and increasingly biodiversity benefit. That is a surface water drainage strategy, and on major development a Lead Local Flood Authority will usually have reviewed it — LLFAs have been statutory consultees on surface water for major development since April 2015.

Building control asks a much narrower question: will these drains carry the flow away without backing up or leaking? Approved Document H, the technical guidance behind Part H of the Building Regulations, is essentially a health and adequacy standard. It has not been substantively revised since the 2015 edition took effect, and it requires no greenfield runoff rate, no attenuation volume and no climate change allowance. A simple connection to a sewer will often satisfy it.

A drainage design can pass building control and still fall well short of what your planning condition demands, and the officer checking it has no duty to know or care what that condition says.

Why does the building control officer just want to connect to the sewer?

Because a sewer connection is the quickest way to satisfy Part H, and there is a statutory right to make one. The officer is not trying to undermine your planning strategy. They are applying a different, lower test and reaching for the simplest solution that meets it.

There is an irony here. Part H has its own hierarchy for surface water, and it puts the sewer near the bottom. On paper it sits very close to the planning and SuDS hierarchy an LLFA applies.

The difference is not the order, it is the enforcement. Building control treats "adequate" as a low bar and rarely polices the hierarchy the way an LLFA does at the planning stage. An LLFA will ask you to prove, with test results, that each step was ruled out before you moved down — typically BRE 365 infiltration testing before any discharge to a sewer is entertained. Building control will generally accept that a sewer is available. Defaulting to the sewer without that evidence is the single most common reason an LLFA objects to a planning application.

The two hierarchies read almost identically on paper. Only one of them is routinely tested with evidence, and it is not the building regulations one.

The right to connect: why the sewer is the path of least resistance

Underneath all of this sits a legal right that pulls everyone towards the sewer. Section 106 of the Water Industry Act 1991 gives a property owner an entitlement to connect foul and surface water drains to the public sewer, and the courts have read it broadly.

The Supreme Court, in Barratt Homes Ltd v Welsh Water [2009] UKSC 13, went further and called it an absolute right. A water company generally cannot refuse the connection or dictate where it is made, even where the extra flow will overload the sewer. Its grounds for refusal under section 106(4) are narrow: essentially that the drain itself is badly built or in poor condition, not that the network cannot cope.

That right sits awkwardly against the drainage hierarchy. Every part of drainage policy tries to keep surface water out of sewers and manage it at the surface instead, yet the developer retains a statutory route to do the opposite. Schedule 3 of the Flood and Water Management Act 2010 was drafted to close this loophole, by making the right to connect surface water conditional on a separate drainage approval. Because Schedule 3 has never been switched on in England, the loophole is still open.

The statutory right to connect is the one part of this system that was designed to be conditional on a drainage approval — and the conditioning mechanism has sat unused for sixteen years.

Which one wins, the planning condition or building control?

The planning condition wins. It is legally binding, it was imposed to make your development acceptable in planning terms, and nothing in the building control process discharges it.

Follow the building control officer, connect to the sewer and you will end up holding a valid completion certificate alongside a live breach of planning control. A local planning authority can enforce against an unmet condition, and an undischarged condition tends to surface on the legal searches when the property is sold or remortgaged, which can stall or sink a transaction. Building control's opinion is no defence, because building control was never asked the question.

If the officer's simpler solution genuinely is better — and sometimes it is, because ground conditions rarely match the assumptions made at application stage — that is still not a decision building control can make on your behalf. The route is back through planning.

1. Stop before you build the change. Deviating first and regularising later is how a technical disagreement turns into an enforcement file.
2. Get the evidence together: failed infiltration tests, a revised groundwater level, a survey that contradicts the assumed outfall. The LLFA will want to see why the approved scheme cannot be built.
3. Talk to the LLFA before you apply. They advised on the original condition and their agreement is what carries the planning officer.
4. Apply formally to vary or discharge the condition. Drainage conditions are exempt from the deemed discharge procedure, so there is no fast track and no silence-means-consent.
5. Only then build to the revised scheme, and keep the discharge notice with the completion certificate.

A completion certificate and a discharged condition are two separate pieces of paper. You need both, and only one of them can be obtained retrospectively without difficulty.

The bigger gap: Schedule 3, SuDS and unadopted drainage

Your standoff on one plot is a small version of a national gap. England has never commenced Schedule 3 of the Flood and Water Management Act 2010, the mechanism that would have made SuDS mandatory, created a SuDS Approving Body to sign off drainage before construction, set statutory standards and provided a route for that drainage to be adopted. It received Royal Assent in 2010 and has sat dormant ever since. Wales commenced it in 2018, with SuDS Approving Body approvals running alongside planning there from January 2019.

In its place, England relies on planning policy. The National Planning Policy Framework was strengthened in December 2024 to expect SuDS on most development, and Defra published National Standards for SuDS in June 2025, but both remain non-statutory. The government's position hardened during 2026. In January 2026 the water minister Emma Hardy set it out plainly.

A final decision is still formally outstanding, but the direction is not ambiguous: planning policy is being asked to do a job that primary legislation was written to do.

The consequences land on homeowners, because without a statutory route to adopt SuDS, most never get adopted. Home Builders Federation research published in October 2025, based on a freedom of information survey covering more than a thousand developments, found that of just over 170 SuDS adoption applications made to the six largest water companies over three years, three were adopted. Sewers fared barely better at 3%. Maintenance then falls to residents through private management companies, on top of the council tax and water charges they already pay — the Competition and Markets Authority found in 2024 that roughly 80% of new homes sold by the largest builders came with estate management charges, averaging around £350 a year.

Of just over 170 applications to adopt SuDS made to the six largest water companies across three years, three succeeded.

That is now being looked at directly. In December 2025 the government opened a consultation on reducing the prevalence of private estate management arrangements, which closed in March 2026 and expressly considered mandatory adoption of certain infrastructure, consistent standards for what counts as adoptable, and removing the financial incentives that make non-adoption attractive. The response has not been published. If it lands with teeth, the adoption half of this problem may move before the approval half does.

What developers and homeowners should do

Treat the planning drainage strategy as the thing you have to build, and treat building control as a separate, additional hurdle rather than the final word. For developers and self-builders, the practical steps are straightforward.

1. Design the drainage properly at the planning stage, so the strategy is buildable rather than merely approvable. Most of these disputes are created by a strategy written to get past an LLFA rather than to be constructed.
2. Do the ground investigation early. Infiltration testing after permission is granted is what turns an approved scheme into an unbuildable one.
3. Build what was approved, and keep the discharge correspondence with the site records.
4. If the site or the economics genuinely point elsewhere, vary the condition through planning before anything changes on the ground.
5. Confirm early who will adopt and maintain any SuDS features, because "no one" is the common and expensive answer.

For anyone buying a new build, the exposure is different. You inherit both the undischarged condition and the maintenance liability, and neither is obvious from the sales brochure.

• Ask whether every drainage condition has been formally discharged — not whether the drainage has been signed off, which usually means building control and answers a different question.
• Ask who maintains the drainage and any shared SuDS, and what that costs annually. If the answer is a management company, ask to see the estate charge history.
• Ask what happens if the water company later declines adoption. On the current numbers, that is the likely outcome rather than the exception.

If the answers are vague, that is exactly the gap this article describes, and it is a great deal easier to resolve before completion than after.

Being caught between a planning drainage condition and what building control will accept is a common problem, and one a specialist drainage consultant resolves regularly. Unda designs schemes that satisfy the planning condition and Part H at once, and handles the formal discharge of drainage planning conditions so the sign-off is clean.

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