Building Regulations vs Planning Permission: The Difference

If we could untangle one confusion for every homeowner in Surrey, it would be this one. Planning permission and building regulations are not the same thing, not versions of each other, and not alternatives. They are two separate systems, run by separate departments, asking two entirely different questions about your project:

• Planning permission asks: are you allowed to build this here?
• Building regulations ask: is it being built safely and properly?

Get the distinction clear and a fog lifts off the whole process. Here's each system in plain English — and the expensive trap that sits between them.

Planning permission: "is it acceptable?"

Planning is about the what and the where: the size and appearance of what you propose, and its impact on neighbours and the area. When Tandridge or any other council assesses a householder application, it's weighing proportionality, overlooking and overshadowing, design and materials — not whether your foundations are deep enough. Nobody from planning will ever check your insulation.

The crucial nuance is that many projects don't need a planning application at all. Permitted development (PD) rights cover a large share of householder work — single-storey rear extensions within depth limits, loft conversions within roof-volume limits, outbuildings within height and garden-coverage limits. We've covered how this plays out locally in our Tandridge planning guide and the loft-specific version, including why a Lawful Development Certificate is worth having even when no permission is needed — your solicitor will ask for it when you sell.

Timelines: a householder application runs to an 8-week statutory target from validation (allow 10–12 weeks end to end); the larger-home PD scheme runs a 42-day prior approval consultation.

Building regulations: "is it built properly?"

Building regulations are a statutory requirement covering how the work is constructed — split into elements: drainage, foundations, floors, walls, ceilings, roofs, windows, doors, insulation, ventilation, plumbing, electrics and so on. Compliance is evidenced by technical drawings and structural calculations, then verified by inspections during the build, ending in sign-off on completion.

Note what's absent from that list: nothing about how the extension looks or whether the neighbours mind. Building control doesn't care about your street scene; it cares that the steel is sized correctly, the escape routes work and the insulation meets standard.

Two routes to approval, and the difference matters:

1. Full Plans — the two-stage professional route. Detailed drawings and calculations are submitted and approved before work starts (typically 4–5 weeks), then inspections follow during the build. All the risks are known up front, which is exactly why we prefer it: the technical assessment exists before anyone prices or builds anything.
2. Building Notice — allows a quick start without approved plans, with compliance checked as the work proceeds. Builders often like it for speed; the costs are similar, but the risks to the homeowner can stay hidden until they surface mid-build as cost challenges.

And two choices of building control body: your council's building control department or a private Registered Building Control Approver (RBCA). Registered building inspectors carry out the regulated assessment and inspection work. A compliant council route ends with a completion certificate; the private route ends with a final certificate from the RBCA, accepted by the local authority.

Our evergreen building regulations guide goes deeper on the process, fees and the approved documents.

The trap: "it's permitted development, so we don't need anything"

Here's the misunderstanding that causes real damage. A homeowner hears their extension is permitted development and concludes no approvals are needed at all. Wrong — PD only removes the planning application. Building regulations are a separate test:

• Ordinary non-exempt home extensions and all loft conversions need building regulations approval, whether or not they are permitted development.
• A qualifying ground-floor conservatory or porch can be exempt if it is no more than 30 m², remains thermally separated from the house, does not extend the house heating system, and meets the applicable glazing requirements. Electrical work must still comply with Part P.
• Even smaller improvements — the plumbing and electrical changes in a new kitchen or bathroom — can technically require approval.
• Skipping building control doesn't make the requirement vanish; it converts it into a problem discovered later — typically by a buyer's solicitor asking for completion evidence you don't have.

The reverse confusion exists too: planning permission granted ≠ building regulations satisfied. A planning approval is not a technical sign-off, and plenty of approved schemes still need their structural and thermal details resolved before building control will pass them.

Side by side

Planning permission

• Question asked: is this development acceptable here?
• Looks at: size, appearance, neighbour impact, policy
• Can you avoid it? Often — permitted development covers many householder projects
• Typical timeline: 8 weeks statutory (10–12 weeks end to end)
• Ends with: a decision notice — or a Lawful Development Certificate for permitted development

Building regulations

• Question asked: is the work built safely and properly?
• Looks at: structure, fire, insulation, drainage, services
• Can you avoid it? Only where a specific exemption applies — permitted development alone is not an exemption
• Typical timeline: Full Plans approval in about 4–5 weeks, then inspections through the build
• Ends with: completion sign-off after inspections

Keep both sets of paperwork forever. Decision notices, certificates, completion evidence — they're part of the house now, and the sale process will ask for all of it.

Five real-world scenarios

Abstract distinctions stick better with concrete cases. How the two systems apply to the five projects we're asked about most:

1. Ordinary single-storey rear extension within PD limits. No planning application (get the Lawful Development Certificate anyway) — but full building regulations approval: foundations, structure, thermal performance, drainage, the lot. A qualifying conservatory or porch is a separate exempt category, subject to its conditions.
2. Single-storey rear extension beyond PD limits. Householder planning application and full building regulations. Two applications, two departments, two sets of drawings doing different jobs — the planning set shows what and where; the building regs set shows how.
3. Loft conversion under PD. No planning application in most cases — but building regulations all the way: floor structure, fire escape, stairs, insulation. The regs package is the bulk of the professional work on a loft, which surprises people who assumed "no planning needed" meant "no paperwork needed."
4. New kitchen in the existing footprint. No planning involvement at all — it's internal. But the electrical and plumbing changes can still technically require building regulations approval, usually handled through certified installers. "It's just a kitchen" is not an exemption.
5. Two-storey side extension. Almost always a full planning application — side and two-storey additions get closer planning scrutiny on street scene and neighbour impact — plus the most involved building regulations package of the lot: structure across two floors, fire, and thermal upgrades where new meets old.

Notice the asymmetry across all five: planning involvement varies from none to full; ordinary structural extensions and loft conversions still need building regulations approval even when they are permitted development. If you remember one thing from this article, make it that.

One project, one team, both systems

In practice the two systems interlock: the planning drawings set what you're allowed to build, the building regulations package determines how it's engineered, and gaps between the two are where projects leak time and money. That's why our architectural planning service handles them as one piece of work — planning strategy and drawings, then the Full Plans technical package, structural coordination and building control liaison, all surveyor-led. It's also why the design-first sequencing we describe in how to plan a home extension matters: approvals aren't an admin chore bolted onto a project; they're the framework the whole build hangs from.

Confused about which approvals your project actually needs? It's a ten-minute conversation. Book a free consultation and we'll tell you plainly: planning application or permitted development, Full Plans or not, what it all costs and how long the clocks really run — before you spend a pound on the wrong assumption.