Most people asking about planning permission are really asking two questions: do I need it at all, and who do I ask? In Hertfordshire the second one is less obvious than it should be, because the county is split across several district councils and your address decides which one you deal with.

Which Council Decides

Planning is handled at district level, not by Hertfordshire County Council. For the towns we cover:

Inside the London Borough of Barnet — High Barnet, Finchley, Mill Hill, Whetstone, Totteridge and the EN and N postcodes — it is Barnet's own planning department. We cover that in the Barnet planning guide.

Permitted Development: When You Don't Need Permission

A great deal of domestic work is already allowed without a planning application, under what are called permitted development rights. These are national rules, so they apply the same way in Tring as in Hertford. The figures below are the general position and there are exceptions to all of them — treat them as a guide to whether it is worth asking, not as a decision.

Loft conversions

Usually permitted development, subject to a volume allowance: broadly 40 cubic metres of additional roof space for a terraced house and 50 cubic metres for a detached or semi-detached one. Any previous roof enlargement counts towards that allowance, including work done by a previous owner.

The other conditions matter as much as the volume. No part of the extension may go beyond the plane of the existing roof slope on the elevation fronting a highway, which is why dormers are almost always at the rear. Materials must be similar in appearance to the existing house. Side-facing windows must be obscure-glazed and non-opening below 1.7m from the floor. Verandas and balconies are excluded.

A hip-to-gable conversion is often still permitted development, but it uses a large share of the volume allowance. A mansard almost always needs a full application, because it changes the shape of the roof front and back.

Rear extensions

A single-storey rear extension is generally permitted development up to 4m deep for a detached house and 3m for any other house, with a maximum height of 4m. Within 2m of a boundary, the eaves height is capped at 3m.

Deeper single-storey extensions — up to 8m detached, 6m otherwise — can be possible through the prior approval process, where the council notifies your neighbours and considers their objections but does not assess the design. It is quicker than a full application but it is not automatic.

Two-storey and side extensions are far more constrained and usually need a full application. See house extensions for what is typically achievable.

What Takes Your Permitted Development Rights Away

This is the part that catches people out, because a neighbour's completed project proves nothing about your own address.

  • Conservation areas. Rights are restricted, side extensions are generally out, and cladding and roof alterations are tightly controlled. Hertfordshire has a lot of them, and the boundaries are drawn street by street.
  • Article 4 directions. A council can formally withdraw permitted development rights for a defined area, so work that is permitted one street over needs an application on yours.
  • Listed buildings. Listed building consent is a separate requirement, needed in addition to planning permission, and it applies to internal work too.
  • Flats and maisonettes. Permitted development rights for houses do not apply at all.
  • Conditions on a newer property. Modern estates frequently have permitted development rights removed by a condition on the original planning permission.
  • Local design control. The original Welwyn Garden City layout carries additional design rules on top of ordinary planning law, principally covering anything visible from the street.

How Long It Takes

A householder planning application has a statutory determination period of eight weeks. Straightforward applications sometimes clear sooner; anything contentious, in a conservation area, or attracting objections can run longer, and the clock only starts once the council validates the application — incomplete submissions sit in a queue before that.

Budget realistically. Between drawings, submission, determination and discharging any conditions, a project needing permission typically adds three to four months before work can start, and around £3,000–£8,000 in design, structural and consultant time.

Get a Lawful Development Certificate Anyway

If your work is permitted development, you are not obliged to tell the council anything. It is still worth applying for a Lawful Development Certificate, which is the council formally confirming the work was lawful.

It costs a fraction of a full application and takes around eight weeks. The reason to bother is that it is the document a buyer's solicitor asks for when you sell, sometimes years later, and reconstructing the evidence after the fact is far harder than obtaining the certificate at the time. It is the cheapest insurance in the whole process.

Planning Is Not Building Control

These are two separate approvals and passing one says nothing about the other. Planning is about what the building looks like and how it affects the area. Building regulations are about whether it is structurally sound, safe in a fire and adequately insulated — and almost all structural work needs Building Control sign-off even when it needs no planning permission at all.

If your work affects a shared wall or involves excavation near a neighbour, there is a third and entirely separate process: see party wall agreements.

Frequently Asked Questions

  • Which council handles planning permission in Hertfordshire?

    It depends on the town, because planning is handled at district level. St Albans City and District Council covers St Albans, Harpenden and Wheathampstead; Welwyn Hatfield covers Welwyn Garden City; East Herts covers Hertford, Ware and Bishop's Stortford; North Herts covers Letchworth and Royston; Hertsmere covers Borehamwood, Elstree, Radlett and Potters Bar; Dacorum covers Berkhamsted and Tring; Three Rivers covers Rickmansworth; and Watford Borough Council covers Watford.

  • Do I need planning permission for a loft conversion?

    Usually not. Most loft conversions fall under permitted development, subject to a volume allowance of roughly 40 cubic metres for a terraced house and 50 for a detached or semi-detached one, plus conditions on materials, side windows and not extending beyond the roof plane facing a highway. A mansard almost always needs a full application. Conservation areas, Article 4 directions and flats change the answer entirely.

  • How long does a householder planning application take?

    Eight weeks is the statutory determination period, starting once the council has validated the application. Allow three to four months in total once drawings, submission and discharging conditions are included.

  • What is a Lawful Development Certificate and do I need one?

    It is the council formally confirming that work you did under permitted development was lawful. You are not required to have one, but it costs a fraction of a full application and it is the document a buyer's solicitor will ask for when you sell. Obtaining it at the time is far easier than proving the point years later.

  • Does planning permission cover building regulations too?

    No. They are entirely separate approvals with separate applications. Planning is about appearance and impact on the area; building regulations are about structure, fire safety and insulation. Most structural work needs Building Control sign-off even when no planning permission is required.

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