Do I need planning permission for an extension?

Two routes exist for most home extensions: permitted development, where the work is already allowed as long as it stays inside a set of limits, and a planning application, where you need consent from the council. Building Regulations approval is separate and is required either way — the two are often confused.

When permitted development usually applies

Broadly, a single-storey rear extension can often proceed without a planning application if it stays within limits on depth, height and how much of the garden is covered, uses materials similar to the existing house, and doesn't extend beyond the side of the property on a designated site. Loft conversions frequently qualify too, within volume limits, provided nothing projects forward of the roof slope on the principal elevation.

The limits differ between England and Wales, so a Hereford property and a Monmouth property are not assessed under the same rules. Check the guidance that applies to your address rather than the first article you find online.

When you will need planning permission

• Listed buildings — listed building consent is required for most alterations, internal ones included
• Conservation areas — permitted development rights are restricted; Hereford, Leominster, Ledbury, Ross-on-Wye, Monmouth, Abergavenny and Chepstow all have designated areas
• Designated landscapes — including much of the Wye Valley
• Two-storey and wraparound extensions — almost always
• Properties already extended — earlier work counts towards the allowance, and it may already be used up
• Estates with rights removed — common on newer developments, written into the planning conditions or the deeds
• Flats and maisonettes — permitted development doesn't apply

The single most common mistake is assuming permitted development applies because a neighbour built something similar. Their house may have had allowance left. Yours may not.

Lawful Development Certificates

If the work falls under permitted development, it's worth applying for a Lawful Development Certificate anyway. It's a formal confirmation from the council that the work was allowed. It costs a fraction of a full application, and it removes a problem that would otherwise surface when you sell the house.

Building Regulations are separate

Planning permission governs what a building looks like and where it sits. Building Regulations govern whether it's structurally sound, insulated, ventilated, safe in a fire and properly drained. Almost all extensions and every loft conversion need Building Regulations approval and inspections, whether or not planning permission was required.

Party Wall Act

If you're excavating near a neighbour's foundations or building on or against a shared wall, you'll usually need to serve notice under the Party Wall etc. Act. It's a legal requirement, not a courtesy, and it's best done early — disputes at this stage delay projects by months.

Realistic timescales

• Drawings and design: 2–6 weeks
• Planning application determination: typically 8 weeks, longer if it goes to committee
• Building Regulations application: allow several weeks alongside the above

Which is why "we'd like it finished by Christmas" needs to be said in spring, not October.

Questions

Can I start work while the application is being decided?

No. Starting before consent risks an enforcement notice and, in the worst case, having to undo the work at your own cost.

What if my neighbours object?

Objections are considered, but only on planning grounds — overlooking, loss of light, scale, materials and similar. Personal disagreements and concerns about property value carry no weight in the decision.

Who submits the application?

We coordinate the drawings and the application as part of the project, and deal with Building Control through to sign-off. You aren't left to work out the council's portal on your own.