If you are planning a home extension near the New Forest or in a conservation area, planning permission is the first question to settle. You are more likely to need it, because the rules are tighter in both. This guide explains how permitted development changes, what the New Forest’s 30% rule means, and how to check your property before committing to a design. See our house extensions in Hampshire for examples of the types of projects involved.
The Short Answer
Often, yes. Permitted development allows many extensions to proceed without an application, but those rights are narrower in conservation areas and National Parks, and can be removed altogether on some properties. The New Forest adds its own size limit on top. Two similar houses can need different permissions, so check your specific address.
Permitted Development in a Conservation Area or National Park
In both places, the standard allowances shrink. Side extensions and two-storey rear extensions require planning permission; cladding is restricted; and a single-storey rear extension is limited to 3 metres deep on a semi-detached or terraced house and 4 metres on a detached house. Some properties are under an Article 4 direction, which removes further rights, and listed buildings need listed building consent for most changes.
New Forest Planning Permission for Extensions: The 30% Rule
Within the National Park, applications are submitted to the New Forest National Park Authority, not the district council. Its local plan limits how far an existing home can be extended, and the figure most homeowners meet is the 30% rule.
- Outside the defined villages of Ashurst, Brockenhurst, Lyndhurst, and Sway, an extension cannot add more than 30% to the house’s floorspace on 1 July 1982.
- Earlier extensions count towards the 30%, and attached garages, outbuildings, and conservatories can count too.
- Homes of 80 square metres or less are treated as small dwellings and receive a separate allowance.
- Permission granted under the policy often removes permitted development rights for further extensions.
Because the calculation starts from the 1982 floor area, find out what your home measured then before commissioning drawings.
Planning Permission for an Extension in a Conservation Area
There are 20 conservation areas in the New Forest National Park alone, including Lyndhurst, Brockenhurst, Beaulieu, and Burley, as well as many more across Hampshire. The controls on householders are the same inside and outside the National Park. Councils look closely at materials, rooflines, and street appearance, and trees in a conservation area are protected, so work near them needs the council’s agreement first.
How to Check What Applies to Your Property
Before paying for drawings, work through these checks:
- Is your address inside the National Park boundary? This decides who the planning authority is.
- Is the property in a conservation area? Check your council’s map.
- Is the building listed?
- Does the planning history show earlier extensions, or conditions removing permitted development rights?
- If inside the National Park, what was the original floor area on 1 July 1982?
If anything is unclear, ask the planning authority before you design, not after.
Getting the Space You Need Within the Rules
When the rules limit what you can add, good design makes up for the space. Opening up the ground floor through structural alterations, such as removing load-bearing walls, makes the existing footprint work harder. A single-storey rear extension designed within permitted development limits may avoid the need for an application. Loft and room conversions, covered under home renovations, add usable space without changing the footprint, although dormers may still need permission. Where an application is needed, matching bricks, tiles, and windows to the original house helps. Our guide to what a house extension costs in Hampshire compares these options in terms of budget.
How We Handle Planning and Design
We check the planning position before any drawings are produced, covering the National Park boundary, conservation area, listing, and property restrictions. We then prepare the design and structural calculations, support the planning application, and manage building regulations and party wall notices. If your property is near the New Forest, our pages for builders in Salisbury, Romsey, and Christchurch explain how we work.
Frequently Asked Questions
Not always. Within the 3-metre (semi-detached or terraced) or 4-metre (detached) depth limit, it can still be permitted development, but Article 4 directions or earlier planning conditions may remove that right. Check your property’s status first.
It is a National Park Authority policy limiting extensions to 30% of a house’s floorspace on 1 July 1982, outside the defined villages of Ashurst, Brockenhurst, Lyndhurst, and Sway. Small dwellings and earlier extensions are treated separately, so check the calculation carefully.
Only with full planning permission, because side extensions are not permitted development in a conservation area. A design that respects the original house, with matching materials, has a much better chance of approval.
The usual decision period for a householder application is eight weeks, though extra information or a listed building consent application can add time. We build the planning stage into the programme before work is booked.
Choose a builder who checks the planning position before quoting and manages the applications for you. Our extension builders in Hampshire page explains how we work, or you can get in touch and we will call you back.
Ready to Plan Your Extension?
If you want to know what is possible on your property before committing to a design, we are happy to help. We will review the planning position and discuss your options. Call Hampshire Building Co. on 01489 358525 or email info@hampshirebuildingco.com to arrange a site visit.
