How Much Do House Extension Plans Cost in Lane End?

Is my Lane End house in the Green Belt?

It depends on which part of the village you live in. The Wycombe District Local Plan, which still applies across the former Wycombe area, describes Lane End as a village in the Area of Outstanding Natural Beauty "which also has Green Belt on its northern and eastern side". It notes that the land on the south side of the village is not Green Belt, though it is still in the protected landscape (Wycombe Local Plan, paragraph 5.5.8).

So two houses a few hundred metres apart can face different tests. We check the council's Policies Map for your address before any design work, because it changes what you can build.

How big can a Green Belt extension be in Lane End?

National policy allows an extension in the Green Belt if it does not result in a disproportionate increase in size over the original building (NPPF chapter 13, GB7(1)(b)). The former Wycombe area turns "disproportionate" into numbers, measured as gross external volume, basement included. Under Policy DM43:

• a house that was under 240 cubic metres as originally built can reach a total of 360 cubic metres;
• a house of 240 to 720 cubic metres can reach its original volume plus 50%;
• a house over 720 cubic metres can reach a total of 1,080 cubic metres.

"Original" means the house as it stood on 1 July 1948, or as first built if later (paragraph 6.229). Every extension since then counts towards the total, including one a previous owner added. Existing outbuildings are not added to the house's volume, but garden buildings have their own cap of 25% of the original volume and 140 cubic metres in total.

In practice, this is where our survey earns its keep. We measure the house as it stands, then work back to the 1948 house from the planning history and the fabric, so the original, existing and proposed volumes on the drawings can be checked by the case officer. On many Lane End cottages that have already been extended, the remaining allowance is smaller than owners expect. Knowing it before design starts saves paying for a scheme the council cannot accept.

Can I use permitted development in Lane End?

Only in part. The whole village lies in the Chilterns, now called the Chilterns National Landscape, and that makes every house here "article 2(3) land". On that land the householder rights are narrower (GPDO 2015, Schedule 2, Part 1, Class A, paragraph A.2):

• no side extensions under permitted development;
• no rear extension of more than one storey;
• no cladding of the outside in stone, render, pebbledash, timber, plastic or tiles.

A single-storey rear extension within the normal depth limits can still be permitted development, and we can draw it for a lawful development certificate instead of a planning application. A side extension, a two-storey rear extension or a wrap-around always needs planning permission in Lane End.

What does the Lane End conservation area ask for?

The conservation area follows the old village: along The Row at the northern tip, down Church Road to the bottom of Ditchfield Common in the south, and along the line of the former Stokenchurch to Marlow turnpike. The character survey describes Lane End as a plateau village, very linear, with large areas of common running through it, and records nine Grade II listed buildings (Lane End Conservation Area Character Survey, Part 1).

Three points from the survey shape an extension here:

• Flint, brick and clay tile. The cottages are knapped flint with brick dressings, or vitreous header brick with red brick dressings, dentil eaves and plain tile roofs. The four mid-Victorian cottages of The Row even carry a diaper pattern in their gable ends.
• Houses that face the commons, not the road. At the north and south ends, groups of houses are turned towards the commons and footpaths. A rear extension can therefore be on show from a common or a footpath, so we draw the view from the open side, not only from the street.
• The village is revealed in stages. The survey says vegetation and topography hide parts of it. Hedges and trees count, so we show the ones you plan to keep.

If your house is in the conservation area, Buckinghamshire asks for a heritage statement with the application. We write it for from £565. The 20th-century estate to the north east, which the survey notes was built outside the conservation area, is judged on the ordinary design rules instead.

Which design rules apply to every Lane End house?

Policy DM36 of the Local Plan asks for an extension that is subservient in scale to the house and respects its character and its neighbours. The council's Householder Planning and Design Guidance (January 2020) gives the detail (SPD):

• leave at least 1 metre to the side boundary at first floor level for any two-storey or first floor extension;
• in the Chilterns, keep the shape, bulk, roof form, chimneys and materials sympathetic to the area, guided by the Chilterns Building Design Guidance;
• a 60-degree line for single-storey rear extensions and a 45-degree line for two-storey ones, taken from the middle of the neighbour's nearest habitable room window, tests loss of light.

How long does it take, and what does it cost in total?

In the year to 30 June 2026, Buckinghamshire decided 842 of 1,361 householder applications within eight weeks without an agreed extension of time (MHCLG live table PS2). An illustrative example, not a real job: a cottage south of Finings Road, outside the Green Belt but in the Chilterns, wanting a single-storey side room. That is not permitted development here, so it goes in as a planning application.

• Our planning drawings and submission: £645 drawings + £250 survey (£895 total).
• Buckinghamshire Council's householder fee: £548.
• A heritage statement in the conservation area: from £565.
• Building regulations drawings and structural calculations after approval: our package is from £1,245 drawings + £250 survey (£1,495 total) for one extension.

Our Buckinghamshire Council page covers validation, and the Buckinghamshire page covers the county. For a village with no Green Belt but the same Chilterns rules, see extension plans in Stokenchurch. For a village inset from the Green Belt, see extension plans in Marlow Bottom.

Frequently asked questions

Is all of Lane End in the Green Belt? No. The Local Plan says the Green Belt lies on the northern and eastern side of the village, and land on the south side is not in it. We confirm your address on the Policies Map.

Can I build a side extension in Lane End without planning permission? No. Lane End is in the Chilterns National Landscape, which is article 2(3) land, and a side extension is not permitted development there.

Does a garden room count towards my Green Belt allowance? Outbuildings are not added to the house's volume, but they have their own limit in the Green Belt: 25% of the original house's volume and 140 cubic metres in total, single level, no more than 4 metres high.

Do I need a heritage statement? Yes, if the house is in the Lane End conservation area or is listed. It is a separate document, from £565.