Extra bedroom and en-suite extensions in Boston

Useful details for planning an extra bedroom and en-suite extension in Boston.

Postcode districts: PE20, PE21 and PE22
County / area: Lincolnshire, England
Price region: East Midlands
Guide price: £55,000–£74,000 (£1,960–£2,650 per m²), plus £5,500–£11,000 for the en-suite
Approval route: It may be permitted development if it goes no more than 3 m beyond the original rear wall (counting any single-storey part) and stays 7 m from the rear boundary; otherwise it needs planning permission.
Nearest towns: Spalding (14.1 miles), Sleaford (16 miles), Skegness (19 miles)
Distance to Lincoln: about 27.4 miles
First visit: Free, no obligation

About an extra bedroom and en-suite extension

An extra bedroom and en-suite extension is a two-storey extension planned around a new double bedroom with its own shower room on the first floor, with a ground-floor room below. It is one of the most effective ways to add space for a growing family. Nationwide's 2025 research linked adding a double bedroom and bathroom to a three-bed, one-bathroom house with value gains of up to 24%.

We cover Boston (PE20, PE21 and PE22) and the places around it, including Spalding (14.1 miles), Sleaford (16.0 miles) and Skegness.

What it costs in Boston

A guide price for Boston: around £55,000–£74,000 (plus £5,500–£11,000 for the en-suite) for a 4 m × 3.5 m footprint on two floors (28 m² of new floor space). That works out at £1,960–£2,650 per m² of new floor space, including VAT at 20%. These are guides, not quotes. Ground conditions, steelwork and access can move the figure either way.

Spec	Per m²	A 4 m × 3.5 m footprint on two floors (28 m² of new floor space)
Essential	£1,800–£2,430 per m²	£50,500–£68,000
Standard	£1,960–£2,650 per m²	£55,000–£74,000
Premium	£2,350–£3,180 per m²	£66,000–£89,000

Planning and building regulations in Boston

In England, an extra bedroom extension at the rear can be permitted development if it goes no more than 3 m beyond the original rear wall and stays 7 m from the rear boundary. Upper side windows, including en-suite windows, must be obscure-glazed and non-opening below 1.7 m. Side or deeper designs need planning permission, costing £548 (or £575 for applications made from 8 December 2026).

Approval in England: Householder planning application: £548 (or £575 for applications made from 8 December 2026). Lawful development certificate: £274 (about £288 for applications from 8 December 2026). Councils should decide householder applications within 8 weeks of validation.

Building regulations: Building regulations approval (full plans recommended) from the council or a registered building control approver, with a completion certificate at the end.

Design points for Boston homes

Connecting to the landing

The new bedroom must be reached from the existing landing, usually through a new opening in the outside wall or by taking part of an existing bedroom as a corridor. We look at the stairs and landing first, because a poor connection can waste much of the new space.

Sound and privacy

Bedrooms above a kitchen or family room benefit from an insulated floor to reduce noise. Side-facing upstairs windows usually have to be obscure-glazed, so we place the main bedroom window to the rear and the en-suite window to the side where possible.

How we'd run your project

Visit and first ideas
One of our team visits your house in Boston, checks the walls, roof and drains, and sketches out options with you.
Get it approved
Once you're happy with the design we submit it to the council for Boston and deal with any questions from the planning officer.
Detail and price
Construction drawings, engineer's calculations and building control sign-off, then a written fixed price for the build.
Build
Foundations, walls, floor, roof, windows, then first and second fix. We break through into the house as late as we can.

Questions about extra bedroom and en-suite extensions in Boston

Do I need planning permission for an extra bedroom and en-suite extension in Boston?

Boston is in England, so England planning rules apply. It may be permitted development if it goes no more than 3 m beyond the original rear wall (counting any single-storey part) and stays 7 m from the rear boundary; otherwise it needs planning permission. If in doubt, a lawful development certificate or a planning application gives you certainty before you build.

Which postcodes do you cover around Boston?

We cover Boston (PE20, PE21 and PE22) and nearby places including Spalding, Sleaford and Skegness, plus the rest of Lincolnshire. The first site visit is free.

How much does an extra bedroom and en-suite extension cost in Boston?

Our guide for the East Midlands, which covers Boston, is £1,960–£2,650 per m² including VAT. A typical project with a 4 m × 3.5 m footprint on two floors (28 m² of new floor space) comes to about £55,000–£74,000 (plus £5,500–£11,000 for the en-suite). Design and approval fees are extra, and we fix the build price in writing once the design is agreed.

How big should a new double bedroom be?

There is no legal minimum size for a bedroom in a house you own, so the test is whether it works. A comfortable double needs room for the bed with space to walk round it, wardrobes and a door that opens freely. We draw furniture on the plans so you can judge the space before anything is built.

What goes on the ground floor below a new bedroom?

Whatever suits you: a bigger kitchen, a family room, a study, a utility or a downstairs shower room. The ground floor usually costs about the same whatever it is used for, apart from kitchen units and bathroom fittings, which are priced separately.

Nearby

The same service in neighbouring towns:

Other extensions in Boston

All two-storey extension services in Boston · Extra bedroom and en-suite extensions across Lincolnshire

Tell us about your house in Boston and we'll call you back to arrange a free, no-obligation visit.