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Large Rear Single-Storey Extension in Chelmsford, Essex

We designed a rear single-storey extension for a large detached house in Chelmsford, Essex.

  • Chelmsford, Essex
  • Detached house
  • 5 star review

The Project — What the Clients Wanted

The clients wanted to open up the back of their house and create a larger, more practical living space. Their existing kitchen was fairly small and separate from the rest of the home. The plan was to turn that into a single generous space for cooking, eating and relaxing, with the seating area looking out over the garden.

Chelmsford is a commuter area with many large detached properties, which is one reason a rear extension Chelmsford homeowners commission is so popular. We regularly work on house extensions Chelmsford-wide and across Essex, and you can read more about our work in Chelmsford.

Project Highlights

A closer look at the key features, finishes and practical improvements that bring the completed space together.

The Design — Pitched Roof, Roof Lantern and Glazing

The new extension has a pitched roof with a roof lantern set into it. The lantern lets daylight in from above, and large glazed windows and doors across the back of the extension add more. Natural light was a main design goal, and the result is a bright, open room.

The layout now flows from the kitchen, through the dining area, to the living room at the rear, which looks straight onto the garden. A large kitchen island sits at the centre of the space. The glazing ties the inside to the garden, and the pitched roof helps the extension sit comfortably alongside the existing detached house. For a large detached property like this one, that balance between a modern interior and a roof that suits the original building matters.

The Build — Structural Steelwork, Stone Flooring and Underfloor Heating

To join the old house to the new extension, the rear wall had to be opened up. That called for significant structural steelwork to form a wide opening between the two. This is the part of the project that demands the most careful engineering, and the structural design was settled before the build started, so the builder could work from clear drawings.

The new floor is natural stone, with underfloor heating beneath it, which keeps a large open-plan room comfortable to live in. We also supplied and fitted the new kitchen within the build price, so the clients did not have to coordinate separate contractors.Our single-storey extensions page shows more of this type of project.

Planning Permission and Chelmsford City Council

Chelmsford City Council is the local authority for planning and building control in the area. This extension fell under permitted development, which means it did not need a planning application. We still obtained a Lawful Development Certificate from the council. That certificate is formal confirmation that the proposed works are lawful, and it gives the clients written proof that the project was properly documented.

For more on Chelmsford City Council planning, see our Chelmsford planning permission guide.

Building Regulations

Building regulations are separate from planning permission: planning deals with the development and its impact, while building regulations cover the technical standards for safety, accessibility and energy efficiency. We prepared the building regulations drawings and the structural engineering information, and that stage took approximately 2 weeks.

Chelmsford City Council also provides the building control service, which covers plan assessment, site inspections and completion certificates. Read more about our structural engineering service.

The Result

The project began with a free Discovery Call. After that, we took care of the design, structural engineering, building regulations and the council certificate. We introduced the clients to a vetted builder to carry out the construction.

The build went smoothly, with no issues or problems, and finished in approximately 12 weeks, including decorating. The clients gave five-star reviews to both Kirkwood and the builder. The old, small kitchen has become a large open-plan kitchen, diner and living room, and the garden is now part of how the clients use the space.

Project Costs

The professional fees for this project were £4,935 including VAT. The build cost was approximately £97,000 + VAT, including the supply and installation of the kitchen.

Item

Cost

Architectural fees

£1,695 including VAT

Structural engineering

£1,745 including VAT

Building regulations

£1,495 including VAT

Total professional fees

£4,935 including VAT

Build cost

Approximately £97,000 + VAT, including kitchen supply and installation

Costs vary with the size and specification of each project. Our guide to house extension costs gives more examples.

Our Complete Service in Chelmsford

From the first Discovery Call to the introduction to a builder, we handle the design, planning route, structural engineering and building regulations in one place. If you are planning a kitchen extension that Chelmsford properties can accommodate, or a larger open-plan project like this one, you deal with one team throughout.

The easiest way to start is a free Discovery Call. You can also look through our other case studies, or see our kitchen extensions page.

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Frequently asked questions

Many single-storey rear extensions are covered by permitted development, so a planning application is not needed. The limits depend on your property and the size of the extension, and a Lawful Development Certificate from Chelmsford City Council gives you written confirmation. We handle that as part of our service.

On this project, the architectural stage took 2 weeks, structural engineering and building regulations took 2 weeks, the council process took 8 weeks, and the build took 12 weeks. That is approximately 24 weeks from instruction to completion.

For this large single-storey rear extension, professional fees were £4,935 including VAT and the build cost approximately £97,000 + VAT, including the kitchen. Costs vary by project size and specification, so treat this as a realistic example.

Yes. We regularly work on house extension projects in Chelmsford and across Essex. The starting point is a free Discovery Call.

On the planning side, the council deals with planning applications and permitted development certificates. On the building control side, it deals with building regulations approval and inspections. Planning looks at the development and its impact, while building regulations set the technical standards for construction.

Project Details at a Glance

  • Location: Chelmsford, Essex
  • Property: Large detached house
  • Works: Rear single-storey extension with pitched roof and roof lantern
  • Design: Open-plan kitchen, diner and living room
  • Features: Kitchen island, natural stone flooring, underfloor heating, large glazed doors and windows, structural steelwork to open the rear wall
  • Planning: Permitted development, with a certificate from Chelmsford City Council
  • Architectural stage: 2 weeks
  • Structural engineering and building regulations: 2 weeks
  • Council process: 8 weeks
  • Build: 12 weeks, including decorating
  • Professional fees: £4,935 including VAT
  • Build cost: Approximately £97,000 + VAT, including kitchen supply and installation.
  • Reviews: Five stars for Kirkwood and five stars for the builder

More Case Studies

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We designed and managed a large single-storey rear extension and loft conversion for a detached property in Shenfield, Brentwood, Essex.
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