A rear extension is the most popular type of home extension in Milton Keynes, and for good reason. By extending into the garden, you can transform a cramped kitchen or dark living room into a bright, spacious area that connects seamlessly with your outdoor space through bi-fold or sliding doors.

At Crownhill Building Services, rear extensions account for the majority of the projects we build. Over 20 years of constructing them across every estate in Milton Keynes has taught us what works — the right proportions, the best glazing options, and how to handle the structural changes needed when you remove the original rear wall of your home.

Most rear extensions are designed around the kitchen. The existing back wall is removed or opened up with a wide structural beam, creating a single flowing space from the front of the house through to the garden. The result is a kitchen-diner or kitchen-living room that feels completely different to the original layout — more light, more room, and a direct connection to outdoors that makes a real difference to daily life.

Permitted Development and Planning

Many rear extensions can be built under permitted development rights, meaning no planning application is needed. The permitted depths depend on your property type:

Detached houses — you can extend up to 4 metres to the rear under standard PD, or up to 8 metres under the larger home extension scheme (prior approval notification required)
Semi-detached and terraced houses — up to 3 metres under standard PD, or up to 6 metres under the larger home extension scheme with prior approval

The larger home extension scheme requires a prior approval application to Milton Keynes Council, which involves notifying your neighbours. We handle the entire process and advise you on which route is best for your property. If your project exceeds PD limits or your home has restrictions, we will prepare and submit a full planning application on your behalf.

Single or Double Storey Rear

Rear extensions do not have to be single storey. A two storey rear extension adds bedrooms or a bathroom upstairs while giving you the open-plan living space downstairs. This is an excellent option for families who need both additional living space and extra bedrooms. Two storey rear extensions have stricter planning rules — permitted development allows a maximum of 3 metres depth, and the upper floor must be set back from the original rear wall with a matching roof pitch.

Natural Light and Garden Living

One of the biggest benefits of extending to the rear is the opportunity to flood your home with natural light. Large bi-fold doors, sliding door systems, or full-height glazed panels create a wall of glass that brings the garden inside. Roof lanterns and skylights add overhead light, eliminating the dark spots that older houses often suffer from. We will help you choose glazing that balances light, thermal performance, and budget.

Timeline and What to Expect

A typical rear extension takes 8 to 12 weeks to build, depending on size and specification. We manage the entire project in-house — from excavating foundations and laying blockwork through to plastering, electrics, plumbing, and final decoration. You receive a fixed-price quote before work starts, and we keep you updated at every stage.

The process begins with a free site visit where we assess your property, discuss your ideas, and give you an honest view of what is possible within your budget.

Our Work