Home Extensions Across Bristol & Somerset

A single-storey rear extension pushes the back of the house out into the garden, usually by up to four metres for a detached house, or three metres for a semi detached house, terraced house or end of terrace house, to create a larger kitchen, dining area, utility room or family room at ground floor level. It is the most common extension we build, partly because it is the type most likely to fall under these rules, and partly because it delivers a large, tangible change to how a home lives without touching the upstairs of the house at all. A single storey side extension, built along the side of a property rather than the back, achieves the same kind of new room and more space where the useful land actually sits to the side rather than the rear.

A side return extension builds into the narrow, often wasted strip of land that runs down the side of many Victorian and Edwardian terraces, and plenty of semi detached homes too, between the kitchen wall and the boundary. On its own it rarely adds huge floor area, but combined with removing the internal wall to an adjoining room it can turn two cramped, separate spaces into one wide, light-filled kitchen diner. A wrap-around extension, sometimes written wraparound, does the side return and the rear extension at the same time, building around the corner of the house to create the largest possible open-plan living space. It is the biggest structural undertaking of the three and it suits homes where neither direction alone would create enough usable width or depth. Done well, a wraparound extension brings in far more natural light through larger windows and bi-fold doors onto the garden, turning a dark, compartmentalised ground floor into one open-plan kitchen, dining area and living space with genuine indoor-outdoor flow onto the outdoor space beyond it. Our case study on a North Somerset rear extension and kitchen renovation shows a rear extension project of this kind through to completion.

A double-storey extension, also written double storey, adds floor area at both ground and first floor level in a single build, typically to create more living space downstairs and an additional bedroom or a larger bathroom upstairs. It is a larger structural project than a single-storey extension of the same footprint, because the ground floor structure now has to carry the load of a full storey above it as well as its own roof, which changes the foundation design, the size of the steel beams required and the sequence the work follows on site. A two-storey extension of this type is also more likely to need full planning permission than a single-storey one, which we cover in more detail below. Two storey extensions and other larger storey extensions of this kind are also where a single project manager matters most, since more trades are on site at once and more can go wrong without one person owning the sequence. Our case study of Tim and Hazel Hayden’s complex multi-level extension and full house renovation is a good example of how far a multi-level project can go when several of these extension types are combined on one property.

Many of the extensions we build include a new kitchen or a kitchen diner, since a rear or wrap-around extension is one of the most common ways to create one. Where that kitchen is the whole focus of the project rather than one part of a wider extension, our dedicated kitchen renovations page covers that work in its own right and publishes the figures for it.

Permitted development is a set of national rules that let certain extensions go ahead without a full planning application, provided the project stays within defined limits on size, height and position relative to the boundary. A single-storey rear extension is the type most likely to qualify, and within those limits a homeowner can often add meaningful floor space at ground level without submitting a planning application at all. This is not the absence of rules, though. It is a fixed set of rules that either your specific project meets or it does not, and the limits are strict enough that a design has to be shaped around them from the first sketch rather than adjusted afterwards. Where a project sits comfortably within those limits, we can often confirm the position at the feasibility visit itself.

For a single-storey rear extension specifically, the current national limits let a detached house extend beyond the rear wall of the original house by up to four metres, and a semi detached house, terraced house or end of terrace house by up to three metres. Under the Larger Home Extension Scheme, and subject to prior approval, those limits rise to eight metres for a detached house and six metres for any other house. Prior approval means the local authority notifies your neighbours, and if any of them object, the council decides whether the impact on their amenity is acceptable. The word original matters here: it means the house as it was first built, or as it stood on 1 July 1948, so an extension added by a previous owner reduces what is left of your own allowance. These are the national rules, and the position for your specific address is always confirmed at the feasibility visit, because these rights can be removed by a planning condition or an Article 4 direction.

A number of situations take a project outside permitted development and into a full planning application, and it is far better to know which applies to your address before you fall in love with a design that cannot be built. Conservation areas restrict what can be changed on the outside of a house, including materials and, in some cases, roof lines. Listed buildings need listed building consent for almost any structural alteration, an extension included, on top of any planning permission required. Article 4 directions remove these rights from a specific area by council order, regardless of how modest the proposed extension is, and they are more common than most homeowners expect. Newer housing developments frequently have those rights removed entirely as a condition attached to the original planning consent for the estate, which catches out households who assume the general rules apply to every house on the street. A double storey extension, a wraparound extension, or any project that goes beyond the size and height limits above will need a full planning application regardless of the property type. We check the planning position for your specific property before you spend money on drawings, and where it would give you or a future buyer’s solicitor useful peace of mind, a lawful development certificate can confirm the position formally in writing.

In practice that means the foundations for a new extension have to be designed and inspected to carry the load of the new structure. The steel beams that carry the load of a knocked-through wall or a new opening are calculated by a structural engineer and inspected before they are covered over, because this is the single most safety-critical part of almost any extension project.

Thermal performance, ventilation, drainage and every piece of electrical work are inspected against current standards, and specifying energy-efficient materials as part of that build, from insulation to glazing, is one of the most effective ways to keep the running costs of your new space down for years afterwards.

At the end of the process Building Control issues a completion certificate. That certificate matters more than most homeowners realise at the outset of a project. It is the paperwork that proves the extension was built to current standards, and it is what a buyer’s solicitor will ask to see when the house is eventually sold, extension included. We manage that entire process on your behalf, coordinate every inspection and hand you the completion certificate at handover.

Everything starts with a free, no-obligation feasibility visit to your home. We look at the property, the plot, side access and garden depth, talk through what you actually want the extra space to do, and check the planning position for your address there and then. From that visit, the design stage translates what you need into drawings, working within the planning position we have already established rather than designing something and hoping it fits the rules afterwards.

Once the design is agreed, we handle whatever the planning position requires, whether that is confirmation under those rules, a lawful development certificate or a full planning application, alongside submitting the Building Regulations application that every extension needs regardless of the planning route. Any Party Wall Act notices required for work near a shared boundary are served at this stage too, well before groundworks start.

Groundworks begin with excavating and laying the new foundations, designed and inspected to carry the specific load of your extension. Where an adjoining wall or an existing foundation is involved, underpinning may be required to support it safely, which we cover in more depth below. This is the stage where an inspector visits before anything is covered over.

With foundations in and inspected, the new external walls, the steel beams spanning any openings, the roof (pitched or one of our flat roof extensions) and the windows and doors go in, closing the building in against the weather. This is usually the point in the build where the shape of the finished extension becomes genuinely visible for the first time.

First fix covers the pipework, cabling and ductwork that has to go in before the walls are closed up, followed by plastering to finish the internal surfaces. Second fix follows, fitting sockets, switches, radiators, doors and skirting, and the project finishes with decoration, flooring and a final snagging walkthrough before handover. Your dedicated Site Manager acts as your single project manager throughout, coordinating every one of these stages and every inspection along the way, so you are never left wondering what happens next or whose job it is.