A high end extension is not just a bigger room with a nicer kitchen in it. It is a piece of building work where the structure, the glazing, the detailing and the finishes all have to be right, because at this level there is nowhere for shortcuts to hide. If you own a home in Fulwood, Penwortham, Broughton or the Victorian terraces around Avenham, here is what to expect before you commission one.
The difference is rarely size. It is the number of decisions that get made properly rather than by default. A standard single storey extension in Preston usually means a blockwork box, uPVC bifolds, a plastered ceiling and whatever the tiler had on the van. A high end job starts from the way the new space joins the old house and works outwards.
In practice that means structural glazing or slim aluminium frames, flush thresholds so the floor runs level into the garden, a roof design that brings daylight into the middle of the plan, and finishes chosen for the room rather than the budget. It also means more engineering, more drawings and longer lead times on the components that matter.
Prices vary a lot with site conditions, glazing specification and finish level, so treat these as ranges rather than quotes. A well built standard extension in the Preston area currently sits somewhere around £2,000 to £2,600 per square metre for the shell and basic finish. A high end scheme with structural glazing, a bespoke kitchen and premium flooring typically lands between £3,000 and £4,500 per square metre, and it can go beyond that where the design is unusual.
The big variables are the glazing package, which can easily reach £25,000 to £60,000 on its own, the kitchen, and any structural work to open up the existing house. Ground conditions matter too. Parts of Preston have clay soils and older drainage, and a deeper foundation or a build over agreement with United Utilities can add several thousand pounds before anything is visible above ground.
VAT at 20 percent applies to extension work on an existing home, so factor that into any figure a builder gives you and ask whether their price includes it.
Many single storey rear extensions on detached and semi detached houses fall within permitted development, which allows up to 4 metres deep on a detached house and 3 metres on a semi or terrace without a planning application. Larger schemes up to 8 metres and 6 metres respectively can use the prior approval route, where neighbours are consulted by Preston City Council before work starts.
High end designs often fall outside these limits because of height, glazing that faces a boundary, or a contemporary look on a property in a conservation area such as Winckley Square or parts of Broughton. In those cases a full planning application takes around eight weeks to decide, and it is worth having good architectural drawings rather than sketches. Listed buildings need listed building consent regardless of size.
Whatever the planning route, Building Regulations approval is always needed. Expect inspections at foundation, drainage, damp course, structural and completion stages.
Ask to see a finished high end extension in person, not just photos. Look at how the glazing meets the floor, whether the plaster is flat under raking light, and how the external brick or render ties into the original house. These are the details that show whether a builder is used to this standard.
Get a full written specification alongside the price, with named products for glazing, insulation, heating and finishes. A quote that says 'bifold doors' with no brand or frame size is not comparable with one that specifies a particular system. Check that the builder carries public liability insurance and can arrange a structural warranty if you want one for resale.
A typical high end single storey extension takes 14 to 22 weeks on site, with glazing lead times of 8 to 14 weeks ordered early. Be wary of anyone promising much faster.
Usually yes, but rarely pound for pound at the top end of the cost range. In the better Preston suburbs a well designed extension typically adds a good proportion of its cost back to the value, and a poorly detailed one can add very little, so the quality of the work matters more than the size.
For permitted development work a competent builder or architectural technician can produce the drawings you need. For a contemporary design, a conservation area, or anything needing full planning permission, an architect will usually get a better result and a smoother application.
Expect several weeks without a usable kitchen if the extension opens into it, plus dust, noise and a skip outside. Many homeowners set up a temporary kitchen in another room and plan the knock through for a period when they can be away.
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