Almost every cost guide you will find online is written from a London desk, which is why the numbers look terrifying. Nottinghamshire sits at the national average. Same steel, same specification, same standard of finish, meaningfully less money.
The short answer
A standard single storey rear extension in Nottingham runs roughly 1,900 to 2,600 pounds per square metre in 2026. For the 20 square metre kitchen extension most people are actually asking about, that lands between 38,000 and 52,000 pounds.
What changes the number
The three things that move the price most are glazing, the roof and the ground.
Glazing
A pair of standard french doors and a single rooflight is a completely different job to a five metre run of aluminium bifolds and a three metre lantern. Glazing is often the single biggest line item after the shell, and it is where a basic specification becomes a premium one.
The roof
A flat roof with an EPDM covering is the cheapest thing that works properly. A pitched roof tied into the existing house costs more but often looks far better and can be worth every penny on the right property. Lanterns and structural glazing push it up again.
What is under the garden
This is the one nobody can price from a photograph. Trees nearby mean deeper foundations. Made up ground, a high water table, an old drain run or a shallow foundation on the existing house all add cost, and you do not find out until the trench is open. Any builder who tells you there will definitely be no groundwork surprises is guessing.
What the figure includes
- Labour, materials and VAT at 20 percent
- Foundations, drainage, blockwork and brickwork
- Roof structure and covering, fascias and guttering
- Windows and external doors to a standard specification
- First fix electrics and plumbing, plastering and decorating
- Building control notices and inspections
And what it does not
- Kitchen units and appliances, which are a separate budget entirely
- Architect and structural engineer fees, typically 2,000 to 5,000 pounds
- Planning application fees where one is needed
- Anything unforeseen in the ground
- Landscaping and making good the garden afterwards
The regional point that actually matters
Labour and logistics in London and the South East run 20 to 40 percent above the national average, and that premium shows up in every published cost guide because most of them are written for that market. Nottinghamshire is at the national rate. If you have been reading numbers that made you close the laptop, check where they were written before you give up on the idea.
How to sanity check a quote
Divide the total by the floor area and see where it lands against the table above. If a quote comes in dramatically under 1,700 pounds per square metre, something is either excluded or somebody has not priced it properly, and you will meet the difference later as a variation. If it comes in above 3,500, you are either in a genuinely premium specification or you are being taken advantage of.
Ask for it itemised. A quote that is one number on one line is not a quote, it is a hope.
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