House Extensionsin NorthamptonBuilt Stage by Stage
More room without moving house, priced by a quantity surveyor, built in clear stages, and paid for only as each stage is visibly done.
21 years in the trade
Founder Rick Humphries started as an apprentice bricklayer at 16.
FMB & Checkatrade members
Federation of Master Builders and Checkatrade.
£5M public liability
Plus employers’ liability for all on-site personnel.
NVQ-qualified team
On-site team members hold trade-specific NVQs.
Free QS estimates
Prepared by a professional quantity surveyor for most projects.
Service overview
What extensions involve
What it is
A house extension adds new floor space to your existing home: a larger kitchen, a family room, a utility, a downstairs bedroom or extra bedrooms above. We build extensions two ways. We can take your project from first idea to finished room as a full design-and-build service, or we can build from architectural drawings and planning permission you already have.
Who it’s for
Our extension work is for homeowners in Northampton and the surrounding Northamptonshire villages who like where they live but have outgrown the space. Growing families, people who work from home, and households that want an open-plan kitchen and living area are the most common reasons people call us.
When you need it
An extension makes sense when moving would cost more in stamp duty, agents’ fees and upheaval than building would, or when you simply don’t want to leave the area. It is also the natural step when your current layout fights against how you live, a cramped kitchen, no space to eat together, or nowhere quiet to work.
Why it needs a professional
An extension joins new structure to an old one. Foundations, drainage, steelwork, insulation and roof junctions all have to meet Building Regulations and tie properly into your house. Rick Humphries has 21 years in the trades, starting as an apprentice bricklayer at 16, and one team handles groundworks, steel, brickwork, joinery and finishes, so nothing falls between separate contractors.
Get it wrong and it costs you
What happens when extensions are rushed or done cheaply
Costs that grow mid-build
A cheap headline quote that leaves out groundworks, drainage or steel tends to rise once digging starts. A quantity surveyor estimate is built from the real scope, so the figure you plan around is honest from the start.
Poor junctions with the old house
Where the new roof, walls and floors meet your existing home is where damp, cracking and cold spots appear if the detailing is rushed. These faults are expensive to put right once finishes are on.
Building Control problems
Work that isn’t inspected at the right stages can delay sign-off. Without sign-off, selling or remortgaging later can become difficult.
Months of uncertainty
Not knowing what happens next, who is on site, or when the next payment is due is the biggest source of stress on an extension. Defined stages remove that.
Common mistakes homeowners make
- Choosing a builder on the lowest number, without checking what the number includes.
- Paying large sums up front before any work is visible on site.
- Leaving drainage, foundations and steelwork as ‘to be confirmed’ until after work starts.
Our process
Five clear steps, start to handover
- 01
Initial enquiry & consultation
We talk through your requirements, plans, drawings or ideas, so we understand what you want the finished space to do.
- 02
Survey & quantity surveyor estimate
We assess the site, then a professional quantity surveyor prepares your estimate from the real scope. It is free for standard projects; on rare, unusually complex schemes a detailed estimate is £250 including VAT, and we tell you before any work on it starts.
- 03
Pre-commencement
Your start date is fixed and the work is scheduled. The first payment is due 72 hours before we start on site, not weeks in advance.
- 04
Staged construction
The work is delivered in 4 to 7 clearly defined physical stages, such as concrete footings, brickwork to roof plate, watertight roof and plasterboard complete. Each stage is invoiced only once you can see it done.
- 05
Practical completion
Final inspection, Building Control sign-off where applicable, handover, and a small remaining balance settled on completion.
Why homeowners choose Prime
What you get when we build your extension
Honest pricing
We give estimates, not ‘fixed quotes’ that grow later. A quantity surveyor builds the figure from the real scope of your home.
You pay for what you can see
Between 4 and 7 stage payments, each tied to a visible milestone. You are never paying far ahead of the work.
One team, every trade
Groundworks, steel, brickwork, joinery and finishes are handled by one team, so nothing falls between separate contractors.
Structural work done to calculation
Steelwork follows engineer’s calculations, from our partner local structural engineering firm or your own engineer.
Cover if something goes wrong
£5,000,000 public liability insurance, employers’ liability for all on-site personnel, and an optional insurance-backed guarantee at 15% of the final project cost.
You always know what’s next
Rick stays in contact from the first visit to handover. Reviewers repeatedly mention clear day-to-day updates and tidy, considerate sites.
In detail
Extensions in Northampton: methods and options
We work on homes only, never commercial property, across Northampton and the surrounding Northamptonshire towns and villages.
Design-and-build or build from your drawings
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With design-and-build, one team carries your project from concept through to completion, so you have a single point of contact for the whole job. If you already have an architect’s drawings and approved planning, we can price and build from those instead. Either way your estimate is prepared by a professional quantity surveyor from the actual scope.
Single-storey, two-storey and kitchen extensions
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Single-storey rear and side extensions are the most common way to create an open-plan kitchen and dining space. Two-storey extensions add bedrooms and living space in one build, sharing one set of foundations and one roof. Kitchen extensions often combine new floor space with removing a load-bearing wall, so the old and new rooms become one.
Foundations, drainage and groundworks
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Every extension starts below ground. Footings are dug and concreted to suit the ground and the design, and any drains under or near the footprint are dealt with before walls go up. Concrete footings are typically one of the first visible stages we invoice for.
Structure, roof and weathertight shell
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Brickwork or blockwork is built up to roof plate level, steel beams are installed where openings into the house are needed, and the roof is covered so the building is watertight. From that point internal work can carry on regardless of the weather.
First fix, plastering and finishes
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Carpentry, plasterboard and plastering follow, then second-fix joinery and finishes. Our on-site team members hold trade-specific NVQs. At practical completion there is a final inspection and Building Control sign-off where applicable.
Residential only
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We work on homes only, not commercial property. That means the methods, programme and site conduct are planned around a family still living in the house.
Related services
Areas we cover
Before you start
Planning, regulations and living at home during extensions
How your estimate for extensions is put together
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We don’t publish package prices, because no two homes are the same: the age of the house, the ground it sits on, where the drains run, what is hidden in the walls and the finish you want all change the cost. Instead, after a site survey, a professional quantity surveyor prepares your estimate from the real scope of work. That means labour, materials, structural elements and the order of work are all accounted for before you agree anything. For most projects this estimate is free, because we pay for the quantity surveyor’s time. Only for unusually large or complex schemes is a detailed estimate charged, at £250 including VAT, and we always tell you before any work on it starts.
We use the word “estimate” deliberately. Existing homes often reveal things once they are opened up, and pretending otherwise with a “fixed price” usually means the number either hides gaps or carries a large margin for risk. When something does change, we talk about it openly with you and agree the way forward together before carrying on.
What a stage payment looks like
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Your project is divided into 4 to 7 milestones depending on its size and value. Typical examples are concrete footings complete, brickwork up to roof plate, roof covering watertight and plasterboard complete. Each milestone is something you can walk out and see for yourself. Only then is that stage invoiced. The first payment falls 72 hours before we start on site, and a small remaining balance is settled at practical completion and handover, so you are never paying far ahead of the work in front of you.
Planning permission and permitted development
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Planning permission is about what a building looks like and how it affects its surroundings. Some residential work can be carried out under permitted development rights without a full planning application, while other projects need approval from the local council. Rules differ for conservation areas, listed buildings and homes where permitted development rights have been removed by an earlier condition. If you already have approved plans, we build to them. If you don’t, we’ll talk through the options at your first consultation.
Building Regulations are separate from planning
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Even where planning permission isn’t needed, most structural and habitable work must meet Building Regulations. These cover structure, fire safety, insulation, ventilation and drainage. A Building Control inspector checks key stages, and on completion you receive the sign-off you’ll need when you come to sell or remortgage. Final inspection and Building Control sign-off, where applicable, are part of practical completion on every project we deliver.
The Party Wall Act
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If your work involves a wall shared with a neighbour, building on the boundary, or digging foundations close to a neighbour’s property, the Party Wall etc. Act 1996 usually requires you to give them formal notice before work starts. It’s worth raising early, because notice periods need to run before that part of the work can begin.
Living at home while we work
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Most of our customers stay in their homes throughout. Work is planned in stages so you know what is happening each week, who will be on site and what part of the house will be affected next. Reviewers regularly mention clear day-to-day updates and clean, considerate sites, the things that make living alongside a build manageable.
Questions to ask any builder
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- Who prepares the price, and what exactly does it include?
- How much is due before work starts, and when are the stage payments?
- What insurance do you hold, and is a guarantee available?
- Who is my day-to-day contact, and how will I be kept updated?
- Do you work to structural calculations and arrange Building Control?
We’re happy to answer every one of these before you commit. Read about Rick and the team, see verified reviews, or request your estimate.
Local to Northampton
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We’re based at The Beren, Blisworth Hill Business Park, just south of Northampton, and carry out extensions across the town and the surrounding villages, from Towcester, Roade and Bugbrooke to Moulton, Brixworth, Daventry and Wellingborough. Back to the homepage or browse all services.
FAQ
Extensions questions, answered
Do I need planning permission for an extension in Northampton?
Some smaller extensions fall under permitted development, while others need full planning permission from the local council. If you already have approval we build to it; if not, our design-and-build route takes you from concept through to completion. We’ll talk it through at your first consultation.
How long does an extension take to build?
It depends on size, design and ground conditions. Your estimate breaks the work into 4 to 7 physical stages so you can see how the programme runs before you commit.
Can we stay living in the house during the build?
Most homeowners do. Much of the early work happens outside the existing house, and the opening into your home is usually made later in the programme.
Do you handle Building Control?
Yes. Building Control sign-off, where applicable, forms part of practical completion.
How much will it cost?
Every home is different, so we don’t publish package prices. A professional quantity surveyor prepares your estimate from the real scope. For most projects that estimate is free; only for unusually large or complex schemes is a detailed estimate charged at £250 including VAT, and we’ll always tell you first.
Why an estimate rather than a fixed quote?
Changes often come up once work begins on an existing home. A QS-prepared estimate reflects the real scope, so you get an honest figure rather than a low number that grows later.
How do the payments work?
The first payment is due 72 hours before we start. You then pay in 4 to 7 stages, each invoiced only when that stage is visibly complete, with a small final balance at handover.
Is the work guaranteed?
An insurance-backed guarantee is available as an option, at 15% of the final project cost. We also hold £5,000,000 public liability insurance and employers’ liability insurance.
Do you take on emergency call-outs?
We carry out planned residential building projects rather than emergency call-outs. If you have a concern about your property, call Rick on 07704 675073 to talk it through.
Know the real cost of your extension before you commit
Share the basics and Rick will call you to talk it through. Free QS-prepared estimate for most projects, no obligation.
FMB & Checkatrade members · £5M public liability · Pay only for stages you can see