Design & Build Extensionsin NorthamptonOne Team, Concept to Completion
One builder from first sketch to final handover, so you have one person to call, one estimate to plan around and no gaps between designers and trades.
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 design & build extensions involve
What it is
Design and build means a single contractor carries your extension from the early concept through to the finished room. Instead of hiring a designer, then finding a builder, then hoping the two agree, you work with one team that is responsible for the whole project.
Who it’s for
It suits homeowners in Northampton and the surrounding villages who know they want more space but don’t yet have drawings or planning permission, and who would rather not manage several separate professionals themselves.
When you need it
Choose design and build at the very start, before drawings are commissioned. That is when decisions about size, layout, steelwork and budget have the biggest effect, and when having the builder involved saves the most time and rework.
Why it needs a professional
Designs drawn without input from the people who will build them can look good on paper and cost far more on site. Bringing construction knowledge in from day one means the design, the structure and the estimate are worked out together.
Get it wrong and it costs you
What happens when design & build extensions are rushed or done cheaply
Drawings you can’t afford to build
When design and build are separated, it is common to receive approved plans and then discover the construction cost is well beyond budget, sending you back to the drawing board.
Blame between professionals
When something doesn’t fit on site, a separate designer and builder can each point at the other. With one team, responsibility is clear.
Lost months
Every handover between consultants adds waiting time. A single team keeps the project moving from one stage to the next.
Decisions made without cost in mind
Choices about openings, rooflights and steel all change the price. Design and build keeps cost in view as those decisions are made.
Common mistakes homeowners make
- Commissioning full drawings before anyone has priced the build.
- Assuming planning approval means the design is buildable within budget.
- Managing designer, engineer and builder yourself without a single point of contact.
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 design & build 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
Design & Build Extensions in Northampton: methods and options
We work on homes only, never commercial property, across Northampton and the surrounding Northamptonshire towns and villages.
How design and build works with us
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It starts with an initial enquiry and consultation about your requirements and ideas. After a site survey, a professional quantity surveyor prepares your estimate. Once you are ready to proceed, we fix a start date, and the first payment is due 72 hours before we start on site.
Structural design
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Where your extension needs steelwork or structural openings into the existing house, we work with a partner local structural engineering firm. Their calculations specify the steel, and we install exactly what is specified.
Building from concept to completion
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The same team then delivers the groundworks, structure, roof, first fix, plastering and finishes. Work is delivered in 4 to 7 clearly defined physical stages, each invoiced only once it is visibly complete.
Single-storey, two-storey and kitchen extensions
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Design and build applies to every type of extension we build: single-storey rear and side extensions, two-storey extensions and open-plan kitchen extensions, including those that combine new space with removing internal walls.
When you already have drawings
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If you have already got architectural drawings and planning permission, design and build isn’t necessary. We can build directly from your approved plans, see our Extensions page.
Areas we cover
Before you start
Planning, regulations and living at home during design & build extensions
How your estimate for design & build 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 design & build 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
Design & Build Extensions questions, answered
Is design and build more expensive than hiring an architect separately?
Not necessarily. Because the design is shaped with construction cost in mind, it avoids paying for drawings that then have to be redrawn. Your QS-prepared estimate is free for most projects.
Who is my point of contact?
Rick Humphries, the founder, stays in contact from the first visit through to handover.
Do you deal with structural engineers?
Yes. We work with a partner local structural engineering firm for steelwork and structural calculations.
What areas do you cover?
Northampton and the surrounding Northamptonshire towns and villages, from our base at Blisworth Hill Business Park.
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 design & build 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