- What Is Traditional Procurement?
- What Is Design and Build?
- The Key Differences Side by Side
- The Real Cost of the Gap Between Designer and Builder
- Budget Oversight: More Than Just an Upfront Quote
- Design Quality: Does Design and Build Mean Compromising on Creativity?
- Which Route Suits a London Extension or Loft Conversion?
- What to Look for in a Design and Build Contractor in London
- Getting a Realistic Cost Before You Commit
- FAQs
You've decided to extend, convert, or refurbish your home. The next question most London homeowners face isn't which contractor to hire — it's which procurement route to use. Get this wrong and you can end up with misaligned teams, disputed costs, and a project that drags on far longer than it should.
This article breaks down the two main approaches — design and build, and traditional procurement — so you can choose the one that actually suits your project, your budget, and your life.
What Is Traditional Procurement?
Traditional procurement separates design and construction into two distinct contracts. You hire an architect or designer first, agree a full set of drawings, then go out to tender and appoint a separate contractor to build from those drawings.
The process typically runs like this:
- Appoint an architect
- Develop designs through planning and technical stages
- Put the project out to tender
- Appoint a builder
- Manage the relationship between both parties throughout the build
It's the older model, and it still dominates large commercial and public-sector projects. For residential work in London, it's also common — particularly among homeowners who want a specific architect's vision and are comfortable managing the process themselves.
Where traditional procurement works well
- You have a strong relationship with a specific architect whose design you want to protect
- Your project is complex enough that independent oversight of the contractor adds real value
- You're comfortable acting as the point of contact between designer and builder
- You have the time to manage the process and resolve disputes when they arise
What Is Design and Build?
Design and build puts a single team in charge of both design and construction. You work with one company from the initial brief through to the finished project — one contract, one point of accountability, one team responsible for making the design work within budget.
For London homeowners, this typically means working with a contractor who employs or closely partners with designers in-house. The design evolves alongside the build programme, which removes the gap between what an architect draws and what a builder can actually deliver.
Where design and build works well
- You want a single point of contact and clear accountability
- Budget certainty matters more than having a standalone architectural vision
- You don't have the time or appetite to manage two separate professional relationships
- You want the design shaped by buildability from the start
The Key Differences Side by Side
| Factor | Traditional Procurement | Design and Build |
|---|---|---|
| Accountability | Split between architect and contractor | Single team, single contract |
| Cost certainty | Harder to pin down until tender stage | Clearer earlier in the process |
| Design control | Higher — architect acts independently | Shared — design informed by cost and programme |
| Time to start on site | Longer — design must be complete before tender | Faster — design and build can overlap |
| Dispute risk | Higher — two parties can blame each other | Lower — one team owns the outcome |
| Complexity for client | Higher — you manage the relationship | Lower — the contractor manages it |
The Real Cost of the Gap Between Designer and Builder
One of the most common frustrations London homeowners report is receiving a beautiful set of drawings from their architect, only to find the first builder to price the job comes back 30% over budget. The architect revises the drawings. The builder re-prices. Weeks pass. Sometimes months.
This happens because traditional procurement separates the people who design from the people who build. The architect's job is to produce the best possible design. The builder's job is to price what's in front of them. Nobody is responsible for making sure those two things align from the start.
Design and build removes that gap. When the same team handles both design and delivery, cost is part of the conversation from day one — not a shock at tender stage.
Budget Oversight: More Than Just an Upfront Quote
A ballpark figure at the start of a project is useful. But what happens to your budget visibility once work begins?
In traditional procurement, cost monitoring often falls to a quantity surveyor — an additional appointment, an additional fee, and another professional relationship to manage. In a well-run design and build contract, budget oversight is built into the service. You should know where your money is going throughout the project, not just at the beginning and the end.
At MVV, monthly progress reports include budget tracking and on-site photography. You see exactly where the project stands — financially and physically — every month. That kind of transparency is what separates a genuinely managed design and build service from one that hands you a quote and goes quiet until practical completion.
Design Quality: Does Design and Build Mean Compromising on Creativity?
This is the most common objection to design and build, and it deserves an honest answer.
Traditional procurement, done well, can produce exceptional architecture. If you have a specific architect in mind and their design vision is central to your brief, traditional procurement protects that vision. The architect works independently, and the contractor builds to the drawings.
Design and build, done well, produces spaces that are both well-designed and buildable. The best teams employ talented designers who work within real-world constraints — planning requirements, structural limitations, your budget. The result is a design that doesn't need to be value-engineered into something unrecognisable once a builder prices it.
The honest answer is that design quality depends far more on the team you appoint than on the procurement route you choose.
Which Route Suits a London Extension or Loft Conversion?
For most residential projects in London — a rear extension, a loft conversion, a kitchen extension, or a full property refurbishment — design and build tends to be the more practical choice.
London projects are often constrained. Party wall agreements, planning restrictions, permitted development rules, and tight urban plots all mean that design decisions carry direct cost and programme implications. A team that handles both design and construction is better placed to navigate those constraints without losing time or money.
You're also, in most cases, living in the property or managing it as a landlord. You don't want to spend your evenings mediating between your architect and your builder. You want one team, one conversation, and monthly reports that tell you what's happening.
That said, if you're undertaking a significant new build, a listed building project, or a development where independent professional oversight genuinely matters, traditional procurement may be the right call.
What to Look for in a Design and Build Contractor in London
Not all design and build contractors operate the same way. Before you appoint anyone, ask these questions:
- Do you have in-house designers, or do you subcontract the design?
- How do you handle budget changes during the project?
- What does your reporting process look like during the build?
- Can I see completed projects similar to mine?
- Who is my single point of contact from design through to completion?
The answers will tell you quickly whether you're dealing with a genuinely integrated team or a builder who has bolted a design service onto their website.
Getting a Realistic Cost Before You Commit
One of the frustrations with both procurement routes is that getting a realistic cost figure often requires significant upfront investment in design fees or lengthy consultation processes.
MVV's instant online cost estimator at themvv.co.uk gives you a ballpark project cost before any consultation, with no commitment required. It's a practical starting point if you want to understand whether your project is financially viable before spending time with any contractor.
FAQs
What is the main difference between design and build and traditional procurement?
Traditional procurement uses two separate contracts — one for design and one for construction. Design and build uses a single team and a single contract for both, which means one point of accountability throughout the project.
Is design and build cheaper than traditional procurement?
Not always, but it tends to produce greater cost certainty earlier. Because the design and build team controls both design and construction, cost is factored into design decisions from the start rather than emerging as a surprise at tender stage.
Does design and build work for London loft conversions and extensions?
Yes. For most residential projects in London, design and build is well-suited because it reduces the gap between what is designed and what can be practically delivered within budget and planning constraints.
Will I have less design control with a design and build contractor?
You'll have a different kind of involvement. Rather than approving an architect's independent vision, you collaborate with a team whose design is shaped by real-world cost and buildability. Many homeowners find this produces a more practical result.
How do I know my budget is being managed properly during a design and build project?
Ask your contractor what their reporting process looks like. A well-run design and build service should provide regular budget updates throughout the project, not just an upfront quote. MVV provides monthly progress reports with budget tracking and on-site photography as a standard part of the service.
Can design and build contractors handle planning permission?
Yes. Most design and build contractors manage the planning process as part of their service, including permitted development assessments, planning applications, and party wall notices where required.
What should I do first if I'm considering a London home extension or loft conversion in 2026?
Start by getting a realistic cost estimate. MVV's free online estimator at themvv.co.uk gives you a ballpark figure with no commitment, so you can make an informed decision before entering any formal process.
The procurement route you choose shapes your entire project experience — your stress levels, your budget visibility, and the quality of the finished result. For most London homeowners planning an extension, loft conversion, or refurbishment in 2026, design and build offers the clearest path from concept to completion. The key is finding a team that genuinely integrates design and construction, keeps you informed throughout, and takes your budget as seriously as you do.