Building an extension to your home is a great way to enhance the value of your home and make it bespoke for your lifestyle. But when it comes to getting the best results from your project, you’ll need to ensure a high level of quality throughout the process. The two main options for achieving this is using an architect or a top design and build company. Here’s a breakdown of the pros and cons for each option to help you decide who’s right for your home extension.

What is a Design and Build Company?

A design and build company gives you access to a complete package of all the professionals you’ll need for your project, including architectural and home designers, high quality builders and trades, project managers and more. Essentially, it’s a one-stop shop for your extension, handling every aspect of the process in-house, from initial design and permits through to building and completion.

In contrast, an architect is a professional who can supply the plans for your project and provide any services needed to get your plans approved. Some architects can then recommend contractors and suppliers or offer project management services at additional cost.

The Pros and Cons of Using an Architect

First, let’s look at the advantages and disadvantages of using an architect.


  • Specialised professional  An architect is a professional with a degree in architecture who has passed the ARE (Architects Registration Board). This makes them a technical specialist in their field, with a statutory code of practice they need to adhere to.
  • Highly-detailed design – Architects are trained in a very technically detailed approach to building, looking at every aspect of the structure and design to make the project work. This is very important in projects where there are multiple systems and highly detailed requirements, from fireproofing buildings and supplying bespoke ventilation systems to eco-friendly building systems, unique structural spaces, and statement features.
  • Large-scale focus – Architects are big picture specialists, focussing on creating an entire environment for work or lifestyle. For example, they may work on creating an innovative, high-tech smart home, a theatre, or a green office building, bringing together every aspect of the building’s design and creation to deliver a space that fulfils that concept from top to bottom.


  • Expensive – Depending on the firm you use and the additional services they provide, an architect’s fees can add anything from 15-25% and upwards to your entire building cost.
  • Focus on larger projects – Many architecture firms don’t focus on small projects like home extensions, since the fees can make up a large portion of the overall cost. Usually, it is easier to find an architect for a full home build than an extension.
  • Fragmentation – You’ll have multiple points of contact, contractors, and subcontractors to deal with, even if your architect is the project manager. Most team members will have never worked together before, and many will have multiple projects on their timeline. This can push out your project delivery timeline and potentially damage the quality of your project if one or more contractors are not doing their best work.
  • Detail you don’t require – Architects usually want to create something in line with their vision, which may not be what you want or need. Maybe you want a warm and traditional space, but they push you towards a more trendy, minimalist, and high-tech design. Or maybe they want to add features and extras that could enhance your space and make it look great in their portfolio, but it pushes you far out of budget and doesn’t suit the rest of your home.

Pros and Cons of Using Design and Build Company

Now that we’ve looked at what architects offer, let’s see the pros and cons of a design and build company.


  • Specialised Professionals Top design and build companies use specialised architectural professionals that give you all of the advantages that you would gain from going directly to an architect. You get the benefits of high-detailed design and large-scale focus at less cost than if you would go directly to the architect.
  • Full-package deal – A top design and build company has all of the specialists you need in-house and will co-ordinate them to work on your project. There’s no need to hire anyone when you have a full package, so there’s no hassle about finding a builder or home designer yourself. They can also handle any planning permissions and permits your project may need.
  • Seamless project management – Project management is part of the deal, so you don’t have to worry about co-ordinating contractors or managing relationships between them. Because it’s all handled in-house, each member of the team knows the other and have worked out a schedule for their portion of your project, ensuring less hassle and faster project delivery times because no one is working other jobs on the side or causing delays for other contractors.
  • One point of contact – You’ll work one-on-one with the project manager who will then co-ordinate the team. This means there’s no back and forth for you to deal with, and if you have any changes you need to make, they can be implemented with minimal hassle.
  • Affordability – A design and build company encompasses all the services you need to create and deliver your extension, which brings down the overall costs. You’ll know all the costs upfront, be able to select from their list of suppliers, and be able to budget for your extension easily. You can even use our cost calculator to get a good idea of how much your project will cost.
  • Trusted work – So many people have building nightmare stories to tell – and a design and build company offers the ideal solution. Each team member is experienced, trained, and has the work experience in the company to prove themselves. You’re not hiring anyone externally who is unknown, who could potentially run over time, supply poor quality work or materials, or cause conflict. Your design and build company can refer you to multiple projects they’ve all worked on, complete with testimonials, so you know it’s work you can trust.


  • Not all design and build companies are equal – Always check the quality of past projects, the experience of past clients, and reviews before you sign on with a design and build company. Poor quality companies are out there, especially in the construction industry, so look for someone who can show you their past projects in person, who specialises in the type of extension you want, and who has a track record of successful projects delivered over an extended period of time.
  • Package quality differences – Some design and build companies specialise in budget extensions while others deliver bespoke services, so carefully check what their packages offer first. A good way to do this is to check out their reviews, and see their past projects in person to get an idea of the build quality, the designs they’ve done in the past, and the areas they’ve worked in. Quality always comes at a price, but the value it adds to your home and lifestyle is priceless!

Bespoke Home Extensions from London’s Leading Design and Build Company

Plus Rooms is a leading design and build firm in London that specialises in custom home extensions, including kitchen, living space, and loft extensions – and you can see our full portfolio here. Our talented team will lead you through the process from start to finish, helping you get the best floor plan, features, and quality for your budget. Whether you want a home for entertaining, for family living, or for your own enjoyment and investment purposes, we’re here to make that dream come true. In over 11 years we’ve helped over 10,000 homeowners transform their houses through high-quality design and build projects – let’s see what we can do for you.