Almost every extension, loft conversion or major renovation starts with drawings. Good drawings help you get planning permission and Building Regulations approval, give builders something accurate to price from and reduce surprises on site. Choosing the right person to produce them is one of the most important early decisions you will make.
This guide explains who can draw up your plans, what drawings you are likely to need, and how to choose and work with a designer in Cornwall. It is general guidance only.
Architect, architectural technologist or designer?
Several kinds of professional can design a home extension:
Architects: in the UK, the title "architect" is protected by law. Anyone using it must be registered with the Architects Registration Board (ARB), which you can check online. Many are also members of the Royal Institute of British Architects (RIBA). Architects are trained in design, planning and construction, and are often a good fit for complex, sensitive or high-design projects.
Chartered architectural technologists: members of the Chartered Institute of Architectural Technologists (CIAT) specialise in the technical side of building design and are often well suited to Building Regulations drawings and straightforward extensions.
Architectural designers and plan drawers: many smaller extensions are drawn by experienced designers who are not registered architects. Quality varies, so look at examples of their work and check their insurance.
Whoever you choose, check that they have professional indemnity insurance and experience of similar projects in Cornwall.
What drawings will you need?
Depending on the project, you may need some or all of the following:
Measured survey: accurate drawings of the existing house and site, which everything else is based on.
Concept or sketch designs: early options to agree the layout, size and look.
Planning drawings: existing and proposed plans and elevations, a location plan and a block plan, to the level of detail needed for a planning application or Lawful Development Certificate.
Building Regulations drawings: more technical drawings and specifications showing structure, insulation, fire safety, ventilation and drainage, for approval by Building Control.
Structural calculations: usually from a structural engineer, for beams, foundations and any structural alterations.
Construction or tender information: extra detail and schedules to help builders price accurately.
Not every project needs every stage. A small single-storey extension under permitted development may not need planning drawings at all, but it will usually still need Building Regulations drawings. Our guides to planning permission in Cornwall, permitted development and Building Regulations explain how each route works.
Why local knowledge matters in Cornwall
Cornwall has its own planning considerations, and a designer who knows them can save time. These include:
conservation areas, listed buildings and the Cornwall National Landscape, where design is looked at closely
neighbourhood development plans, which many Cornish parishes now have
coastal exposure, which affects materials and detailing
traditional construction such as granite, slate, cob and mundic block
issues such as bats, radon, mining history and drainage on rural plots
Our guides to building in an AONB or conservation area, bat surveys and radon protection cover some of these in more depth.
Writing a good brief
The clearer your brief, the better the result. Before meeting a designer, think about:
what you need the space for and how you want to use it
your overall budget, including VAT, fees and contingency
must-haves and nice-to-haves
the style you like, with photos if you can
your timescale, including when you would like work on site to start
any known constraints, such as listed status, boundaries, trees or drainage
Be honest about budget from the start. A design that cannot be built for the money available wastes time and fees. Our guides to kitchen extensions and two-storey extensions give a sense of what drives cost.
Fees and appointments
Design fees vary widely depending on the size and complexity of the project and how many stages are included. Fees may be quoted as a fixed fee per stage, an hourly rate or a percentage of the build cost. Treat any figures you see online as general guidance only, and get written fee proposals from two or three designers. Check exactly what is included, for example the survey, planning submission, Building Regulations drawings, structural engineering and visits during the build, and what will be charged as extras. Council planning and Building Control fees are usually separate.
Ask for a written appointment setting out the scope of work, fees and who owns the drawings. Since the Building Safety Act changes in 2023, the Building Regulations also set out duties for clients, designers and contractors, including appointing a principal designer and principal contractor where more than one contractor is involved. Your designer and builder should be able to explain how this applies to your project.
Bringing in your builder early
Many homeowners wait until the drawings are finished before speaking to a builder. Involving a builder earlier can help, because they can comment on buildability, access, programme and likely costs before the design is fixed. Our project management and quantity surveying service can help keep design and budget in step, and our guide to project management and quantity surveying explains how. When quotes come in, our guide to reading a builder's quote explains what to compare.
Frequently asked questions
Do I need an architect for an extension?
No. There is no legal requirement to use an architect. Many extensions are designed by architectural technologists or designers, but you should check experience and insurance.
How can I check someone is a registered architect?
Search the Architects Registration Board's online register. Only people on that register can call themselves architects.
Do I still need drawings if my extension is permitted development?
Usually yes. You will normally need Building Regulations drawings, and drawings help builders price accurately.
Planning an extension? Talk to us
Cornish Building Company works across the whole of Cornwall and can talk you through the next steps. See our home extensions service, our process and the areas we cover. Call us on 01208 816991 or contact us to talk through your project.
