Straight answers about costs, process, and what to expect when working with an affordable, client-led architectural design service in London.
Not always by law, but it’s strongly recommended. For most home extensions and loft conversions in London, you’ll need drawings to apply for planning permission and to give a contractor an accurate basis to quote and build from. An architectural designer produces these drawings, helps you avoid costly mistakes, and makes sure the design genuinely works for how you live — not just on paper.
Full architectural services from a traditional practice typically run from 8 to 15 percent of build cost, which on a typical extension can mean tens of thousands of pounds. At Terrence, we offer a fixed-fee, drawings-only service starting from £700 for internal renovations and from £1,100 for extensions and loft conversions. This keeps costs predictable and proportionate to a residential project.
Planning drawings are submitted to obtain planning permission and permitted development approval. They show the proposed layout, external appearance, and materials of your project. Construction drawings are a more detailed set used to get accurate quotes from contractors and to build from — they include the technical information, sections, and details your builder needs to price and deliver the work.
A lot — this is a genuinely collaborative process. Most of our clients already have a good understanding of their home and a clear sense of how it could work better. We start from those ideas rather than a blank page, and work alongside you to shape them into a design that’s spatially considered, technically sound, and buildable — bringing design and technical expertise to refine and strengthen your thinking, not replace it. That collaboration is part of how we keep the process efficient and the fees affordable.
Most London councils aim to determine a householder planning application within eight weeks of validation, though this can run longer depending on the borough and the complexity of the project. Well-prepared, clear drawings reduce the chance of requests for further information, which is one of the most common causes of delay.
Yes. We have a network of trusted, vetted tradespeople we know personally and who offer cost-effective, reliable work. We can introduce you once your drawings are ready. We don’t take referral fees from contractors — we recommend people we’d use ourselves.
We’re based in Peckham, South East London, but we work with homeowners right across London and beyond — from Southwark, Hackney, and Lewisham to projects further afield, wherever the right brief takes us.
For most extensions and loft conversions, yes — a structural engineer will be needed to calculate beam sizes, foundations, and other structural elements, and to produce calculations for building control. This is a separate fee to our architectural drawing services. We can recommend engineers we’ve worked with before.
Under the Construction (Design and Management) Regulations 2015, projects involving more than one contractor legally require a Principal Designer to manage health and safety risks during the design and pre-construction phase. We can provide this service and produce the required documentation, but it sits outside our drawings-only fee — it’s quoted separately, with the cost depending on the complexity and scale of your project.
Yes. Our two packages can be taken individually or together. Some clients only need planning drawings to secure permission and arrange their own construction drawings or builder relationship afterwards. Others come to us already having permission and just need construction-ready drawings. You can select whichever combination applies to your project.
Yes we do, though this sits outside our standard drawing packages and is quoted separately. We’re very happy to explore other design services you might need alongside the architectural drawings — just mention it when you get in touch and we can discuss what would work best for your project.