What Does an Architectural Design Service Include? A Clear Guide for Essex Homeowners
When people talk about ‘architectural design’ for an extension, what they actually get is a measured survey of the property, a full set of existing and proposed drawings, and either a planning application or an assessment of your permitted development rights, with Kirkwood managing all of it on your behalf. What tends to catch people out is what isn’t included: structural engineering and building regulations are handled as their own separate stages, not folded into the design fee.
This guide explains exactly what the design stage covers, what is not included, and how the three professional stages of a residential extension project fit together. If you are planning an extension in Essex and want to understand the process before you commit to anything, this is the right starting point.
- What an Architectural Design Service Includes
- What Is Structural Engineering, and Why Is It a Separate Stage?
- What Are Building Regulations Drawings?
- The Three Professional Stages — Summary
- How Much Does an Architectural Design Service Cost in Essex?
- Where Kirkwood Provides Architectural Design Services
- The Complete Package
- Frequently Asked Questions
What an Architectural Design Service Includes
There are five distinct pieces that make up an architectural design service for a residential extension, and Kirkwood bundles all five into a single package rather than splitting them across different suppliers.
- A full measured survey. Nothing gets drawn until someone from the design team has physically been to the property and measured it properly, every room, every wall, window and door, ceiling heights included. Everything that follows is built on these measurements.
- Drawings of the property as it stands. Floor plans and elevations showing the house exactly as it currently is, before any work happens. This becomes the official baseline against which the proposed changes are compared.
- Drawings of the proposed extension. The actual design, new floor plans showing how the space will work, elevations showing what it’ll look like from outside. Nothing gets submitted anywhere until you’ve signed off on these.
- The planning route sorted. With the design finalised, Kirkwood works out whether it falls under Permitted Development or needs a proper planning permission for a house extension application, then handles submitting it and dealing with the council directly.
- A Lawful Development Certificate, where relevant. If the project proceeds as Permitted Development, Kirkwood applies for this certificate to put it in writing that the work is lawful. It’s not a legal requirement, but it’s worth having; it saves headaches later if a solicitor asks questions when you come to sell.
The design rarely lands perfectly on the first attempt, and that’s expected. You’ll typically go through one or two rounds of changes with the design team until it feels right. Nothing gets submitted to the council until you’re genuinely happy with what’s on the drawings.
What Is Structural Engineering, and Why Is It a Separate Stage?
Structural engineering sits apart from architectural design as its own professional stage, and there’s no getting around it; almost every extension needs it.
A structural engineer working on a house extension typically does the following:
- Works out the size of steel beam needed anywhere an internal wall comes out, so the floor or roof above stays properly supported.
- Sorts out the foundation design for the new build, how deep, how wide, and what it’s made of.
- Sets the sizes for the floor joists in the new structure.
- Puts together the structural drawings a builder will actually work from on site.
- Hands over the calculations building control (the council department that checks construction work meets legal standards) needs to sign the project off.
This stage is kept separate from architectural design for two reasons. First, the structural calculations cannot be finalised until the design is fixed, because the structural requirements depend on the layout, the loads, and the span of the beams involved. Second, structural engineering is a regulated profession requiring specific qualifications, distinct from what a design team produces.
At Kirkwood, structural engineering is produced by the same in-house team as the architectural drawings; both stages are managed together, which means the drawings are coordinated from the start.
Structural engineering for a standard single-storey extension in Essex is typically priced similarly to the architectural design stage, reflecting the level of technical detail, calculation, and liability involved.
For a full explanation of what structural engineering involves for a house extension, see the structural engineering for house extensions page.
Want to understand the costs before you commit?
What Are Building Regulations Drawings?
Building Regulations drawings are the last of the three stages before anyone can pick up a tool, and unlike planning permission, there’s no route around them. Every extension needs this stage, full stop.
Building Regulations drawings cover:
- How the foundations are actually constructed
- Wall build-up, insulation levels, and thermal performance
- Roof construction and how it’s kept watertight
- Fire safety, including escape routes
- Ventilation
- Drainage
- The structural details carried over from the engineering stage.
It’s easy to mix these two up, but they serve different purposes. Planning drawings are about appearance and position, how the extension looks and where it sits on the plot, and it’s the council’s planning department that reviews them. Building Regulations drawings are about construction, how the thing actually gets built, and those go to building control instead, whether that’s the council’s own team or an approved private inspector.
The practical reason this stage matters: a builder simply can’t construct the extension properly without these drawings in hand. And skip Building Regulations approval, and you’re left without a completion certificate at the end, something both solicitors and mortgage lenders will ask for the moment you try to sell or remortgage.
Kirkwood produces Building Regulations drawings as part of its complete service; see the Building Regulations drawings page for a full breakdown.
The Three Professional Stages — Summary
Getting an extension built in Essex nearly always means working through three distinct professional stages before a single brick gets laid. Each one produces its own paperwork, aimed at a different audience: the council, building control, and eventually the builder. Here’s how they line up.
Stage | What It Produces | When It Applies | |
Stage 1 | Architectural Design | Existing and proposed drawings, planning application or PD assessment | Needed for all residential extensions and conversions |
Stage 2 | Structural Engineering | Beam calculations, foundation design, joist specifications, structural drawings | Needed for all projects where walls are removed, or structure is altered |
Stage 3 | Building Regulations | Technical construction drawings, compliance information, building control submission | Needed for all extensions — required by law regardless of planning route |
In theory these three stages run one after another, though in practice structural engineering and Building Regulations often overlap once the design itself has been signed off. Kirkwood keeps all three in-house rather than farming them out, which means one team is responsible for the lot, so the drawings, the calculations, and the final technical package all line up with each other rather than being stitched together after the fact.
How Much Does an Architectural Design Service Cost in Essex?
What you’ll pay for architectural design work on an extension in Essex comes down largely to how big and how complicated the project is.
A few factors affect the cost most:
- How big the extension is — a modest 3x3m single-storey addition is a much smaller job than a double-storey wraparound.
- Whether you need full planning permission, or the project can go ahead under Permitted Development.
- How many rounds of revisions the design goes through.
- Whether extras like party wall notices need sorting out alongside the main package.
As general market context: architectural design fees for a standard single-storey rear extension in Essex typically represent around 5 to 10 per cent of the total build cost. Structural engineering and Building Regulations are priced separately and are broadly similar in scale to the design fee. Together, all three professional stages typically account for 10 to 15 per cent of the total project cost.
None of this needs to stay a mystery, either; Kirkwood walks through a clear, itemised fee breakdown as part of the free Discovery Call, well before you’ve committed to anything.
For full extension cost information including build costs, see our house extension costs in Essex page.
Where Kirkwood Provides Architectural Design Services
Kirkwood provides architectural design services throughout Essex and into parts of East London. Recent work spans Chelmsford, Brentwood, Billericay, Wickford, Basildon, Rayleigh, Leigh-on-Sea, Southend-on-Sea, Benfleet, Hornchurch, Colchester, Braintree, and the towns and villages around them.
No two projects are quite the same, because no two councils apply quite the same rules; what flies in Chelmsford under Chelmsford City Council isn’t necessarily what flies in Brentwood under Brentwood Borough Council, and Kirkwood’s team has worked with both closely enough to know the difference. That local knowledge counts for a lot at the planning stage, especially in conservation areas or on plots where a previous application has already been turned down.
The Complete Package
Between them, the survey, the design work, and the planning stage make up what most people mean by architectural design. Structural engineering and Building Regulations pick up from there, priced on their own, but just as essential. Put the three together, and you’ve got the full professional package a builder actually needs before they can start work.
If a house extension is somewhere on your radar and you’d like to actually understand what’s involved and roughly what it costs before deciding anything, Kirkwood’s Discovery Call is free and comes with no strings attached.
Frequently Asked Questions
What does an architectural design service include?
An architectural design service for a house extension includes a full measured survey, existing and proposed drawings, a planning application or permitted development assessment, a Lawful Development Certificate application, and communication with the council throughout. It does not include structural engineering or Building Regulations drawings; those are separate professional stages that follow the architectural design.
What is not included in an architectural design service?
Structural engineering calculations, Building Regulations drawings, and the build itself are not included in the architectural design stage. These are separate professional stages. Structural engineering follows the design and produces beam calculations, foundation designs, and structural drawings. Building Regulations drawings follow after structural engineering and form the technical package submitted to building control.
What is the difference between planning drawings and Building Regulations drawings?
Planning drawings show what the extension will look like and are assessed by the council’s planning department. Building Regulations drawings show how the extension will be constructed, covering foundations, insulation, fire safety, ventilation, and drainage, and are assessed by building control. Both sets of drawings are required for most extensions, but they are produced at different stages of the project.
Do I need structural engineering for a house extension?
Yes. All extensions require structural engineering calculations, particularly where internal walls are removed, or new structural elements are introduced. A structural engineer calculates steel beam sizes, foundation depths, and floor joist specifications. At Kirkwood, structural engineering is produced by the same in-house team as the architectural drawings, ensuring both are coordinated from the start.
How much does an architectural design service cost in Essex?
Architectural design fees for a standard single-storey extension in Essex typically represent around 5 to 10 per cent of the total build cost. Structural engineering and Building Regulations are priced separately and are broadly similar in scale. Together, all three professional stages typically account for 10 to 15 per cent of the total project cost. Kirkwood provides a clear, itemised fee breakdown during the free Discovery Call.
What is a Lawful Development Certificate, and is it included in the architectural design service?
A Lawful Development Certificate is a formal document from the council confirming that an extension qualifies as Permitted Development and is therefore lawful. It is strongly recommended even when full planning permission is not required, as solicitors and buyers routinely ask for it when a property is sold. Kirkwood includes the Lawful Development Certificate application as part of its architectural design service for applicable projects.
How long does the architectural design stage take?
The measured survey and initial design typically take 4 to 6 weeks. Once the design is agreed, a planning application or Lawful Development Certificate application takes a further 5 to 10 weeks for the council to determine. The architectural design, structural engineering, and Building Regulations stages together typically take 10 to 18 weeks before construction can begin.
Can the same company provide architectural design, structural engineering, and Building Regulations?
Yes, and this is the most efficient approach. Kirkwood provides all three stages in-house with the same coordinated team, which eliminates the gaps that can arise when separate companies handle each stage. The drawings, structural calculations, and Building Regulations package are all produced together, ensuring they are consistent and complete when submitted to the council and building control.
Book a free discovery call
30 to 45 minutes, no charge, no obligation. Get started below.
Explore our Services
Get an instant design & build quote
Where would you like to extend?
Detached
Semi Detached
Terrace
Bungalow
Kirkwood articles
Straight-talking architecture
Areas We Cover in Essex
We’re proud to help homeowners all across Essex. Some of the areas we serve include: