Interior Designer vs Architect: Understanding the Differences
When planning a renovation, extension, or full home transformation, one question comes up time and time again: do you need an interior designer, an architect — or both?
It’s an important decision, especially in the UK where planning permission, Building Regulations, and budget considerations can shape your project from the very beginning. But beyond the practicalities, there’s something else that matters just as much:
how you want your home to feel once it’s finished.
At Speaking of Interiors, we believe great interiors are never accidental. They are layered, intentional, and thoughtfully designed — creating spaces that work beautifully while reflecting the life you actually live. To help you make the right choice, we’ve outlined the top 5 differences between an interior designer and an architect, with UK-specific examples and a general cost comparison.
1. What They Design: Structure vs Atmosphere
Architect (UK)
Architects focus on the building itself — the architecture, the structure, and how the property functions as a physical form. In the UK, this often includes:
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structural alterations and spatial reconfiguration
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extensions, loft conversions, and remodelling
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technical drawings for planning and construction
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ensuring compliance with Building Regulations
Interior Designer (UK)
Interior designers focus on what happens within the walls — how your home looks, flows, and feels day to day. This typically includes:
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intelligent space planning and furniture layouts
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colour, materials, and finishes that feel cohesive
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lighting design that enhances mood and usability
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bespoke joinery concepts and storage solutions
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final styling that brings the space to life
Luxury perspective:
An architect may create the room — but an interior designer curates the experience of being in it.
2. When You Need Them: Timing Matters
You’ll likely need an architect if you’re:
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building an extension (rear, side return, wraparound)
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reworking the footprint of the home
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changing windows/doors or adding structural openings
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submitting for planning permission
You’ll likely need an interior designer if you’re:
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renovating without structural changes
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redesigning your kitchen, bathroom, or living spaces
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refining a whole-house colour and finishes scheme
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aiming for a cohesive, elevated end result
Best-in-class approach:
For premium results, interior design works best when brought in early — not after the builders have finished. Decisions like lighting, flooring transitions, and joinery proportions are far more impactful when planned from the outset.
3. Regulations & Responsibilities in the UK
Architect
In the UK, architects are trained to support and navigate:
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planning applications (where required)
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technical construction documentation
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Building Regulations coordination
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integration with structural engineers and consultants
It’s also important to note: the title “Architect” is legally protected in the UK. Only registered professionals can use it.
Interior Designer
Interior designers may not submit structural planning drawings, but they often manage:
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detailed interior plans and specifications
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lighting plans and electrical layouts
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finishes schedules and design documentation
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supplier coordination and procurement support
For clients, this often translates into one key benefit: clarity.
No rushed decisions, no expensive missteps, no “we’ll deal with it later” moments.
An interior designer does more than improve aesthetics—they strategically guide your investment by optimising space planning and selecting the right finishes that add lasting value to your home.
4. Deliverables: Drawings vs Fully Realised Design
Architect Deliverables Typically Include:
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measured survey & site assessment
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existing and proposed layouts
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elevations and sections
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planning drawings (if applicable)
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construction drawings (depending on package)
Interior Designer Deliverables Typically Include:
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concept direction and moodboards
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room layouts and furniture plans
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lighting design (decorative + functional)
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colour palettes and material selections
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joinery concepts and storage planning
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FF&E sourcing (furniture, fixtures & equipment)
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styling guidance to complete the look
The difference in outcome:
Architectural plans help you build it. Interior design makes it liveable, timeless, and visually exceptional.
5. Cost Comparison: Architect vs Interior Designer (UK Guide)
Every project varies, but here’s a general UK cost overview to help you plan realistically.
Architect Fees in the UK (General Range)
Architect fees are often calculated as:
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5% to 15% of build cost (depending on scope and involvement), or
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£1,500 to £5,000+ for planning drawings on smaller projects
More complex design, detailing, or full project involvement can increase fees.
Interior Designer Costs in the UK (General Range)
Interior design support is often priced as:
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£50 to £250 per hour, or
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Fixed-fee packages (commonly £1,500 to £10,000+), or
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a percentage-based fee for full-service projects
Worth noting:
Interior design is often where budgets are either protected or lost. A designer helps avoid costly changes, ill-fitting furniture, poorly planned lighting, and unfinished “almost there” results.
Example: Ground Floor Extension for Victorian Terraced House in London
You’re extending the back of your home (common in Victorian terraces) to create an open-plan kitchen, dining, and family area.
You’ll need:
Architect — for structural planning, layouts, drawings, and compliance
Interior Designer — for kitchen design, finishes, lighting, flooring, furniture planning, and the “whole” look
Why both matters:
You can build a beautiful extension, but without interior planning, you may end up with:
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awkward lighting placement
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a kitchen layout that doesn’t flow
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not enough storage
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mismatched finishes across zones
The result can feel new — but not necessarily luxurious.
Final Thoughts: The Most Beautiful Homes Are Designed From the Inside Out
Architects and interior designers serve very different purposes — and in the UK, knowing which professional to bring in (and when) can shape your entire project experience.
At Speaking of Interiors, we specialise in creating interiors that feel effortless, elevated, and personal — balancing timeless design with everyday practicality.
If you’re unsure what support you need, we’re happy to help you find the right direction for your home.
FAQs : Interior Designer vs Architect
Do I need an architect or an interior designer first?
If you’re doing structural work (extension, major layout changes, loft conversion), start with an architect. If you’re not changing the structure and want a cohesive design direction, start with an interior designer. For the best results, involve an interior designer early alongside the architect.
What is the biggest difference between an architect and an interior designer?
An architect focuses on the building’s structure, layout, and compliance, while an interior designer focuses on how the space looks, feels, and functions day to day — including finishes, lighting, furnishings, and flow.
Can an interior designer replace an architect?
Not usually. In the UK, architects are needed for structural design work and for producing drawings for planning permission and Building Regulations. Interior designers complement architectural work by refining the interior layout, finishes, and overall aesthetic.
Is an interior designer worth it in the UK?
Yes — especially for renovations and full-room redesigns. Interior designers help prevent costly mistakes, improve layout and functionality, and create a cohesive, premium finish that would be difficult to achieve through piecemeal decisions.
How much does an architect cost in the UK?
Architects often charge between 5% and 15% of the build cost depending on involvement, or a fixed fee for planning drawings (often £1,500 to £5,000+ depending on project size and location).
How much does an interior designer cost in the UK?
Interior designers may charge hourly rates (often £50 to £250 per hour) or fixed packages typically starting around £1,500 and increasing depending on project scope and service level.
About Speaking of Interiors Ltd.
We’re a small yet thriving Interior Design Studio based in Clapham. We offer a range of expert, affordable and personalised services for residential and commercial projects in South West London. Would you like to discuss your project with us? Book a complimentary initial consultation call to speak to our expert team.