House Extension Design Services

MCIAT-Chartered Design. 350 Planning Approvals. Sussex & Surrey.

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Why Sussex and Surrey Homeowners Choose ArchEvolve

MCIAT-chartered and based in Rustington, ArchEvolve brings 15 years of experience and genuine local planning knowledge to every house extension project across West Sussex, East Sussex and Surrey.

      
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   Jonathan Gilbert 
 
 
 
 Trustindex verifies that the original source of the review is Google. I would highly recommend Alex and his company. He has amazing suggestions as well as taking into account our preferences and ideas too. He is easily accessible and has been so helpful in answering all our many questions! Looking forward to seeing our vision come to life!
  
 
      Posted on Google  
   
   James Riley 
 
 
 
 Trustindex verifies that the original source of the review is Google. Alex was really helpful throughout the whole process. This was our first ever project like this and he was on hand to answer MANY questions!
  
 
      Posted on Google  
   
   Nick Rutter 
 
 
 
 Trustindex verifies that the original source of the review is Google. Alex was so helpful from start to finish, great communication throughout. Would strongly recommend and will definitely use their services again in the future!
  
 
      Posted on Google  
   
   arron tully 
 
 
 
 Trustindex verifies that the original source of the review is Google. Alex at Arch Evolve assisted with obtaining planning permission for a couple of extensions that we were intending on doing. Very professional and offered allot of very helpful advice. Very Happy Thank you.
  
 
      Posted on Google  
   
   Marcus Eaton 
 
 
 
 Trustindex verifies that the original source of the review is Google. I have worked with Alex on many projects over the years and he has always been brilliant! Looking forward to working together again soon. Very professional and smooth process throughout the whole process.
  
 
      Posted on Google  
   
   Charlotte Morley 
 
 
 
 Trustindex verifies that the original source of the review is Google. Archevolve has completed a number of plans for us due to changing my mind regularly. They have been consistently patient & listened to my requirements at all time. Alex has then been on hand for our builders if required. Fantastic company & highly recommended
  
 
      Posted on Google  
   
   Peter Proto 
 
 
 
 Trustindex verifies that the original source of the review is Google. Used Alex for our large project, loft conversion, side garage and rear extension. Unbelievable service from start to finish. We are over the moon with the finish. Thank you so much!!
  
 
      Posted on Google  
   
   Tony Maio 
 
 
 
 Trustindex verifies that the original source of the review is Google. Great service, they had an excellent understanding of my requirements. They applied great attention to detail, with a  fast and very efficient service together very reasonable costs. I highly recommend this firm.

Our services

Every Type of House Extension, Designed In-House

House extensions come in very different shapes depending on your site and budget. ArchEvolve designs every configuration: single storey extensions, double storey extensions, rear extensions, side return extensions, wrap around extensions, kitchen extensions and glass extensions. Still weighing up which suits your property? Our guide to planning a home extension is a good place to start.

Completed rear extension at Oldfield Crescent

17 services · Sussex & Surrey

Residential

Extensions, conversions and whole-home projects for homeowners, with site visits across West Sussex, East Sussex and Surrey.

Extensions

House extensions Single storey extensions Double storey extensions Rear extensions Side return extensions Wrap around extensions Kitchen extensions Glass extensions

Conversions

Loft conversions Garage conversions Basement conversions Barn conversions

Whole home

House refurbishment Interior design Listed building design Self-build design Sustainable design

20 services · Nationwide

Developers & Commercial

Planning and technical design for developers and commercial clients across England.

Developer services

Design for developers Planning for developers Technical design for housing

Site & feasibility

Housing development feasibility Development site appraisals Residential masterplanning

Conversions

Commercial conversions Office to residential Flat conversions

Development types

New build schemes Residential developments Blocks of flats Infill housing Brownfield sites Affordable housing Mixed-use developments Care homes Student accommodation HMOs Rooftop developments

3D visualisation of a rear extension design

15 services · Homeowners and developers

Planning & Drawings

From the first feasibility check to construction drawings, in the order a project needs them.

01Feasibility & survey

Feasibility studies Measured building surveys Pre-application advice 3D visualisations

02Planning

Planning applications Planning drawings Permitted development Design and access statements Outline planning Reserved matters Discharge of conditions

03Technical & construction

Building regulations drawings Construction drawings Technical design for housing Contract administration

House Extension Design: Where Most Projects Go Wrong

A house extension is the single most common project ArchEvolve designs, and also the one where poor early decisions cost homeowners the most. Getting the design and planning strategy right before drawings are produced saves months and thousands of pounds.

Common challenges

Planning refusals from designs that ignore local policy
Extensions that lose light and feel like an afterthought
Slow revisions from designers still working in 2D CAD
Building Regulations issues caught after construction starts
Fees that creep past the original quote
Designers with no professional accreditation or indemnity insurance

How ArchEvolve solves them

Extension designs built around your local council’s planning policy
Space planning that prioritises light, flow and how you actually live
Revit 3D workflow for fast, accurate revisions before submission
Full Building Regulations drawings produced in-house
MCIAT-chartered accreditation with professional indemnity
MCIAT-chartered accreditation with professional indemnity

How an ArchEvolve Project Works

Every project follows a clear, stage-by-stage process aligned with the RIBA Plan of Work framework.

Initial Consultation

We discuss your brief, site and budget for your house extension project, along with any planning constraints specific to your council. Free, no obligation.

Feasibility Assessment

We assess planning viability and site constraints before any design fees are committed. This includes checking permitted development rights and any restrictions such as conservation areas.

Concept Design

We develop the house extension design in 3D and produce Enscape renders for your review before planning is prepared.

Planning Application

We prepare and submit the full application to your local planning authority and manage it through to decision.

Building Regulations

We produce the full Building Regulations package covering structure, thermal performance, drainage and fire safety. Extensions typically require additional structural calculations, which we coordinate directly with a structural engineer.

Construction Drawings

We deliver the complete technical drawing set your contractor needs to build your house extension accurately on site.

Construction Support

We remain available during the build to respond to queries and issue drawing updates where required.

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Areas we cover

Proudly Serving Homeowners Across Sussex and Surrey

Residential projects across West Sussex, East Sussex and Surrey, with site visits and local planning knowledge. Developer and commercial projects are delivered across England.

3Counties

14Towns

UKDevelopers

Town not listed? Ask us

West Sussex11 towns

Storrington Worthing Horsham Chichester Crawley Littlehampton Bognor Regis Burgess Hill Steyning Findon Hassocks

East Sussex2 towns

Brighton Eastbourne

Surrey1 town

Guildford

Developer or commercial project outside Sussex?

We work across England →

A Different Standard of Design for House Extensions in Sussex and Surrey

Most practices in the region still work in 2D CAD. ArchEvolve designs house extension projects in Revit and renders in Enscape, so you see the finished space before planning is submitted.

3D Visualisations Included

Every house extension project is modelled in Revit and rendered in Enscape. You see accurate light, materials and spatial quality before a planning application goes in.

Faster Planning Submissions

Drawings produced in a coordinated 3D environment are more complete and less prone to officer queries, which keeps your house extension timeline on track.

Local Planning Knowledge

ArchEvolve has submitted house extension applications across West Sussex, East Sussex and Surrey planning authorities. Your submission is prepared for the specific council from day one.

End-to-End Service

From feasibility through to construction drawings, Alex Page manages every stage of your house extension project personally. No handoffs, no junior staff taking over mid-project.

House Extension Design Across Sussex and Surrey

ArchEvolve designs house extensions for homeowners across the region, working directly with each local planning authority.

Many single storey rear extensions fall under permitted development and do not require a full planning application, but this depends on the size, your property type and any existing extensions. Larger extensions, side extensions, and properties in conservation areas usually need full planning permission. Our planning permission guide covers the thresholds in detail, and ArchEvolve confirms your specific position at the free initial consultation before any design fees are committed.

Design fees depend on the size and complexity of the extension, and whether the project also needs Building Regulations and construction drawings. ArchEvolve agrees fixed-scope fees in writing before any work begins, so there are no surprises. For typical build cost ranges, see our house extension cost guide.

In most cases, yes, provided the extension is well designed and proportionate to the property. Poorly planned extensions that reduce garden space or create awkward layouts can have the opposite effect. Our article on whether a house extension adds value breaks down the factors that matter most.

Design and planning typically take 8 to 13 weeks depending on your council’s determination period, with Building Regulations and construction drawings running in parallel once planning is granted. Construction time depends on the scope of the extension and your chosen contractor. ArchEvolve manages the design and approvals stages so your project reaches site as quickly as the process allows.

The service covers feasibility assessment, concept design in Revit with Enscape renders, planning application preparation and submission, full Building Regulations drawings, and construction drawings your builder can quote and build from. Support continues through the construction phase for queries and drawing updates.

Extension costs can escalate through structural surveys, party wall matters, drainage diversions and unforeseen ground conditions. Our guide to the hidden costs of a house extension sets these out clearly so they can be planned for from the outset rather than discovered mid-build.

ArchEvolve is based in Rustington and designs house extensions across West Sussex, East Sussex and Surrey, including Worthing, Horsham, Chichester, Crawley, Guildford and Brighton. A free initial consultation is offered to homeowners throughout the region.

Frequently Asked Questions

Start Your House Extension Design Today

Free initial consultation for homeowners across Sussex and Surrey. Get in touch to discuss your extension.