Double Storey Extension Design Services

More Floor Area, One Planning Application. Sussex & Surrey.

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Why Sussex Homeowners Trust ArchEvolve With Double Storey Extensions

Double storey extensions carry more structural and planning risk than single storey projects. ArchEvolve is MCIAT-chartered with 350 planning approvals secured 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!
  
 
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   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!
  
 
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   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

Double Storey Extensions Alongside Related Services

A double storey extension delivers more floor area for a single planning application, but is not always the right fit for every plot. Compare it against a single storey extension, or discuss a wrap around extension if width rather than height suits your garden better. See the full range on our house extension design services hub.

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

Double Storey Extensions: Where Structure Meets Planning

A double storey extension changes the massing and street impact of a property far more than a single storey addition, which means planning officers scrutinise these applications more closely. Structural coordination also becomes essential rather than optional.

Common challenges

Massing that overwhelms the existing property or streetscape
Overlooking objections from first floor windows
Structural loading issues discovered after planning approval
Roof tie-in details that create leaks or cold bridging
Party wall complications with attached and semi-detached properties
Designers without in-house Building Regulations capability

How ArchEvolve solves them

Massing and roof form designed to match the existing property
Window positioning assessed against neighbour overlooking distances
Structural coordination with an engineer built into the design stage
Roof and junction detailing resolved before planning submission
Full Building Regulations package produced in-house
Full Building Regulations package produced in-house

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 double storey 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 an early view on structural feasibility given the additional floor loading involved.

Concept Design

We develop the double storey 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. Double storey extensions require detailed structural calculations, which we coordinate directly with a structural engineer as standard.

Construction Drawings

We deliver the complete technical drawing set your contractor needs to build your double storey 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 Double Storey Extensions in Sussex and Surrey

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

3D Visualisations Included

Every double storey 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 double storey extension timeline on track.

Local Planning Knowledge

ArchEvolve has submitted double storey 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 double storey extension project personally. No handoffs, no junior staff taking over mid-project.

Double Storey Extension Design Across Sussex and Surrey

ArchEvolve designs double storey extensions for detached, semi-detached and terraced properties throughout the region.

Yes, in almost all cases. Double storey extensions fall outside permitted development rights more often than single storey projects, particularly where they affect roof form, overlooking or the character of the property. ArchEvolve confirms your specific requirements at the free initial consultation.

Costs are higher than single storey projects due to structural work, scaffolding and roof alterations. See our house extension cost guide for typical ranges across extension types.

This is the most common reason double storey applications face objections. ArchEvolve positions first floor windows and assesses overlooking distances at concept design stage, before the application is submitted, to reduce the risk of delay.

ArchEvolve coordinates directly with a structural engineer during design so loading, foundations and roof tie-ins are resolved before Building Regulations drawings are produced, rather than discovered during construction.

Planning determination typically takes 8 to 13 weeks depending on your council, with structural coordination and Building Regulations running alongside. Our guide to planning a home extension covers the wider timeline.

Yes, although party wall matters and structural tie-ins with the neighbouring property need careful handling. ArchEvolve has designed double storey extensions across all property types throughout Sussex and Surrey.

ArchEvolve covers West Sussex, East Sussex and Surrey, including Worthing, Horsham, Chichester, Crawley, Guildford and Brighton, with a free initial consultation offered throughout the region.

Frequently Asked Questions

Start Your Double Storey Extension Design Today

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