17 services · Sussex & Surrey
Residential
Extensions, conversions and whole-home projects for homeowners, with site visits across West Sussex, East Sussex and Surrey.
Extensions
Rooftop Development Design Services
Extra Storeys and New Flats on Existing Roofs. Nationwide.
Why Developers Trust Our Rooftop Development Design Services
Building on top of an occupied building leaves little room for error: the structure, the residents below and the freeholder all have to be satisfied. ArchEvolve is MCIAT-chartered and models the existing building and new storeys together in Revit, so problems show up early.
- 15 years of experience
- 350 planning approvals secured
- 500 projects completed
- Revit 3D modelling as standard
- MCIAT-chartered accreditation
Our services
Rooftop Development and Related Services
Before committing to an upward extension, a feasibility study tests structure, access and planning in one report. Extra floors on family homes fall under our loft conversion and house extension services. Where new floors sit above shops or offices, see mixed use development design.
20 services · Nationwide
Developers & Commercial
Planning and technical design for developers and commercial clients across England.
Developer services
Site & feasibility
15 services · Homeowners and developers
Planning & Drawings
From the first feasibility check to construction drawings, in the order a project needs them.
01Feasibility & survey
02Planning
03Technical & construction
Rooftop Development: Adding Storeys to Existing Buildings
Our rooftop development design services help freeholders and developers add new flats on top of existing blocks, terraces and commercial buildings. Airspace development can create homes without buying land, but it only works if the structure can take the load, residents can reach the new floors safely and the planning route is clear. We test all three before you commit, then design the new storeys and their connection to the building below.
Common challenges
- Existing foundations and frame unable to carry extra storeys
- No practical way to extend stairs or lifts to new floors
- Disruption to residents and tenants living below during works
- Uncertainty over permitted development eligibility for upward extensions
- Added height pushing the building into stricter fire safety rules
- New storeys that look bolted on in the street scene
How ArchEvolve solves them
- Lightweight construction options assessed early with a structural engineer
- Core extension or new stair tested in the 3D model
- Off-site and lightweight methods considered to shorten time on the roof
- Eligibility checked against current conditions before choosing prior approval or full planning
- Final height and storey count checked against safety thresholds before design
- Proportions, materials and setbacks designed to suit the existing facade
How an ArchEvolve Project Works
Every rooftop development follows a sequence that proves the building can take new storeys before design fees escalate.
Building and Title
We review existing drawings, the building's age and use, its planning history and who controls the roof, including leaseholder rights to consider.
Measured Model
The existing building and roof are modelled in Revit, giving the structural engineer and planning case an accurate base to work from.
Structural Capacity
With a structural engineer, we establish how much additional load the frame and foundations can take and which construction methods suit.
Massing and Access
We test how many storeys and flats are achievable, how residents will reach them and how the extension sits in the street.
Planning Route
We prepare a prior approval application where permitted development applies, or a full planning application with Enscape views where it does not.
Technical Design
Fire strategy, sound separation from the floors below, drainage and services connections are developed into a Building Regulations package.
Construction Information
We issue construction drawings coordinated with engineers and your contractor, with a sequence that limits disruption to occupants below.
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Rooftop Developments Designed for Sites Across the UK
The 3D Difference When Building on Top of a Building
Rooftop schemes depend on how new floors meet old ones. ArchEvolve models existing and proposed storeys together in Revit and renders them in Enscape, so stairs, structure and services line up, and freeholders, residents and officers can see the result clearly.
3D Visualisations Included
Every rooftop scheme is rendered in Enscape in its street context, which helps freeholders, residents and planning officers understand the change.
Early Feasibility Answers
Structure, access and planning route are tested first, so you know whether the airspace is viable before paying for full design.
UK-Wide Remote Delivery
Rooftop developments are designed for developers and freeholders across the UK over Microsoft Teams, with site visits arranged as needed.
End-to-End Service
Alex Page runs your rooftop development personally from first review to construction drawings. No handoffs and no junior staff on your scheme.
Rooftop Development Design Across the UK
ArchEvolve designs rooftop developments and upward extensions for freeholders and property developers anywhere in the UK, working remotely over Microsoft Teams with site visits when needed.
What do your rooftop development design services include?
The service covers a review of the building and title, a measured Revit model, structural capacity checks with an engineer, massing and access studies, the prior approval or planning application, a Building Regulations package and construction drawings sequenced around the occupants below.
Can I add storeys under permitted development?
In England, Part 20 of the General Permitted Development Order allows additional storeys on certain blocks of flats, commercial buildings and houses, subject to prior approval. Eligibility depends on building type, age, height and location, and listed buildings are excluded. Our permitted development service checks your building against the current conditions.
How do I know if my building can take extra floors?
A structural engineer needs to assess the frame and foundations, often using original drawings and site investigations. Lightweight construction such as steel or timber frame can make the difference. We coordinate this assessment early, so you do not pay for design that the building cannot support.
Do I need the freeholder's permission?
Yes. Whoever owns the roof and airspace must agree, and leases often restrict building works or give leaseholders rights. If you are not the freeholder, a legal review of the title and leases should run alongside our design work, before any application is made.
Does adding storeys change the fire safety requirements?
It can. Extra height can bring a building into stricter rules, including sprinklers in taller blocks and the higher-risk building regime under the Building Safety Act. We check the final height and storey count against these thresholds before the scheme is fixed.
Will residents have to move out during the works?
Not usually, though there will be some disruption. Lightweight and prefabricated construction can reduce time spent working on the roof, and the design should protect existing flats from water and noise during the build. We plan the sequence with your contractor and engineer.
Have you designed upward extensions before?
Yes. Our Kentish Town project added two new storeys to an existing building, housing a bar and a cinema room, while preserving its historic facade. ArchEvolve delivered the building control documentation and construction drawings. See more in our commercial portfolio.
What about party walls on a terrace?
Where new storeys are built on or against a shared wall, the Party Wall etc. Act 1996 usually requires notice to neighbours in England and Wales. We flag party wall issues during design and prepare construction drawings your party wall surveyor can work from.
Frequently Asked Questions
Start Your Rooftop Development Today
Free initial consultation for freeholders and developers UK-wide. Send us the address and any existing drawings to get started.
