Dorset · Est. 2010
Fabric-First Home Design · Planning Strategy · Natural Fibre Materials
Architectural & Interior Design
New build, extensions, renovation and retrofit — residential, hospitality and commercial — from concept and masterplanning through technical design, building control and delivery coordination.
View work →Planning
Planning strategy, applications and conservation consents, prepared with the supporting case — sustainability, materials, energy — developed as evidence, not decoration.
Planning →Plot Potential
A structured route for landowners with subdividable plots: planning funded and managed by Number 39 under an option-style agreement.
Plot Potential →"Get your envelope right, and you simply don't need, and won't need the tapes, membranes, glues and mechanical gubbins conventional construction says you need."— The Number 39 method
UK Building Regulations assess U-value alone. They do not measure thermal mass, decrement delay, or hygroscopic performance — the qualities that determine how a building actually feels, in summer heat and winter cold, and how much energy it takes to keep it comfortable. Natural fibre insulation addresses all three. Materials such as hemp, wood fibre, and sheep's wool can achieve a decrement delay of 12–18 hours, against 4–6 hours for synthetic insulation — the time it takes for heat to pass through the wall at all.
12–18h
Decrement delay
Natural fibre insulation — hemp, wood fibre, jute, flax
4–6h
Decrement delay
Synthetic insulation — polyurethane, polystyrene, mineral wool
0.13
U-value W/m²K
Hempcrete at 365mm — high-performance fabric; MVHR often not essential
The Royal Institute of British Architects (RIBA) sets out seven distinct design stages for design and build projects of any size — a framework for best practice, efficiency and project success. Number 39 works to this structure, incorporating the planning permission design process below within it.
1
Development of objectives, outcomes, aspirations, budget, feasibility and site information. We agree the schedule of services, appoint the design team and principal designer, and conduct initial pre-application discussions — while advising you of your regulatory and health and safety responsibilities from the outset.
2
Development of outline proposals: structural design, services, systems and outline specifications, together with preliminary cost information and project strategies. The project brief is finalised at this stage.
3
Coordination of the structural proposals, services, systems and outline specifications, with updated cost information and the project strategies established in stages 1 and 2. The planning application is submitted at this stage, along with any third-party consultations required.
4
Preparation and issue of all technical, architectural, structural, services and specialist contractor designs and specifications — the design programme — including Building Regulations submission and any other third-party consents, in accordance with the preceding stages.
5
Off-site manufacturing and on-site construction, with resolution of queries as they arise. We administer the building contract through to practical completion, including regular site inspections and progress reviews, collate the Health and Safety File, and ensure compliance with any construction-specific planning conditions.
6
Handover of the building and conclusion of contracts, together with compliance — and guidance on your own compliance — with any pre-occupancy and in-use planning conditions.
7
Not yet a requirement of Building Regulations, but valuable nonetheless: a periodic review of how your building is performing — its services, its systems, its general use — offers regular opportunity to ensure best performance and continuing cost effectiveness, and adds to the wider body of knowledge on what makes a well-designed built environment work.
1
We meet to discuss your project aspirations, design ideas and budget targets — and, where relevant, the potential land value or final build value your project could realise. For smaller projects, we establish whether planning permission is required at all. Not every development needs it: some minor improvements fall under permitted development.
2
A: Planning application. We work with you to understand and develop the full potential of your project, producing a preliminary design and feasibility study that sets out its viability against local planning policy and site constraints.
B: Planning application + option agreement. If you are looking to create the right kind of sustainable design project and investment value from your plot — or part of it — Number 39 can work with you to do so, and to find the right kind of buyer. This route is set out fully under Plot Potential, below.
3
Before a formal application is submitted, seeking pre-application advice gives an early reading of how the local authority is likely to regard your proposal — and surfaces any potential issues while they are still straightforward to address.
4
Drawing on the pre-application feedback, the feasibility study and your approval to proceed, we develop the detailed planning proposal. Designed well, this also becomes a solid platform of outline information for the subsequent Building Regulations submission.
5
We complete all required architectural drawings, visualisations, photographs and the application form, and prepare or commission the necessary accompanying documents, which may include:
6
The local planning authority reviews the application — typically eight weeks for minor applications, thirteen for major. They consider the proposal's impact on the surrounding area and local infrastructure, alongside any comments from neighbours or the local community.
7
The authority will either grant or refuse permission. If refused, reasons are given — and in many cases the design can be revised to address them and resubmitted.
8
If your application is refused, you have the right to appeal to the Secretary of State within six months of the decision. It can be a complex and lengthy process, and one to consider carefully with your architectural designer.
It's a process best navigated together. We work closely with you throughout — interpreting the planning policies and regulations that apply to your project, anticipating issues before they arise, and making the application process as smooth as it can reasonably be.
Number 39 prepares sustainability-led planning applications for homeowners with subdividable plots, carrying the time and cost of the planning process under an option-style agreement. If consent is achieved and the plot is sold, Number 39 receives an agreed share of the uplift — you retain ownership of the land throughout. If planning is not achieved, we carry that cost, not you.
Full details →Number 39 funds and manages the planning process for qualifying garden or side plots under an option-style agreement. There is typically no upfront planning cost. You retain ownership and decision control; we carry the sunk cost if consent is not achieved.
Learn how it works →
