Summary
- Over 90% of UK domestic extensions, loft conversions and small commercial projects are non-HRBs — under 18 metres and fewer than 7 storeys — so the HRB Gateway process does not apply to them.
- But the Building Safety Act 2022 dutyholder regime does apply: on every project subject to Building Regulations, a Principal Designer (BSA) must plan, manage and monitor design work for compliance — and on domestic jobs the duties default to the lead designer if nobody is appointed in writing.
- This library covers every Approved Document (Parts A–T) with non-HRB compliance guides for small practices, plus a plain-English comparison of BSA and CDM Principal Designer duties.
What changed for small practices on 1 October 2023
The Building Regulations etc. (Amendment) (England) Regulations 2023 brought the Building Safety Act 2022 dutyholder regime into force for all building work in England — not just high-rise. Every project subject to Building Regulations now has a client, designers and contractors with defined legal duties, and where there is more than one contractor, a Principal Designer (BSA) and Principal Contractor (BSA) must be appointed in writing.
The trap for small practices is the domestic default: where a domestic client fails to make the appointments, the Principal Designer duties pass automatically to the designer in control of the design phase — usually the architect or architectural technologist who drew the scheme. You can hold the role without ever agreeing to it, and without pricing for it.
The duty itself is coordination: take all reasonable steps to ensure the design, if built, would comply with all relevant requirements of the Building Regulations — the functional requirements set out in Approved Documents Parts A to T. That is why an evidence trail per Part, per project, is the working core of BSA compliance for a small practice.
Non-HRB vs HRB: why the distinction matters
Most national BSA commentary is written for high-rise residential towers. If your workload is extensions, lofts, one-off houses and small commercial refurbishments, the Gateway articles do not apply to you — but the Principal Designer duties, competence requirements and Parts A–T compliance coordination absolutely do.
| Aspect | Non-HRB project (this library) | Higher-Risk Building (HRB) |
|---|---|---|
| Definition | Under 18 m and fewer than 7 storeys; not a hospital or care home meeting the height test | ≥18 m or ≥7 storeys with 2+ residential units, or hospital/care home meeting the test |
| Approval route | Local authority or Registered Building Control Approver | Building Safety Regulator, Gateways 1–3 |
| Gateway process | Does not apply | Mandatory hard stops at planning, pre-construction and completion |
| Dutyholder regime (PD/PC) | Applies in full | Applies, with additional HRB-specific duties |
| Golden thread | No formal statutory golden thread, but evidence of compliance is expected | Statutory golden thread of building information |
How to use this library
Each guide below covers one Approved Document: what the BSA requires on non-HRB jobs, the design risks and evidence needed at RIBA Stages 2–4, the specific BS/PAS standards to cite, and the pitfalls that catch out sole practitioners. Start with the parts your current project engages — Part B and Part L touch nearly everything — and use the BSA vs CDM comparison to get the two Principal Designer roles straight in your appointment documents.
Approved Documents Parts A–T: non-HRB compliance guides
Every Approved Document in force in England (there is no Part I or Part N), each covered for non-HRB domestic and small commercial work.
- Part A — Structure
- Part B — Fire Safety (Volume 1: Dwellings)
- Part C — Site Preparation and Resistance to Contaminants and Moisture
- Part D — Toxic Substances
- Part E — Resistance to the Passage of Sound
- Part F — Ventilation (Volume 1: Dwellings)
- Part G — Sanitation, Hot Water Safety and Water Efficiency
- Part H — Drainage and Waste Disposal
- Part J — Combustion Appliances and Fuel Storage Systems
- Part K — Protection from Falling, Collision and Impact
- Part L — Conservation of Fuel and Power (Volume 1: Dwellings)
- Part M — Access to and Use of Buildings (Volume 1: Dwellings)
- Part O — Overheating
- Part P — Electrical Safety (Dwellings)
- Part Q — Security in Dwellings
- Part R — Infrastructure for Electronic Communications
- Part S — Infrastructure for the Charging of Electric Vehicles
- Part T — Toilet Accommodation
Principal Designer duties explained
Frequently asked questions
Do Principal Designer (BSA) duties really apply to a small house extension?
Yes. The BSA 2022 dutyholder regime applies to all work subject to Building Regulations in England, regardless of size. On a domestic project with more than one contractor, a Principal Designer must be appointed in writing — and if the client does not appoint one, the duties default to the designer in control of the design phase.
What is a non-HRB?
A non-higher-risk building: one that is under 18 metres in height and has fewer than 7 storeys, and is not a hospital or care home meeting the height threshold. Non-HRB projects avoid the Building Safety Regulator's Gateway process entirely, but the dutyholder regime and Parts A–T compliance duties still apply.
Is the golden thread required on non-HRB projects?
The statutory golden thread applies to HRBs. On non-HRB work there is no formal golden-thread duty, but the Principal Designer must still be able to demonstrate that design work was planned, managed and monitored for Building Regulations compliance — which in practice means keeping a structured evidence record per Approved Document.
Track this natively instead of in Word templates
PD Pathway gives small practices an automated Parts A–T relevant-requirements tracker, stage-by-stage Principal Designer checklists and one-click compliance documents — built strictly for non-HRB projects. First project free, then from £10 per project or £99/yr unlimited.