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 hub
This is the home page for PD Pathway's non-HRB Building Regulations compliance library. Each card below opens a full guide to one Approved Document: what the Building Safety Act 2022 requires on non-HRB jobs, the design risks and evidence needed at RIBA Stages 2–4, the standards to cite, and the pitfalls that catch out sole practitioners.
- Starting a project? Use the quick-reference table below to see which Parts your project type typically engages, then open those guides.
- New to the BSA dutyholder regime? Read the featured BSA vs CDM comparison first — it untangles the two Principal Designer roles that share one name.
- Building your evidence file? Every Part guide ends with the records to keep — or let PD Pathway track them for you automatically.
Featured companion read
BSA vs CDM Principal Designer Duties: What's the Difference on Non-HRB Projects? The difference between the Building Safety Act 2022 and CDM 2015 Principal Designer roles — legal basis, triggers, domestic client defaults and competence requirements in one clear comparison table. Read the comparison →Approved Documents Parts A–T: non-HRB compliance guides
All 18 Approved Documents in force in England (there is no Part I or Part N), grouped by theme and each covered for non-HRB domestic and small commercial work.
Structure & Fire
The two Parts with the highest stakes on any project — load paths and life safety.
Health & Comfort
Moisture, air, sound, water, waste and heat — the fabric-of-daily-life requirements.
Energy & Sustainability
Fabric performance and future-ready infrastructure for energy, broadband and EVs.
Access & Safety
Getting into, moving around and safely using the building — stairs, access, electrics, security and sanitary provision.
Which Parts apply to typical non-HRB projects?
Almost every project engages Parts B and L; the table below shows the Parts that most commonly drive design decisions and evidence on typical small-practice work. It is a starting point, not a substitute for a project-specific relevant-requirements review.
| Project type | Parts that typically apply |
|---|---|
| Loft conversion | A (new steels), B (protected escape route), E (sound between rooms), F (ventilation), K (stair pitch and headroom), L (roof insulation), P (new circuits) |
| Rear or side extension | A (openings and lintels), B (fire spread), C (DPC and ground moisture), F (ventilation), H (drains and build-over), L (U-values and photo evidence), P (electrics) |
| Garage conversion | B (fire separation), C (floor damp-proofing), E (sound to habitable rooms), F (background ventilation), L (upgrading the fabric), P (electrics) |
| Kitchen or bathroom refit | F (extract ventilation), G (hot water safety and efficiency), H (waste connections), P (notifiable electrical work) |
| New-build dwelling | Every Part applies — including O (overheating), Q (security), R (broadband), S (EV charging) and M4(1) access |
| Small commercial refurbishment | B (means of escape), K (guarding and glazing), L Volume 2, M Volume 2 (access), T (toilet accommodation, 2024) |
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.