PAS 2035 for Traditional Buildings: Risk Paths, BS 7913 and Competence

Why Traditional Buildings Need Their Own Approach

PAS 2035 is the UK specification for retrofitting homes of every age and type, and that includes traditional buildings. They also cause some of the most expensive retrofit failures. Treat a solid-walled Victorian terrace as if it were a 1980s cavity-wall semi and the fabric can end up damaged for decades.

This guide works through the main points from a training session on PAS 2035 and traditional buildings. The session was recorded in 2021, when PAS 2035:2019 was the current edition. The principles still hold, but check the current edition for exact role and qualification requirements before you rely on them in practice or in an exam.

What PAS 2035 Means by “Traditional”

Many people assume “traditional” just means “built before 1919”. PAS 2035 is more precise. It defines a traditional building by how it is built:

• External walls of solid brick or stone, or
• Pre-1919 timber frame walls with any infill.

This changes the numbers a lot. If you count only pre-1919 buildings, you get about a quarter of UK housing. Apply the PAS 2035 construction-based definition to BRE statistics and it rises to around a third of UK building stock, roughly 8 million buildings.

Did you know? Plenty of solid-walled homes built between the wars fall inside the PAS 2035 definition even though they are not “period” properties in the everyday sense.

How Traditional and Modern Buildings Differ

Two houses can look alike from the street and still behave very differently. The main contrast is how the walls handle moisture:

Characteristic	Traditional building	Modern building
Wall type	Usually solid brick or stone	Usually cavity wall
Materials	Vapour permeable (breathable)	Largely impermeable
Moisture management	Moisture is absorbed and released through the fabric	Moisture is kept out with barriers and cavities
Retrofit risk	High if modern methods are applied without thought	Better understood, but still not risk-free

Traditional walls take up moisture and let it evaporate again. Fit impermeable insulation, cement renders or non-breathable paints and moisture can get trapped in the fabric. The results include damp, mould, decay in embedded timbers and frost damage to masonry.

The Hidden Problem: Past Alterations

The speaker stressed one point in particular. Many traditional buildings have already been treated as if they were modern buildings at some point. Cement pointing, gypsum plaster, plastic paints and impermeable renders have often been added over the years. These redirect moisture and concentrate it in certain areas, which causes unintended consequences.

So the assessment has to find out whether those problems already exist before any retrofit work begins. Adding insulation on top of an existing moisture problem makes it worse. For a closer look at how moisture drives these failures, see our guide to damp, mould and condensation. Our post on external wall insulation and cold bridges shows how moisture management decides whether a measure succeeds.

Tip: When you assess a traditional home, record previous interventions such as cement repointing, modern renders and blocked vents alongside the fabric itself. They are often the real cause of existing damp.

The Standards Framework: PAS 2035, PAS 2030 and BS 7913

The BSI retrofit standards framework has three parts that matter for traditional buildings:

1. PAS 2035: the core document. It sets out the standards, the whole-house approach and the retrofit process.
2. PAS 2030: covers the installation stage of that process and is incorporated into the framework.
3. BS 7913: the UK standard for work on historic buildings, including traditional, protected and designated ones.

If you follow the whole framework, you have good guidance for traditional buildings. PAS 2035 refers to BS 7913 in several areas but does not reproduce all of it. On heritage-sensitive jobs, experienced coordinators go back to BS 7913 itself.

For a refresher on the six stages, six roles and risk pathways, read PAS 2035 and PAS 2030 explained.

Key Issues Under PAS 2035

Risk-Based, Not Automatically Fabric First

Many people say fabric first is always the right way to retrofit. For traditional buildings, PAS 2035 does not say that. It says that for older, traditionally built and protected buildings, a risk-based approach is usually appropriate.

In practice, you look at the risks first: moisture, heritage and technical compatibility. The measures come after that. Fabric improvements may still happen, but they are chosen to suit the building rather than taken straight from a standard list.

Remember: “Fabric first” and “risk-based” are different ideas. For traditional buildings, PAS 2035 puts the risk-based approach first.

Technical Difference and Assessment

Traditional buildings behave differently from modern ones, so assessing them may differ too. Assessors need to understand breathable construction, moisture pathways and how the building’s condition has changed over time.

Significance and Heritage Value

Traditional buildings often have heritage value that needs to be understood and handled properly. Some features that save energy on paper could destroy the very features that make the building significant.

Risk Paths

PAS 2035 sorts buildings into different risk paths, so different traditional buildings will follow different routes. Risk Path C covers traditional buildings with special protection, such as listed buildings and buildings in conservation areas. This path brings the strictest requirements.

Key Issues Under PAS 2030

The installation side has its own requirements for traditional buildings:

• Continuous supervision: on Risk Path C, the installation company must supervise its installation workforce continuously.
• Vocational competence: PAS 2030 puts strong emphasis on this. On a traditional building, installers need to be competent in working on traditional buildings specifically.

Qualifications and Competence by Role

PAS 2035 has a lot to say about qualifications, memberships and competence. The main qualification named for traditional building work is the Level 3 Award in Energy Efficiency and Retrofit of Traditional Buildings. Here is how the session described each role:

Role	Traditional buildings qualification	Notes
Retrofit Advisor	Not required	Advisable anyway
Retrofit Assessor	Required on Risk Path C	Many expected future revisions to extend this to traditional buildings on all paths
Retrofit Coordinator	Required	Usually also the Retrofit Evaluator
Retrofit Designer	Not required	Must belong to a building conservation accreditation or certification scheme, such as the RIBA or CIOB schemes
Retrofit Evaluator	Required	Evaluates traditional building projects

The Retrofit Coordinator is the key role in PAS 2035. They normally act as the Retrofit Evaluator too, so they need the traditional buildings qualification in practice. They also carry responsibility for ensuring that everyone else on the project is competent.

Tip: Exam questions often test which role needs which competence on which risk path. Learn the table above against the current edition of PAS 2035. Don’t rely only on older course notes.

Suggested Revision Routine

1. Learn the PAS 2035 definition of a traditional building word for word.
2. Practise explaining in two sentences why vapour permeability matters.
3. Map each of the five roles to its competence requirements.
4. Revise what makes Risk Path C different for assessment, design and installation.
5. Test yourself with mixed questions on risk, fabric and ventilation.

Our Retrofit Coordinator Level 5 topic map shows where traditional buildings fit in the wider syllabus.

How RetrofitReady Fits Into This

Traditional buildings bring together several parts of the coordinator syllabus: risk assessment, moisture, fabric, ventilation and competence management. RetrofitReady: Coordinator offers Level 5 Retrofit Coordinator preparation with 600 PAS 2035 questions. They cover domestic retrofit, risk, fabric, services, ventilation, MTIP and monitoring, so you can test your understanding of risk paths and moisture-safe decisions before the exam.

The full RetrofitReady suite contains 1900+ questions across 4 apps, covering Assessor, Coordinator, DEA and Installer routes. Start with the free quizzes, check the recommended books and tools for building conservation and building physics reading, or browse the full RetrofitReady app suite.