BS 6229:2025 – Why a British Standard Still Matters for Flat Roof Design in Ireland?

In recent years, flat roof design has come under increased scrutiny, particularly around fire safety, durability, and long-term performance. Against that backdrop, BS 6229 was revised in 2025, introducing clearer expectations around how flat roofs should be designed, specified, and delivered.

A common question from Irish design teams is: Why does a British Standard still matter in Ireland, especially post-Brexit? And just as importantly: what has actually changed in the 2025 revision?

This article addresses both.

Why BS 6229 is still relevant in Ireland

First, it is important to be clear about what BS 6229 is — and what it is not.

BS 6229 is not legislation, and it has never been mandatory in Ireland. Instead, it is a code of practice that sets out recognised good practice for the design and construction of flat roofs.

Irish Building Regulations, including TGD B (Fire Safety), rely heavily on European harmonised standards, such as EN 13501-5 for external fire performance of roofs. BS 6229 does not replace those standards; rather, it explains how they should be applied in real roof systems, including drainage, insulation, fire performance, interfaces, and maintenance.

In practice, Irish fire engineers and specifiers continue to reference BS documents where there is no equivalent Irish code of practice, particularly where system design and responsibility need to be clearly defined. Brexit did not change this technical reality.

As a result, BS 6229 remains a widely recognised reference point in Irish projects, especially for apartments, mixed-use developments, balconies, podiums, and roofs with multiple functions.

What has changed in BS 6229:2025?

The 2025 revision does not radically reinvent flat roof design, but it does tighten expectations and reflect modern construction risks. The key updates fall into six main areas.

1. Stronger emphasis on drainage and falls

BS 6229:2025 reinforces the requirement for effective drainage, with a minimum finished fall of 1:80. The update places more responsibility on the design team to ensure that structural decks are suitable before roofing works commence, rather than relying on the waterproofing contractor to resolve poor falls on site.

This is particularly relevant on concrete decks, refurbishment projects, and roofs with attenuation or blue-roof functions, where standing water can have both performance and fire implications.

2. Enhanced thermal performance guidance

The revised Standard places greater emphasis on insulation performance, particularly for inverted warm roofs and blue roofs, where retained water can affect thermal efficiency.

Designers are now expected to apply appropriate calculation methods to confirm that insulation thickness remains adequate under operational conditions, not just in dry scenarios. This reflects the increasing use of roofs as part of sustainable drainage strategies.

3. Clearer fire safety expectations

Fire performance is one of the most significant areas of change.

BS 6229:2025 reinforces that fire performance must be considered at roof-system level, not simply by referencing a membrane or surface finish in isolation. Where roofs serve multiple purposes — for example as terraces, escape routes, or amenity spaces — designers must ensure that both external and internal fire performance requirements are addressed.

The Standard also makes it clear that fire performance depends on the complete build-up, including deck type, insulation, fixing method, and whether the waterproofing layer is exposed or protected.

4. Recognition of “multi-functional finishes”

A notable update is the formal introduction of terms such as “multi-functional finishes”.

This captures podium decks, roof terraces, play areas, and landscaped roofs - all of which introduce additional loads, interfaces, and fire considerations. The Standard now explicitly recognises that these roofs require robust waterproofing, protection layers, and careful coordination with the overall fire strategy.

This is particularly relevant in the Irish market, where podium and balcony roofs are increasingly common in residential developments.

5. Greater focus on workmanship and maintenance

BS 6229:2025 strengthens guidance on workmanship, sequencing, and inspection. Examples include:

• avoiding leaving insulation exposed overnight,

• inspecting each layer before covering,

• and ensuring comprehensive handover documentation.

The Standard also recommends regular inspection and maintenance, typically at least twice per year, reinforcing the idea that roof performance is a lifecycle issue, not just a construction-stage concern.

6. Condensation risk and acoustic performance

The updated Standard requires a project-specific condensation risk analysis for each roof build-up, rather than relying on generic assumptions. This is especially important in buildings with high internal humidity, such as sports facilities or swimming pools.

There is also expanded guidance on sound attenuation, recognising that roofs increasingly play a role in overall acoustic performance, particularly in urban environments.

What this means for Irish building designers

The most important takeaway is that BS 6229:2025 pushes the industry toward clearer, system-based thinking.

For designers, this means:

• roofs should be described and coordinated as complete systems,

• fire performance should be considered in context, not assumed,

• interfaces with façades, parapets, and terraces need early attention,

• and responsibility boundaries should be clearly defined within the design team.

None of this contradicts Irish Building Regulations. Instead, it supports them by providing a practical framework for applying European standards in real projects.

A shift toward clarity, not complexity

BS 6229:2025 does not impose new legal obligations in Ireland. What it does do is reflect the way flat roofs are now being assessed by fire engineers, building control authorities, and insurers.

For building designers, understanding its intent helps:

• reduce late-stage design changes,

• avoid ambiguity at tender stage,

• and deliver roofs that perform as intended over their full service life.

As flat roofs continue to evolve into multi-functional building elements, the principles set out in BS 6229:2025 provide a useful reference point for good practice — regardless of jurisdiction.