Status	2026 Claims & Liability Reality
Regulator	Building Safety Regulator (BSR) / Single Construction Regulator (SCR)
Applicability	London Higher-Risk Buildings (HRBs) – Designers, Contractors & Dutyholders
Compliance Window	Active (Claims Allocation Shifting)

 

In 2026, the line between design responsibility and installation risk is no longer blurred — it is being actively tested.

One of the most common questions emerging across London construction projects is simple: when something fails, who is actually liable? Under the Building Safety Act regime and the Single Construction Regulator (SCR), claims are increasingly landing not where contracts assumed they would — but where control, knowledge and decision-making can be proven.

The historic comfort that “designers design, contractors install” is breaking down. Modern HRB claims frequently cut across both, particularly where systems, substitutions or constructability decisions sit between intent and execution.

This allocation is now being tested most visibly at Gateway 3 and post-completion scrutiny, where records and evidence define where responsibility ultimately lands.

1. Why the design vs installation divide is collapsing

Three forces are driving the collapse of the traditional boundary:

• System-based regulation: safety is assessed at system level, not component level.
• Change during construction: substitutions and sequencing alter original intent.
• Evidence-led enforcement: regulators look at who knew, approved and proceeded.

When a failure occurs, the question is no longer “who had it in their scope?” It is “who had the opportunity and obligation to prevent it?”

This thinking aligns directly with how the SCR now assigns product and system liability.

2. Where design responsibility is now extending

Designers are increasingly exposed where design intent directly influences installation outcomes. Claims are landing where designers:

• Specify systems without fully understanding constructability.
• Rely on generic performance classifications rather than tested assemblies.
• Approve substitutions without reassessing safety performance.
• Allow design intent to drift without formal change control.

This is particularly acute on HRBs, where façade, fire stopping and structural interfaces dominate risk. The façade example is explored in Façade Strategy, Fire Performance and Liability Exposure in London HRBs.

Designers who cannot demonstrate active control through construction face increasing scrutiny under Principal Designer competence expectations.

3. Where installation risk still firmly sits

Installation risk has not disappeared — but it is being more precisely defined. Contractors remain exposed where failures arise from:

• Deviation from approved details.
• Poor workmanship or sequencing.
• Failure to follow tested system requirements.
• Installing substituted products without approval.

These risks surface most clearly at completion, particularly where evidence is incomplete or inconsistent, as outlined in Completion Certificates and Gateway 3 failures.

Where contractors cannot prove what was installed, or why, installation risk becomes indefensible.

4. The grey zone where most claims now sit

The majority of 2026-era claims sit in the grey zone between design and installation. Common examples include:

• Value-engineered substitutions approved informally.
• Details issued late and “made to work” on site.
• Legacy structure assumptions not validated during works.
• Interfaces between trades left unresolved.

Legacy structural uncertainty is a frequent trigger, linking directly to structural investigation expectations for legacy concrete frames.

In these cases, claims land where evidence of control is weakest — regardless of contractual intent.

5. How Gateway 3 records decide claim outcomes

Gateway 3 submissions now act as a permanent record of responsibility. Decisions, caveats and unresolved issues are preserved — and increasingly relied upon in disputes.

This is why failures at Gateway 3 have consequences beyond approval delay, as explained in Developer Liability After Completion: What No One Is Pricing Correctly.

6. A practical claims-defence checklist

For designers

✔ System-level performance understood and documented.
✔ Substitutions formally assessed and approved.
✔ Design intent tracked through construction.

For contractors

✔ Installation matches approved details and tested systems.
✔ Deviations escalated and resolved formally.
✔ As-built evidence complete and traceable.

For both

✔ Change control enforced.
✔ Interfaces clearly owned.
✔ Golden Thread records maintained in real time.

Key takeaway

In 2026 London HRBs, claims no longer follow neat contractual lines. They land where responsibility, knowledge and control intersect — and where evidence fails to show otherwise. Designers and contractors who treat Gateway compliance, construction control and Golden Thread evidence as claim-defence tools are the ones protecting themselves.

image: constructionmagazine.uk

Expert Verification & Authorship: Mihai Chelmus Founder, London Construction Magazine | Construction Testing & Investigation Specialist