Approved drawings are supposed to be the single source of truth on a construction site. Under the Building Safety Act regime, they are no longer just design guidance, they are regulated control documents used by the Building Safety Regulator to assess whether a building can legally proceed, complete and be occupied.
When approved drawings are unclear, ambiguous, incomplete or internally inconsistent, the risk is no longer limited to rework or commercial dispute. It becomes a regulatory risk.
On Higher-Risk Building projects, building against unclear drawings can invalidate Gateway approvals, compromise the Golden Thread and expose dutyholders to enforcement action.
In London, where phased delivery, late design development and complex interfaces are the norm, drawing clarity has become one of the most critical compliance risks on site.
This article explains what site teams must do when approved drawings are unclear, how the Regulator expects the issue to be managed, and how to protect the project and the people delivering it.
Why drawing clarity now matters more than ever
Under the Building Safety Act, construction can only proceed in accordance with the drawings and information approved at Gateway 2.
Those drawings define the regulated design intent.
If site teams build something that deviates from those approved documents without formal change control, the project may no longer be compliant with its Gateway approval. That puts Gateway 3 at risk and can prevent the building from being legally occupied.
In effect, unclear drawings are no longer a design problem. They are a regulatory problem.
What counts as unclear drawings
Approved drawings are considered unclear when they fail to provide unambiguous instruction for construction. This includes situations where:
In London projects with layered design teams and specialist subcontractor input, these issues often only become visible once work reaches site.
At that point, the regulatory exposure begins.
The regulatory position on building with unclear drawings
The Building Safety Regulator expects construction to follow the approved design. If the approved design is unclear, construction must pause on the affected scope until the issue is resolved. Building first and clarifying later is no longer acceptable on BSR-regulated projects.
From a regulatory perspective:
When approved drawings are unclear, ambiguous, incomplete or internally inconsistent, the risk is no longer limited to rework or commercial dispute. It becomes a regulatory risk.
On Higher-Risk Building projects, building against unclear drawings can invalidate Gateway approvals, compromise the Golden Thread and expose dutyholders to enforcement action.
In London, where phased delivery, late design development and complex interfaces are the norm, drawing clarity has become one of the most critical compliance risks on site.
This article explains what site teams must do when approved drawings are unclear, how the Regulator expects the issue to be managed, and how to protect the project and the people delivering it.
Why drawing clarity now matters more than ever
Under the Building Safety Act, construction can only proceed in accordance with the drawings and information approved at Gateway 2.
Those drawings define the regulated design intent.
If site teams build something that deviates from those approved documents without formal change control, the project may no longer be compliant with its Gateway approval. That puts Gateway 3 at risk and can prevent the building from being legally occupied.
In effect, unclear drawings are no longer a design problem. They are a regulatory problem.
What counts as unclear drawings
Approved drawings are considered unclear when they fail to provide unambiguous instruction for construction. This includes situations where:
- Details conflict across different drawing packages
- Dimensions are missing or contradictory
- Interfaces between trades are undefined
- Fire, structural or life-safety elements are ambiguous
- Construction sequencing is not coordinated
- Specifications contradict drawing intent
- Design responsibility boundaries are unclear
In London projects with layered design teams and specialist subcontractor input, these issues often only become visible once work reaches site.
At that point, the regulatory exposure begins.
The regulatory position on building with unclear drawings
The Building Safety Regulator expects construction to follow the approved design. If the approved design is unclear, construction must pause on the affected scope until the issue is resolved. Building first and clarifying later is no longer acceptable on BSR-regulated projects.
From a regulatory perspective:
- Unclear drawings create uncontrolled change
- Uncontrolled change breaks Gateway approval
- Broken Gateway approval invalidates completion
- Invalid completion prevents occupation
This is why the Regulator treats drawing clarity as part of the safety case.
The moment a drawing issue is identified on site
When a site manager, engineer, supervisor or subcontractor identifies unclear approved drawings, the response must be immediate and structured. This is not a commercial query, it is a compliance event.
The correct sequence is:
Continuing work while waiting for clarification creates an unapproved design condition. That exposes the project to enforcement risk.
The role of the Principal Designer
Under the Building Safety Act, the Principal Designer is legally responsible for managing design compliance. When drawings are unclear, the Principal Designer must:
Site teams must not attempt to interpret unclear drawings themselves. Interpretation is design. Design without approval is a breach of the Gateway regime.
The role of the Principal Contractor
The Principal Contractor is legally responsible for ensuring construction follows the approved design.
When drawings are unclear, the Principal Contractor must:
Commercial pressure to maintain programme does not override regulatory duty. If construction proceeds against unclear drawings, the Principal Contractor carries the liability.
The change control pathway
Where clarification results in a change to the approved design, the formal change control process must be followed.
This includes:
On BSR projects, not all changes require full Gateway resubmission, but all changes must be controlled, recorded and auditable. Uncontrolled change is now a primary enforcement trigger.
The Golden Thread implications
Every drawing clarification, revision and approval must be captured within the Golden Thread.
This includes:
The Golden Thread must show a complete audit trail from approved design to as-built reality. If the Golden Thread cannot demonstrate that the building was constructed in accordance with the approved and controlled design, Gateway 3 can be refused.
The commercial reality on London projects
London delivery models are particularly exposed to drawing clarity risk.
Factors include:
Each of these increases the likelihood of unclear drawings reaching site. Without a strict regulatory control process, London projects are now carrying significant compliance exposure.
What site managers and supervisors must do in practice
Site managers are now frontline compliance officers. When drawings are unclear, the site response must be disciplined and documented.
This means:
Every ambiguity must be escalated, every clarification must be approved and every change must be controlled. If it is not approved, it must not be built.
What happens if construction continues regardless
If construction proceeds against unclear drawings, the consequences can include:
In extreme cases, buildings may be forced to remain vacant until compliance is restored.
The long-term impact
The Building Safety Act is creating a permanent shift in how drawings are treated. They are no longer guidance documents, they are regulatory instruments. Future London projects will be delivered under regimes similar to nuclear, rail and aviation, where design control is absolute.
The days of we’ll sort it on site are over.
Conclusion — unclear drawings are now a regulatory event
On BSR-regulated construction sites, unclear approved drawings are no longer just a technical inconvenience. They are a compliance failure waiting to happen.
When drawings are unclear:
If it is not approved, it must not be built. That is the new reality of construction under the Building Safety Act.
When a site manager, engineer, supervisor or subcontractor identifies unclear approved drawings, the response must be immediate and structured. This is not a commercial query, it is a compliance event.
The correct sequence is:
- First, stop work on the affected element.
- Second, record the issue formally.
- Third, notify the Principal Contractor and Principal Designer.
- Fourth, initiate the regulated change control process.
Continuing work while waiting for clarification creates an unapproved design condition. That exposes the project to enforcement risk.
The role of the Principal Designer
Under the Building Safety Act, the Principal Designer is legally responsible for managing design compliance. When drawings are unclear, the Principal Designer must:
- Review the issue against the approved Gateway design
- Assess whether the clarification constitutes a design change
- Determine whether a change control submission is required
- Coordinate the resolution across disciplines
- Update the regulated design information
Site teams must not attempt to interpret unclear drawings themselves. Interpretation is design. Design without approval is a breach of the Gateway regime.
The role of the Principal Contractor
The Principal Contractor is legally responsible for ensuring construction follows the approved design.
When drawings are unclear, the Principal Contractor must:
- Suspend affected works
- Secure the workface
- Preserve evidence of the issue
- Initiate formal technical queries
- Control any temporary works
- Maintain Golden Thread integrity
Commercial pressure to maintain programme does not override regulatory duty. If construction proceeds against unclear drawings, the Principal Contractor carries the liability.
The change control pathway
Where clarification results in a change to the approved design, the formal change control process must be followed.
This includes:
- Design revision
- Regulatory impact assessment
- Fire and structural review
- Gateway change submission where required
- Controlled approval before construction resumes
On BSR projects, not all changes require full Gateway resubmission, but all changes must be controlled, recorded and auditable. Uncontrolled change is now a primary enforcement trigger.
The Golden Thread implications
Every drawing clarification, revision and approval must be captured within the Golden Thread.
This includes:
- Original approved drawings
- Technical queries
- Design responses
- Change approvals
- Revised drawings
- Construction sign-off
The Golden Thread must show a complete audit trail from approved design to as-built reality. If the Golden Thread cannot demonstrate that the building was constructed in accordance with the approved and controlled design, Gateway 3 can be refused.
The commercial reality on London projects
London delivery models are particularly exposed to drawing clarity risk.
Factors include:
- Design development continuing during construction
- Specialist contractor design portions
- Late-stage planning conditions
- Fire strategy evolution
- Value engineering cycles
- Interface-heavy packages
- Phased handovers
Each of these increases the likelihood of unclear drawings reaching site. Without a strict regulatory control process, London projects are now carrying significant compliance exposure.
What site managers and supervisors must do in practice
Site managers are now frontline compliance officers. When drawings are unclear, the site response must be disciplined and documented.
This means:
- No verbal instructions
- No site-based interpretation
- No workaround solutions
- No build-and-fix approach
- No commercial shortcuts
Every ambiguity must be escalated, every clarification must be approved and every change must be controlled. If it is not approved, it must not be built.
What happens if construction continues regardless
If construction proceeds against unclear drawings, the consequences can include:
- Gateway 3 refusal
- Completion certificate rejection
- Occupation delay
- Enforcement notices
- Stop work orders
- Remedial works
- Criminal liability for dutyholders
- Uninsurable buildings
- Unmortgageable assets
In extreme cases, buildings may be forced to remain vacant until compliance is restored.
The long-term impact
The Building Safety Act is creating a permanent shift in how drawings are treated. They are no longer guidance documents, they are regulatory instruments. Future London projects will be delivered under regimes similar to nuclear, rail and aviation, where design control is absolute.
The days of we’ll sort it on site are over.
Conclusion — unclear drawings are now a regulatory event
On BSR-regulated construction sites, unclear approved drawings are no longer just a technical inconvenience. They are a compliance failure waiting to happen.
When drawings are unclear:
- Work must stop.
- The issue must be recorded.
- The design must be clarified.
- The change must be controlled.
- The Golden Thread must be updated.
If it is not approved, it must not be built. That is the new reality of construction under the Building Safety Act.
Image © London Construction Magazine Limited
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Expert Verification & Authorship: Mihai Chelmus
Founder, London Construction Magazine | Construction Testing & Investigation Specialist |
