Confusion over who is responsible for producing as-built drawings is one of the most common causes of delay at project handover. Main contractors expect subcontractors to deliver them. Subcontractors assume the main contractor will coordinate and compile. The result is often a scramble in the final weeks, incomplete documentation, and withheld retention payments.
Understanding contractual responsibility, what the standard forms say, and how the process should work in practice is essential for M&E contractors, building services engineers, and project managers working on UK construction projects.
What the Standard Contracts Say
Most UK construction contracts place the obligation to produce as-built and record drawings on the party executing the work. Under JCT and NEC forms, the contractor—or subcontractor where work is sublet—is typically required to provide accurate record information showing what was actually installed.
JCT Standard Building Contract, for example, refers to the provision of "as-built drawings and information" as part of the completion requirements. The subcontract forms mirror this, making it clear that domestic subcontractors must supply record drawings to the main contractor, who then consolidates them for the client.
NEC4 includes similar provisions under the definition of completion and the information requirements schedule. The party doing the work is responsible for documenting what they installed, in the format and to the level of detail specified in the Works Information or Scope.
Why Responsibility Is Often Unclear
Despite what the contracts say, confusion arises because responsibility is rarely spelled out in plain language at tender stage. Subcontract enquiries may request a price for "installation as shown on the drawings" without specifying whether as-builts, O&M manuals, or record information are included.
Many M&E subcontractors assume as-built production is an extra, particularly if redline markups are extensive or if design changes were made during construction. Main contractors, on the other hand, expect the subbie's price to include everything needed to achieve practical completion, including documentation.
This gap in understanding leads to disputes, especially when the main contractor withholds retention or issues a non-conformance notice because the subcontractor has not delivered the required drawings.
The M&E Subcontractor's Obligation
For mechanical and electrical subcontractors, the obligation is clear: if you installed it, you document it. That means updating the design intent drawings to reflect what was actually built—cable routes, pipe runs, valve locations, control panel positions, changes to equipment specifications, and any site variations.
Typically, this involves marking up site copies of the design drawings during installation, then producing final CAD as-builts from those redlines. The subcontractor is responsible for accuracy, ensuring that the drawings match what's accessible in the ceiling voids, under floors, and inside risers.
In practice, this work is often subcontracted back out to a specialist redline markup incorporation service or CAD bureau. That's a pragmatic solution, but the legal and contractual responsibility still rests with the installing subcontractor, not the drafting provider.
The Main Contractor's Role
The main contractor's role is to coordinate, compile, and submit the as-built information to the client or design team. They do not usually produce the drawings themselves, but they are responsible for ensuring all subcontractors deliver compliant, checked, and timestamped record information on time.
This includes checking that the drawings are properly titled, referenced, and formatted in line with the project's CAD standards. It also means ensuring that mechanical, electrical, drainage, and architectural as-builts are coordinated and clash-free before they're handed over.
Where a main contractor has produced the design—such as on a design-and-build project—they may also be responsible for updating their own architectural, structural, or civils drawings to reflect any site changes.
Coordination and Document Control
On larger projects, document controllers or project coordinators manage as-built registers, track submission dates, and chase subcontractors for outstanding information. This is essential for avoiding delays to sectional completion, building control sign-off, or final account settlement.
Where BIM Level 2 is specified, the main contractor also ensures that as-built models and COBie data are compiled and uploaded to the Common Data Environment in line with the BIM Execution Plan.
Specialist Subcontractors and Design Responsibility
When a subcontractor has design responsibility—common for M&E and building services packages—the obligation to provide as-builts is even clearer. The subcontractor is not just recording what they installed; they are updating their own design deliverables to reflect the final installation.
This includes updating single-line diagrams, schematic layouts, equipment schedules, control logic, and any performance data required for commissioning or operation and maintenance.
In these cases, withholding as-built drawings is a breach of contract, and the main contractor is entitled to backcharge the cost of producing them or to withhold payment until they are delivered.
What Should Be Included in the Subcontract Scope
To avoid disputes, the subcontract scope should explicitly state what record information is required, in what format, and by when. This should include the number of copies, file formats (DWG, PDF, Revit), naming conventions, and whether redline markups or full CAD as-builts are expected.
It should also specify whether the subcontractor is required to attend as-built coordination meetings, provide information for the O&M manual, or support building control inspections with updated drawings.
Clear scope definition at tender stage avoids the "not included" argument later and ensures subcontractors price the work correctly.
What Happens When As-Builts Are Not Delivered
Failure to provide as-built drawings can delay practical completion, trigger liquidated damages, and prevent release of retention. It can also expose the subcontractor to backcharges if the main contractor has to commission someone else to produce the drawings retrospectively.
In some cases, clients refuse to accept handover until all record information is complete, which means the entire project remains open and costs continue to accrue.
From a legal perspective, the obligation to provide as-builts is usually a condition precedent to final payment, meaning the subcontractor cannot claim their retention until the information is submitted and accepted.
Outsourcing As-Built Production
Many subcontractors now outsource the production of as-built drawings to avoid bottlenecks and ensure timely delivery. Site teams collect redline markups during installation, then send them to a CAD provider who produces the final AutoCAD or Revit files.
This keeps internal resource free for new projects and ensures the as-builts are produced to a consistent standard. Outsource CAD supports M&E contractors across the UK with as-built production from redlines, working to tight handover deadlines and project-specific CAD standards.
Whether outsourced or produced in-house, the responsibility remains with the party executing the work. The contract makes that clear—and so should the project team at the start of every job.
If you need support producing as-built drawings from site redlines or clarifying scope at tender stage, contact Outsource CAD at info@outsourcecad.com or call +44 28 9009 8876.
