As-built drawings are one of the most important deliverables at the end of any construction or engineering project, yet they are also one of the most frequently neglected. This guide explains what as-built drawings are, when they are legally required, who is responsible for producing them, and how the process works in practice on UK projects.

What are as-built drawings?

As-built drawings are technical drawings that record the final built condition of a construction or engineering project. They capture every modification and change made during construction — deviations from the original design, re-routed services, amended structural elements, changed equipment locations — and produce an accurate record of what was actually built.

As-built drawings are also known as record drawings or as-constructed drawings. They are typically produced at practical completion and form part of the handover documentation package passed from contractor to client.

As-built drawings vs construction drawings

Construction drawings show what is intended to be built based on the design at the time of issue. As-built drawings show what was actually built, incorporating all changes made during the construction process.

The gap between the two can be significant on complex projects where site conditions, material substitutions, coordination clashes, and client changes result in numerous deviations from the original design.

When are as-built drawings required?

As-built drawings are required in several circumstances under UK practice and legislation. Under CDM Regulations 2015, the principal designer must ensure the health and safety file contains as-built drawings and other record information needed for future maintenance. This is a legal obligation on all notifiable construction projects.

Under UK Building Regulations, completion drawings showing the as-built state are required by building control authorities before issuing completion certificates.

For operational facilities such as process plants, utilities infrastructure, and commercial buildings, maintaining accurate as-built drawings is essential for facilities management and future modification work.

What should as-built drawings include?

As-built drawings should capture all changes made during construction, including revised dimensions and levels, re-routed mechanical and electrical services, changes to structural elements and connections, substituted materials and components, revised equipment locations and specifications, and any site-specific adaptations.

Who is responsible for producing as-built drawings?

Under traditional contracts, the main contractor is typically responsible for coordinating and producing as-built drawings from their own records and those of subcontractors. Under design-and-build contracts, the contractor is responsible for the full drawing package.

In practice, the coordination and production of as-built drawings from site records, redline markups, and survey data is often outsourced to a specialist CAD company.

How are as-built drawings produced?

As-built drawings are produced from redline markups made during construction, site surveys of the completed works, point cloud data from 3D laser scanning, or photographic records. Outsource CAD works with all of these sources.

How to outsource as-built drawing production

Outsource CAD provides fast, high-quality as-built drawing services from your redline markups, site survey data, or point cloud scans. Contact us for a free quote.