What Are As-Built Drawings and Why Does Your Project Need Them?

What Are As-Built Drawings?

As-built drawings — also called existing condition drawings, as-existing drawings or record drawings — are accurate CAD drawings that show a building as it currently exists. They record the actual dimensions, layout, structure and features of the building as surveyed on site, rather than how it was originally designed or approved.

This distinction matters. A building's original planning drawings or building regulations plans often differ from what was actually built — modifications during construction, alterations over the years and undocumented changes mean the paper record and the physical building frequently don't match. As-built drawings are a fresh, accurate record of what's actually there today.

What Do As-Built Drawings Show?

A standard set of as-built drawings for a residential or commercial building typically includes:

• Floor plans — a plan view of each level showing wall positions and thicknesses, door and window openings, room layout, stairs, sanitary ware and key built-in features
• Elevations — drawings of each external face showing window and door positions, heights, materials and architectural features
• Sections — vertical cuts through the building showing storey heights, floor-to-ceiling dimensions and the relationship between levels
• Roof plan — a plan view of the roof showing ridge lines, valleys, pitches and rooflights

All drawings are produced to professional CAD standards in DWG format, typically at 1:50 for plans and sections and 1:100 for elevations, and issued as DWG and PDF files.

When Do You Need As-Built Drawings?

Planning Applications

Most planning applications for alterations, extensions or change of use to existing buildings require both existing and proposed drawings. The existing drawings must accurately show the building before any works take place — this is where as-built drawings come in. Using old, potentially inaccurate drawings as the "existing" basis for a planning application can cause problems if the drawings don't match what planning officers see during a site visit.

Refurbishment and Extension Design

Architects need accurate existing condition drawings before they can design a refurbishment or extension. Rather than starting from old drawings that may be inaccurate, a fresh set of as-built drawings gives the design team confidence that their proposals are based on correct existing dimensions — avoiding costly surprises when work starts on site.

Building Regulations

Change of use applications, structural alterations and fire safety upgrades all typically require existing condition drawings as part of the building regulations submission. These need to show the building accurately as it exists before the proposed works.

Property Transactions

Commercial property purchasers increasingly commission as-built surveys before exchange to verify that the actual floor areas and layout match the vendor's stated figures. Discrepancies in floor area can affect valuation significantly.

Facilities Management

Building owners and facilities managers use as-built drawings as the record of what is in the building — for maintenance planning, space management, tenant fit-outs and compliance documentation. As-built BIM models are increasingly used for this purpose as they allow facilities data to be linked directly to the model elements.

As-Built Drawings vs Original Planning Drawings — Why They're Different

It's common for clients to ask whether they can use the original planning drawings instead of commissioning a new survey. The answer depends on how old the drawings are and how much confidence there is that they accurately reflect the current building. In practice, for most existing buildings the answer is no — for several reasons:

• Buildings are often built slightly differently from the approved plans
• Subsequent alterations may not have been formally drawn up
• Old drawings may be at the wrong scale or in formats that don't work with current CAD software
• Planning authorities increasingly scrutinise existing drawings carefully and will reject applications where the existing drawings clearly don't match the building

A fresh measured survey takes the guesswork out of this and gives everyone in the project team — architect, engineer, planning officer — a reliable, accurate record of what's actually there.