Existing vs As-Built Surveys – What’s the Difference?

If you’re planning alterations, refurbishments or extensions, you may come across two similar terms: existing building surveys and as-built surveys. Although they are often mentioned together, they serve very different purposes.

Understanding the distinction ensures you commission the correct type of survey for your project. Choosing the right survey at the right time can prevent delays, reduce costs and improve design accuracy.

What Is an Existing Building Survey?

An existing building survey — often referred to as a measured building survey — records the current layout and dimensions of a property.

Surveyors capture accurate data from the building and produce scaled drawings that reflect its present condition.

These drawings typically include:

• Floor plans

• Elevations

• Sections

• Internal room layouts

• Structural elements

• Window and door positions

Architects rely on existing building surveys before designing extensions, refurbishments or internal alterations. In short, the survey provides a precise record of what currently exists.

Existing building surveys are commonly required for:

• Planning permission

• Building regulation drawings

• Residential refurbishment projects

• Commercial fit-outs

Without accurate existing drawings, proposed designs may be incorrect from the outset.

What Is an As-Built Survey?

An as-built survey is carried out after construction work has been completed.

Rather than recording what was originally designed, it documents what has actually been built. This is important because changes often occur during the construction process.

As-built surveys usually involve:

• Verification of completed works

• Production of record drawings

• Developer handover documentation

• Compliance and certification records

As a result, the final drawings accurately represent the completed building. These documents are often required for future reference, legal records or property management.

Key Differences Between Existing and As-Built Surveys

Although both surveys measure buildings, the difference lies in timing and purpose.

Existing Building Survey

• Conducted before alterations or design work

• Records the current state of a building

• Used to inform planning and design

As-Built Survey

• Conducted after construction is completed

• Records the finished building

• Used for compliance, certification and documentation

Importantly, the difference is not based on the measurement technology used. Both surveys may utilise laser scanning, total stations or other advanced equipment. Instead, the distinction relates to when the survey is undertaken and why it is required.

Which Survey Do You Need?

In most cases, if you are planning alterations to an existing property, you will require an existing measured building survey.

However, if construction has recently been completed and accurate final drawings are needed, an as-built survey is the correct option.

For larger projects, both surveys may be necessary — first to inform the design process and later to document the completed works.

If you are unsure, it is always advisable to seek professional guidance before proceeding.

Professional Existing and As-Built Surveys

At Line Surveying, we provide accurate existing building surveys and as-built surveys for residential and commercial projects across the UK.

Using professional laser scanning and advanced data capture technology, we deliver clear, reliable drawings suitable for planning, design and compliance purposes.

If you are unsure which survey your project requires, contact us today for expert advice.

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