Site survey types and what each one shows

Boundary, topographic and as-built surveys answer different questions. Know which one you need before you design or price a foundation.

Why survey

A survey ties the project to the real ground: where the boundaries are, how the land falls, and where utilities and easements run. Drawings made without one risk a building in the wrong place or a foundation that does not suit the slope.

Common survey types

• Boundary survey: locates property lines and corners, and often easements and encroachments.
• Topographic survey: records ground elevations as contours and spot levels, plus trees, structures and drainage features.
• Utility survey or locate: marks the position of buried and overhead services.
• As-built survey: records where things were actually built, used for closeout and sometimes by the AHJ.
• Construction staking: marks building corners and levels on the ground for the builder.

Who does it

In most places surveys are done by a licensed land surveyor. Ask who signs the document and whether it can be relied on by your lender or the AHJ.

What to check on the result

• Datum and benchmark: what the elevations are measured from.
• Date: ground and fences change.
• Easements, rights of way and flood information shown or noted.
• Units and scale.

Using it

Give the designer, engineer and contractor the same survey so everyone works from one set of numbers. See also reading the soils report.

Quick answers

• Is a boundary survey enough for design? Not usually; you often also need a topographic survey for slope and drainage.
• How old can a survey be? There is no universal rule. Ask the designer and lender, and recheck if the site has changed.
• Does a survey show soil conditions? No. That is the job of a geotechnical investigation.

Rules differ by country, state and city. Confirm requirements with your local authority having jurisdiction and with the licensed professionals on your project; nothing here is legal, engineering or financial advice.

Questions people ask

Is a boundary survey enough for design?

Not usually; you often also need a topographic survey for slope and drainage.

How old can a survey be?

There is no universal rule. Ask the designer and lender, and recheck if the site has changed.

Does a survey show soil conditions?

No. That is the job of a geotechnical investigation.

Sources and further reading

• National Society of Professional Surveyors
• USGS

Text Digital Oro

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