What contour interval is best for a house site?

It depends on site relief, source quality, sheet scale and purpose. A smaller interval improves display detail only when the source supports it.

It is a point with an established or assumed elevation used as a reference for the survey or design.

Can I estimate slope from contours?

Yes for preliminary screening by comparing elevation change with horizontal distance, but use appropriate source data and verify critical locations.

Why include nearby street elevations?

They help evaluate driveway transitions, drainage, utilities and finished-floor relationships that cannot be understood from the parcel interior alone.

Topographic Site Plan Guide: Contours, Elevations and House Fit

Learn how a topographic site plan uses contours, spot elevations, benchmarks, slope, and existing features to support house placement, access, grading, and drainage.

What topographic information describes

Contours connect points of equal elevation; spot elevations describe selected locations; benchmarks establish a reference; and breaklines capture curbs, walls, channels and abrupt grade changes. Existing buildings, trees, utilities and drainage structures often appear because elevation alone cannot explain the site.

Read interval, spacing and direction

The contour interval is the vertical difference between adjacent lines. Close spacing indicates a steeper surface than wide spacing at the same interval. V-shaped contours commonly point upstream across a swale. Labels and spot elevations help determine which direction rises rather than relying on visual intuition.

Understand source accuracy

Surveyed topography, lidar-derived surfaces and other public elevation grids have different precision, resolution, dates and vertical datums. Drawing two-foot contours from a coarse source does not create two-foot accuracy. State the source and reserve critical design for accepted survey information.