What Does "Below Grade" Mean in Construction?
In construction, "below grade" means below the finished ground level around a building. "Grade" is the surface of the soil after construction and landscaping are finished. Any part of a structure that sits lower than that surface, such as a basement, a foundation wall, or the ground under a crawl space, is below grade, and it's in constant contact with soil moisture.
That last part is why the term matters. Everything below grade has to deal with water in the surrounding soil, and in Central Texas clay that water doesn't go away quickly. Scott Lockhart Drainage Contractor has been protecting below-grade spaces across Austin since 1984, on more than 10,000 projects.
Above Grade, At Grade, and Below Grade
Builders, inspectors, and appraisers use three related terms:
Above grade: anything higher than the finished ground level, such as walls, windows, and the main living floors.
At grade (on grade): built at ground level. A slab-on-grade foundation, the most common type in Austin, is a concrete slab poured directly on the prepared ground.
Below grade: anything lower than the finished ground level, such as basements, cellars, crawl spaces, and the buried portion of foundation and retaining walls.
You'll also hear finished grade (the final ground surface after construction) and natural grade (the original ground before anything was built). When the two differ, water patterns on the property change too.
What Counts as a Below-Grade Structure?
Common below-grade structures include:
Basements and cellars, fully or partly underground
Crawl spaces, the open area under a pier-and-beam home
Foundation walls and footings, the buried portion of any foundation
Retaining walls, which hold soil back and have one side below the grade they support
Sunken rooms, stairwells, and window wells
Underground vaults, utility pits, and pool equipment areas
Appraisal standards also treat below-grade space differently: finished square footage that sits partly below grade is generally reported separately from above-grade living area.
Why Below-Grade Spaces Are Hard to Keep Dry
Three forces work against anything below grade:
Soil moisture. The surrounding soil is almost never fully dry, so moisture is always pressing in.
Water pressure. When soil becomes saturated after heavy rain, water pushes against walls and floors with real force. This is called hydrostatic pressure, and it finds every crack and seam.
Grading that sends water the wrong way. If the ground slopes toward the building, every storm delivers more water to the below-grade parts.
Why It Matters in Central Texas
Basements are rare in Austin because of shallow limestone and expansive clay soil. But plenty of local homes still have important below-grade areas:
Pier-and-beam crawl spaces, common in older Austin neighborhoods. Here's why those crawl spaces stay damp.
The buried edges of slab foundations, where soil moisture swings drive seasonal movement.
Retaining walls on sloped lots. See retaining walls in Austin: maintenance and repair.
Sunken living rooms and lower levels on Hill Country homes.
Our clay makes the challenge sharper. It swells when wet and presses against anything below ground, then shrinks as it dries. That cycle is hard on every below-grade surface it touches.
How Below-Grade Spaces Are Protected
Lasting protection does two jobs:
Keep water off the structure with barriers, membranes, or vapor barriers. For crawl spaces this is crawl space encapsulation.
Give the water somewhere else to go with grading that sheds water away, drains that relieve pressure at the base, and a real discharge point.
A barrier alone eventually loses to standing water. A barrier paired with drainage lasts. Read the full breakdown in how below-grade waterproofing works in Central Texas.
Frequently Asked Questions
Is a crawl space considered below grade? Usually, yes. The ground inside a crawl space typically sits at or below the surrounding finished grade, so it's exposed to the same soil moisture as any below-grade space.
Is a slab-on-grade foundation below grade? The slab itself sits at grade, but its edges and footings extend below grade, which is why grading and drainage around a slab still matter.
What's the difference between "grade" and "elevation"? "Grade" refers to the ground surface around a building. "Elevation" is a measured height relative to a reference point, often used on survey and flood maps.
How do I know if my below-grade space has a water problem? Watch for musty smells, damp or stained walls, efflorescence (white mineral deposits on concrete), floors that move with the seasons, or water appearing after storms. Any of these is worth a closer look.
Get a Straight Answer
Call Scott directly for a free consultation: 512-790-8564 Scott Lockhart Drainage Contractor · Austin, Texas · Since 1984
