Foundation Inspection Cedar Park, TX.

How the elevation survey actually runs at your home

What the numbers tell us about Cedar Park ground

Cedar Park straddles the line where Central Texas limestone uplands give way to the valleys carved by Brushy Creek and its tributaries. That geology produced a building pattern you see all over town: lots graded by cutting into rock on the high side and placing engineered fill on the low side. The survey exists to find the boundary between those two conditions on your specific slab.

On the cut portion, limestone can sit just inches below the slab, so the foundation bears almost entirely on rock. On the fill side, the picture changes. Fill that was placed too thick, too fast, or without moisture control will consolidate under the weight of the house, and the cut half essentially holds still while the fill half drifts down. That differential movement is the mechanical origin of most of the cracking we document here.

Soil chemistry still matters even on a rocky lot. Where Houston Black and related high-plasticity clays show up in the fill or in pockets between outcrops, the plasticity index can top 40, meaning those soils swell hard when wet and shrink in summer drought. The active zone runs roughly 8 to 15 feet across Central Texas, though shallow bedrock compresses it in many Cedar Park locations, and even a thin active zone moves enough to rack a door frame.

What the inspector checks beyond the floor readings

A useful survey looks at the conditions driving the movement, not only the movement itself:

• Surface drainage and fall, whether the grade carries water at least six inches of fall over the first ten feet, since chronic re-wetting undermines any pier system.
• Step cracks at the fill-to-rock line, diagonal cracks from window corners toward grade that widen at the bottom flag differential settlement along a fill boundary.
• Plumbing penetrations, on rocky lots a slow leak can travel along the limestone surface and erode fill voids well away from the source, so a hydrostatic test is worth running.
• Irrigation and moisture habits, drip lines set 18 to 24 inches off the foundation edge keep clay-bearing fill from cycling through extreme shrink-swell.
• Interior versus exterior signs, sticking doors, drywall cracks fanning from corners, and gaps at the ceiling line are correlated against the elevation map.
• Garage and slab cracks, checked for whether they trace a settlement plane or are simple shrinkage.

Questions Cedar Park homeowners ask us