Retrofitting an egress window into an older Des Moines basement is not a window replacement; it is a violent structural engineering project. The contractor must slice a massive hole straight through the load-bearing foundation of your home without causing the wall to collapse or the basement to flood.

Building code dictates that the new window must provide a minimum "net clear opening" of 5.7 square feet so a fully geared firefighter can dive through it with an oxygen tank. Here is the step-by-step reality of how elite contractors execute this dangerous excavation.

Step 1: The Exterior Excavation

Before touching the concrete, the crew must dig the "Window Well" outside.

• Hand Digging: While a Bobcat is faster, high-end contractors often dig the hole by hand. Bringing heavy machinery 3 feet from a residential foundation risks snagging buried 220v electrical lines or rupturing high-pressure gas lines.
• The Depth Code: The hole must be dug nearly 4 feet deep. Building code requires the bottom of the exterior window well to sit several inches below the bottom of the new window sill, otherwise, snow-melt will pour directly onto the glass.

Step 2: The Concrete Cutting

This is the loudest, most dangerous part of the operation.

• The Track Saw: If your home has 8-inch thick poured concrete walls heavily reinforced with steel rebar, the contractor cannot use a hand saw. They physically bolt a heavy steel track directly to your wall. A hydraulic diamond-blade saw rides this track, plunging completely through the concrete and steel, guided by lasers to ensure a perfectly square cut.
• Water Suppression: Slicing thick concrete generates explosive amounts of silica dust. The contractor must pump thousands of gallons of water directly onto the spinning blade throughout the cut to trap the dust and prevent the diamond blade from instantly melting.
• The "Block" Removal: Once the perimeter is cut, a massive 800-pound rectangular block of concrete is left floating in the wall. The crew uses sledgehammers or small machinery to push the block entirely outside into the hole, where it is broken down andhauled away.

Step 4: The Hardware and Steel Well

With the hole cut and drained, the actual window frame is installed. The crew bolts the heavy corrugated steel (or poly-composite) well shield to the exterior foundation using concrete anchors and coats the seams with extreme waterproofing mastic. Finally, 6 inches of clean, washed river rock is poured into the bottom of the well to filter debris before the water hits the drain tap.

Code Requirement: If the window well is deeper than 44 inches, the contractor must legally bolt a steel escape ladder to the inside of the well well to pass the city inspection.