Radon Mitigation in Denver, CO

Three Eras of Foundation Inside One City

Denver's housing splits by decade, and the decade tells you most of what you need to know before opening the door. The pre-1930s streets — Baker, Berkeley, Highland, the older parts of Park Hill — are brick over rubble-stone stem walls, often with a partial cellar and a dirt-floored crawl beside it. The post-war belt east of Colorado Boulevard is ranches and bungalows on half basements. And the infill going up across Sunnyside, RiNo and the north side is slab-on-grade townhouse construction with no below-grade level at all. Those three do not leak soil gas the same way, and no single approach fixes all of them.

Porous Walls, Not Just Porous Floors

The thing that makes the old Denver stock distinctive is that the gas is not only arriving through the floor. An unmortared or lime-mortared stone stem wall is permeable across its entire height, so the perimeter is a source in its own right. That usually means considerably more sealing than a modern basement needs, sometimes a parge coat on the interior face, and occasionally more than one suction point to hold a pressure field in a space that leaks in every direction at once. It is slower work and it is the reason a 1908 bungalow and a 1998 two-storey are not the same quote.

Claystone Under Most of It

Much of the city sits on the dense claystones and interbedded sandstones of the Denver Formation. Heavy clay is far less permeable than the creek gravel out toward Wheat Ridge or the arkosic sandstone under Douglas County, which cuts both ways: gas migrates toward the house more slowly, and a mitigation fan also reaches less far under a slab from a single hole. Sub-slab material is the first thing we check, because it decides whether one suction point covers the basement or three do.

Finished Basements Are the Whole Problem

Denver basements are not storage. They are rental units, home offices, guest rooms and the room the television is in. That is the specific combination that produces a health risk rather than a curiosity — the highest concentration in the house, in the room somebody sleeps in. It also constrains the work, because running a suction point through a finished floor and a pipe through finished walls is a different job from doing it in bare concrete.

Working Across the City

We cover the whole of Denver, from the old streets around Baker and Highland out to Green Valley Ranch and the neighbourhoods near the airport. It is a compact city and no part of it counts as a trip. Most jobs start with a 48-hour test; where the number comes back high, the fix is usually a sub-slab system, or a sealed crawlspace membrane on the older stock where there is no slab to work with.

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