Radon Mitigation
Most Twin Cities houses have full basements, which is why crawl spaces catch people out. They turn up under additions and three-season porches that were closed in, under older houses with a partial cellar, and under some split-levels. Where the ground is bare dirt there is nothing between the soil and the house at all, and the crawl can undo a basement system next to it. The fix is to build the floor that is missing: a heavy membrane over the ground, sealed to the foundation walls, with suction drawn from beneath it — tied into the same fan as the basement where that works.
Full basements are the norm across the Twin Cities, which is exactly why crawl spaces get overlooked. They turn up under additions built onto older houses, under three-season porches that were later closed in and heated, under the rear section of some split-levels, and under a handful of older homes with only a partial cellar. The main basement may be tested and even mitigated while the crawl next to it sits on bare dirt, feeding soil gas into the house through the floor above and through any opening into the basement.
Where there is no slab, the membrane becomes the slab. We lay a heavy, reinforced sheet over the ground, overlap and seal the seams, run it up the foundation walls and seal it to them, and seal it around every pier and pipe. A suction point goes beneath the membrane and connects to a fan — often the same fan and riser that serves the basement, joined through the wall. The fan then holds the space under the membrane at low pressure exactly as it would under concrete.
A Minnesota crawl space has its own constraints. Many are shallow, with ductwork and plumbing running through them, and some addition crawls have only a small access hatch. Crawls under additions and porches are often less protected from the cold than the main basement, so pipe routing has to keep condensate from freezing. We look at all of it before quoting so the price reflects the space you actually have.
A sealed membrane is one of the most effective things you can do about crawl space dampness, and most owners notice the difference. We mention it because it is true, but the system is designed and priced for radon. If moisture is the main complaint, there may be a better-targeted fix.
The test still goes in the lowest lived-in level — usually the basement, or the room above the crawl if that is where people spend their time. If the result is high, the basement system and the crawl membrane are designed together so neither leaves the other as a shortcut, and a follow-up test confirms it.
How long does it take? One to two days depending on headroom, how much of the ground is obstructed by ductwork and piping, and whether the space has to be cleared first.
These usually come up in the same conversation:
The standard fix for a Twin Cities basement or slab: suction under the floor, the gaps sealed, a fan outside the living space and a discharge above the roof — built for a Minnesota winter.
Learn More →A continuous monitor in the lowest lived-in level for at least 48 hours, logging every hour — a curve you can read, not one number that might be a fluke.
Learn More →An open sump basket or a dry floor drain is a direct line to the soil. Sealing them is what lets a system work — and where cheap installs cut corners.
Learn More →Free · No Obligation
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