Crawl space radon mitigation
Crawl spaces, slab additions and split foundations each need their own plan. Here's how radon companies handle them.
Not every house in the Grand Forks area is a simple full basement. Older homes may have a basement under the original house and a crawl space under a back addition. Others have a slab family room, a slab garage, or a newer addition with its own footing. Radon can enter through any of those, so a system may need to reach each one.
How is radon fixed in a crawl space?
With sub-membrane depressurization. A heavy plastic sheet is laid over the soil, lapped and sealed at the seams, and sealed to the foundation walls and piers. A pipe pulls from under the sheet, and a fan sends the gas out above the roof, the same principle as a sub-slab system but with plastic instead of concrete holding the seal.
Can I just open the crawl space vents?
It's not a dependable fix, and in a Red River Valley winter it can freeze plumbing and cool the floors above. Sealed membrane suction is the standard approach.
What about mixed foundations?
- Basement plus crawl space: often a sub-slab suction point tied into a crawl space membrane on one fan.
- Basement plus slab addition: may need a second suction point if air doesn't move under the footing between them.
- Additions on their own foundation: often treated as a separate zone.
What else should I think about?
- If you store things in the crawl space or need to reach plumbing, ask how the membrane will be protected from foot traffic.
- A sealed membrane also cuts down on ground moisture coming up into the crawl space.
- Moved or raised houses from the post-flood years can have newer foundations under older framing; tell the radon company what you know about the history.
Pricing comes from the radon company once it knows your foundation and has usually seen the house in person. We don't quote prices, and any figure given over the phone is a rough starting point, not a bid.
Where we connect you with help
Common questions
Do slab-on-grade houses get radon?
They can. Any part of a house that touches the soil can let radon in. Test every home, whatever the foundation.
Will a membrane work on a gravel crawl space?
Usually, yes. The radon company will look at the surface and decide how to lay, seal and protect the membrane.
Related services
More background: Red River Valley radon guide.
Radon kit came back over 4?
Call and a local radon mitigation company will look at your house and quote a system.