Crawl space and slab radon mitigation
Not every house sits on one tidy basement. Crawl spaces, slabs and add-ons each need their own piece of the system.
Plenty of Yellowstone County houses have more than one kind of foundation: a basement under the original house with a crawl space under a later addition, a slab-on-grade family room, or a manufactured home over a dirt crawl. Radon can come in through any part of the house that touches the soil, so each section may need its own treatment.
How is radon fixed in a crawl space?
The standard method is sub-membrane depressurization. A heavy plastic or rubber sheet is laid over the dirt floor, overlapped and sealed at the seams, and fastened and sealed along the foundation walls. A pipe goes through the membrane, and a fan pulls soil gas from underneath it and vents it above the roof. It's the same idea as a sub-slab system with a membrane standing in for concrete.
What about slab-on-grade houses?
A home or addition built on a slab without a basement can take a suction point through the slab, with the pipe often going up through a garage wall or closet. Large slabs, or slabs broken up by thickened footings, may need more than one point.
How do mixed foundations get handled?
- Basement plus crawl space: a sub-slab point in the basement tied into a membrane in the crawl, often on one fan.
- Basement plus slab addition: a second suction point if the soil under the two sections isn't connected.
- Manufactured homes: a membrane over the ground under the home, with the skirting and access in mind.
Can I just open the crawl space vents?
Ventilating a crawl space sometimes lowers radon a little, but the results are inconsistent, and in a Billings winter open vents can freeze water lines in the crawl. A sealed membrane with a fan is the dependable fix.
Anything else to plan for?
A sealed membrane also cuts the ground moisture coming into the crawl. If you store things down there or need to reach plumbing and ducts, ask the installer how they'll protect the membrane, and whether heavier material makes sense where people crawl.
The radon company sets the price after it learns about your house, and usually after someone has looked at the foundation. We don't quote prices, and a number given over the phone is only a rough starting point.
Where we connect you with help
Common questions
Does a slab house need a radon test?
Yes. Any house in contact with the ground can have radon, basement or not. Test it.
Can a mobile or manufactured home have radon?
Yes. Radon can collect under the home and come in through floor openings. A test tells you, and a membrane system can fix it.
Related services
- Radon testing
- Radon mitigation systems
- Radon for home buyers and sellers
- Radon fan replacement and repair
More background: Montana radon guide.
Got a radon number you don't like?
Call now and a local radon mitigation company will look at your house and quote a system.