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Do I need a radon test if I don't have a basement?

By Radon411 Editorial TeamUpdated How we research

Short answer

Yes: any home can have a radon problem, with or without a basement, because radon enters through any part of the building in contact with the ground, such as a slab or the floor over a crawlspace. Test in the lowest lived-in level, which without a basement is the first floor.

Next step: pick the right test for your home. Which test to use

Radon moves up from the ground into buildings through openings in floors or walls that are in contact with the ground: cracks in floors, floor-wall junctions, gaps around pipes or cables, and sumps or drains. None of those routes needs a basement, and the lower air pressure inside a home draws radon in through them.

Without a basement, test on the first floor, in a room used regularly, such as a living room or bedroom, but not the kitchen or bathroom. Over a crawlspace, test the living space above it, never the crawl space itself. In an apartment, use the lowest level within your unit.

Foundation type changes how a high level would be fixed, not whether a test is worthwhile. Slab homes are usually fixed with soil suction, and crawlspace homes most effectively with submembrane suction.

What to do next: run a of at least 48 contiguous hours under , or a of more than 90 days, then read the result with the interpreter.

Why a home without a basement can have radon

Radon moves up from the ground into buildings through openings in floors or walls that are in contact with the ground. A basement is only one kind of ground contact: a slab poured at ground level and a floor over a crawlspace sit on the soil too. That is why any home can have a radon problem: new and old homes, well-sealed and drafty homes, and homes with or without basements.

Cross-section drawing of a house with a basement and a crawl space, numbered at the seven ways EPA lists for soil gas to get in: cracks in solid floors, construction joints, cracks in walls, gaps in suspended floors, gaps around service pipes, cavities inside walls, the water supply.
Read this figure as text
House in cross-section showing where soil gas entersGround levelSoil and rockBasementSolid floorCrawl spaceSuspended floor1234567
  1. Cracks in solid floors
  2. Construction joints
  3. Cracks in walls
  4. Gaps in suspended floors
  5. Gaps around service pipes
  6. Cavities inside walls
  7. The water supply
The routes soil gas takes into a house. Most of them exist whether or not the house has a basement.

Pressure does the rest. Air pressure inside a home is usually lower than in the soil around its foundation, so the house acts like a vacuum, drawing radon in through cracks and other openings, and then traps it inside, where it can build up.

Foundations without a basement

Common foundations and how radon reaches the living space
FoundationWhat it isWhere radon can get in
Slab-on-gradeConcrete poured at ground levelCracks in the floor, floor-wall junctions, gaps around pipes or cables, and drains
CrawlspaceA shallow unfinished space under the first floorOpenings between the crawlspace and the rooms above, such as gaps around pipes or cables
MixedA basement under part of the home and a slab or crawlspace under the restAny part of the building in contact with the ground

Radon levels are usually higher in basements, cellars and living spaces in contact with the ground. In a slab home, the main floor is that living space. See can a house have radon without a basement.

Where to test in a home without a basement

The test goes in the lowest lived-in level: the basement if it is frequently used, otherwise the first floor. Without a basement, that is the first floor, in a room used regularly, such as a living room, playroom, den or bedroom, but not the kitchen or bathroom.

Where the test goes, by type of home
HomeWhere to place the test
Slab-on-gradeA regularly used room on the ground floor
Over a crawlspaceThe living space above it, never in the crawl space itself
Apartment or condo below the third floorThe lowest level within your unit
Mixed foundationThe lowest level you use regularly; in a sale, the lowest level that could be used regularly, finished or not

Wherever it goes, set the device at least 20 inches above the floor, where it won't be disturbed, away from drafts, high heat, high humidity and exterior walls. Every radon test should run for a minimum of 48 hours. More on where a radon test should be placed.

If the level is high: fixes without a basement

A slab-on-grade home is fixed much like a basement home: radon is usually reduced by one of four types of soil suction. In a crawlspace home, the most effective way is submembrane suction: the earth floor is covered with a high-density plastic sheet, and a vent pipe and fan draw the radon from under the sheet and vent it outdoors.

  • Slab-on-grade

    Concrete poured at ground level.

    • Active subslab suctionThe most common and usually the most reliable radon reduction methodSuction pipes may also be inserted below the concrete slab from outside the home.
    • Drain-tile suctionSuction on drain tiles or perforated pipe is often effective in reducing radon levels.
    • Passive subslab suctionUsually associated with radon-resistant features installed in newly constructed homes.

  • Crawlspace

    A shallow unfinished space under the first floor.

    • Submembrane suctionWhen properly applied, the most effective way to reduce radon levels in crawlspace homesA high-density plastic sheet covers the earth floor, and a vent pipe and fan draw the radon from under the sheet and vent it to the outdoors.
    • Active crawlspace depressurizationA less-favorable option that draws air directly from the crawlspace using a fan; it generally does not work as well as submembrane suction.
    • Crawlspace ventilationIn some cases, radon levels can be lowered by ventilating the crawlspace passively, or actively, with the use of a fan.

Any type of home

  • Sealing cracks and openingsA basic part of most approaches, but EPA does not recommend the use of sealing alone to reduce radon.
  • House or room pressurizationShould only be considered after the other, more-common techniques have not sufficiently reduced radon.
  • Heat recovery ventilator (HRV)More effective in reducing radon levels when used to ventilate only the basement.
  • Natural ventilationShould normally be regarded as only a temporary radon reduction approach.

Some homes have more than one foundation design feature. In these situations, a combination of radon reduction techniques may be needed to reduce radon levels to below 4 pCi/L.

The reduction methods listed for slab-on-grade and crawlspace homes.
Fixes for homes without a basement
MethodFoundationWhat to expect
Subslab suctionSlab-on-gradeTypically 50 to 99 percent lower
Submembrane suctionCrawlspaceTypically 50 to 99 percent lower; the most effective crawlspace method when properly applied
Active crawlspace depressurizationCrawlspaceA less-favorable option that generally does not work as well as submembrane suction
Crawlspace ventilationCrawlspaceCan lower levels in some cases, but brings more outdoor air into the home, with moisture and energy penalties

Upper floors and apartments

Radon is usually highest near the ground, but considerable radon can be found above the ground floor, so testing is recommended for all homes below the third floor. Neighbors are no guide: homes next to each other can have different indoor radon levels, and high levels have been found in every state.

Questions about testing without a basement

Can a house without a basement have high radon?

Yes. Any home can have a radon problem, with or without a basement, because radon enters through any part of the building in contact with the ground.

Where do I put a radon test in a slab home?

In a regularly used room on the ground floor, such as a living room or bedroom, at least 20 inches above the floor.

Should I test in the crawl space?

No. A crawl space is on the list of places not to test. Put the device in the living space above it.

Do apartments need a radon test?

Testing is recommended for all homes below the third floor. In a multi-unit building, place the device in the lowest level within your unit.

Is radon lower in homes without basements?

Not necessarily. Levels are usually higher in living spaces in contact with the ground, and in a slab home that is the main floor. Only a test tells you the level.

How is radon fixed in a crawlspace home?

Usually with submembrane suction: a plastic sheet over the earth floor, with a vent pipe and fan drawing radon from under it.

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