Healthy homes
Radon and a new Eastside home: what to decide before construction
Radon is invisible and odorless. The easiest time to make a house ready for mitigation is while it is being built, before the slab, walls, and mechanical systems are finished.
On this page4 sections
Start with testing and local information
Radon levels can vary from house to house. A map can show regional patterns, but it cannot tell you the level in a specific finished home.
Washington’s Department of Health explains testing, health risks, and radon-resistant construction on its radon information page.
Make future mitigation easy
- Discuss a gas-permeable layer and sealed slab penetrations.
- Plan a vent pipe route from below the slab to above the roof.
- Provide an accessible location and electrical connection for a future fan.
- Test after the home is enclosed and occupied, then mitigate if needed.
Coordinate it with the plans
Ask the architect and mechanical team to show the intended route and details. A small amount of planning now can avoid opening walls later.
Practical worksheet
Put this guide to work
Worksheet updated . This is a planning example. Regulatory sources and data have their own dates.
Put testing and a future mitigation path in the project scope
A new home has a planned passive vent route, but no one is assigned to test the completed home or respond if the result is elevated. The rough-in is helpful preparation. It is not evidence that the occupied home's radon level is acceptable.
- Before the slab
- Ask the qualified design team which radon-resistant details are required or appropriate for the project and how they will be documented. Confirm the pipe route and future service access.
- Before walls close
- Have the contractor document the installed system and coordinate any future fan location and electrical provision with the design team. Preserve the details for the owner.
- At completion
- Assign testing to a named person and use the test provider's placement, duration and operating-condition instructions. Save the result with the home records.
- After the result
- Follow Washington Department of Health and EPA guidance on interpretation, confirmatory testing and mitigation. If mitigation is installed, arrange follow-up testing rather than assuming the installation solved the problem.
Regional maps, a neighbor's test and a passive-system label cannot substitute for testing this home. Ask for the cost of the rough-in, testing and any future activation separately so the owner understands what is and is not included.
Action plan
Make the home radon-ready
- 1
Review Washington’s radon map for context, but do not use it as a substitute for testing the finished house.
- 2
Ask the architect to show the below-slab gas layer, sealed penetrations, vent route, roof termination, fan location, and nearby power source.
- 3
Keep the vent route away from windows and coordinate it with plumbing, structure, and mechanical shafts.
- 4
Test the lowest regularly occupied level after construction under the kit or professional’s instructions.
- 5
If results are elevated, activate or improve mitigation and retest to confirm the result.
Official resources