Sump and crawlspace sealing

Sumps, slab joints and exposed-earth crawlspaces can provide paths for soil gas. Sealing may be part of a mitigation plan, but a certified mitigator should assess the home and a representative long-term test should confirm the result.

A sump, slab joint or crawlspace may need sealing as part of a mitigation plan. Ask a certified mitigator which openings matter in this home and how the sump will remain accessible for maintenance.

A slab-to-wall joint may be an entry path. Its condition and appropriate sealant should be assessed at the property; sealing alone does not establish that radon is below the guideline.

Cracks, penetrations and drains should be assessed as part of the system design. A drain must keep working; ask the provider how any proposed sealing will preserve its function.

An exposed-earth crawlspace can be a radon entry path. A qualified mitigator can assess whether a sealed membrane and depressurization are appropriate, and specify the installation details.

How long it takes. The time and curing requirements depend on the home, materials and scope. Ask the provider for a project-specific schedule and commissioning plan.

Costs vary with the property, testing method, system design and provider. Ask for a current itemized quote and confirm what testing and follow-up are included.

Sumps, drains, slab joints and crawlspaces differ by property. Ask the provider to identify which openings exist and how they affect the mitigation plan.

Sealant choice depends on the joint, substrate and system design. Ask the provider which product is specified and how movement and moisture will be handled.

Ask a C-NRPP certified mitigation professional to assess sealing when it forms part of a radon repair. Confirm the proposed scope and the applicable standard in the written quote.

What to ask before you hire. Which sealant product, and is it flexible. Will the sump lid let me service the pump without breaking the seal, and does it have a view port. For a crawlspace, what membrane thickness, how are the seams joined, how is it sealed at the walls, and do I have to empty the space first. And the important one: will sealing alone get me below the guideline, or is this part of a system.

A last word on limits. Sealing reduces entry paths. It does not reverse the pressure difference pulling soil gas in, which is what a fan does. Health Canada treats sealing as a supporting measure alongside depressurization. A qualified mitigation professional can assess whether sealing is appropriate as part of a plan. Use a long-term retest to confirm the resulting annual-average estimate.