Additional Radon Pathways

The following foundation openings may allow soil gas to bring in radon:

• The opening between the basement and crawl space.
• Cracks in concrete slabs and walls.
• Sump holes (may be connected to earth, gravel drainage, perimeter drain pipes, waterline, or a variety of other transport paths).
• Floor drains (connected as above).
• Holes through slabs under tubs, showers, or toilets where space was left around traps.
• Holes in the slab around pipes.
• Heating ducts run under slabs.
• Pores, cracks, gaps in mortar, and open tops in concrete block walls.
• Holes in slabs where wooden stair stringers or pieces of blocking penetrate the slab.
• Cracks in slab around support columns.
• Support walls for fireplaces.
• Cracks at the wall joint in a basement (especially the perimeter expansion joints and canal drains).
• Cracks around water, gas, and utility entry lines.

Figure 3-21 illustrates radon entry into buildings by transport mechanisms and pathways that typically facilitate radon entry.

• A) Cracks in concrete slab
• B) Cracks between poured concrete & blocks
• C) Pores & cracks in concrete blocks
• D) Slab-footing joints
• E) Exposed soil, as in sump
• F) Weeping tile
• G) Mortar joints
• H) Loose fitting pipes
• I) Granite
• J) Water