Basement Radon Mitigation in Spokane

Suction and sealing, fan, manometer, electrical permit, post-mitigation test, written guarantee below 4.0 pCi/L, 5-year fan and workmanship warranty.

Old block and stone walls

Hollow block and fieldstone walls leak in different ways.

Hollow block walls are rows of open cells. Where the top row has no solid cap, soil gas can rise through the cells into the basement. We close the open tops, cracks and pipe gaps first. EPA lists block-wall suction for these walls, and the standard requires the cells to be closed wherever it is used. We add it only when the pressure readings call for it.

Fieldstone walls have no cells. Gas moves through the mortar joints, and suction under the slab may not reach the soil behind them, so we take readings near the wall before we settle the design.^{3, 4, 5}

Finished basements

Finished rooms limit where we can drill and run the pipe, not how suction works under the slab. We look for a utility room, storage closet or the space under the stairs, and the pressure readings confirm the suction reaches under the finished rooms.

Flooring and framing also hide most cracks. In a 1986 study of crack sealing in Spokane River Valley homes, Lawrence Berkeley Laboratory named finished basements as the place where most defects could not be reached.

Planning to finish the basement later? Tell us first, so the pipe stays in an unfinished corner. After a remodel, EPA advises a retest in the lowest lived-in area.^{6, 3}

Sumps and floor drains

A sump pit opens into the gravel and drain tile under the floor, one of the largest gaps in a basement. The standard calls for a rigid lid on any sump that connects to soil, fastened so it comes off for pump work and sealed with a gasket or silicone. The pit keeps draining as before.

We use the sump as the main suction point only when other spots cannot reach far enough, since the standard’s guidance warns of harder pump access and more noise.

Floor drains that run to soil can let gas up and pull basement air into the system. EPA’s technical guidance says such a drain must be trapped. A waterless trap with a floating ball keeps its seal even when dry.^{4, 5}

Living with the system

The standard recommends checking the system monitor each quarter and testing at least every two years, and again after a sump or drain tile is added or altered or a never-tested lower room is put to use. Fans may last five years or more. At Avista’s Washington rate, a 20 to 150 watt fan costs about $25 to $191 a year.^{4, 3}