Hillside Drainage Debacle Causes Odor

By Barry Stone

Dear Barry,

My hillside home has had water in the subarea, runoff from the uphill neighbors. I have had French drains installed across the back and down the sides of my property. The previous owners also tried to improve the drainage, but with no luck. To make matters worse, I am experiencing a musty odor inside the house. Someone suggested enlarging the air openings around the exterior to allow more air circulation. Would this be sufficient to relieve the odor? --Gail

Dear Gail,

Your question involves two separate and distinct issues: 1) whether the drainage problem has been adequately addressed; 2) whether additional subarea ventilation is needed.

If ground water intrusion is occurring beneath the building, further drainage mitigation is apparently needed. Since previous attempts to rectify the ground moisture problem have not been successful, it is fitting to ask whether the existing French were drains professionally designed by a qualified drainage specialist? Are they the work of a geotechnical engineer or merely a landscape contractor? A geotechnical engineer begins by evaluating the geological structure of your hillside and lot to determine the drainage characteristics that would promote subsurface water movement in adverse ways. A mitigation system would then be designed according to the findings of that analysis.

As to ventilation, mustiness in a subarea or within a dwelling typically calls for additional venting. The minimum requirement for foundation vents would be one square foot of vent opening for every 150 square feet of floor space, and these vents would need to be on opposing sides of the building to enable cross ventilation. But remember, these are minimum standards. Additional vents would be needed if ground moisture conditions posed a problem. It is also preferable that these vents be covered with screens, rather than louvers, to provide unrestricted air flow. In some cases, where subarea moisture is excessive and where passive ventilation has not been effective, special vent fans are needed.

Finally, be sure to have the framing structure beneath you home checked for possible fungus and dryrot damage, and have the interior evaluated for possible mold infection.

Copyright 2003-2006 Barry Stone. Distributed by Inman News Features.