Exterior – The importance of exterior grading

To maximize surface drainage around the perimeter of the home to effectively shed water away from the building. 

i) Utilizing a clay based soil, a grade that is not less than 1” fall per ft. run, must be maintained for not less than 4 ft. out from the foundation.

ii) The additional fill added, should maintain not less than 6 in. clearance to the underside of all siding and windows.

iii) Where this clearance cannot be maintained the installation of window wells will be necessary.

iv) The depth of the window well, when possible, should extend not less than 16” in. below the underside of the window. When possible, the undisturbed earth at the bottom of the window well should also be such that this grade runs away from the foundation.

v) Area around the window well will then be backfilled with a fast draining material, earth build up should not be closer than 8” in. to the underside of the window within the well.

vi) Window well covers can be of value during the winter months to minimize snow build up within this space.

vii) With the grade established, the installation of a geotextile cloth (landscape paper) will minimize erosion and reduce the ability of greenery growth which could otherwise obstruct surface drainage.

viii) With geotextile cloth installed, the installation of a coarse granular, two inch minus (river rock, granite, or limestone) will promote a less obstructive drainage medium.

ix) In areas where fill cannot be added, it will be necessary to remove earth 4 ft. out from the cottage to establish the desired drainage slope. 

x) Where applicable, drainage ditches and swales are most effective when kept clear of all foliage and debris. The incorporation of a geo-cloth, and a coarse granular in this situation will also accelerate drainage and reduce future maintenance.

In dealing with wet basements, and wet basement “professionals” the status quo is often focused on the excavation and re-sealing of the foundation. While it can be expected that this will have some positive effects, it will typically only deal with approximately 10% of the water infiltration being experienced. 

Ground water (water table) fluctuation is a slow process and will often take up to 4 or 5 days after prolonged rain or melt to have a negative impact on the foundation and basement alike. When water infiltration is apparent within the 24 hours of prolonged rain, or snow melt this is most often surface drainage oriented. Focus should be on eaves, downs, and grades. This will be the most effective means of remediation.

Following these guidelines, and with proper maintenance, wet basement concerns will often be reduced to only the need for dehumidifying the basement area to manage moisture. I am hopeful that these steps will better assist you in managing your basement, and its moisture levels.