Insufficient Roof Overhang
An insufficient roof overhand delivers rainwater close to the foundation. Moisture in rain saturated earth eventually penetrates the foundation and migrates to the interior. A traditional 12-inch eave side overhang is not recommended. An 18 to 24-inch eave side overhang is preferable for our wet climate.
Ineffective Gutter Downspouts
Ineffective gutter downspouts allow rainwater to migrate through the foundation to the interior. Gutter downspouts deliver a concentrated volume of water and are often a source of rainwater penetration.
Downspouts require vigilant maintenance and must be connected to an effective disbursement pipe which automatically diverts rainwater away from the building.
Improperly Installed Flashing
Improperly installed roof, door and window flashing and ice dams can funnel water into walls. Complicated roof systems, dormers and skylights leak over time and saturate lower areas of the building creating microclimates that encourage mold growth. Staining of wood and drywall indicate conditions that require prompt consultation with an experienced professional. All saturated drywall and wet insulated ventilation ducts should be replaced.
Improper Exterior Grading
When exterior grading allows ground water to run toward the foundation, instead of positively drain away, ground water migrates through the foundation to the interior of the home.
Exterior grading must positively descend away from the structure to carry surface water away from the window wells, bulkhead and foundation. Special attention needs to be given to home additions that trap surface water. When undulating building masses dam surface water intervention by an experienced professional is required.
Unprotected Window Wells
Unprotected window wells fill with rainwater during periods of heavy winter and early spring rain. When water levels are high enough to penetrate the perimeter of a basement window water runs into the basement.
Covers can be purchased for most window wells but a better protection is installation of perforated PVC drain piping and a T section descending below the frost line toward a sub-grade drainage system.
Improper Perimeter Drains
Structures lacking properly designed and built perimeter drains, that positively drains away to daylight, are likely to flood. Some insurance policies don’t cover damage from such flooding, creating serious issues for homeowners with expensively finished basement space. It is critical to remember when extending your yard by adding fill that old day-light drainage pipe needs to be extended as well.
Properly designed and laid perimeter drains are critical for basement and crawlspace protection from ground water penetration and for prudent ground water management. This is not difficult to do, but if not done correctly, failure is likely and remediation is messy and expensive.
If water is running through your basement or crawlspace, the condition MUST be stopped or isolated by a water barrier. Streams, groundwater bubbling up and vapor transmission must be controlled. Solutions for automatic removal include interior perimeter drains, French drains and sump pumps.
What additional measures are required should be evaluated by an experienced technician. A recommended solution is a bed of crushed stone, with no fines, followed by a 20 ml water barrier membrane to seal from moisture below. For a comprehensive solution, such systems typically seal to water barrier membranes covering the sidewalls.