By: Christopher Brooks
Proper drainage is an essential component of waterproofing your basement — and the rest of your home. Even before a new home is constructed, effective drainage and grading must be "built" into the landscaping plan in order to prevent and minimize future problems with moisture, mold and leakage in the home.
Dave Polk, president of epro Waterproofing Services (www.eproserv.com), manufacturers of waterproofing systems for above-and below-grade applications based in Derby, Kan., says that this is a vital step.
"Many potential new homeowners don't realize the degree of importance these elements play in keeping their homes' interior dry."
Two types of drainage
Polk pointed out that for professional landscapers, the term "drainage" generally refers to either the flow of water over an area of land or the seepage of water into soil. Either way, correcting faulty drainage — even if it means moving earth to reshape the land — is often necessary. In the long run, however, it can make a positive difference in the performance of your waterproofing system.
"The drainage and slope of the terrain needs to be considered during the home's initial design. Let's consider a project where an architect observes that the house is to be built on a hillside," Polk said. He noted the following scenarios are likely:
- There is going to be significant water drainage from the hillside.
- The design dictates there is going to be some
accumulation of water near the foundation, and it
cannot be directed away.
- The backfill is going to be native soil, which consists
of clay and rock.
- The slope of the grade drainage is toward the house.
- The type of backfill (clay) does not let water drain through soil.
Polk added the problem might not be in liquid form, but rather moisture.
"What if the architect has another situation?" He listed the following:
- The soil survey indicated underground water 10 feet below anticipated elevation of the foundation slab.
- There have been other buildings in this area that have significant water problems, which resulted in
mold and mildew.
- The elevation of the structure cannot be raised because of design and code issues.
- The owner intends to install hardwood flooring
in the lower level.
"The architect wants to avoid these problems in his project. An appropriate solution would be the installation of a moisture barrier."
Polk offers the following "dos" and "don'ts" to consider when designing — and building — your next structure:
*Minimize the irrigation systems near the house.
*Extend downspout drainage 15 to 20 feet beyond
the house perimeter.
*Sump pump discharge should always be piped 5 to 20 feet away from the perimeter of the house (to prevent recycling water).
*The slope of the grade should always be away
from the house.
*The roof should always have proper guttering and
downspouts to handle water runoff (rain and snow).
*Direct drainage water from surrounding areas
(hills, other lots, etc.) from the structure through
the use of retaining walls, terraces, etc.
*Seal with a water repellant above-grade bricks and
masonry units to prevent moisture migrating the
units and down the basement walls.
- Have irrigation system discharging water
onto the walls of the structure.
- Have backfill and grade exceed more than an inch
or so above waterproofing on the wall.
- Plant trees or shrubs next to the structure unless a
root-resistant protection course has been placed over the waterproofing material (roots from large plants can grow through waterproofing and small cracks in walls into the basement carrying mold with them).
- Place hard cast structures (patios, decks, sidewalks)
next to the structure without proper slope away
from the structure.
- Bring grade onto the bricks of the structure without installing waterproofing on the brick ledge and
behind the brick.
Attention to proper landscaping design and a surface water management plan will go a long way toward keeping basements dry.
Discuss drainage, grading, plant/tree placement and other landscaping elements with the homeowner. Use an architect and landscape designer on your next project.
Effective decisions now will support and help empower your waterproofing system later.
Based in Bucks County, Penn., Christopher Brooks writes about the home — inside and out — for consumer and trade magazines.