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Code Green

CODE TIP: Footing Drains and Foundation Waterproofing

Building codes require perimeter drains around the outside of basement footings. They are not difficult to install properly before the foundation has been backfilled, but they are costly and disruptive to put in after the fact.

Sections 404, 405, 406, and 801 of the International Residential Code (IRC) relate to foundations and below-grade habitable space. All code references are to the IRC unless otherwise specified.

Drainage

Concrete & CMU foundations that contain habitable or usable space need drains [405.1], unless there is good natural drainage [405.1X]. Use filter fabric over drain fields [405.1] and at least 2 inches of stone under pipes [405.1]. If the soil is expansive or collapsible, extend gutter downspouts 5 feet from the building or to an approved drainage system [801.3].

Waterproofing, Damp-proofing, & Backfilling

Below-grade basement walls need damp-proofing [406.1], but if the water table is high, use waterproofing instead [406.2]. Parge CMUs before damp-proofing [406.1], and lap and seal all joints in waterproofing [406.2].

Don’t backfill until foundation walls are anchored to the floor framing [404.1.7] (except walls supporting less than 4 feet of unbalanced backfill [404.1.7X]).


GREEN POINTS

LEED for Homes: ID2 (Durability Management Process) has prerequisites and 3 points for third-party certification of durability processes/practices.

NGBS/ICC 700: Under Ch. 6, Resource Efficiency: 4 points for well-designed foundation perimeter drainage as part of durability measures (602.3).

LEARN MORE

Foundation Drains

BROWSE THE PRODUCT GUIDE

Green Products for Foundations, Footings, and Slabs


3 Comments

  1. Mark | | #1

    Where would the Drain Tile drain to
    I have a 1958 Ranch style home in southeaster South Dakota. It has a concrete block uninsulated basement that has a continuous, uniform clay soil grade about 5-6 feet deep. No water issures, a few areas of cracks in the mortor. A sump inside the basement, with no interior or exterior drain tile, always has two inches of water in the bottom when conditions are dry. I am thinking of excavating arround the exterior to install waterproofing, drain tile, rock and filter fabric as noted above, and enough EPS rigid foam for R20 (do I need more???). With no option for draining to daylight, where would you run the Drain Tile to--a drywell 15 or more feet away from the house or into the interior of the basement to the sump? Thanks

    Mark Dahlhoff Vermillion, SD

  2. User avater GBA Editor
    Martin Holladay | | #2

    "Draining to daylight"
    Mark,
    In hilly Vermont, it's usually easy to "drain to daylight." In the flatter sections of South Dakota, a drain to daylight may require running your 4" or 6" pipe all the way to Missouri — not a good solution.

    It makes little sense to connect exterior drain tile to an interior sump until you have a good plan for draining the sump. A sump is usually drained with a sump pump, either over the surface of the ground to a suitable distance away from the house, or to a town sewer (where such a connection is permitted).

    The other option is a distant dry well, as you propose. The farther away from your house, the better.

  3. Brett Moyer | | #3

    Flat Lot, Dry Climate
    Is there a section in the IRC that covers perimeter foundation drains in dry climates? We get about 16 inches of precipitation in our area, and it's not very common to see a perimeter drain around the foundation unless the site has a high water table.
    Daniel referenced the IRC stating "Concrete & CMU foundations that contain habitable or usable space need drains [405.1], unless there is good natural drainage [405.1X]" Does this mean ALL foundations with out good natural drainage? And what is "good" natural drainage by the way? Im assuming good slope, and somewhat permeable soils. And what about flat lots in dry climates? Sloped lots in dry climates?
    I know that good sized roof overhangs can deflect the moisture away from the foundation wall. I also know to grade away from the building, but this may not be sufficient drainage in the eyes of some building inspectors...

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