Final Grade

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Climate

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Description

Because no waterproofing system is 100% foolproof, the best defense against water intrusion through the foundation is to prevent water from saturating the soil around the foundation. This can be done by constructing the foundation and grading the site so that water drains away from the house on all sides. 

How to Grade the Site

  1. Grade to build up the site before construction, if needed, to raise elevation of walls above grade.
  2. After construction, back-fill, grade slope, cap with 2 to 4 inches of silty clay, and mechanically compact it to achieve a final grade slope of  >= 0.5 inch per foot away from home for >= 10 feet.
    • Tamping of back-fill is not required if either:  proper drainage can be achieved using non-settling compact soils, as determined by a certified hydrologist, soil scientist, or engineer; OR, the builder has scheduled a site visit to provide in-fill and final grading after settling has occurred (e.g., after the first rainy season). See note below for alternatives.
    • If setbacks limit the space to less than 10 feet, install either: swales or perimeter drains designed to carry water away from the foundation. (Swales are typically vegetated, trapezoidal channels, which receive and convey storm water flows. Swales slow storm water runoff and remove pollutants through vegetation.)

Site grading and groundwater control

Figure 1 - Site grading and groundwater control Reference

Ensuring Success

Visually inspect that back-fill has been tamped and final grade sloped >= 0.5 in. per ft. away from home for >= 10 ft. Where setbacks limit space to less than 10 ft., see that swales or drains are installed to carry water from foundation shall be provided.

Scope

Water Managed Site and Foundation

Back-fill has been tamped and final grade sloped >= 0.5 inch per foot away from home for >= 10 feet.

  • Slope final grade away from the house at least 0.5 inch per foot for 10 feet.
  • Back-fill tamp to prevent settling.

If setbacks limit the space to less than 10 feet, install either:

  • Swales
  • Drains designed to carry water away from the foundation.

ENERGY STAR Notes:

Swales or drains designed to carry water from foundation are permitted to be provided as an alternative to the slope requirements for any home, and shall be provided for a home where setbacks limit space to less than 10 ft. Also, tamping of back-fill is not required if either: poper drainage can be achieved using non-settling compact soils, as determined by a certified hydrologist, soil scientist, or engineer; OR, the builder has scheduled a site visit to provide in-fill and final grading after settling has occurred (e.g., after the first rainy season).

Training

Right and Wrong Images

Presentations

None Available

CAD Images

None Available

Compliance

ENERGY STAR Version 3, (Rev. 07)

Water Management System Builder Checklist, Water-Managed Site and Foundation. Back-fill has been tamped and final grade sloped >= 0.5 in. per ft. away from home for >= 10 ft. Where setbacks limit space to less than 10 ft., swales or drains designed to carry water from foundation shall be provided. Also, tamping of back-fill is not required if either:  proper drainage can be achieved using non-settling compact soils, as determined by a certified hydrologist, soil scientist, or engineer; OR, the builder has scheduled a site visit to provide in-fill and final grading after settling has occurred (e.g., after the first rainy season).

DOE Challenge Home

Exhibit 1: Mandatory Requirements. Certified under ENERGY STAR Qualified Homes Version 3.

2009 IRC

Section R408.6 Finished grade. Finished grade of under-floor surface may be located at the bottom of the footings.  If there is evidence that the groundwater table can rise to within 6 inches of finished floor at the building perimeter or where there is evidence that surface water doesn’t readily drain from the building site, the grade in the under-floor space must be as high as the outside finished grade unless an approved drainage system is provided.*

2012 IRC

Section R408.6 Finished grade. Finished grade of under-floor surface may be located at the bottom of the footings.  If there is evidence that the groundwater table can rise to within 6 inches of finished floor at the building perimeter or where there is evidence that surface water doesn’t readily drain from the building site, the grade in the under-floor space must be as high as the outside finished grade unless an approved drainage system is provided.*

*Due to copyright restrictions, exact code text is not provided.  For specific code text, refer to the applicable code

More Info.

Case Studies

  1. Author(s): PNNL
    Organization(s): PNNL
    Publication Date: April 2012

    Case study about energy efficienct new home construction that also incorporated moisture management techniques for durability in the damp Northwest climate.

References and Resources*

  1. Author(s): DOE
    Organization(s): DOE
    Publication Date: June 2013

    Standard requirements for DOE's Challenge Home national program certification.

  2. Author(s): EPA
    Organization(s): EPA
    Publication Date: June 2013

    Standard document containing the rater checklists and national program requirements for ENERGY STAR Certified Homes, Version 3 (Rev. 7).

  3. Author(s): BSC
    Organization(s): BSC
    Publication Date: May 2009

    Information sheet about groundwater control.

  4. Author(s): EPA
    Organization(s): EPA
    Publication Date: February 2011

    Guide describing details that serve as a visual reference for each of the line items in the Water Management System Builder Checklist.

Last Updated: 08/15/2013

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