Frost-Protected Shallow Foundations by vwp15099


YOUR BLUEPRINT FOR USING ADVANCED BUILDING TECHNOLOGY                             Shallow Foundations


  DOLLARS & SENSE                 MAKING THE SWITCH               RESULTS FROM THE FIELD           FOOD FOR THOUGHT                  TECH CHECK

  Costs for materials and labor   What it takes to switch from    Field evaluation results from    What to consider to be sure       Steps you need to take if you
  to use FPSFs…                   conventional slab on grade      Colorado, New Jersey, and        FPSFs are right for your          decide to start using this
                        Page 2    foundations to FPSF…Page 2      Iowa...    Page 2                project…              Page 3      building technology… Page 3

                                                                                                               THE BASICS
                                                                                                               Frost protected shallow foundations
                                                                                                               (FPSFs) eliminate the need for excavating
BENEFITS (+) / DRAWBACKS (-)                          may restrict the use of rigid foam on the outside        below the frost line in order to protect
+ AFFORDABILITY: Reduced excavation;                  of the foundation, or may require termite-               foundations against freezing. Traditional
  reduced foundation labor and material costs         resistant insulation.                                    foundations are protected from freezing
+ MARKETABILITY: May increase homeowner                                                                        because they are installed below the frost
  comfort and decrease heating energy costs due       RESULTS FROM THE FIELD                                   line, which can be 48 inches or more below
  to increased insulation at the perimeter of slab-   Two PATH Field Evaluations examined FPSFs:               grade. FPSFs are placed only 12 to 16
  on-grade foundations                                Oakwood Homes in Denver, CO and K.
                                                                                                               inches below finished grade, and use heat
– CODE ACCEPTANCE: Some local codes may               Hovnanian in Freehold Township, N.J.
  not accept FPSFs; use of rigid foam on the                                                                   from the earth and the building to maintain
  exterior may be restricted in heavy termite         WARRANTY                                                 sub-slab soil temperatures well above
  infested areas                                      Not applicable.                                          freezing, thereby effectively raising the
                                                                                                               frost depth around a building’s perimeter.
INITIAL COST                                          MAKING THE SWITCH
FPSFs offer excavation, construction, material        FPSFs are relatively easy to implement because           Construction and excavation, labor and
and labor cost savings. One case study in             they are usually less expensive to install than          material costs are usually less for FPSF
Denver, Colo. showed savings of 15 to 17              traditional foundations. The construction
                                                                                                               than for conventional foundations, and are
percent compared to a conventional foundation;        schedule is usually expedited due to reduced
and an Iowa builder reported a $10 to $15             excavation depth and concrete work. FPSFs                an inexpensive method for building a well-
savings per lineal foot when compared to              also use conventional construction materials,            insulated and comfortable foundation.
basement foundations. Cost savings will vary by       and install similar to traditional foundations.
regional code-specified frost depth – colder                                                                   FPSFs use conventional materials that are
climates offer greater opportunities for savings                                                               readily available. The insulation used is
than more temperate climates.                                                                                  either rigid expanded or extruded
                                                                                                               polystyrene foam (EPS or XPS), suitable
                                                                                                               for below-grade application.
Operational cost for FPSF is similar to
conventional foundation types that are insulated
to current energy code levels.                                                                                 Provisions for FPSFs are included in the
                                                                                                               2000 and 2003 International Residential
CODE ACCEPTANCE                                                                                                Code (IRC) and the 2003 International
Provisions for FPSFs are included in the 2000                                                                  Building Code (IBC) for buildings when the
and 2003 International Residential Code (IRC                                                                   interior space will be conditioned to a
Section 403.3).The American Society of Civil                                                                   minimum of 64o F, year round. The
Engineers (ASCE) developed a standard,
                                                                                                               American Society of Civil Engineers
"ASCE/SEI 32-01, Design and Construction of
Frost-Protected Shallow Foundations,” which is                                                                 (ASCE) standard "ASCE/SEI 32-01,
adopted by the 2003 IRC and International                                                                      Design and Construction of Frost-
Building Code (IBC). However, use of FPSFs is                                                                  Protected Shallow Foundations,” is also
still governed by locally-specified codes.                                                                     referenced in the 2000 and 2003
                                                                                                               International Residential Code (IRC).
In areas of heavy termite infestation, local codes

                                                                                                                                  TECH SPECS >     1
                                               Frost-Protected Shallow Foundations

DOLLARS AND SENSE                              RESULTS FROM THE FIELD

Cost savings have been realized in field       This technology has been used by other builders in real-world building situations – learn
evaluations of the FPSF technology.            from their experiences.
The following savings in excavation and
foundation costs have been reported:           Denver, Colorado, Oakwood Homes (PATH
                                               Field Evaluation)
• 15 to17 percent for 1,300 to 1,500           • 15 and 17 percent savings were achieved on
  square foot homes (Oakwood                     1,300 and 1,500 square foot homes,
  Homes Field Evaluation)                        respectively, compared to conventional slab-
• $11 to $15 per lineal foot of                  on-grade with 48-inch deep footings
  foundation (Bill Eich Construction)          • For climate with an Air Freezing Index of 710o
• $750 for a 2,500 square foot home              F-days, foundation depth of 12 inches and
  (K. Hovnanian Field Evaluation)                vertical insulation of R-4.5 required by code
                                               • In order to comply with Denver’s Uniform
                                                 Building Code for footings supporting two
                                                 stories and a roof, and accommodate soil
  THE BASICS continued                           conditions at the site, 18-inch deep footings
                                                 were required
  However, FPSF use is still governed by       • Trencher rather than backhoe was used to dig
  local building codes. In areas of heavy        the footings, which reduced cost and impact of
  termite infestation, local codes may           heavy machinery on site
  restrict the use of rigid foam insulation
  on the outside of the foundation, or may     Freehold, New Jersey, K. Hovnanian (PATH Field Evaluation)
  require termite-resistant insulation.        • Builder reported saving about $750 in foundation costs by using the FPSF system
                                               • FSPS did not prove cost-effective for the unheated garage due to the CABO requirement
  Cost savings of FPSFs over traditional         for full sub-slab insulation
  foundations are greater in colder            • Synthetic stucco proved to be best choice for providing protective covering of above-
  climates with deeper frost depths, and         grade foam insulation
  lower in more temperate climates.
                                               Spirit Lake, Iowa, Bill Eich Construction
  Insulation details are critical to prevent   • Since 1985, builder estimates savings between $11 and $15 per linear foot of foundation
  “cold bridges” that can undermine FPSF         by using FPSFs
  effectiveness. Crews may need training
  in installation techniques to ensure
  proper insulation details. Exterior
  foundation insulation requires an exterior
  durable finish to protect the insulation      MAKING THE SWITCH
  from ultraviolet deterioration and
  mechanical damage.                            What is required to transition from your current building practices to using this technology?

                                                Educate Yourself on FPSF Design – Use resources such as the PATH and NAHB Research
                                                Center publication Revised Builder’s Guide to Frost Protected Shallow Foundations
                                                (available on to learn how to incorporate FPSFs in your area.

                                                Consult Local Codes – Review local codes to determine if local amendments impact FPSF
                                                design in your area.

                                                Evaluate Your Home Designs – Look for opportunities in your common home designs to use
                                                FPSFs. FPSFs can be incorporated into slab-on-ground construction, as well as stemwall,
                                                floating slab, and unvented crawlspace foundations.

                                                Tools – FPSFs require the same tools as traditional slab on grade foundations. They can,
                                                however, allow the use of a trencher rather than a backhoe if desired.

                                                Work With Your Trade Contractors – Work with your masonry contractor to review the design
                                                of FPSFs. FPSFs employ readily-available conventional building materials. Many steps,
                                                including rough grading, foundation layout, preparation of subgrade, wall forming, steel
                                                reinforcing, and concrete placement are similar to conventional practices.

                                                                                                              TECH SPECS >    2
                                                 Frost-Protected Shallow Foundations

FOOD FOR THOUGHT                                                                                     DEFINITIONS

This section provides some things to think about before switching to this building                   Air Freezing Index (AFI)
technology – make sure it’s the right choice for you.
                                                                                                     The AFI is a measure of the combined
                                                                                                     magnitude and duration of air
FPSF technology is relatively easy to              foundation may require termite                    temperatures above and below freezing
implement, and is suitable for colder              protection appropriate to the regional            during any given winter. The 100-year
climate regions in the United States.              termite threat. Below-ground foam is not          return period of the AFI is available for
Buildings must be conditioned to a                 recommended in areas of “very heavy               3,110 cities in the U.S. and Puerto Rico
minimum of 64o F, year round. Proper               termite infestation probability,” such as         from the National Climatic Data Center
design and installation of insulation is           South Carolina, Georgia, Florida,                 (NCDC)
key to the success of FPSFs, in order to           Alabama, Mississippi, Louisiana,
prevent “cold bridges” and maintain                Eastern Texas, and most of California             Cold Bridge
above-freezing soil temperatures around            — unless special provisions are                   Cold bridges are created when building
the foundation. Crews may need training            followed. However, FPSF would not be              materials with high thermal conductivity,
to learn correct insulation and forming            cost-effective in those regions, anyway.          such as concrete, are directly exposed to
                                                                                                     outside temperatures. They result from an
                                                   The exterior foundation insulation above          interruption in the integrity of foundation
Initial cost savings depend on the region          grade must be protected against                   insulation. Cold bridges may increase the
and local code-required frost depth.               ultraviolet deterioration and mechanical          potential for frost heave, or at the least,
Builders in temperate climates with                damage by use of a durable protective             create localized lower temperatures or
shallow frost depths will not have cost            coating or covering.                              condensation on the slab surface.
savings as much as those in colder
climates. Additionally, use of below-                                                                Mean Annual Temperature (MAT)
ground foam plastics over the                                                                        The MAT is used in addition to the AFI to
                                                                                                     determine design requirements for FPSFs
                                                                                                     used in unheated buildings.


Below is a checklist of steps to follow if you decide to implement this technology in your next building project.

□ Evaluate if FPSFs are practical in                 Revised Builder’s Guide to Frost                    above-grade vertical wall insulation to
   your region. Cost savings increase in             Protected Shallow Foundations (Sept.                6 inches below grade and ensure that
   colder climates with deeper frost                 2004) to help determine proper                      the landscaping design does not
   depths. Generally, this technology is             foundation design and insulation details.           interfere with horizontal insulation.
   worth considering if the frost depth is           The guide contains detailed drawings of
   30 inches or deeper.                              prescribed methods of construction.             □ Ensure good drainage away from
                                                                                                         foundation. As with any foundation
□ Determine insulation needs. Builders           □ Provide necessary training for crews.                 design, proper drainage is extremely
   can establish proper FPSF design for              Proper installation of insulation is vital to       important. Protect drain tile with filter
   any given location with the Air                   FPSF effectiveness, and crews must be               fabric; surround drain tile with stone;
   Freezing Index (AFI). Unheated                    trained accordingly. However, FPSFs                 backfill with topsoil or gravelly material
   buildings also require a Mean Annual              use no special tools or materials, which
   Temperature (MAT). Builders must                  eases the learning process.                     □ Design landscape properly. Avoid
   calculate an effective R-value for                                                                    interference with any horizontal
   below-ground insulation, where                □ Excavate. Generally, FPSFs require                    insulation. Keep plantings beyond
   insulation must perform in a moist                only minor excavation using lightweight             horizontal insulation or at least 3 feet
   environment for the expected life of the          equipment. A trenching machine may be               away from foundation.
                                                     used for FPSFs that do not require
                                                     horizontal insulation.                          □ Complete construction. The
□ Review standards and design                                                                            foundation should be completed and
   guidelines. The American Society of           □ Ensure the integrity of the insulation.               the building enclosed and heated prior
   Civil Engineers (ASCE) standard,                  Completely insulate foundation edges to             to freezing weather.
   "ASCE/SEI 32-01, Design and                       prevent cold bridges. Provide good
   Construction of Frost-Protected                   drainage to prevent water from
   Shallow Foundations," should be                   damaging insulation or collecting below
   followed. The PATH and the NAHB                   the footing and freezing. Incorporate any
   Research Center published the                     necessary termite protection. Protect

                                                                                                                    TECH SPECS >    3
                                              Frost-Protected Shallow Foundations


                                              ToolBase Services                         "Design and Construction of Frost-
                                              Information on this building technology   Protected Shallow Foundations"
                                              and many others is brought to you by      ASCE/SEI 32-01
                                              PATH and the building scientists at the   American Society of Civil Engineers
The Partnership for Advancing Technology      NAHB Research Center.                     1801 Alexander Bell Drive
in Housing (PATH) is dedicated to                             Reston, VA 20191-4400
accelerating the development and use of                                                 800.548.2723
technologies that radically improve the       “Revised Builder’s Guide to Frost
quality, durability, energy efficiency, and   Protected Shallow Foundations”
affordability of America's housing.           PATH and NAHB Research Center             National Association of Home Builders
Managed by HUD, the PATH partnership                         (NAHB)
includes the homebuilding, manufacturing,                                               1201 15th Street, NW
insurance and financial industries, and       EPS Molders Association (EPSMA)           Washington, DC 20005-2800
Federal agencies concerned with housing.      1298 Cronson Blvd, Suite 201              800.368.5242
                                              Crofton, MD 21114               
PATH addresses barriers to innovation,        410.451.8341
provides information on advanced building                        International Residential Code (IRC)
technologies, and advances housing                                                      and International Building Code (IBC)
technology research; making affordable,       Extruded Polystyrene Foam                 International Code Council (ICC)
quality American homes a reality.             Association (XPSA)                        5203 Leesburg Pike, Suite 600
                                              4223 Dale Blvd                            Falls Church, VA 22041
For more information on the PATH              Woodbridge, VA 22193                      888.ICC.SAFE (422-7233)
program, visit               703.730.1601
                                                                  National Climatic Data Center
                                                                                        Federal Building
                                              European Foundations for Seasonally       151 Patton Avenue
                                              Frozen Ground, Monograph 92-1             Asheville, NC 28801-5001
                                              U.S. Army Cold Regions Research and       828.271.4800
Tech Specs are Prepared for PATH by the
                                              Engineering Laboratory (CRREL)  
NAHB Research Center.

                                                                                                    TECH SPECS >   4

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