PART 42003 NEW MEXICO EARTHEN BUILDING MATERIALS CODE AGENCY:  Construction Industries Division of the Regulation and Licensing Department.
[ NMAC - Rp, NMAC, 11-19-04]  This rule applies to all earthen building materials contracting work performed in New Mexico on or after November
19, 2004, that is subject to the jurisdiction of CID, unless performed pursuant to a permit for which an application was
received by CID before that date.
[ NMAC - Rp, NMAC, 11-19-04] AUTHORITY:  NMSA 1978 Section 60-13-9 and 60-13-44.
[ NMAC - Rp, NMAC, 11-19-04]  Permanent.
[ NMAC - Rp, NMAC, 11-19-04] DATE:  November 19, 2004, unless a later date is cited at the end of a section.
[ NMAC - Rp, NMAC, 11-19-04]  The purpose of this rule is to establish minimum standards for earthen building materials construction in New
[ NMAC - Rp, NMAC, 11-19-04]
A.Amended soil means improving an unqualified soil to a qualified state with the addition of other soils or amendments.
B.Amendments means additive elements to soil, such as lime, portland cement, fly ash, etc. which are “dry-mixed” into the main
soil body as a percentage of total weight to achieve stabilization.
C.Buttress means a projecting structure providing lateral support to a wall.  The buttress shall be incorporated into the foundation
and wall system. (Refer to figure 1 of the earthen building materials auxiliary workbook, hereafter referred to as “workbook
D.CEB means compressed earth block.
E.Keyway means a groove on the vertical rammed earth wall surface for interlocking purposes.  Refer to figure 3.
F.Lift means a course of rammed earth, placed within the forms, and then compacted.
G.Nailer means any material rammed into the wall that serves as an attachment device.  Refer to figure 4.
H.Optimum moisture means sufficient water (generally no more than ten (10) percent) mixed into the soil to attain sufficient
I.psi means pounds per square inch.
J.Qualified soil means any soil, or mixture of soils, that attains 300 psi compression strength and attains 50 psi. modulus of
K.Rammed earth means qualified soil that is mechanically or manually consolidated to full compaction.
L.Stabilization, stabilized means qualified soils that pass the wet strength test under ASTM D1633-00 or contain a minimum of six
(6) percent portland cement by weight.  Stabilization is achieved through the use of amendments.
M.Wet strength compression test means an approved testing laboratory process in which a fully cured rammed earth cylinder is
completely submerged in water a minimum of four hours according to ASTM D1633-00, then subjected to a compression test.
A.General.  The provisions of this rule, 14.7.4 NMAC, shall control the design and construction of one- and two-family dwellings in
which earthen building materials form the bearing wall system.
B.Allowable wall heights for earthen structures.  All earthen structures whether adobe, burned adobe, compressed earth block,
rammed earth or terrón, shall conform to table 1.  For purposes of using table 1, height is defined as the distance from the top
of the slab or top of stem wall to the underside of the bond beam.

Maximum SdsWall ThicknessMaximum HeightMaximum SdsWall ThicknessMaximum Height
.25                         10                    120”                .3                    10                   120”
                             12                   128                                         12                  128
                             14                   144                                         14                  144
                             16                   144                                         16                  144
                             18                   144                                         18                  144
                             24                   144                                         24                  144

.35                         10                   120”                 .4                     10                  120”
                            12                    128                                         12                   128
                            14                    144                                         14                   144
                            16                    144                                         16                   144
                            18                    144                                         18                   144
                            24                    144                                         24                   144

.45                        10                     104”                .5                     10                     96”
                            12                    128                                         12                    112
                            14                    144                                         14                    136
                            16                    144                                         16                    144
                            18                    144                                         18                    144
                            24                    144                                         24                    144
This table is based on two story maximum, one and two family residential with seismic soil site class D1.
A.General.  Compressed earth block shall not be used in any building more than (2) stories in height.  The height of every wall of
compressed earth block without lateral support shall be defined in Subsection B of NMAC, table 1.  The height of the
wall is defined as the distance from the top of the slab or top of stem wall to the underside of the bond beam.  Heights for
exterior walls, which are laterally supported with those supports located no more than twenty-four (24) feet apart, are defined in
Subsection B of NMAC, table 1.  The bottom story of a two-story is allowed a minimum thickness of fourteen (14)
inches with the upper story allowed a thickness of ten (10) inches, providing the structure meets the provisions of Subsection B
of NMAC, table 1.
B.Fireplaces.  Adobe or masonry fireplaces and chimneys in compressed earth block structures shall comply with NMAC.
They shall be integrated into adjacent compressed earth block walls during construction or secured to them by suitable steel
ladder reinforcement or reinforcing rods.
C.Count Rumford fireplaces.  Count Rumford fireplaces are allowed as designated in NMAC.
D.Stop work.  The building inspector shall have the authority to issue a “stop work” order if the provisions of this section are not
complied with.
E.Stabilized compressed earth blocks.  The term “stabilized” is defined to mean a block with certain admixtures that retains
minimum strength requirements as specified in Subsection J of NMAC after saturation in water.  Saturation is defined
as a minimum four (4) hours of submersion in water as defined in ASTM D1633-00.
F.Unstabilized compressed earth blocks.  Unstabilized blocks are defined as not meeting the minimum strength requirements as
defined in Subsection J of NMAC after saturation in water.  Use of unstabilized compressed earth blocks is prohibited
within four (4) inches of the finished floor grade.  Stabilized compressed earth blocks, poured concrete, or waterproof masonry
units and mortar may be used for the first four (4) inches above floor grade.
G.Materials.  The material must be a mineral soil with the aggregate content not exceeding one (1) inch in diameter.  The material
shall not contain more than two (2) percent soluble salts.
H.Testing.  Each of the tests prescribed in this section shall be applied to sample units selected at random of five (5) units per
building project prior to construction.  Test may be waived if block manufacturer provides certification of compliance.  The
certification must be dated within one year of the date on the application for the building permit.
I.Shrinkage cracks.  Shrinkage cracks are allowed, providing that these cracks do not jeopardize the structural integrity of the
J.Compressive strength.  Cured units shall have a minimum compressive strength of three hundred (300) pounds per square inch
when tested.  The compressed earth block shall be tested in the flat position.  The length of the test unit must be a minimum of
twice the width.  The surfaces must be smooth.  The test unit shall be subjected to a uniform compressive load that is
gradually increased at a rate of five hundred (500) psi/minute until failure occurs.  A true platen should be used in the testing
machine, along with swivel head to accommodate nonparallel bearing surfaces.  The compressive strength is defined as P/A,
where P = load and A - area of compression surface.
K.Modulus of rupture.  Units shall have a minimum compressive strength of fifty  (50) pounds per square inch in modulus of rupture
when tested according to the following procedures:  A cured unit shall be laid over two-inch (2”) diameter cylindrical supports
two (2) inches from each end and extending across the full width of the unit.  A cylinder two (2) inches in diameter shall be laid
midway between and parallel to the supports.  Load shall be applied to the cylinder at a rate of five hundred (500) psi/minute
until rupture occurs.  The modulus of rupture is equal to:  3PL/2bt2 (P= rupture load in pounds, L= span between supports, b=
width of block, t= thickness of block).
[ NMAC - Rp, NMAC, 11-19-04]
A.General.  The use of earth mortar is allowed if the earth mortar material is compatible with the compressed earth blocks.
Conventional lime/sand/cement mortars of Types M, S, and N are also allowed.  Mortar “bedding” joints shall be fully grouted.
Head joint mortar is not required provided that the blocks are initially laid in contact.  Partially open “head” joints are allowed if
the surface is to be plastered.  All joints shall be lapped at least twenty-five (25) percent of the visible block length.
B.Slip mortars.  Liquid mud slip mortar is allowed, providing it is made of a compatible soil that is screened to eliminate aggregate
larger than one-eighth (1/8) inch in diameter.  Water may be substituted for slip or other mortars, providing adequate adhesion
is demonstrated.
C.Stacking.  “Dry stacking” of compressed earth blocks is allowed providing that adequate adhesion is demonstrated, the wall is to
be stuccoed or plastered and the wall is not less than ten (10) inches in thickness.
D.Use.  Compressed earth block may be cured prior to use or laid directly from the press into the wall in an uncured state.
E.Foundations.  Compressed earth blocks may not be used for foundations or basement walls.
F.Footings.  All compressed earth block walls shall have a continuous footing at least ten (10) inches thick. The footing width must
be a minimum of thirty-three (33) percent greater than the wall width, but not less than two (2) inches on each side.  The stem
wall must be centered on the footing.
G.Stem walls.  All stem walls that support CEB units shall extend to an elevation not less than eight (8) inches above the exterior
finish grade.  Stem walls shall be as thick as the exterior wall.  Where perimeter insulation is used, a variance is allowed for
the stem wall width to be two (2) inches smaller than the width of the CEB wall it supports.
H.Concrete grade beam.  Rubble-filled foundation trench designs with a reinforced concrete grade beam above are allowed to support
CEB construction.  An architect or engineer registered in the state of New Mexico shall certify the grade beam/rubble-filled
trench design portion.  Other alternative foundation systems must be approved by the building official.
[ NMAC - Rp, NMAC, 11-19-04] BEAMS:
A.General.  All bearing walls shall be topped with a continuous bond beam (except patio walls less than six (6) feet high above
stem).  All bond beam construction shall be in accordance with accepted engineering practices.
B.Concrete bond beam.  Concrete bond beams shall be a minimum of six (6) inches high by ten (10) inches wide for walls up to
fourteen (14) inches thick.  Where CEB walls are wider than one course, two-thirds (2/3) of each visible course top shall be
covered by the concrete bond beam.  All concrete bond beams shall be reinforced with a minimum of two (2) no. 4 reinforcing
rods at each floor and ceiling plate line.
C.Wood bond beam.  Wood bond beams shall be a minimum of six (6) inches deep by ten (10) inches wide for walls up to fourteen
(14) inches thick.  Where CEB walls are wider than one course, two-thirds (2/3) of each visible course top shall be covered by a
wood bond beam and the roof load shall be distributed over both bond beams.  Wood bond beams may be solid in the six inch
(6”) dimension, or may be built up by applying layers of lumber.  Ends of wood bond beams are to be lapped in minimum of the
width of the wall and fully nailed.  Galvanized metal straps or perforated metal straps, 18 gauge minimum and twelve (12) inches
long, may be used to join the ends of wood bond beam members.  Full nailing of straps is required.  No wood layer shall be less
than one (1) inch nominal thickness.  The building official shall approve all wooden bond beams for walls wider than fourteen (14)
[ NMAC - Rp, NMAC, 11-19-04]
A.General.  Lintels of wood or concrete are allowed.  The bearing length of any lintel shall not be reduced by an angled or splayed
window or door opening.  Other lintel designs are accepted providing that engineering is submitted for review by the building
B.Wood lintels.  When an engineer’s drawing and seal is not provided for lintels, all wood lintels shall conform to table 5 and have a
fiber stress rating of at least 850 psi.


WallWidthMax. SpanSizeBearing length on earth wallLoadCapacity
10”4'-0”   10” x 6” 12”860 PLF
    6'-0”  10” x 8” 12”       1020 PLF
    8'-0”  10” x 10”       18”      1150 PLF
  10'-0”  10” x 12”24”      1000 PLF
  12'-0”  10” x 14”24”      1000 PLF
12”4'-0”  10” x 6”  12”860 PLF
   6'-0”   10” x 8”  12”     1020 PLF
   8'-0”   10” x 10”18”      1150 PLF
  10'-0”  10” x 12” 24”      1000 PLF
  12'-0”  10” x 14”        24”      1000 PLF
14”4'-0”   12” x 6” 12”                               950 PLF
   6'-0”    12” x 8”12”                      1150 PLF
   8'-0”    12” x 10”             18”                       1300 PLF
                10'-0”    12” x 12”              24”                       1300 PLF
                12'-0”    12” x 14”              24”                       1200 PLF

C.Concrete lintels.  When an engineer’s drawing and seal is not provided for lintels, all concrete lintels shall conform to table 6 and
have a minimum strength of 3000 psi.

Table 6                      CEB WALL CONCRETE LINTEL SCHEDULE                  MIN. 3000 psi
Maximum SpanMinimum depth *ReinforcingMaximum Capacity per linear footBearing length on earth wall
Less than 6’ - 0”          8”              2 - # 4                      1500 lbs.                                 12”
6' - 0" to 10' - 0”         12”              3 - # 5                      1500 lbs.                                 18”
11' - 0" to 16'- 0”        16”              3 - # 6                      1500 lbs.                                  24”

* SIZE - Wall width X depth of lintel

Compressed Earth Block Code
The following code, developed by the state of New Mexico, is currently the only code specific to Compressed Earth Block (CEB) construction.  This is the code that we have followed in the Midwest.  However, CEB construction can also be approved under the Uniform Building Code (UBC) under “unfired clay masonry.”  CEB can also fall under the code for Adobe which also appears in the new International Building Code (IBC) and the Southern and Standard Building Codes under “adobe”.
Earth Block Code