14.7.4.23               COMPRESSED EARTH BLOCK CONSTRUCTION (CEB):

                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 14.7.4.8 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 14.7.4.8 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 14.7.4.8 NMAC, table 1.

                B.            Fireplaces.  Adobe or masonry fireplaces and chimneys in compressed earth block structures shall comply with 14.7.3.18 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 14.7.3.18 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 14.7.4.23 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 14.7.4.23 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 blocks.

                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/2bt 2(P= rupture load in pounds, L= span between supports, b= width of block, t= thickness of block).

[14.7.4.23 NMAC - Rp, 14.11.11.8 NMAC, 11-19-04]

14.7.4.24               MORTAR:

                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.

[14.7.4.24 NMAC - Rp, 14.11.11.8 NMAC, 11-19-04]

14.7.4.25               BOND 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) inches.

[14.7.4.25 NMAC - Rp, 14.11.11.8 NMAC, 11-19-04]

14.7.4.26               LINTELS

                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 official.

                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.

                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.