TITLE 14               HOUSING AND CONSTRUCTION

CHAPTER 7         BUILDING CODES GENERAL

PART 4                 2003 NEW MEXICO EARTHEN BUILDING MATERIALS CODE

 

14.7.4.1                 ISSUING AGENCY:  Construction Industries Division of the Regulation and Licensing Department.

[14.7.4.1 NMAC - Rp, 14.11.11.1 NMAC, 11-19-04]

 

14.7.4.2                 SCOPE:  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.

[14.7.4.2 NMAC - Rp, 14.11.11.2 NMAC, 11-19-04]

 

14.7.4.3                 STATUTORY AUTHORITY:  NMSA 1978 Section 60-13-9 and 60-13-44.

[14.7.4.3 NMAC - Rp, 14.11.11.3 NMAC, 11-19-04]

 

14.7.4.4                 DURATION:  Permanent.

[14.7.4.4 NMAC - Rp, 14.11.11.4 NMAC, 11-19-04]

 

14.7.4.5                 EFFECTIVE DATE:  November 19, 2004, unless a later date is cited at the end of a section.

[14.7.4.5 NMAC - Rp, 14.11.11.5 NMAC, 11-19-04]

 

14.7.4.6                 OBJECTIVE:  The purpose of this rule is to establish minimum standards for earthen building materials construction in New Mexico.

[14.7.4.6 NMAC - Rp, 14.11.11.6 NMAC, 11-19-04]

 

14.7.4.7                 DEFINITIONS:

                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 compaction.

                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 rupture.

                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.

[14.7.4.7 NMAC - Rp, 14.11.11.7 NMAC, 11-19-04]

 

14.7.4.8                 EARTHEN BUILDING MATERIALS:

                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.

 

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

 

14.7.4.9                 ADOBE CONSTRUCTION:

                A.            General.  Adobe shall not be used in any building more than (2) stories in height.  The maximum height of every wall of adobe block without lateral support is specified in 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.  The maximum height of exterior walls, which are laterally supported with those supports located no more than twenty-four (24) feet apart, are as defined in 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 14.7.4.8 NMAC, table 1.

                B.            Fireplaces.  Adobe or masonry fireplaces and chimneys in adobe structures shall comply with 14.7.3.18 NMAC.  They shall be integrated into adjacent adobe 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 provided in 14.7.3.18 NMAC.

                D.            Soil.  Soil for use in adobe blocks should have a mixture of coarse sand, sand, silt and clay, naturally occurring, or amended with sand or straw, that will make a sun-dried brick without serious warping or cracking.  The best way to determine the fitness of a soil is to make sample blocks and allow them to cure in the open, protected from moisture.  Then test as specified by Subsections C and D of 14.7.4.11 NMAC.  The soil shall not contain more than two (2) percent soluble salts.

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

 

14.7.4.10               CLASSES OF ADOBE:

                A.            Stabilized adobe.  The term “stabilized” is defined to mean water-resistant adobe made of soil to which certain admixtures are added in the manufacturing process in order to limit water absorption into the adobe.  Exterior walls constructed of stabilized mortar and adobe requires no additional protection.  Cement stucco or other waterproof coating is not required.  The test required is that a dried four (4) inch cube cut from a sample unit shall not gain more than 2.5% in weight when placed upon a constantly water-saturated porous surface for seven (7) days.  An adobe unit that meets this specification shall be considered “stabilized.”

                B.            Unstabilized adobe.  Unstabilized or “natural” adobes are adobes that do not meet the water absorption specifications indicated in Subsection A of 14.7.4.10 NMAC above.  Use of unstabilized adobes is prohibited within four (4) inches of the finished floor grade.  Stabilized adobe or waterproof masonry units and mortar may be used for the first four (4) inches above floor grade.

                C.            Terrón.  The term “Terrón” shall refer to a cut sod brick.  Their use is permitted if units are dry and the wall design is in conformance with this code.

                D.            Burned adobe.  The term “burned adobe” shall refer to mud adobe bricks that have been cured by low-temperature kiln firing.  This type of adobe is not generally dense enough to be “frostproof” and may deteriorate with seasonal freeze-thaw cycles.  Its use for exterior locations is discouraged in climate zones with daily freeze-thaw cycles.

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

 

14.7.4.11               PROPERTIES, SAMPLING AND TESTING:

                A.            General.  Each of the tests prescribed in this section shall be applied to sample units selected at random at a ratio of five (5) units per twenty-five thousand (25,000) bricks to be used or at the discretion of the building official.

                B.            Shrinkage cracks.  Shrinkage cracks are allowed, providing that these cracks do not jeopardize the structural integrity of the blocks.

                C.            Compressive strength.

                    (1)     Cured units shall have an average minimum compressive strength of three hundred (300) pounds per square inch when tested.  One (1) sample out of five (5) may have a compressive strength of not less than two hundred fifty (250) psi.

                    (2)     The adobe 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.

                D.            Modulus of rupture.  Cured units shall average fifty (50) psi 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) .

                E.             Mortar.  The use of earth mortar is allowed if the earth mortar material is of the same type as the adobe blocks.  Conventional lime/sand/cement mortars of types M, S, and N are also allowed.  Mortar “bedding” joints shall be fully grouted, with partially open “head” joints allowable if the surface is to be plastered.  All joints shall be lapped at least twenty-five (25) percent of the visible block length.

                F.             Use.  No adobe shall be laid in the wall until fully cured.

                G.            Foundations.  Adobes may not be used for foundations or basement walls.  All adobe walls, except as noted under group M buildings, shall have a continuous footing at least eight (8) inches thick and not less than two (2) inches wider on each side that supports the foundation stem walls above.  All foundation stem walls that support adobe units shall extend to an elevation not less than six (6) inches above the finish grade.  Foundation stem walls shall be at least as thick as the adobe walls they support.  Where perimeter insulation is used, a variance is allowed for the stem wall width to be two (2) inches narrower than the width of the adobe wall it supports.  Alternative foundation systems must be approved by the building official.

                H.            Bond beams.  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.

                I.              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 adobe 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.

                J.             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 adobe 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 a minimum of the width of the wall and fully nailed.  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.

                K.            Lintels.  Lintels of wood or concrete are allowed.  When an engineer’s drawing and seal is not provided, all lintels shall conform to table 2 or 3 below.  The required bearing of any lintel shall not be reduced by a splayed or angled window or door opening.

                L.            Wood lintels.  When an engineer’s drawing and seal is not provided for lintels, all wood lintels shall conform to table 2 and have a fiber stress rating of at least 850 psi.

 

 

                M.           Concrete lintels.  When an engineer’s drawing and seal is not provided for lintels, all concrete lintels shall conform to table 3 and have a minimum strength of 3000 psi.

 

 

                N.            Anchorage.  Roof and floor structures will be suitably anchored to bond beams.  Wood joists, vigas or beams shall be attached to the wood or concrete bond beams with adequate metal fasteners.  Door and window bucks shall be secured to the adobe wall with adequate metal fasteners.  “Gringo blocks” or wood nailers, placed in the adobe walls as they are laid up, are allowed.  Wood and metal partitions may be secured to nailing blocks laid up in the adobe wall or by other approved methods.

                O.            Plastering.  Unstabilized exterior adobe walls can be protected with portland cement plaster with a minimum thickness of seven-eighths (7/8) inch, if adequate roof, parapet, canal and window flashing is provided.  If portland cement plaster is used, it must be reinforced with metal wire mesh, minimum seventeen (17) gauge by one-and-a-half (1 1/2) inch openings, securely attached to the exterior adobe wall surface by nails or staples with a minimum penetration of one-and-a-half (1 1/2) inch.  Such mesh fasteners shall have a maximum spacing sixteen (16) inches from each other.  Any wood surfaces to be covered with stucco or plaster must be protected from moisture with asphalt felt, reinforced with expanded metal lath.  Protective coatings other than plaster are allowed.  Interior gypsum or mud plasters may be applied directly to the wall, provided that adobe head joints have been left partially open.  Expanded metal lath shall be used around window and door openings.  If desired, exterior adobe walls may be protected with mud plaster.  Alternative plastering systems shall be submitted for approval by the building official.

                P.            Wall insulation.  All methods of wall insulation shall comply with the manufacturer’s recommendations.

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

 

14.7.4.12               RAMMED EARTH CONSTRUCTION:

                A.            General.  The following provisions shall apply.

                    (1)     Rammed earth shall not be used in any building more than (2) stories in height.  The height of every wall of rammed earth without lateral support is specified in 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.

                    (2)     Exterior rammed earth walls shall be a minimum of eighteen (18) inches in thickness.

                    (3)     Interior rammed earth walls shall be a minimum of twelve (12) inches in thickness.

                    (4)     Unstabilized rammed earth walls must be covered to prevent infiltration of moisture from the top of the wall at the end of each workday and prior to wet weather conditions, whether  the walls are contained within forms or not.

                    (5)     Fully stabilized rammed earth walls may be left unprotected from the elements.

                    (6)     In no case shall a rammed earth wall be reduced in thickness with back to back channels or nailers.  Channels or nailers rammed on both sides of a running wall shall not be opposite each other to avoid an hourglass configuration in the wall section.  Channels or nailers on both sides of a running wall shall be separated from each other vertically at a distance no less than the rammed earth wall thickness.  (Refer to figure 4 of the workbook.)

                    (7)     An architect or engineer registered in the state of New Mexico shall design and seal structural portions of two-story residential rammed earth construction documents.

                    (8)     The general construction of the building shall comply with all provisions of the 2003 New Mexico Residential Building Code (NMRBC), unless otherwise provided for in this rule.

                B.            Fireplaces.  Adobe or masonry fireplaces and chimneys in rammed earth structures shall comply with 14.7.3.18 NMAC.  They shall be integrated into adjacent rammed earth 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 provided 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.             Lateral support.  Lateral support shall occur at intervals not to exceed twenty-four (24) feet.  Rammed earth walls eighteen (18) inches to less than twenty-four (24) inches thick shall be laterally supported with any one or combination of the following:  A rammed earth wall of bond beam height that intersects the running wall with at least sixty 60 degrees of support (refer to a figure 5 of the workbook.); an adobe wall of bond beam height and at least fourteen (14) inches in width that intersects with and attaches to the running wall with at least sixty (60) degrees of support (refer to figure 5 of the workbook.); a minimum 20 gauge steel frame or wood frame wall of full height that intersects with and attaches to the running wall with ninety (90) degrees of support, that is properly cross-braced or sheathed (refer to figure 6 of the workbook); a buttress configuration that intersects the running wall at (90) degrees, of adobe or rammed earth.  The buttress base must project a minimum of three (3) feet (or thirty-three (33) percent of the wall height) from the running wall and support at least seventy-five (75) percent of the total wall height (refer to figure 7 of the workbook.)  The thickness of a rammed earth buttress shall be at least eighteen (18) inches.  The thickness of an adobe buttress shall be a minimum fourteen (14) inches.  Rammed earth walls greater than twenty-four (24) inches in thickness are self-buttressing and do not require lateral support provided their design adheres to 14.7.4.8 NMAC table 1 and the other applicable provisions of this rule.

                F.             Openings.  Door and window openings shall be designed such that the opening shall not be any closer to an outside corner of the structure as follows:

                    (1)     In rammed earth walls eighteen (18) inches to less than twenty-four (24) inches thick, openings shall not be located within three (3) feet of any corner of the structure. (Refer to figure 8 of the workbook.)  Exception:  Openings may be located within three (3) feet of any corner provided a buttress extending at least three (3) feet from the structure supports the corner.  A continuous footing below and a continuous bond beam above, shall be provided across such openings.

                    (2)     Rammed earth walls greater than twenty-four (24) inches thick are self-buttressing, with no special consideration for placement of openings within the area of the wall.

                G.            Piers.  Rammed earth piers supporting openings shall measure no less than three (3) square feet in area and no dimension shall be less than eighteen (18) inches. (Refer to figures 9-A and 9-B of the workbook.)

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

 

14.7.4.13               FOUNDATIONS:

                A.            General.  Foundation construction shall comply with applicable provisions of the 2003 New Mexico Residential Building Code, and the following:  A minimum of three (3) continuous #4 reinforcing rods are required in minimum 2500 psi. concrete footings supporting rammed earth walls.  Stem walls shall be the full width of the wall supported above or wider to receive forming systems.  Footings shall be a minimum of ten (10) inches in depth.

                B.            Perimeter insulation.  For the purposes of placement of perimeter insulation, rammed earth walls may overhang the bearing surface up to the thickness of the perimeter insulation, but in no case greater than two (2) inches.

                C.            Keyway.  A key way shall be provided where the rammed earth wall meets the foundation system.  The keyway shall be established at the top of the stem a minimum of two (2) inches deep by six (6) inches wide formed at the time of the pour, and shall run continuously around the structure to include any intersecting rammed earth wall sections.  The rammed earth wall shall be fully rammed into this keyway (refer to figure 2) Exception:  Placement of vertical reinforcing rods extending a minimum twelve (12) inches into the rammed earth wall.  The vertical rods shall be minimum #4, imbedded into the concrete and spaced forty-eighty (48) inches on center, maximum.

                D.            Concrete grade beam.  Rubble filled foundation trench designs with a reinforced concrete grade beam above are allowed to support rammed earth wall construction.  An architect or engineer registered in the state of New Mexico shall certify the grade beam/rubble-filled trench design portion.

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

 

14.7.4.14               RAMMED EARTH SOIL SPECIFICATIONS:

                A.            General.  The soil shall not contain rock more than one-and-a-half (1 1/2) inch in diameter.  The soil shall not contain clay lumps more than one-half (1/2) inch in diameter.  The soil shall be free of all organic matter.  The soil shall not contain more than two (2) percent soluble salts.

                B.            Soil compressive strength.  Prior to the start of co