N.M. Admin. Code § 14.7.4.11

Current through Register Vol. 35, No. 21, November 5, 2024

Section 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 units per 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 300 pounds per square inch when tested. One sample out of five may have a compressive strength of not less than 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 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 50 psi in modulus of rupture when tested according to the following procedures. A cured unit shall be laid over two-inch diameter cylindrical supports two inches from each end and extending across the full width of the unit. A cylinder two inches in diameter shall be laid midway between and parallel to the supports. Load shall be applied to the cylinder at a rate of 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 percent of the visible block length.

F.Use. No adobe shall be laid in the wall until fully cured. Adobes shall be laid in level courses so that the top of any course shall be at the same height above the stem around the structure.

G.Foundations. Adobes may not be used for foundations or basement walls. All adobe walls, except as noted, shall have a continuous footing at least eight inches thick and not less than two 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 inches above the finish grade. Foundation stem walls shall be at least as thick as the adobe walls they support. 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 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 inches high by 10 inches wide for walls up to 14 inches thick. Where adobe walls are wider than one course, two-thirds 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 no. 4 reinforcing rods at each floor and ceiling plate line.

J.Wood bond beam. Wood bond beams shall be a minimum of six inches deep by 10 inches wide for walls up to 14 inches thick. Where adobe walls are wider than one course, two-thirds 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 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 inch nominal thickness. The building official shall approve all wooden bond beams for walls wider than 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.

Table 2 ADOBE WALL WOOD LINTEL SCHEDULE
MINIMUM FIBER STRESS 850 psi
Wall Width	Max. Span	Size	Bearing length on earth wall	Load Capacity
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

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.

Table 3 ADOBE WALL CONCRETE LINTEL SCHEDULE MIN. 3000 psi
Maximum Span	Minimum depth*	Reinforcing	Maximum Capacity per linear foot	Bearing 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

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.

(1) Portland-based stucco or lime-based plaster used over insulation board or foam shall follow Subsection P of 14.7.4.11 NMAC.

(2) Unstabilized, uninsulated exterior adobe walls can be protected with plasters or stuccos with a minimum thickness of seven-eighths inch, if adequate roof, parapet, canal, and window flashing is provided.

(3) Portland-based plaster covering unstabilized, adobe walls must be reinforced with self-furring metal wire mesh, minimum 17 gauge by one and one-half inches openings, securely attached to the exterior adobe wall surface by nails or staples with a minimum penetration of one and one-half inches. Such mesh fasteners shall have a maximum spacing 16 inches from each other. Wood surfaces or areas of dissimilar materials to be covered with Portland-based plaster must be protected from moisture with asphalt felt, covered with expanded metal lath, securely attached to the adobe wall.

(4) Type S hydrated lime stuccos covering unstabilized adobe walls are allowed providing that adobe head joints are left partially open as provided by Subsection E of 14.7.4.11 NMAC. Lime-based stuccos do not require a wire mesh cover except when used over wood or dissimilar materials in which case the surface must be protected from moisture with asphalt felt, covered with expanded metal lath.

(5) Other plasters or coatings are allowed providing they do not constitute a vapor barrier. Interior gypsum or clay 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 clay plaster. Alternative plastering or coating systems shall be submitted for approval by the building official.

P.Wall insulation.

(1) Insulating boards or foams not exceeding two inches in thickness may be adhered to the exterior of the adobe wall. When insulation board is used, round-cap nails shall attach it to the adobe wall, with nails placed to avoid bed joints between courses. Cap nails shall have a maximum spacing of 16 inches from each other. Additionally, cap nails shall secure the rigid insulation boards around their perimeter edges, with nails spaced no less than two inches apart. All cap nails shall penetrate a minimum of two inches into the adobe wall. Insulating boards or foams shall not be used to form architectural shapes exceeding two inches in thickness.

(2) Insulations exceeding two inches in thickness may be used providing they do not form a vapor barrier. Their weight shall be supported by the stem wall below and contained within vertical furring strips, securely attached to the adobe wall. A sectional, scaled drawing for the proposed insulation scheme must be submitted for review by the building official.

Q.Parapets.

(1)Plastered parapets, whether of adobe or frame construction, shall require a seamless impermeable waterproof cover or weather barrier, capping the entire parapet and wrapping over each side. The cover shall extend past the bond beam a minimum of four inches on the wall side. On the roof side, the cover shall properly lap any rising roof felts or membranes and be properly sealed. A layer of expanded metal lath shall be installed over the cover before plaster or stucco is applied. The lath shall extend past the bond beam on the wall side a minimum of five inches and on the roof side, the same distance as the cover below, allowing for plaster stops or seals. No penetrating fasteners are allowed on the horizontal surface of parapets.

(2)Exposed parapets of adobe shall be laid in level courses of fully stabilized block and mortar. Bed and head joints shall be fully grouted and tightly tooled. Bedding joints at bond beams and around vents and canales shall be fully grouted and tightly tooled. The horizontal top of exposed adobe parapets shall be covered with a minimum three-fourths inch layer of fully stabilized mortar, troweled to conform with the parapet. Waterproof sealers are allowed, providing they are permeable. Other parapet covers, such as flagstone, Spanish mission tile or cement mortar are allowed providing they are securely attached to the parapet. A scaled, sectional drawing shall be provided to the building official showing the attachment scheme.

N.M. Admin. Code § 14.7.4.11

14.7.4.11 NMAC - Rp, 14.7.4.11 NMAC, 1-28-11, Adopted by New Mexico Register, Volume XXVII, Issue 21, November 15, 2016, eff. 11/15/2016, Amended by New Mexico Register, Volume XXXIV, Issue 11, June 13, 2023, eff. 7/14/2023