(A) Wall height and length.
(1) Adobe masonry of unburned clay units shall be classified as natural (raw) adobe or stabilized adobe and shall not be used in any building more than one story in height. The unsupported height or length of every wall of these units shall be not more than ten times the thickness of such walls; provided, however, when the wall is laterally supported at the ceiling line by means of ceiling joists or rafters, the length may be increased to 24 times the thickness of such walls.
(2) Exterior walls shall in no case be less than 14 inches thick and interior adobe walls shall not be less than ten inches thick. Foundation (stem) walls which support masonry of unburned clay units shall extend to an elevation of not less than six inches above the adjacent ground at all points and shall be of the same thickness as the wall they support. Frame interior walls shall be of standard construction and anchored to the exterior walls by use of “gringo” blocks or other approved methods.
(3) Adobe shall not be used for foundation (stem) or basement walls. Footing shall be of a continuous concrete design. The footing width and depth shall be governed by the allowable bearing pressure of the soil and allowable concrete' stresses.
(B) Classes of adobe.
(1) The term
STABILIZED ADOBE UNIT(S) is defined as adobes made of soil to which certain admixtures, emulsified asphalt, or other approved material is added in the manufacturing process in order to limit the adobe's water absorption capacity to comply with the Uniform Building Standard.
(2) Natural (raw) or untreated adobes are adobes which do not meet the water absorption specifications. This shall hold even if some water absorption protective agent has been added.
(C) Material.
(1) Adobe is defined as clay masonry units made from a suitable mixture of soil, day and stabilizing agent. The soil used shall contain not more than ten-hundredths percent of soluble salts and shall contain not less than 25% and not more than 45% of material passing a No. 200 mesh sieve and 100% shall pass through a one-fourth-inch mesh sieve and be free from deleterious matter. The soil shall contain sufficient clay to bind the particles together and be mixed with clean potable water to the proper working consistency.
(2) Units shall be protected from moisture while curing, be sun-baked for at least one week and stacked for another two weeks before being laid in the wall. Weather conditions may require a longer curing period.
(D) Testing.
(1) All units shall be tested in accordance with Uniform Building Code Standard 24-14.
(a) Compressive strength. The units shall have an average compressive strength of 300 pounds per square inch. One sample out of five may have a compressive strength of not less than 200 pounds per square inch.
(b) Modulus of rupture. The unit shall average 50 pounds per square inch.
(c) Moisture content. The moisture content of each unit shall be not more than four percent by weight.
(d) Absorption. A dried four-inch cube cut from a sample of a stabilized adobe unit shall absorb not more than two and one-half percent moisture by weight. If the sample absorbs more than two and one-half percent moisture by weight, the material shall be classified as natural (raw) adobe.
(e) Shrinkage cracks. No unit shall contain more than three shrinkage cracks, and no shrinkage crack shall exceed three inches in length or one-eighth inch in width.
(2) Sample testing shall be made daily by the manufacturer. A minimum of monthly random tests shall be made for the manufacturer by an independent testing laboratory. Test reports shall be maintained a minimum of three years.
(E) Construction. At the time of laying, all units shall be clean and damp at the surface. All joints shall be solidly filled with mortar. Units may be laid with adobe mortar made of the same materials as the units or with Type M or S mortar. In all cases bond must be achieved between the mortar and the adobe units. No more than seven courses per day shall be laid when using adobe mortar. Units shall be laid in a running bond with a 50% lap. Use of natural (raw) adobes is prohibited within four inches above the finish floor grade.
(F) Plastering.
(1) Natural (raw) adobe shall have all exterior walls plastered on the outside with Portland cement plaster, minimum thickness three-fourths inch in accordance with Chapter 47, Uniform Building Code, current edition. Protective coatings other than plaster are allowed, provided such coating is equivalent to Portland cement plaster in protecting the untreated adobes against deterioration and/or loss of strength due to water. Plaster screens shall be used around the bottom row of adobe to prevent water wicking.
(2) Natural (raw) adobes may be left exposed on the exterior walls if the following protection or other approved methods are provided against any flow of water on, or upon those walls, other than falling rain:
(a) A cap or cornice of brick or concrete units, or equal, or parapet walls, laid to drain water onto the roof.
(b) Canals or scruppers, properly flashed, of sufficient length to drain water from the roof so that it will not fall against the wall.
(c) Window sills of brick or concrete units, or equal, sloped and with sufficient lip, to drain water so that it will not fall against the wall.
(G) Lintels. Members supporting unburned clay masonry units shall be reinforced concrete, masonry, steel or pressure treated heavy timber. The adobe units may overhang the lintel a maximum of two inches on each face. Heavy timber lintels shall be limited to eight-foot openings.
(H) Bond beams and anchorage. Bond beams shall be provided to support and anchor all roof construction. Bond beams utilizing adobe shall have continuous rows of joint reinforcing between the required member of courses to resist uplift forces. Ledger and partition bolts shall extend through exterior and interior adobe walls and the attaching member. It shall be required to provide plate washers on the exterior face of the adobe wall. Plate washers shall be a minimum of one-eighth inch thick by four inches by four inches in size or equivalent anchorage. Top wall plates and anchor bolts shall be designed to resist the uplift forces (minimum one-half inch in diameter and 20 inches embedment, 24 inches on center spacing) and provided with washers at least one-eighth inch by four inches by six inches in size embedded in the adobe. Oversize washers, minimum two inches in diameter, shall be used on the wood top plate.
(I) Stresses. Unburned clay masonry (adobe) units shall conform to the stresses set forth in Table I (§ 150-033).
(J) Joint control. Joint control shall be maintained as follows:
(1) Raw adobe: All joints shall be struck smooth or concave to allow stucco.
(2) Stabilized adobe: All style joints are permitted.
(K) Wood appendage. Wood appendage, including vigas, latillas and corbels, shall be permitted.
('80 Code, § 7-59) (Ord. 2021, passed 7-1-81) Penalty, see § 150-999