SECTION 406B – MATERIALS REQUIREMENTS

406B.1  General.  All materials permitted by this chapter, including their appropriate allowable design values and those existing configurations of materials specified herein, may be utilized to meet the requirements of this chapter.

406B.2  Existing Materials.  All existing materials utilized as part of the required vertical load-carrying or lateral force-resisting system shall be in sound condition or shall be repaired or removed and replaced with new materials. All unreinforced masonry materials shall comply with the following requirements:

   1.   The construction (lay-up) of the masonry units complies with Section 406B.3.2 and the quality of bond between the units has been verified to the satisfaction of the Building Official.

   2.   Concrete masonry units are verified to be load-bearing units complying with ASTM Standard Specification C 90 or such other standard as is acceptable to the Building Official.

   3.   Hollow clay tile units are verified to be structural load-bearing units complying with ASTM Standard Specification C 34 or such other standard as is acceptable to the Building Official.

   4.   The compressive strength of plain concrete walls shall be determined based on cores taken from each class of concrete wall. The location and number of tests shall be the same as prescribed for strength tests in Sections 406B.3.3.2 and 406B.3.3.3.

406B.3  Existing Unreinforced Masonry Walls.

406B.3.1  General.  All unreinforced masonry walls utilized to carry vertical loads or seismic forces parallel and perpendicular to the wall plane shall be tested as specified in this section. All masonry that does not meet the minimum standards established by this chapter shall be removed and replaced with new materials, repaired or alternatively shall have its structural functions replaced with new materials and shall be anchored to supporting elements.

406B.3.2  Construction (lay-up) of walls.

406B.3.2.1  Multi-wythe solid brick.  The facing and backing shall be bonded so that not less than 10 percent of the exposed face area is composed of solid headers extending not less than 4 inches (101.6 mm) into the backing. The clear distance between adjacent full-length headers shall not exceed 24 inches (609.6 mm) vertically or horizontally. Where the backing consists of two or more wythes, the headers shall extend not less than 4 inches (101.6 mm) into the most distant wythe or the backing wythes shall be bonded together with separate headers whose area and spacing conform to the foregoing. Wythes of walls not bonded as described above shall be considered as veneer. Veneer wythes shall not be included in the effective thickness used in calculating the height to thickness and the shear capacity of the wall.

406B.3.2.2  Grouted or ungrouted hollow concrete or clay block and structural hollow clay tile.  These materials shall be laid in a running bond pattern.

   Other lay-up patterns may be acceptable if their performance can be justified as being at least equal to those specified above.

406B.3.3  Mortar.

406B.3.3.1  Tests.  The quality of mortar in all masonry walls shall be determined by performing in-place shear tests in accordance with Section 414B. Alternative methods of testing may be approved by the Building Official for masonry walls other than brick.

406B.3.3.2  Location of tests.  The shear tests shall be taken at locations representative of the mortar conditions throughout the entire building, taking into account variations in workmanship at different building height levels, variations in weathering of the exterior surfaces, and variations in the condition of the interior surfaces due to deterioration caused by leaks and condensation of water and/or by the deleterious effects of other substances contained within the building. The exact test locations shall be determined at the building site by the engineer or architect in responsible charge of the structural design work. An accurate record of all such tests and their location in the building shall be recorded, and these results shall be submitted to the Department for approval as part of the structural analysis.

406B.3.3.3  Number of tests.  The minimum number of tests per class shall be as follows:

   1.   At each of both the first and top stories, not less than two tests per wall or line of wall elements providing a common line of resistance to lateral forces.

   2.   At each of all other stories, not less than one test per wall or line of wall elements providing a common line of resistance to lateral forces.

   3.   In any case, not less than one test per 1,500 square feet (139.355 m2) of wall surface nor less than a total of eight tests.

406B.3.3.4  Minimum quality of mortar.

   1.   Mortar shear test values, vto, in psi shall be obtained for each in-place shear test in accordance with the following equation:

      vto = (Vtest/Ab) - p D+L      (4B-1)

   2.   The mortar shear strength, vt, is the value in psi that, after discarding the lowest 20 percent of the mortar shear test values, vto, is the lowest of the remaining 80 percent of the mortar shear test values.

   3.   Any unreinforced masonry bearing wall with vto, or with mortar shear strength, vt, less than 30 psi (206.84 kPa) shall be either removed, entirely pointed and retested or have its structural function replaced and shall be anchored to supporting elements in accordance with Section 406B.3.1 and Section 413B.8. When existing mortar in any wythe is pointed to increase its shear strength and retested, the condition of the mortar in the adjacent bed joints of the inner wythe or wythes and the opposite outer wythe shall be examined for extent of deterioration. The shear strength of any wall class shall be no greater than that of the weakest wythe of that class.

(Amended by Ord. 65-19, File No. 190136, App. 4/12/2019, Eff. 5/13/2019)

406B.3.3.5  Collar joints.  The collar joints shall be inspected at the test locations during each in-place shear test, and estimates of the percentage of the surfaces of adjacent wythes which are covered with mortar shall be reported along with the results of the in-place shear tests.

406B.3.3.6  Unreinforced masonry classes.  All existing unreinforced masonry shall be categorized into one or more classes based on quality of construction, state of repair, deterioration and weathering. A class shall be characterized by the allowable masonry shear stress determined in accordance with Section 408B.2. Classes shall be defined for whole walls, not for small areas of masonry within a wall.

406B.3.3.7  Pointing.  All deteriorated mortar joints in unreinforced masonry bearing walls shall be pointed according to Section 416B. Nothing shall prevent pointing of any deteriorated masonry wall joints before the tests are made, except as required in Section 407B.1.