Masonry Magazine April 1992 Page. 27
TABLE 4
Thickness of Foundation Walls¹
| Foundation wall construction | Nominal thickness, in. | Maximum depth of unbalanced fill, ft |
| - | - | - |
| Masonry of hollow units, ungrouted | 8 | 4 |
| | 10 | 5 |
| | 12 | 6 |
| Masonry of solid units | 8 | 5 |
| | 10 | 6 |
| | 12 | 7 |
| Masonry of hollow or solid units, fully grouted | 8 | 7 |
| | 10 | 8 |
| | 12 | 8 |
| Masonry of hollow units reinforced vertically with #4 bars and grout at 24 in. on center. Bars located not less than 4% in. from pressure side of wall | 8 | 7 |
¹ 1 in. = 25.4 mm
1 ft = 0.3048 m
Foundation walls must conform to minimum thickness requirements which are shown in Table 4. Foundation walls must be constructed of either Type M or S mortar. The height of unbalanced fill (height of finished ground above the basement floor or inside ground level) and the height of the wall between lateral supports must not exceed 8 ft (2.4 m), and the equivalent fluid weight of unbalanced fill must not exceed 30 pcf (480.5 kg/m³). Most well-drained sand and gravel backfills have an equivalent fluid weight of less than 30 pcf (480.5 kg/m³). When these conditions are not met, foundation walls must be designed in accordance with Chapters 5 and 6 or 5 and 7 of ACI 530/ASCE 5. Parapets are required to have a minimum thickness of at least 8 in. (200 mm). Their height cannot exceed three times their thickness.
Bonding (9.7)
Multi-wythe masonry walls may be bonded together by either masonry headers or metal wall ties. Limitations on the area and spacing of masonry headers or metal ties for both solid and hollow units are contained in Chapter 9 of the code.
Masonry headers are typically used when bonding barrier type walls (walls of solid units built without air spaces) or hollow walls composed of solid masonry units. Metal ties can be used for barrier type walls (with grouted collar joints) and drainage type walls (a clear air space between wythes of masonry).
The necessary requirements for bonding multi-wythe walls with masonry headers is shown in Fig. 3. Masonry headers of solid units must comprise not less than 4 percent of wall surface area and extend at least 3 in. (75 mm) into each wythe. The distance between adjacent full-length headers should not exceed 24 in. (610 mm) horizontally or vertically along the wall surface.
Two options exist when bonding multi-wythe walls with metal ties, the use of unit metal ties and the use of prefabricated horizontal joint reinforcement. When using unit metal ties, such as Z-ties or rectangular ties (box ties), one tie must be provided for each 4% ft² (0.42 m²) of wall area. Ties should be at least % in. (4.76 mm) in diameter and be corrosion resistant. The maximum vertical distance between ties should not exceed.