Construction Business & Technology Conference

Minimum Walls Per Code

In the 1997 Uniform Building Code, the section titled Division IV - Conventional Light-Frame Construction specifies standard construction to be used for smaller buildings. Minimum construction requirements for "braced wall panels" (shear walls) from Section 2320.11.4 are as follows:

In one-story buildings, each panel shall have a length of not less than 2 feet 8 inches and a height of not more than 10 feet. Each panel shall be sheathed on one face with 3/8-inch-minimum-thickness plywood sheathing nailed with 8d common or galvanized box nails in accordance with Table 23-II-B-1 (6" o.c./12" o.c.) and blocked at all edges. Two (1/2" diameter) anchor bolts installed in accordance with Section 1806.6, shall be provided in each panel. Anchor bolts shall be placed at panel quarter points. Each panel end stud shall have a tie-down device capable of providing an approved uplift capacity of not less than 1,800 pounds.
In the first story of two-story buildings, each braced wall shall be in accordance with the above except that the plywood sheathing shall be provided on both faces, three anchor bolts shall be placed at one-fifth points, and tie-down device uplift capacity shall not be less than 3,000 pounds.

If we use these descriptions and work backwards through the shear wall design steps, we should be able to come up with maximum allowable lateral loads for each:

Walls in Single-Story Buildings Walls At Ground Floor in Two-Story Buildings

3/8" plywood with 8d's at 6"/12" can resist as little at 160 pounds per foot if a siding grade was used. For now, assume C-D, C-C Sheathing at 220 pounds per foot. Total load = 585 pounds. 3/8" plywood each face will double the value at left. Use 1170 pounds total.

The 1/2" diameter bolts will resist 2 * 480 * 1.33 = 1276 pounds. By adding one more bolt, we increase to 1915 pounds.

No assumptions are made regarding the weight of the wall, therefore we must assume that Mr = 0. If the wall is 10 feet tall and the hold-down has a capacity of 1800 pounds, the worst case loading would make Mot = (Tiedown)*(Distance to Tiedown) = (1800)*(2.67 - 0.5) = 3906 ft-lbs. Thus the force at the top must not exceed (3906 ft-lbs.) / (10 feet tall) = 390 pounds...the limiting load. At Mot = (Tiedown)*(Distance to Tiedown), the limiting force at the top of wall would be 651 pounds...the limiting load. At this point you should be thinking about the compression on the end member as it is close to the allowable value for a 2 x 4 D.F. No.1.

Walls in Single-Story Buildings	Walls At Ground Floor in Two-Story Buildings
3/8" plywood with 8d's at 6"/12" can resist as little at 160 pounds per foot if a siding grade was used. For now, assume C-D, C-C Sheathing at 220 pounds per foot. Total load = 585 pounds.	3/8" plywood each face will double the value at left. Use 1170 pounds total.
The 1/2" diameter bolts will resist 2 * 480 * 1.33 = 1276 pounds.	By adding one more bolt, we increase to 1915 pounds.
No assumptions are made regarding the weight of the wall, therefore we must assume that Mr = 0. If the wall is 10 feet tall and the hold-down has a capacity of 1800 pounds, the worst case loading would make Mot = (Tiedown)(Distance to Tiedown) = (1800)(2.67 - 0.5) = 3906 ft-lbs. Thus the force at the top must not exceed (3906 ft-lbs.) / (10 feet tall) = 390 pounds...the limiting load.	At Mot = (Tiedown)*(Distance to Tiedown), the limiting force at the top of wall would be 651 pounds...the limiting load. At this point you should be thinking about the compression on the end member as it is close to the allowable value for a 2 x 4 D.F. No.1.