School buildings with more than one story above ground shall have the exterior walls constructed of properly bonded masonry of stone, concrete, brick or structural terra cotta or a suitable combination of these materials and of not less than the following thicknesses:

SCHEDULE OF WALL THICKNESSES

1st Story 2d Story 3d Story 4th Story

Ext. Int. Ext. Int. Ext. Int. Ext. Int.

One-Story .......... 12"

Two-Story .......... 12" 00 12" 00

Three-Story ........ 16" 00 12" 00 12" 00

Four-Story ......... 16" 12" 16" 12" 16" 12" 12" 12"

In each case the foundation walls shall be at least four inches thicker than the first-story walls and the footings shall have a further spread of at least four inches on each side and be so proportioned as to give approximately equal loading on all parts of the foundation. In case of concentrated loads the walls shall be increased in thickness or reinforced by pilasters or buttresses so that the load shall not exceed the following unit stresses:

Structural terra cotta .................................. 5 tons per sq. ft.

Coursed rubble stone .................................... 6 tons per sq. ft.

Brick work--lime mortar ................................. 6 tons per sq. ft.

Brick work--cement mortar ............................... 10 tons per sq. ft.

Concrete ................................................ 10 tons per sq. ft.

Where walls are very short or are properly braced or reinforced by piers, pilasters or buttresses the State Superintendent of Education may, at his discretion, permit thinner walls than those given in the schedule of wall thicknesses, but in no case shall a fire wall be less than twelve inches thick and in no case shall the loadings be heavier than in the schedule of wall loads.