Window openings in foundation wall

Window openings in a #foundation wall weaken the ability of the wall to resist inward #pressures. Any horizontal earth pressure on the portion of the wall beneath the #window must be resisted by the weight of the #wall, or be transferred to the #masonry or #concrete on either side of the #opening. As the width of an individual window increases, the masonry or concrete becomes less able to transfer these #loads, and a point is reached where the wall beneath the window may be pushed inward.

If windows are too close together, there is an insufficient amount of wall to withstand the load transferred from the wall beneath the window. This also must be controlled. Even if the openings are kept relatively small and reasonably spaced, however, as the percentage of wall openings increases, the overall strength of the wall decreases, and failure could occur.

When a foundation wall contains an opening greater than 1.2 m (4 ft.) in length, or contains openings whose combined total length exceeds 25% of the total wall length, then the portion of the wall beneath such openings is considered laterally #unsupported, and the wall around the opening must be reinforced to withstand the earth pressure. In addition, when the length of solid wall between openings is less than the average length of the openings it separates, the openings are considered as a single opening. These conditions are shown in Figure 9.15.-14.

Quoted from Illustrated Users' Guide - NBC2015

#foundationwall #earthpressure