A single-story heated residential building located in the suburban area of Lancaster, PA is considered partially exposed. The roof of the building slopes at 1 on 20, and it is without overhanging eaves. What is the design snow load on the roof

 A single-story heated residential building located in the suburban area of Lancaster, PA is considered partially exposed. The roof of the building slopes at 1 on 20, and it is without overhanging eaves. What is the design snow load on the roof?

Solution

According to Figure 7.2-1 in ASCE 7-16, the ground snow load for Lancaster, PA is

рg = 30 psf.

Since 30 psf > 20 psf, the rain-on-snow surcharge is not required.

To find the roof slope, use θ = arctan 

According to ASCE 7-16, since 2.86° < 15°, the roof is considered a low-slope roof. Table 7.3-2 in ASCE 7-16 states that the thermal factor for a heated structure is Ct = 1.0 (see Table 2.11).

According to Table 7.3-1 in ASCE 7-16, the exposure factor for terrain category B, partially exposed is Ce = 1.0 (see Table 2.10).

Table 1.5-2 in ASCE 7-16 states that the importance factor Is = 1.0 for risk category II (see Table 2.9).

According to equation 2.6, the flat roof snow load is as follows:

Since 21 psf > 20Is = (20 psf)(1) = 20 psf. Therefore, the design flat roof snow load is 21 psf.