Wind and Snow Loads in Utah

In Utah, rooftop solar systems must be able to withstand both wind and snow loads, and the modified version of the Solar ABCs model expedited solar permit now includes wind and snow load components. Generally speaking, most buildings in Utah built to international building codes should easily be able to accommodate solar; however, before a rooftop system can be installed a building permit must be issued certifying that the roof is strong enough to hold this extra load. 

Wind

In Utah, solar systems installed on rooftops must be able to withstand a 90 mph 3-second wind gust--the same as all roof structures. To meet these design criteria, the mounting system holding the panels must be strong enough for the task, and the installation must follow applicable wiring and building codes.

For more information see the State of Utah's design criteria for buildings [PDF].

Snow

The State of Utah's building codes establish strict requirements for how strong a roof must be to hold the snow-load in different parts of the state. Adding a solar installation adds weight to the roof and the total weight that the structural components of the roof must hold have to be taken into account when determining if the roof is strong enough for solar.

According to Title 15A Chapter 3 Section 107 of the Utah Code a roof's snow load may be determined with the following equation rounded to the nearest 5 psi:

Pg = (Po2 + S2(A-Ao)2)0.5 for A greater than Ao, and Pg = Po for A less than or equal to Ao.

WHERE:

Pg = Ground snow load at a given elevation (psf);
Po = Base ground snow load (psf) from Table No. 1608.1.2(a);
S = Change in ground snow load with elevation (psf/100 ft.) From Table No. 1608.1.2(a);
A = Elevation above sea level at the site (ft./1,000);
Ao = Base ground snow elevation from Table 1608.1.2(a) (ft./1,000).

The following table (a combination of tables 1608.1.2(a) and (b)) summarizes the amount of snow that must be designed for, and the variable inputs to the above formula, for different counties around the state. This table can be downloaded as an MS Excel file at the bottom of the page.

Jurisdiction Elevation (ft) Roof Snow Load (PSF) Ground Snow Load (PSF) Po S Ao
Beaver County       43 63 6.2
            Beaver 5,920 ft. 43 62      
Box Elder County       43 63 5.2
            Brigham City 4,300 ft. 30 43      
            Tremonton 4,290 ft. 30 43      
Cache County       50 63 4.5
            Logan 4,530 ft. 35 50      
            Smithfield 4,595 ft. 35 50      
Carbon County       43 63 5.2
            Price 5,550 ft. 30 43      
Daggett County       43 63 6.5
            Manila 5,377 ft. 30 43      
Davis County       43 63 4.5
            Bountiful 4,300 ft. 30 43      
            Farmington 4,270 ft. 30 43      
            Layton 4,400 ft. 30 43      
            Fruit Heights 4,500 ft. 40 57      
Duchesne County       43 63 6.5
            Duchesne 5,510 ft. 30 43      
            Roosevelt 5,104 ft. 30 43      
Emery County       43 63 6
            Castledale 5,660 ft. 30 43      
            Green River 4,070 ft. 25 36      
Garfield County       43 63 6
            Panguitch 6,600 ft. 30 43      
Grand County       36 63 6.5
            Moab 3,965 ft. 25 36      
Iron County       43 63 5.8
            Cedar City 5,831 ft. 30 43      
Juab County       43 63 5.2
            Nephi 5,130 ft. 30 43      
Kane County       36 63 5.7
            Kanab 5,000 ft. 25 36      
Millard County       43 63 5.3
            Millard 5,000 ft. 30 43      
            Delta 4,623 ft. 30 43      
Morgan County       57 63 4.5
            Morgan 5,064 ft. 40 57      
Piute County       43 63 6.2
            Piute 5,996 ft. 30 43      
Rich County       57 63 4.1
            Woodruff 6,315 ft. 40 57      
Salt Lake County       43 63 4.5
            Murray 4,325 ft. 30 43      
            Salt Lake City 4,300 ft. 30 43      
            Sandy 4,500 ft. 30 43      
            West Jordan 4,375 ft. 30 43      
            West Valley 4,250 ft. 30 43      
San Juan County       43 63 6.5
            Blanding 6,200 ft. 30 43      
            Monticello 6,820 ft. 35 50      
Sanpete County       43 63 5.2
            Fairview 6,750 ft. 35 50      
            Mt. Pleasant 5,900 ft. 30 43      
            Manti 5,740 ft. 30 43      
            Ephraim 5,540 ft. 30 43      
            Gunnison 5,145 ft. 30 43      
Sevier County       43 63 6
            Salina 5,130 ft. 30 43      
            Richfield 5,270 ft. 30 43      
Summit County       86 63 5
            Coalville 5,600 ft. 60 86      
            Kamas 6,500 ft. 70 100      
            Park City 6,800 ft. 100 142      
            Park City 8,400 ft. 162 231      
            Summit Park 7,200 ft. 90 128      
Tooele County       43 63 4.5
            Tooele 5,100 ft. 30 43      
Uintah County       43 63 7
            Vernal 5,280 ft. 30 43      
Utah County       43 63 4.5
            American Fork 4,500 ft. 30 43      
            Orem 4,650 ft. 30 43      
            Pleasant Grove 5,000 ft. 30 43      
            Provo 5,000 ft. 30 43      
            Spanish Fork 4,720 ft. 30 43      
Wasatch County       86 63 5
            Heber 5,630 ft. 60 86      
Washington County       29 63 6
            Central 5,209 ft. 25 36      
            Dameron 4,550 ft. 25 36      
            Leeds 3,460 ft. 20 29      
            Rockville 3,700 ft. 25 36      
            Santa Clara 2,850 ft. 15 (1) 21      
            St. George 2,750 ft. 15 (1) 21      
Wayne County       36 63 6.5
            Loa 7,080 ft. 30 43      
            Hanksville 4,308 ft. 25 36      
Weber County       43 63 4.5
            North Ogden 4,500 ft. 40 57      
            Ogden 4,350 ft. 30 43      

 

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