Sample House

 

ROOF LEVEL

 

Roof

• dimensions
  • building footprint: 48' x 28'
  • roof pitch: 4:12 
  • eave overhang: 24"  (actually about 1.25 ft in AutoCAD drawing)
  • rafter rise and run: 61 in. vertical, 15.25 ft horizontal  (AutoCAD drawing)
• dead load
  • pressure
    • shingles: 30 lb. felt and asphalt shingles = 2.2 psf x 3 layers of shingles = 6.2 psf
    • sheathing: 1/2" plywood = 3.0 x 1/2 = 1.5 psf
    • rafter: 2x8 at 16" OC = 1.6123 psf
    • D = 9.4 psf  (angled) = sqrt (4² + 12²)/12 x 9.4 = 9.9 psf  (horizontal)
  • load to rafter
    • w_D = 9.9 psf x 16 in. (1 ft/12 in.) = 13.20 lb/ft
  • load to stud in pony wall
    • A_T = 16 in. (1 ft/12 in.) x (7 ft) x 2 sides = 18.67 ft²
    • P_D = D A_T = 184.8 lb
  • load to stud in exterior side wall
    • A_T = 16 in. (1 ft/12 in.) x (8.25 ft) = 11.00 ft²
    • P_D = D A_T = 108.9 lb
• live load
  • pressure
    • L₀ = 20 psf  (horizontal, ASCE 7 table 4-1)
  • load to rafter
    • A_T = 16 in. (1 ft/12 in.) x (15.25 ft) = 20.33 ft²
    • R₁ = 1  (ASCE 7 section 4.9.1)
    • R₂ = 1 (F ≤ 4)
    • L_r = 1 * 1 * 20 psf = 20 psf
    • w_Lr = 20 psf x 16 in. (1 ft/12 in.) = 26.67 lb/ft
  • load to stud in pony wall
    • A_T = 16 in. (1 ft/12 in.) x (7 ft) x 2 sides = 18.67 ft²
    • R₁ = 1  (ASCE 7 section 4.9.1)
    • R₂ = 1 (F ≤ 4)
    • L_r = 1 * 1 * 20 psf = 20 psf
    • P_Lr = L_r A_T = 373.4 lb
  • load to stud in exterior side wall
    • A_T = 16 in. (1 ft/12 in.) x (8.25 ft) = 11.00 ft²
    • R₁ = 1  (ASCE 7 section 4.9.1)
    • R₂ = 1 (F ≤ 4)
    • L_r = 1 * 1 * 20 psf = 20 psf
    • P_Lr = L_r A_T = 220.0 lb
• snow load  (ASCE 7 section 7.4)
  • pressure
    • P_g= 20 psf
    • C_s = 1  (not slippery)
    • C_e = 0.9  (fully exposed)
    • C_t = 1  (heated)
    • I = 1  (residential)
    • S = 0.7 C_s C_e C_t I p_g = 18.00 psf
  • load to rafter
    • w_S = 18.00 psf x 16 in. (1 ft/12 in.) = 24.00 lb/ft
  • load to stud in pony wall
    • A_T = 16 in. (1 ft/12 in.) x (7 ft) x 2 sides = 18.67 ft²
    • P_S = D A_T = 336.1 lb
  • load to stud in exterior side wall
    • A_T = 16 in. (1 ft/12 in.) x (8.25 ft) x 2 sides = 22.00 ft²  (that looks like a mistake; it should probably be 1 side)
    • P_S = D A_T = 396.0 lb
• wind load
  • ignore
• seismic load
  • ignore
• deflection limits  (IBC table 1604.3)
  • not supporting ceiling
  • L/180 for L = 14 ft x 12in./ft / 180 = 0.9333 in.
  • L/180 for S or W = 0.9333 in.
  • L/120 for D + L  (or L + 0.5D if under dry conditions) = 1.400 in.