Beam Span and Size for Pool House
This is an engineering matter, the beam size is provided for your first-hand information use only. Confirmation from a structural engineer is required for construction.
Deck length tributary to the beam = (20' - 5' - 0.5)/2 + 2.5 = 9.75', say 10'. Assume 5 psf misc. wt. on top of the snow load (S), the uniform distribute load on beam (with 10% increase for beam self wt.), w = 1.1*(S+10)*10. Beam span length (column - column), L = 27', deflection limit = L/240 = 1.35&quot;.
The roof snow load across the province of Ontario varies from 40 psf to 70 psf (approx.) Per the Allowable Stress Design (ASD) method, and Fy = 36 ksi, fb = 21.6 ksi, the estimated wide flange beam sizes for the corresponding snow loads are as listed below:
Snow Load - Beam size*
40 - W10x30
50 - W10x33
60 - W10x39
70 - W10x45
(*) - All beam sizes are governed by the deflection criteria.