Rafters are the primary load-carrying members in pitched roof construction. For commercial portal frame buildings, the rafter is the inclined portion of the frame, spanning from apex to eaves and transferring combined dead, wind, snow, and imposed loads to the column. Structural engineers check rafter capacity under all Eurocode load combinations when assessing a roof for solar PV.
In residential and light commercial construction, timber or cold-formed steel rafters span between the wall plate and ridge board. Section sizes and centres are critical to capacity. Engineers measure rafter spacing during on-site structural surveys where drawings are unavailable, and calculate utilisation ratios against published section capacities.