Answer: There is no set standard spacing, but 24 in. O.C. is common. Spacing is generally chosen such that the sheathing edges will fall at the centerline of the trusses.
The number of trusses required for a roof depends completely on the design. However, typical roof truss spacing means that they are usually 400mm (16 inches) or 600mm (24 inches) from centre – this means from the centre of one truss to the centre or the next truss.
403.12.2.3 Truss Spacing
Metal-plate-connected wood trusses shall be spaced no more than 24 inches (610 mm) on center and designed for all applicable dead and live loads.
In general, the rafter spacing for the porch roof is typically either 16” or 24” on-center. Rafter spacing for pergola may vary depending on the size of the pergola or your visual preference.
Most homes use two-by-six-foot joists spaced 16 inches on center, but you might be able to use a two-by-ten-foot or two-by-twelve-foot joist in a large room. Depending on the size of the room, you can space larger joists further apart (up to 24 inches on center).
16” o.c. is the traditional spacing, but 24” o.c. can often be more economical and decrease construction time. The proper solution often depends on the project's structural, financial, and performance goals.
The truss spacing for wood shake roofs is typically around 24 inches on center, but the quality and treatment of the shakes influence spacing requirements. Treated shakes can usualy use the standard 24-inch spacing. Untreated shakes may need closer spacing because they vary in strength and thickness.
There is no set standard spacing, but 24 in. O.C. is common. Spacing is generally chosen such that the sheathing edges will fall at the centerline of the trusses. As a result, truss spacing usually divides evenly into a common plywood sheet (8 ft.).
In most situations, the trusses/joists bear on the double 2x top plates of the wall assembly below. The most direct load path would be to always align a stud (or studs if necessary) directly below each truss/joist.
This spacing is wider than the traditional building practice of 16-inch centers. Using 16-inch centers instead of wider spacings provides a stronger structure as it reduces the amount of weight each framing member has to support. This also reduces the amount of deflection or bending that occurs in the structure.
Depending on your builder or building designer, the usual range is anywhere from 2′ on center to 10′ on center with the majority of builder's either using 4′ or 8′ on center or a mix of the two.
As a guide, the spacing of roof trusses can be kept 1 / 4 of the span up to 15 m and 1 / 5 of span for 15 - 30 m spans of roof trusses.
Trusses are usually made in a factory and shipped to the construction site. Comprised of prefabricated lightweight wood, trusses are made most commonly made from 2x4 or 2x6 beams but can sometimes be as large as 2x8.
Unlike rafters, trusses transfer all their load to the outer bearing points, so they don't need support from interior room partition walls. This design efficiency offers more flexibility in interior layout and potentially reduced costs.
The distance between two trusses is considered a bay, and this term is commonly used in structural engineering and architecture.
Consider your budget, desired timeline, and design preferences. If you prioritize a one-of-a-kind look and have some flexibility in time and cost, rafters might be the way to go. However, if speed, budget, and a traditional design are your top concerns, trusses are a great option.
Truss Spacing
The spacing varies from about 4 m for short span structures to 10 m for relatively long span construction. Spacing as large as 10 m has occasionally been used for truss spans of 40-50 m. A good thumb rule for the truss spacing is 1/5 to 1/3 of their span.
Where the distance from the top of the braced wall panel to the top of the rafters or roof trusses above is between 91/4 inches (235 mm) and 151/4 inches (387 mm), blocking between rafters or roof trusses shall be provided above the braced wall panel in accordance with Figure R602.
Ridge beams are required by code if the roof slope is less than 3:12 (IRC section R802. 4.4) and/or if there is not adequate thrust resistance (ceiling joists). For ridge beam sizing see Ridge Beam Sizing Calculator or ForteWEB®.
Roof trusses are typically spaced 2′ on center for residential and commercial projects. That spacing can be reduced if needed to better support additional truss loads, longer truss spans, or other factors.
Board placement should be 16″ on center.
It is common in the US to space ceiling joists 16″ on center, yet in some cases they are laid out 24″ on Center and in other circumstances 48″ on center. The spacing is dependent on the size of the lumber and the distance between it's supports. A heavy second floor may require 12″ on center or other changes.
To summarize, studs at 24-inch spacing will save money and resources, and are safe. With 2x6s, it's a no-brainer for most residential construction—they're plenty strong in nearly any configuration. With 2x4 studs you can also get by with 24-inch spacing, but walls should be 9 feet tall or less and the loads modest.
The distance a 2×6 can span is determined by the species, grade, location, use, load, and spacing. Based on building codes, a 2×6 can span anywhere from 2'-1” to 20'-8” depending on the affecting factors. Ceiling joists don't normally have the same load restrictions, and so can span greater distances.”
For the curious – 7/16” OSB has a span rating of 24/16 and with supports every 24 inches is good for a roof live load of 40 psf (pounds per square foot) with a 10 psf dead load.