Rafters shall be framed not more than 11/2-inches (38 mm) offset from each other to ridge board or directly opposite from each other with a gusset plate as a
A: Christopher DeBlois, a structural engineer with Palmer Engineering Co. in Tucker, Ga., responds: Rafters can be safely staggered across a ridge board in most situations.
Rafters on opposite sides of the ridge should be installed directly opposite each other in pairs -- although, if you see a few that don't align, it's really not a defect. Rafters sometimes have to be moved a little to accommodate components of other home systems.
Lower One-Third
For example, if an unfinished garage has a roof with a 4:12 slope and the roof span is 24 feet, the rafter ties should be located no more than 16 inches up from the plate, according to modern building standards.
The standard roof rafter is cut from a two-by-ten piece of lumber, but two-by-eights and two-by-twelves are also common, depending on the loads and lengths of the rafters. The space between roof rafters can range from 12 to 24 inches, with 16 inches being the standard.
“A 2×6 spaced 16 inches apart can span a maximum distance of 13 feet 5 inches when used as a rafter, 10 feet 9 inches when used as a joist, and 6 feet 11 inches when used as a deck beam to support joists with a 6-foot span.”
The standard roof rafter spacings measured on-center are 12″, 16″, 19.2″, and 24″.
❖ The requirements of this section describe connections to resist horizontal thrust from gravity loads and ridge uplift from wind loads. Ceiling joists or rafter ties are the framing members used to resist the horizontal thrust from gravity loads. A ceiling joist or rafter tie is required at every rafter.
Hurricane ties themselves are not too expensive, but you do need one for each rafter, and the labor costs of installation can quickly add up.
Although joist hangers are not technically required in construction, they are necessary if you want to increase the strength, durability and longevity of your construction - particularly if it's a large one! Joist hangers can add peace of mind and real sturdiness to your wooden beams.
The rafters or joists shall be centered over the studs with a tolerance of not more than 1 inch (25 mm). 3. Omission of the top plate is permitted over headers where the headers are adequately tied to adjacent wall sections in accordance with Table R602.
The rafters are usually spaced at 400mm centres. In most houses, the guttering is supported by the facia board. This is fixed to the feet of the rafters and it can be flush against the wall or it can form an overhang. Lean-to roofs can achieve only modest spans.
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.
Rafters shall be framed not more than 11/2-inches (38 mm) offset from each other to ridge board or directly opposite from each other with a gusset plate as a tie. Ridge board shall be not less than 1-inch (25 mm) nominal thickness and not less in depth than the cut end of the rafter.
A 25mm - 50mm air gap must be left between the material and the roof underside for adequate ventilation.
A notch not exceeding 1/3 the depth of the member is permitted in the top of a rafter or ceiling joist not further from the face of the support than the depth of the member. The tension side of members 4" or greater in thickness must not be notched except at the ends of the members.
Each space between the rafters needs a baffle, and you must fit each one snuggly into the bay.
Fasteners with Hurricane Ties
While many hurricane ties have been evaluated with 8d x 1½” nails for compatibility with nominal 2x roof framing, some require the use of a longer, 8d common (2½” long) nail and others require a larger-diameter 10d nail.
If the bracing provided is not used entirely, positioned incorrectly or not securely fixed, it can result in a distortion or failure of individual trusses or in a worst case scenario – the whole roof so it's safe to say they're pretty important!
Wood rafter ties shall be not less than 2 inches by 4 inches (51 mm × 102 mm) installed in accordance with Table R802. 5.2(1) at a maximum of 24 inches (610 mm) on center. Other approved rafter tie methods shall be permitted.
On most occasions, these will be used together to provide the best possible support for your roof. Rafters provide the primary support for the roof's slope, while purlins act as a secondary support system.
Outrigger. An outrigger is sometimes called a "lookout". These are pieces of wood installed perpendicularly across rafters, from the common rafters in past one roof rafter and secured into the next.
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.
This 2x6, 24-inch on-center stud spacing is one of many components of advanced wall framing that reduce costs and provide materials and energy savings. Techniques for installing 24-inch on-center exterior and interior wall framing and single top plates are described below.
A #1 grade of Southern yellow pine (SYP) 2×8 roof rafter can span a maximum of 16'- 6” far apart at 16” OC. For the same size rafter, grade and spacing, SPF can allow to maximum span of 15'-1".