Snap a chalk line horizontally across the roof two feet down from the top. Lay the first purlin at the ridge of the roof down to the chalk line beginning at either corner. Fasten the purlin with 16d common nails into each vertical rafter. Insert two equally spaced nails into the rafter.
How are purlins attached?
Purlins come in two basic shapes: C and Z. Both are connected to the framing by attaching the web of the C or Z purlin to a clip that is welded to the column or rafter. … Holes are often predrilled or punched into the purlins and girts, as well as the columns and rafters.
How far apart are purlins on a metal roof?
For lighter materials such as lightweight aluminum, the common spacing length is 4 inches of the clear gap. For heavier material such as gage steel, the metal roof purlins spacing length could go up to 4 feet. The typical spacing standards for residential and commercial buildings are about 1 to 2 feet.
Should you use purlins for metal roof?
In general, purlins are used instead of traditional decking when it comes to metal roofs. … Metal roofing is one of the best upgrades you can make to your home, letting you install a more permanent roofing system that will require less maintenance and will last for decades to come.
How far apart do purlins need to be?
The spacing of purlins on roofs and girts on wall is usually 4 to 6 ft. Numbers 20 and 22, U.S. Standard gage, are generally used for roofing; No. 24 for siding.
Which is stronger Z purlin or C purlin?
Z Shaped Purlin:
Another form of Z purlin is stronger than C purlin and is mostly used together at joints and overlaps.
Are purlins load bearing?
In architecture or structural engineering or building, a purlin (or purline) is a horizontal structural member in a roof. Purlins support the loads from the roof deck or sheathing and are supported by the principal rafters and/or the building walls, steel beams etc.
Does a metal roof need furring strips?
When installing a metal roof over an existing roof, insulate the spaces between the wood strips with rigid insulation to prevent condensation before installing the roofing. You also need to add furring strips. … Twenty-four inches is a common spacing of furring strips for a metal roof.
Do you need strapping under metal roofing?
Single wood strapping is better than no strapping as it creates a wider gap between the existing roof decking and the metal roof but doesn’t afford enough ventilation to resolve condensation issues. It also does not allow leveling of the roof, which corrects swells and swales on the roof.
How far can a 2×6 span for a metal roof?
For a 2×6, the maximum span would be 9 feet, since 6 times one and a half equals 9. This rule of thumb is based on using Doug fir lumber, and is only a rule of thumb.
What do you put under a metal roof?
The traditional and most common material used for roof underlayment on a steep-slope metal roof is non-perforated, asphalt-impregnated felt underlayment. There are several types of felt underlayment including both organic reinforced and inorganic reinforced.
Can metal roofing be installed over plywood?
Can Metal Roofing Be Installed Directly to Plywood? Metal roofing should not be installed directly over the top of bare plywood. You do not have to install roofing shingles or other roofing material, but a felt sheet over the plywood is the bare minimum.
What should I use for purlins?
With a 2′ on center truss spacing 7/16″ osb or plywood sheathing can be used to strengthen the structure (replacing purlins), provide excellent sound deadening when it rains or hails, and simplifies walking around on the roof, especially higher pitched roofs.
How far can a 2×8 Rafter span without support?
Span is determined by species, grade, dimensions, spacing, use, and load. A rule of thumb is 1.5 times a joist’s depth but in feet when spaced at 16” centers. In general, a 2×8 will span 1.5 x 8, so 12-feet. Based on all factors though, a 2×8 joist span is 7′-1” to 16′-6”, and a rafter 6′-7” and 23′-9”.
How far can 2×4 purlins span?
2×4 purlins may also be nailed on top of the rafters with one 60-d nail or attached with metal clips at each rafter. Rafters may be spaced up to twelve feet, dependent on purlin size, when purlins are turned edgewise.
How thick should purlins be?
The substructure to which the metal panels are fastened must be properly spaced and sufficiently thick to provide a roof or wall system able to meet required design loads. A 2″ nominal lumber thickness or 1″ nominal thickness are both acceptable purlins.