C Purlin Prices, Sizes & Spacing (4, 6, 8 inch red-oxide)

The three sections we stock

• 4 × 2-1/2 in, 16 gauge. The light section. Roof purlins on bays up to 15 ft, lean-to rafters to a 15 ft projection, wall girts, and framing repairs. Lowest price per foot.
• 6 × 2-1/2 in, 16 gauge. The workhorse. Roof purlins on bays up to 20 ft and lean-to rafters out to a 20 ft projection. Most of what we sell.
• 8 × 2-1/2 in, 16 gauge. Lean-to rafters and gable-extension purlins out to 25 ft, and anywhere a long reach is needed. Never used as purlins on trusses. Highest price per foot, fewest pieces.

All three come red-oxide primed, the standard finish for enclosed and open agricultural framing. Red oxide is a primer, not a finish coat: it protects the steel through construction and under a roof, and it can be painted. If your project needs galvanized C-purlin, say so in the notes and we will check availability and price rather than guess.

How C purlin pricing works

Purlin is sold by the linear foot, cut to length. The price per foot depends on the section (4, 6 or 8 in), the day's steel price, and in some cases the total footage of the order. There is no separate cutting charge in our pricing; you give us the lengths and quantities, and the configurator totals the footage by section and prices it. Cut-to-length steel is made for your order and is non-returnable, which is why the configurator shows the full list before anything is paid.

Because the per-foot rate moves with steel, we do not print it on this page. The honest answer to "how much do C purlins cost" is the real figure for your section and footage: enter your list, verify your phone by text, and the configurator shows your exact delivered total instantly, good for one week.

Spacing: the rules PRC uses to count materials

• Roof purlin rows are never farther apart than 48 in on center, running the full length of the building on each slope. A 4/12 roof on a 30 ft wide barn gets five rows per side; a 40 ft barn gets six.
• Bay length (truss to truss) decides the section: 4 in to 15 ft bays, 6 in to 20 ft bays. 8 in is never used as a purlin on trusses. The configurator prices both where both qualify and shows the cheaper.
• Lean-to rafters: 4 in C to a 15 ft projection, 6 in C to 20 ft, 8 in C to 25 ft. There is no ledger: a top C-purlin ties into each barn post, there is a post under every rafter on the low side with a C header, and rafters are cut to the projection plus 2 in with no overhang.
• Wall girts, where a building is enclosed, are typically 4 in on the same 48 in rhythm.

These are PRC's working rules for counting a kit, drawn from manufacturer guidance and what our crews build. They are not a substitute for engineering, and your permit office may require sealed drawings.

Span: what we will and will not tell you

People search for a C purlin span chart, and we are not going to publish one. Allowable span for a C-section depends on gauge, section depth, the load it carries (dead load, live load, wind uplift and, where it applies, snow), the spacing between purlins, and how the ends are fastened. A single number pulled off a web page without those inputs is how roofs end up sagging or lifting.

What we do instead: the manufacturer's span table for the exact sections we sell is available with every PRC order. It lists allowable spans by section, gauge, spacing and load, and it is the document your engineer or permit office will actually accept. Ask for it, read it against your bay length and your local wind and load requirements, and if you are unsure, have an engineer look at it. PRC cuts purlin to your list; we do not design spans or spacing for you.

Related

C-purlin by the foot · Lean-to kits · Gable end extensions · Pole barn kits · 30x40 layout and purlin section · 40x60: 4 in vs 6 in purlin layouts