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Building Code Reference

Got a CRC R802.4 correction?

Rafter truss sizing

For builders in California, Greater Seattle, the Las Vegas area, the Denver area and Kansas City · CrossBeam Permits

What this code requires, how to fix it, and how cities and counties review it

What this code requires

CRC R802.4 is the California Residential Code section that governs rafter sizing for roof framing. It requires rafters to be sized using the span tables in Tables R802.4.1(1) through R802.4.1(8) based on lumber species, grade, size, spacing, and the combined roof dead load and live or snow load. The species, grade, size, and on-center spacing must all be called out on the roof framing plan. A generic "per code" note does not pass plan check in most jurisdictions.

How to fix it

  1. Pull the horizontal rafter span from the drawings

    Measure the horizontal span from the inside face of the top plate to the ridge board, or to the centerline of a ridge beam. This is the span you look up in Table R802.4. Do not confuse rafter length along the slope with the horizontal span the table uses. They are different numbers on a pitched roof. Write the horizontal dimension clearly on the framing plan so the plan-checker reads the same number you used in the table lookup.

  2. Confirm which dead-load column applies to your roofing material

    Table R802.4.1(1) is organized by dead load, typically 10 psf and 20 psf columns. Lightweight roofing (composition shingle, metal panel, lightweight tile) falls in the 10 psf group. Concrete tile, clay tile, and heavy built-up roofing are closer to 20 psf. If you are unsure where your specified roofing lands, call the manufacturer for the installed weight per square foot and round up to the next table column. Using the 20 psf column when in doubt is conservative and will not hurt your plan-check result.

  3. Look up the allowable span in Table R802.4.1(1)

    Use Table R802.4.1(1) (or R802.4.1(2) where the ceiling is attached to the rafters). Find the row for your rafter spacing and your species and grade (for example, Douglas Fir-Larch No. 2 or Hem-Fir No. 2), then read across to your dead-load column and rafter size. The span shown is the maximum allowable horizontal span for that combination. If your actual span exceeds the table value, you need to increase member size, tighten spacing, add a purlin to shorten the span, or switch to engineered lumber. A purlin with a bearing post is often the cheapest fix when the span is only a foot or two over the limit.

  4. Add species, grade, size, and spacing to the framing plan

    Put a rafter schedule or explicit general note on the framing plan that calls out all four items: species, grade, size, and on-center spacing. For example: "Roof rafters: Douglas Fir-Larch No. 2, 2x10 at 16 in. OC, max span 19 ft-6 in. per Table R802.4.1(1), 20 psf DL." Do not use a blanket "per code" note. The plan-checker needs the actual values to verify compliance without doing extra legwork on your behalf.

  5. Confirm your lumber grade is covered by the span tables

    Tables R802.4.1(1) through R802.4.1(8) cover common visually graded species and grades only. For other grades and species, including machine stress-rated (MSR) lumber, the code refers you to the AWC STJR. If the plan calls for MSR lumber, note the Fb and E values from the grade stamp on the plan. This matters because MSR lumber often allows longer spans than visually graded lumber at the same size, but the plan has to call it out explicitly for the plan-checker to credit it.

  6. Check whether a ridge beam requires separate sizing under R802.3

    Where rafters frame into a ridge beam instead of a ridge board, the beam must be designed under CRC R802.3 by accepted engineering practice and supported at each end by a wall or column. R802.4 covers rafter spans from bearing point to bearing point. It does not size the ridge member. A correction citing R802.4 on a cathedral ceiling plan may include a companion comment about the ridge beam or a note that engineering documentation is required. Address both in the same resubmittal.

  7. Resubmit with revision clouds on the corrected framing sheets

    Mark the corrected area on your framing plan with a revision cloud and a revision triangle. Note the correction letter number in the title block. Some plan-checkers pull only clouded sheets on resubmittal, so if you redo the roof framing plan without revision marks they may not see what changed. A clean, specific callout of species, grade, size, and spacing on the clouded sheet is what closes the R802.4 comment.

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Why you got flagged

Plan-checkers flag CRC R802.4 when the roof framing plan is missing the information they need to verify the rafters will carry the load. That happens in a few predictable ways.

The most common trigger is a framing plan that shows rafter layout but omits species and grade. A plan that says "2x10 rafters at 24 OC" is incomplete. Without species and grade, the plan-checker cannot look up the allowable span in Table R802.4.1(1) and has no way to confirm the members are adequate. Expect a correction until both appear on the plan.

A second scenario: the rafter span on the drawings exceeds what Table R802.4.1(1) allows for the stated species, grade, and spacing. This comes up most on shallow-pitch roofs or rooms with long clear spans. The contractor or designer specifies a common rafter size, say 2x8 at 24 OC, without checking whether the actual horizontal span from ridge to bearing wall clears the table limits for the lumber specified. When it does not, the plan-checker catches it and the correction letter cites R802.4.

A third trigger is mismatched load assumptions. Table R802.4.1(1) has separate span values for different dead-load conditions, typically a 10 psf and a 20 psf dead load column. If the plan notes a heavy roofing material like concrete tile but the rafter sizing was pulled from the 10 psf column, that is a R802.4 correction. The plan-checker will flag the mismatch between the specified roofing and the load assumption behind the span selected.

Finally, some plans call out "rafters per Table R802.4.1(1)" without stating which table row applies. That generic note does not pass. The plan must show the actual species, grade, size, and spacing so the calculation can be independently verified.

The official code

CRC R802.4 — Rafter Sizing, 2025 California Residential Code (Title 24 Part 2.5)

Read the source →

Common questions

Does CRC R802.4 apply to roof trusses?
No. R802.4 and its span tables apply to site-cut dimensional lumber rafters. Factory-built trusses are covered under CRC R802.10, which requires a deferred truss submittal with engineer-stamped drawings from the truss manufacturer. The truss package goes through a separate review after the main permit issues. If your plan shows trusses but got a R802.4 correction, check whether the plan-checker is flagging missing truss submittal documentation rather than a span-table issue. The fix is usually a note that reads "Roof trusses: deferred submittal per CRC R802.10, truss manufacturer to provide stamped drawings."
What lumber species and grades work for rafter sizing in California?
Table R802.4.1(1) covers the most common species used in California framing: Douglas Fir-Larch (No. 1, No. 2, No. 3), Hem-Fir (No. 1, No. 2), Spruce-Pine-Fir, and Southern Pine. Douglas Fir-Larch No. 2 is the default spec on most OC residential jobs because it is widely available from local lumber yards. Hem-Fir No. 2 has slightly lower allowable spans for the same size and spacing, so if your supplier delivers Hem-Fir when you spec'd DF-L, the span values are different and your plan may not comply. Confirm the species on the grade stamp matches what is on the plan.
What dead load should I assume for composition shingle?
Composition asphalt shingle, metal roofing, and lightweight synthetic tile all fall in the 10 psf dead-load category for Table R802.4.1(1) purposes. Concrete tile and clay tile are in the 20 psf range, and some heavy concrete tiles run even higher. If you are unsure, call the roofing material supplier for the installed weight in pounds per square foot and round up to the next table column. Choosing the 20 psf column when you are on the fence is the conservative call and will not create compliance problems. What creates problems is using 10 psf spans with a 20 psf roofing material.
Can I use 2x6 rafters at 24 OC for a small shed roof addition?
It depends on the horizontal span and your species. With Douglas Fir-Larch No. 2 at 24 in. OC and 20 psf dead load, Table R802.4.1(1) allows roughly 9 to 10 feet of horizontal span. If your shed roof spans more than that between bearing points, 2x6 at 24 OC will not clear the table. Tightening to 16 in. OC picks up roughly a foot of allowable span. Going to 2x8 picks up more. Pull the actual table for your lumber species before you commit to a size. Getting it wrong means a correction letter and another review cycle.
Do I need an engineer stamp to size my rafters?
Not for conventional residential roof framing within the CRC's prescriptive scope. The span tables handle it, and no engineer stamp is required as long as your design stays within the table limits. Engineering comes into play when you go outside the prescriptive scope: unusually long spans, loads beyond what the tables cover, irregular roof forms, or a ridge beam design. Trusses require engineer-stamped drawings from the truss manufacturer under R802.10, but that is the truss manufacturer's licensed engineer, not a project engineer of record.
My rafter span is a foot over the table limit. What are my options?
A few options that do not require switching to engineered lumber. Tightening spacing from 24 in. to 16 in. OC adds allowable span. Moving up one depth (2x8 to 2x10) adds more. Switching from No. 2 to No. 1 grade bumps the allowable span modestly, maybe 6 to 8 inches depending on species and size. If none of those close the gap, adding a purlin with a bearing post can split the rafter into two shorter spans, each of which clears the table. If the gap is larger or the geometry does not allow a purlin, LVL or LSL rafters sized by an engineer are the practical answer.

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