RafterIQ
IRC 2021 and 2024
Rafter spans checked against IRC R802, plus the layout math for common, hip, valley and jack rafters. Bird's mouth, plumb cut and overhang included.
What it calculates
- Rafter span check for a given species, grade, size, and spacing
- Common rafter length from run and pitch, with plumb and seat cut angles
- Hip and valley rafter lengths and their compound cut angles
- Jack rafter lengths and the common difference between them
- Bird's mouth layout and remaining heel depth
- Pitch conversions between rise-over-run, degrees, and percent slope
Code sections it cites
RafterIQ names the section behind every result so you can look it up, defend it to an inspector, or check it against the edition your town adopted. It describes what each section requires in plain language — it does not reproduce the code text itself. Why that matters.
IRC R802
Wood roof framing as a whole — the parent section for the rafter references below.
IRC R802.3
Framing details at the ridge and how opposing rafters are connected.
IRC R802.4
Rafter and ceiling joist requirements, including the allowable span tables.
IRC R802.5
Ridge, collar tie, and rafter tie requirements, and when a structural ridge is needed.
IRC R802.11
Roof assembly uplift resistance and the connections that carry it.
IRC R301.6
Roof live load, which combines with snow load to drive the span check.
IRC Table R301.2
The jurisdiction-specific design criteria — including ground snow load — that you enter before sizing.
Screenshots
Coming once the interface settles.
What it costs
Free
$0Ad-supported. No account required.
- Every calculator: rafter spans, common rafter cuts, hip/valley/jack layout, pitch conversion
- Span checks across species, grade, spacing and snow load
- Section citation on every result
- Works fully offline
Remove ads
$3.99One payment, no subscription. It removes the banner and nothing else changes.
Get told when RafterIQ launches
One email when it hits Google Play. No newsletter, no drip sequence, no passing your address to anyone else.
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