Screen framing or rebar spacing with practical defaults. Switch units, enter data, get instant checks. Export a neat report for review and coordination today.
| Mode | Span | Spacing | Loads | Key Output | Status |
|---|---|---|---|---|---|
| Framing | 4.0 m | 400 mm | 0.5 + 2.0 kN/m² | Suggested max spacing ≈ 460 mm | PASS |
| Framing | 12 ft | 16 in | 10 + 40 psf | Suggested max spacing ≈ 15 in | FAIL |
| Rebar | — | 150 mm c/c | 16 mm bar, 20 mm aggregate | Clear spacing = 134 mm | PASS |
Spacing controls tributary width. If on-center spacing increases from 400 mm to 600 mm, line load rises by 50%. That single change can push bending stress and deflection beyond limits, even when the member size is unchanged.
For early screening, many residential floors use about 40 psf live load and 10 psf dead load. Roof live loads often range near 20 psf, but snow regions can be higher. Deflection limits are commonly expressed as L/360 for floors and L/240 for roofs, depending on finish sensitivity.
The framing mode models a simply supported member under a uniform area load converted into a line load using spacing. It then evaluates maximum moment (wL²/8), bending stress (M/S), and midspan deflection (5wL⁴/384EI). If either bending or deflection fails, the tool reports FAIL and proposes a reduced spacing that satisfies both.
The rebar mode focuses on concrete placement. Clear spacing equals center spacing minus bar diameter. A common baseline minimum is the largest of bar diameter, 25 mm, or 4/3 of the maximum aggregate size. This supports consolidation and helps reduce honeycombing risk during vibration.
Use the “Suggested maximum spacing” as a planning target, not a final detailing instruction. If the suggestion is close to your actual spacing, consider increasing member depth, selecting a stiffer material (higher E), or tightening deflection criteria for brittle finishes. Always confirm load combinations, support conditions, and code-specific limits before construction.
This is a screening calculator. It uses simplified assumptions to help compare spacing options. Final design should follow your governing standard, verified loads, and detailed support and connection conditions.
The framing check assumes a simply supported member with a uniformly distributed load. Cantilevers, continuous spans, point loads, or composite action can change moments and deflections significantly.
The load factor multiplies total area load before calculations. Use 1.0 for unfactored screening, or apply your project factor for quick conservatism. It does not replace full load combination checks.
Bending depends strongly on section modulus S, while deflection depends on EI and L⁴. A member can be strong enough (pass bending) but too flexible (fail deflection), especially at longer spans.
The tool scales spacing down until both bending stress and deflection meet their allowable limits. If you enter an optional maximum spacing, the suggestion will not exceed that limit.
The minimum clear spacing is the maximum of bar diameter, 25 mm, and 4/3 of aggregate size (plus any override). Standards may add requirements for bundles, layers, or congestion near laps.
The PDF is a convenient record of inputs and outputs. It is not a sealed calculation package. Use it to document checks, then attach your code-based design or engineer verification as required.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.