How the masonry wall calculator works
This free masonry wall calculator designs a reinforced concrete masonry (CMU) wall for out-of-plane wind using TMS 402-16 strength design, the edition referenced by the Florida Building Code, 8th Edition (2023). Choose a one-story wall pinned at the floor and roof, or a parapet cantilevered from the roof. Enter the block size, vertical bar size and spacing, grouting, f'm, wind pressure and roof loads, and the checks update as you type.
What it checks
- Flexure with the second-order (P-delta) moment for the pin–pin wall: Mu = wuh²/8 + Pufe/2 + Puδu, iterated to convergence (TMS 402-16 §9.3.5.4)
- Nominal moment strength from the 0.80f'm stress block, including a T-section when compression extends past the face shell of a partially grouted wall, with φ = 0.90
- Service deflection limit δs ≤ 0.007h using cracked and uncracked moments of inertia (§9.3.5.5)
- Axial stress limit Pu ≤ 0.20f'mA (0.05f'mA when h/t > 30)
- Out-of-plane shear with φ = 0.80, and the maximum reinforcement ratio for information
- Parapet base moment and shear, and the top deflection
Method
All values are per foot of wall. Section properties come from the face shells plus the grouted cells, and the modulus of rupture is interpolated between hollow and fully grouted values on the fraction of cells grouted. Each bar acts with an effective compression width equal to the least of the bar spacing, six times the nominal wall thickness and 72 in.
Loads follow the ASCE 7-22 strength combinations 0.9D + 1.0W, 1.2D + 1.0W + 0.5Lr and 1.2D + 1.6Lr + 0.5W. The 0.9D + 1.0W combination usually governs flexure because less axial load means less moment strength.
Assumptions and limitations
- Reinforced CMU in running bond with one curtain of vertical bars. Only the cells with bars are grouted unless the wall is fully grouted.
- Out-of-plane loads only. Lintels and unreinforced masonry are not covered; for in-plane shear walls use the masonry shear wall calculator.
- The pin–pin wall and the parapet are checked separately. A wall that continues above the roof as a parapet should also be checked as one continuous member, and the wall below the roof must resist the parapet base moment.
- Parapet P-delta effects are neglected. Its top deflection is reported for information because TMS 402 sets no limit for cantilevers.
- Wall weight is estimated from typical unit densities unless you enter it.
Frequently asked questions
Why does 0.9D + 1.0W usually govern?
In a lightly loaded wall, axial compression adds to the moment strength because it increases the compression force at the face of the wall. The combination with the least dead load therefore gives the lowest φMn, while the 1.2D combinations add more P-delta moment. The calculator checks all of them and reports the governing one.
What wind pressure should I use for a CMU wall?
Most walls are designed as components and cladding, so use the C&C wall pressure for Zone 4, or Zone 5 near corners, at an effective wind area of the span times one-third of the span. For parapets, use the parapet pressure. The Florida wind load calculator gives these values.
What is the effective compressive width?
TMS 402-16 §5.1.2 limits the width of masonry that can act with each bar in compression to the least of the bar spacing, six times the nominal wall thickness and 72 in. Wider bar spacing therefore does not add proportional strength.
Can I enter ASD wind pressures?
Yes. Choose ASD (0.6W) next to the pressure and the calculator converts it to strength level by dividing by 0.6.
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For educational and preliminary design purposes only. Always verify results with a licensed PE.