Brick Wall Calc

Step 4 Stability moment of wall panel Table 4

Select wall type — tap to choose

Table 4 — Wall type notes (§5.3.1)

Single leaf90 or 110 mm. Stability moment from self-weight only. Usually requires piers for walls over ~1.2 m in N3+. Most economical with reinforced piers at ≤2.1 m spacing.

Solid twinTwo leaves bonded with collar joint filled with mortar (AS 3700). Stability moment = sum of both leaves. 190 mm = 2×90, 230 mm = 2×110. Higher stability, no piers often required for moderate winds.

Cavity wallIf using cavity wall with ties (not solid bonded), stability moment = sum of individual leaf moments — same as single leaf values combined. Not listed separately in Table 4.

DiaphragmCavity wall with brickwork webs connecting the two leaves at intervals (≤2400 mm for freestanding). Acts as composite section. Overall thickness drives stability — 290 mm or 350 mm. Most stable unreinforced option. Webs bonded with headers every 4th course or medium duty ties at ≤300 mm vertically.

Single
leaf 90

Single
leaf 110

Solid
twin 190

Solid
twin 230

Diaphragm
290

Diaphragm
350

Stability moment Mr = 0.9mt²H/2

Self-weight restoring moment

—kN·m/m

Table 8 Return wall at end? (optional) §5.4.3

Include return wall buttressing

Table 8 — Buttressing effect of return walls (§5.4.3)

Most fences incorporate corners which provide considerable stability. The return wall adds a stability moment Mr = 0.9 × m × tw × H × L² / 2, where L = return length in metres. L should not be taken greater than H. The buttressing moment is added to the wall panel stability moment from Table 4 before checking if additional lateral support is required.

Leaf thicknessUse the leaf thickness of the return wall. Single leaf 90 or 110mm. Solid/cavity uses the individual leaf thickness.

Return lengthCount in brick units (1 unit ≈ 230mm for standard brick). Maximum effective length = wall height H. Longer returns give disproportionately higher stability moments.

When to useOnly at the end of a wall run where a perpendicular wall is bonded in. Do not use for free ends or control gap ends.

No return

Has return wall

Return leaf thickness

Return length (brick units)

Return buttressing moment (Table 8)

—

—kN·m/m

Total stability moment Mr + Table 8

—kN·m/m

Step 5 Does the wall need lateral support? §5.4.1(a)

Additional moment required M_req = M − Mr(total)

—

—kN·m/m

Step 6 Max allowable pier spacing Table 5 · Fig. 2

End condition at pier — tap to choose (Fig. 2)

Figure 2 & §5.4.5 — End condition notes

A — engagedWall panel is fully bonded into the pier or buttress. Provides rotational restraint. M_max = pHS²/12. Use when wall is bonded to a reinforced brickwork pier (most common case). Gives the longest allowable spans in Table 5.

B — simpleWall panel is laterally restrained but not rotationally fixed — e.g. connected to a metal or timber post with wall ties, or a pier that provides only lateral support. M_max = pHS²/8. Spans are shorter than Condition A.

C — free endWall panel projects past a pier or has a free end at a control gap. Acts as a cantilever from the last support. M_max = pHS²/2. Gives the shortest allowable span. Wall ties at a control gap provide lateral restraint only — not rotational fixity.

Fully engaged
Rotational restraint

Simply supported
Lateral only

Projects past
pier / control gap

Maximum pier spacing Sp,max

—

—m

Step 7 Moment & shear at the pier §5.4.1(c)

Chosen pier spacing Sp (m)

Design moment at pier M* = M_req × Sp

—kN·m

Design shear at pier V* = V × Sp

—kN

Step 8 Select lateral support system Tables 6 & 7

Brick compressive strength f'uc

Masonry strength f'm (1c:1L:6s mortar)

5.4MPaAS 3700 Table 3.1

Pier type — tap to choose (Tables 6 & 7, Figs. 3 & 4)

Table 6 — Hollow grouted piers (§5.4.2)

Reinforcement extends into the footing — this is the key to their strength. Reo resists tensile stress from wind; the pier acts like a post. All four types use 4 bars divided between each end of the grout pocket. 15 mm grout cover is adequate for marine exposure but not severe marine (within 1 km of surf coast). Grout mix: 1 cement : 2 sand : 4 aggregate. Pour in lifts of 300–600 mm; rod thoroughly. Do not pour into brickwork less than 24 hours old.

Type A470w × 350d mm. Largest hollow grouted pier. Projects both faces. Highest capacity. Use for long spans or high wind.

Type B390w × 290d mm. Medium hollow grouted pier. Projects both faces.

Type C350w × 350d mm. Projects on one face only. Use where one side must stay flush.

Type D290w × 290d mm. Smallest hollow grouted pier. Projects one face. Use for lighter loads.

Table 7 — Simple reinforced piers (§5.4.2)

Steel placed in mortar bed joints or in a small grouted pocket. Must be galvanised. Built in fresh mortar completely surrounding steel. Lower capacity than Table 6 but simpler construction. Suitable for lower walls and lighter wind regions.

Type ESolid or cavity pier, steel in mortar bed joints. Reo A or D. Three size options.

Type FPier projects on one face. Reo E or F. Two size options.

Type GCentral grouted pocket. Reo A, B or C. Two size options. Intermediate capacity.

Brick requirement

Use only bricks with permanent moisture expansion e ≤ 1.0 mm/m. f'uc must meet values in Tables 6 & 7.

Table 6
Hollow grouted

Table 7
Simple reinforced

None
Self-stable wall

Pier type — tap to choose

Type A
350w × 470d
110mm wall

Type B
290w × 390d
90mm wall

Type C
350w × 350d
110mm wall

Type D
290w × 290d
90mm wall

Pier type — tap to choose

Type E
simple solid

Type F
projects 1 face

Type G
grouted pocket

Bar diameter — tap to choose

Table 6 — Bar diameter notes (§5.4.2)

N10Minimum bar size. Use for lightly loaded piers — low walls (≤1.2 m) or N1/N2 wind class.

N12Common general-purpose. Suits most suburban walls ≤1.8 m in N2–N3 wind regions at 2–3 m pier spacing.

N16Use for taller walls (2.1–3.0 m), higher wind classes (N4–N5), or wider pier spacing.

N20Maximum Table 6 bar. Use for tall walls in high wind. Check pier fails in tension not compression per AS 3700 §8.

Grade 250N per AS/NZS 4671. 4 bars per pier, split between each pocket end. Galvanised preferred.

N10

N12

N16

N20

Type E — pier size (wp × tp)

230w × 230d mm

290w × 190d mm

190w × 290d mm

Type E — reinforcement

Reo A
1 × N10 plain

Reo D
1 × 25×6 flat

Type F — pier size (wp × tp)

230w × 230d mm

190w × 290d mm

Type F — reinforcement

Reo E
2 × N10 plain

Reo F
2 × 25×6 flat

Type G — pier size (wp × tp)

230w × 280d mm

290w × 210d mm

Type G — reinforcement

Reo A
1 × N10 plain

Reo B
1 × N12 def.

Reo C
2 × N12 def.

—

Width wp

—

Depth tp

—

Wall leaf thickness tw

—

Reinforcement

—

f'uc (brick strength)

15 MPa

φ Bending

—

φ Shear

—