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Stucco calculator

360 SF of stucco21 lath sheets · 36 base coat bags · 6 finish bags
Wall to plaster
360 SF
WRB (2 layers)
3 rolls (306 SF net each)
Metal lath 27" × 97"
21 sheets (3 bundles of 10)
Lath nails or staples
463 nails or staples
Scratch coat — QUIKRETE 1139
18 bags
Brown coat — QUIKRETE 1139
18 bags
Finish coat
6 bags
Control joint (minimum)
18' 0" · 2 pieces of 10'
Weep screed
40' 0" · 4 pieces of 10'
Total thickness
7/8"

These sketches are here to help you order material and price the work quickly. They are not engineered or shop drawings — always build from your approved project drawings.

Section through the wall. Coats drawn thicker than real so they can be read.

System
Wall
Size by

Coats

Base coat (80 lb premix)
Finish coat

Coverage is the low end of the maker's published range, scaled to your thickness. SPEC MIX says its numbers already include typical waste. Site-mixed plaster isn't offered yet (no published bag yields found).

Water-resistive barrier and lath

Climate zone
WRB (IRC R703.7.3)
WRB roll
Stud spacing (lath fasteners)

Rolls lapped 2" across and 6" at the ends. Moist and marine zones also need a 3/16" drainage space or mat behind the stucco.

Trim, openings and control joints▾

Control joints are laid out from length × height: panels no larger than 144 SF, no side over 18 ft, no more than 2.5 : 1 (ASTM C1063). That's a minimum — openings and design joints add more.

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  1. Wall to plaster
    length × height
    40 × 9 (ft) = 360.00
  2. Lath sheets
    SF ÷ 17.67 SF per sheet (27" × 97" less laps), rounded up
    360 ÷ 17.67 = 21
  3. Lath bundles
    sheets ÷ 10, rounded up
    21 ÷ 10 = 3
  4. Lath nails or staples
    SF × (12 ÷ stud spacing) × (12 ÷ 7"), rounded up
    360 × (12 ÷ 16) × (12 ÷ 7) = 463
  5. WRB per roll
    (roll width − 2") × (roll length − 6")
    (40 − 2) ÷ 12 × (97.2 − 0.5) (ft) = 306.22
  6. WRB rolls
    layers × SF ÷ SF per roll, rounded up
    2 × 360 ÷ 306.22 = 3
  7. Scratch coat bags
    SF ÷ (SF per bag at 3/8" × 3/8 ÷ thickness), rounded up
    360 ÷ (20 × 0.375 ÷ 0.375) = 18
  8. Brown coat bags
    SF ÷ (SF per bag at 3/8" × 3/8 ÷ thickness), rounded up
    360 ÷ (20 × 0.375 ÷ 0.375) = 18
  9. Finish coat bags
    SF ÷ (SF per bag at 1/8" × 1/8 ÷ thickness), rounded up
    360 ÷ (70 × 0.125 ÷ 0.125) = 6
  10. Control joints (minimum)
    (panels across − 1) × height + (panels up − 1) × length; panels ≤ 144 SF, ≤ 18 ft, ≤ 2.5 : 1
    (3 − 1) × 9 + (1 − 1) × 40 (ft) = 18.00
  11. Control joint pieces
    control joint LF ÷ 10 ft, rounded up
    18 ÷ 10 = 2
  12. Weep screed pieces
    base LF ÷ 10 ft, rounded up
    40 ÷ 10 = 4

Where the numbers come from

  • Coats and thickness: 3 coats over lath (scratch 3/8" + brown 3/8" + finish 1/8" = 7/8" nominal); 2 coats over masonry, at least 1/2"; at least 3/4" over self-furring or expanded metal lath (measured from the back of the lath)2021 IRC R703.7.2 and Table R702.1(1) with footnote a (3/4" from the back plane of expanded metal lath or with self-furring lath; read from the City of Seattle reprint); the 7/8" build-up is ASTM C926 as quoted in the Penn State PHRC handout. Over masonry the split 3/8" base + 1/8" finish is the page's own math to reach 1/2". Lath is not needed on masonry or concrete prepared per C1063 (R703.7.1 Exception).Source
  • Metal lath: 27" × 97" sheets, 10 per bundle; laps 1/2" on the long edges and 1" at the ends → 26.5 × 96 = 2,544 in² = 17.67 SF per sheetSheet size and bundle: ClarkDietrich lath catalog. Laps: Sika lath and trim bulletin, MVMA guide. 2.5 lb/SY self-furring lath is the usual choice on sheathed walls (C1063 as quoted by PHRC). Extra lath wrapped around corners is not added.Source
  • Lath fasteners: At most 7" apart along each stud: SF × (12 ÷ stud spacing) × (12 ÷ 7) — 1.29 per SF at 16" o.c., 0.86 at 24"IRC R703.7.1: 1-1/2" 11 ga nails with 7/16" head or 7/8" 16 ga staples, 3/4" into the wood. A count only — extra fasteners at laps and openings are not added, and box sizes vary.Source
  • Water-resistive barrier: Over wood sheathing: two layers of 10-minute Grade D, or one 60-minute layer plus a separation layer; moist (A) and marine (C) zones also need a 3/16" drainage space or mat. Rolls lapped 2" across and 6" at the ends.2021 IRC R703.7.3 (also quoted in the PHRC handout). Roll presets: Henry Jumbo Tex 40" × 97.2' (306 SF net), Henry Super Jumbo Tex 60 Minute 40" × 72' (226 SF net). One end lap per roll is assumed.Source
  • Base coat (scratch and brown): 80 lb premixed bags, SF per bag at 3/8": QUIKRETE 1139 20–24, SPEC MIX 20–24 (includes typical waste), Sika Fastwall Sanded 20–25, Omega Diamond Wall Sanded 19.8–22.5The page uses the low end and scales by thickness (SF × 3/8 ÷ thickness): QUIKRETE's 0.75 ft³ per bag ÷ 3/8" = 24 SF, and its 1/2" range (15–18) matches the scaling. Site-mixed plaster is left out: no primary source for bag volumes or sand yield was found.Source
  • Finish coat: QUIKRETE Finish Coat 80 lb: about 70 SF at 1/8"; Sika Exterior Stucco Color Coat 90 lb: float 135–180 SF, light Spanish 90–135 SFTexture changes coverage a lot. The page uses the low end and scales by thickness from 1/8".Source
  • One-coat stucco: 80 lb bags at 3/8": Sika Fastwall Concentrate 75–90 SF + 200–240 lb sand; Omega Diamond Wall Concentrate 72–90 + 160–240 lb; QUIKRETE One Coat Concentrated 73–87 + 210–250 lb; QUIKRETE One Coat FRS 20–24 (no sand); Dryvit StucCoat Sanded 24.75; StucCoat Concentrate 72 + about 200 lbOne-coat systems are proprietary: their code report sets thickness (3/8" minimum for those listed), lath and foam. The page uses the low end of each range.Source
  • Control joints: Panels no larger than 144 SF, no side over 18 ft, length ÷ width no more than 2.5ASTM C1063 limits as quoted by ClarkDietrich and Sika (C1063 itself not opened). The page finds the fewest panels that meet all three — a minimum; openings and design joints add more.Source
  • Trim pieces: Weep screed, casing bead, corner bead and control joint in 10 ft pieces; Cornerite in 8 ftClarkDietrich catalog. Weep screed (26 ga, 3-1/2" flange, 4" above earth or 2" above paving) is required at the base of stud walls (IRC R703.7.2.1); the page leaves it off masonry walls.Source

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Materials for a portland cement stucco wall: 3-coat over lath on a framed wall, 2 coats straight on block or concrete, or a one-coat system. Bag coverages are the makers' published numbers; code rules are the 2021 IRC.