Cornice Calculation & Coating Guide

How cornice dimensions map to calculator fields, which surfaces get coated, and a potential issue with the current coating area formula.

1. Cornice Anatomy (Cross-Section)

A cornice (crown molding) is a decorative trim piece that sits at the junction of wall and ceiling. The profile shape is the cross-section; the piece runs continuously along the wall for 96" (8 ft).

Coated surface

Not coated

Four surfaces of the cross-section:

A side (back) — flat against the wall, not coated
Top face — flat against the ceiling, not coated
Front contour — the decorative curve, coated
Side faces — butt against next piece, not coated

Perimeter = total outline of the rectangular cross-section bounding box: (H + W) × 2

Coated length = only the front contour. Should exclude both the A side (back) and the top face (ceiling).

Coating override: Each cornice entry has a coatingOverride set to perimeter - H - W, which excludes both the back (wall) and top (ceiling) faces. If a cornice is installed at the top of a building without an eave, the top face may need coating — clear the override to include it.

2. Calculator Field Mapping

How physical dimensions map to the calculator's Item Input fields:

Calculator Field	Cornice Meaning	Example (CIN-101 A=10")
H (Height)	Profile height — how far the piece drops down the wall = A size	10"
W (Width)	Profile width — how far the piece extends from the wall along ceiling	8"
L (Length)	Length of the piece running along the wall	96" (8 ft)
A Size	Same as H for cornices	10
Perimeter	Auto: (H+W)×2 = bounding rectangle outline	36"
Coating Override	Not set for any cornice (uses auto formula)	—
Coat Sides	OFF — side faces butt against adjacent pieces	OFF
Corners	Mesh hand-press points (4 per piece)	4
Coating Mode	Manual (CIN-101) or Machine (all others)	Manual

3. Coating Override

The auto formula coatingLength = perimeter - aSize is designed for standard trim that sits flat on a wall (only the back face is hidden). But cornices sit in a wall-ceiling corner — the top face is hidden against the ceiling too.

To handle this, every cornice entry has a coatingOverride that subtracts both hidden faces:

coatingOverride = perimeter - H - W
= (H + W) × 2 - H - W = H + W

Subtracts the back face (against wall) and top face (against ceiling). Only the decorative front contour is coated.

CIN-101 A=10": coatingOverride = 10 + 8 = 18"

Same approach as corbels: Both corbels and cornices use a coatingOverride to subtract hidden faces that the auto formula doesn't account for. If a cornice is installed at the top of a building without an eave, the top face may need coating — clear the override to include it.

4. Step-by-Step Cost Calculation

Example using CIN-101 A=10" (H=10, W=8, L=96, manual coating):

1Geometry

perimeter = (10 + 8) × 2 = 36" (auto, rectangular approximation)
coatingOverride = 36 - 10 - 8 = 18" (excludes back + ceiling faces)
coatingCalc = 18" (uses override)
lengthFactor = 96 / 12 = 8 ft
sideArea = 0 (Coat Sides OFF)
coatSurfArea = (18/12) × 8 = 12.00 sq ft

2Foam Cost

costPerCuIn = $350 / (47 × 52 × 96) = $0.001493
foamCost = ((10.2 × 8.2 × 96) × $0.001493) / 1 piece
= 8,029.44 cu in × $0.001493 = $11.99

Foam block = (H+0.2) × (W+0.2) × L. Unaffected by coating area.

3Mesh & Glue

meshCoverage = 38 × (150/12) = 475 sq ft
meshLengthWithOverlap = 18 + 4 = 22"
meshArea = (22/12) × 8 = 14.67 sq ft
meshCost = ($30.64 / 475) × 14.67 = $0.95
glueCost = $0.2237 × 14.67 = $3.28

Mesh and glue use (coatingCalc + 4") × lengthFactor, not coatSurfArea.

4Base Coat (Cement)

cementCostPerSqFt = $12 / 30 = $0.40/sq ft
baseCost = $0.40 × 12.00 sq ft = $4.80

5Labor: Coating (Manual Mode — CIN-101)

manualP = (ln(60/60) - ln(20/60)) / (ln(29.19) - ln(2.04))
= (0 - (-1.0986)) / (3.374 - 0.713) = 1.0986 / 2.661 = 0.413

manualK = (20/60) / 2.04^0.413 = 0.3333 / 1.342 = 0.2483

coatTime = 0.2483 × 12.0^0.413 = 0.2483 × 2.957 = 0.734 hrs (44.1 min)
laborCoating = 0.734 × $20 × 1 crew = $14.69

5bLabor: Coating (Machine Mode — CIN-102 through CIN-121)

coatingPerSqFt = ($20 × 2.5) / 250 = $0.20/sq ft
laborCoating = (coatingCalc / 12) × $0.20 × laborCoatingMult
= (18/12) × $0.20 × 8 = 1.5 × $0.20 × 8 = $2.40

Machine mode uses (coatingCalc/12) × coatingPerSqFt × laborCoatingMult, not coatSurfArea.

6Other Labor

laborCutting = 36 × ($20/60/30) = 36 × $0.0111 = $0.40
laborMeshCut = $20 / 120 = $0.17
laborGlue = ($20/30)/4 × 4 corners = $0.67

Cutting uses full perimeter (36"), unaffected by coating override. Mesh cut is fixed. Glue uses corners.

7Totals (CIN-101 A=10", Manual)

materialTotal = $11.99 + $0.95 + $3.28 + $4.80 = $21.02
laborTotal = ($0.40 + $0.17 + $0.67 + $14.69) × 1.15 = $15.93 × 1.15 = $18.32
total = $21.02 + $18.32 = $39.34
totalWaste = $39.34 × 1.05 = $41.31
listPrice (3×) = $41.31 × 3 = $123.93

5. Base Coat Across All Sizes (CIN-101, Manual)

Base coat cost for each CIN-101 size with the coating override applied (top face excluded):

A Size	H	W	Coating Override	Surface Area	Base Coat
7"	7	5.625	12.63"	8.42 sq ft	$3.37
8"	8	6.375	14.38"	9.58 sq ft	$3.83
9"	9	7.25	16.25"	10.83 sq ft	$4.33
10"	10	8	18.00"	12.00 sq ft	$4.80
11"	11	8.75	19.75"	13.17 sq ft	$5.27
12"	12	9.625	21.63"	14.42 sq ft	$5.77

6. Full Cost Breakdown (CIN-101 A=10")

Complete cost breakdown for a single 8-foot piece:

Cost Component	Amount
Foam	$11.99
Mesh	$0.95
Glue	$3.28
Base Coat	$4.80
Material Subtotal	$21.02
Labor: Cutting	$0.40
Labor: Mesh Cut	$0.17
Labor: Glue	$0.67
Labor: Coating (manual)	$14.69
Labor Subtotal (×1.15 tax)	$18.32
Total	$39.34
With Waste (×1.05)	$41.31
List Price (×3)	$123.93

7. Cornices vs Corbels vs Standard Trim

Attribute	Standard Trim	Cornices	Corbels
Mounting	Flat on wall	Wall-ceiling corner	Wall bracket (standalone)
Hidden faces	Back only (A side)	Back + top	Back + top
Side faces coated?	No (continuous run)	No (continuous run)	Yes (standalone)
Coating Override	Not needed (auto works)	Set: perim - H - W	Set: perim - H - topWidth
Coat Sides	OFF	OFF	ON
Coated length	H + 2W (auto)	H + W (override)	override value

Key point: The auto formula coatingLength = perimeter - aSize only subtracts the back face. It works for standard trim (flat on a wall). Both cornices and corbels have a second hidden face (top), so both use a coatingOverride to subtract it.

8. Cornice Catalog Overview

20 models × 6 sizes (A=7" through A=12") = 120 entries total.

Model	Coating Mode	Sizes	Notes
CIN-101	Manual	7, 8, 9, 10, 11, 12	Only manual-coated cornice model
CIN-102	Machine	7, 8, 9, 10, 11, 12	All use machine coating mode with laborCoatingMult = 8
CIN-103	Machine	7, 8, 9, 10, 11, 12
CIN-104	Machine	7, 8, 9, 10, 11, 12
CIN-105	Machine	7, 8, 9, 10, 11, 12
CIN-106	Machine	7, 8, 9, 10, 11, 12
CIN-108	Machine	7, 8, 9, 10, 11, 12
CIN-109	Machine	7, 8, 9, 10, 11, 12
CIN-110	Machine	7, 8, 9, 10, 11, 12
CIN-111	Machine	7, 8, 9, 10, 11, 12
CIN-112	Machine	7, 8, 9, 10, 11, 12
CIN-113	Machine	7, 8, 9, 10, 11, 12
CIN-114	Machine	7, 8, 9, 10, 11, 12
CIN-115	Machine	7, 8, 9, 10, 11, 12
CIN-116	Machine	7, 8, 9, 10, 11, 12
CIN-117	Machine	7, 8, 9, 10, 11, 12
CIN-118	Machine	7, 8, 9, 10, 11, 12
CIN-119	Machine	7, 8, 9, 10, 11, 12
CIN-120	Machine	7, 8, 9, 10, 11, 12
CIN-121	Machine	7, 8, 9, 10, 11, 12

9. Notes

How the override was applied

All 120 cornice entries have coatingOverride = perimeter - H - W set in the catalog. This uses the existing override mechanism (same as corbels) without changing the global formula. When a new cornice is added, set its coating override the same way.

Coat top option (planned)

Some cornices are installed at the top of a building without an eave, where the top face is exposed and needs coating. A future "coat top" toggle will allow including the W face when needed. Until then, clear the coatingOverride field for those entries to revert to the auto formula (which includes the top face).

Last updated: April 2026. See Formula Reference for complete formula documentation. See Corbel Guide for comparison.