Stone veneer flats = wall area − openings − (corner feet × 0.67 sq ft), plus 10% for cuts. A 20 × 8 ft wall with 30 sq ft of windows and doors and two 8 ft outside corners is 130 sq ft net, so it needs 131 sq ft of flats and 17.6 linear feet of corner stone. The calculator also counts lath, veneer mortar and pointing mortar, and checks the stone's weight and thickness against the published limits.
How the stone veneer is calculated
Stone is sold in two pieces: flats by the square foot and corners by the linear foot. A corner piece wraps two faces of the wall, so each foot of corner replaces some flat stone. Donley Brick's estimating guide puts it at 1 linear foot of corner = ⅔ sq ft of flats; Stoneyard says about 0.75. The calculator starts at 0.67 and lets you type your maker's figure.
Flats to order = (wall area − openings − corner ft × 0.67) × (1 + waste)
Corners to order = corner ft × (1 + waste)
Worked example: the wall is 20 × 8 = 160 sq ft, less 30 sq ft of openings, so 130 sq ft. Two corners of 8 ft are 16 linear feet, which replace 16 × 0.67 = 10.7 sq ft of flats, leaving 119.3 sq ft. With 10% extra that is 131.2 sq ft of flats and 17.6 linear feet of corners. If a box holds 10 sq ft of flats and 5 linear feet of corners, that is 14 boxes of flats and 4 of corners; enter your box coverage to see your own count.
Waste and openings
Stoneyard suggests 10% over on regular layouts and 12 to 15% where the pattern needs more cuts, such as ledgestone; use the 15% chip for those. It also notes that windows and doors typically take 15 to 25 percent of a house's wall area, so measure them rather than guess.
Mortar for stone veneer: scratch coat, setting bed and joints
Adhered veneer goes on in layers. On a frame wall the MVMA installation guide calls for lath and a scratch coat of Type N or S mortar at least ½ in thick; the setting bed then sticks the stone to it, and grouted joints get pointing mortar last. The IBC (1404.11) has a nominal ½ in scratch coat and a setting bed that ends at ⅜ in once the stone is pressed in. Quikrete Veneer Stone Mortar, a preblended Type S, covers about 17 sq ft per 80 lb bag as a ½ in scratch coat.
For the 130 sq ft wall with 10% extra that is 9 bags for the scratch coat (143 sq ft × ½ in ÷ 8.5), 7 for a ⅜ in setting bed and 2 for pointing at about 1 bag per 100 sq ft (Donley Brick), 18 bags in all. That is more than the distributors' rules of thumb: Stoneyard gives one 80 lb bag per 20 to 25 sq ft for the scratch coat and one per 30 to 40 sq ft for the setting bed, and Donley Brick gives 2 bags of Type S per 100 sq ft for both plus 1 for the joints. Treat the data-sheet figure as the safe order and return what you do not open. Dry-stack patterns need no pointing mortar. On block or concrete the scratch coat is optional, so turn the frame-wall switch off there.
How thick is stone veneer, and what does it weigh
An IAPMO evaluation report for a manufactured stone lists units from 1½ to 2⅝ in thick, with an average saturated weight of no more than 15 psf as ASTM C1670 requires. Typical manufactured stone is 8 to 12 psf. So with a ½ in scratch coat, a ⅜ in setting bed and 1½ in stone, the finished wall grows by 2⅜ in, which matters at window returns and door trim. On the example wall, 10 psf over 130 sq ft is 1,300 lb of stone. The calculator flags stone heavier than 15 psf or thicker than 2⅝ in so you check the maker's evaluation report.
Stone veneer dimensions
Pieces vary in face size, but adhered units are small: the IBC (1404.11.2) limits the heavier ones to 48 in in any direction and 9 sq ft of face. Boxes state their coverage, and that number, not the piece size, is what turns square feet into boxes. Enter it in the "Flats per box" and "Corners per box" fields.
Lath and water barrier
The MVMA guide wants two layers of water-resistive barrier over wood sheathing, lath lapped at least 1 in at vertical seams and ½ in at horizontal ones, and fasteners every 7 in on studs no more than 16 in apart. Donley Brick counts a sheet of wire mesh at 16 sq ft, which the calculator uses.
Before and after the stone
Blocks behind the veneer need mortar, and the rest of the house may be stucco or siding. Work out the wall's area in the square footage calculator, or the block count in the cinder block calculator. See the brick calculator for thin brick. Every block, brick and concrete tool is in the concrete and masonry calculators.