Siding calculator: wall area, squares and pieces
One row per wall: its length, its height, the gable rise if it has one, and the openings you deduct. Enter your waste and the pieces per square read from the maker's chart: the calculation gives the squares and the pieces.
Pieces per square: the makers' charts (reference)
The pieces per square depend on the piece length and its exposure: read your product's row. These charts include no waste. HardiePlank's Canadian chart also gives the planks per m².
| Chart | Piece and exposure | Per square (100 sq ft) |
|---|---|---|
| HardiePlank (US) | 12 ft planks, 6 in exposure | 17 |
| LP SmartSide | 12 ft lap, 6-7/8 in reveal | 15 |
| LP SmartSide | 16 ft lap, 4-7/8 in reveal | 16 |
| LP SmartSide | 16 ft lap, 5-7/8 in reveal | 13 |
| LP SmartSide | 16 ft lap, 6-7/8 in reveal | 11 |
| LP SmartSide | 16 ft lap, 10-7/8 in reveal | 7 |
Sources: James Hardie, HardiePlank (US); LP SmartSide, coverage chart; James Hardie, HardiePlank (Canada)
Waste and openings: the VSI manual (reference)
The Vinyl Siding Institute's installation manual, cited as a guide: your waste and your deductions stay yours.
| VSI manual | |
|---|---|
| Waste | Add 10 percent to all material estimates |
| Openings | Windows and doors are usually not deducted |
| Square | 100 sq ft |
Source: VSI installation manual
Rainscreen: when Canada's NBC asks for a capillary break (reference)
In the US, the IRC asks for a way for water that gets past the siding to drain out. In Canada, NBC 2020 (9.27.2.2) asks for a capillary break, for example a drained and vented air space at least 9.5 mm deep over the whole wall, or drainage material at least 10 mm thick: below 3400 degree-days where the moisture index is over 0.90, at 3400 degree-days or more where it is over 1.00. Examples from its Table C-2:
| Place | Degree-days and index | Capillary break |
|---|---|---|
| Montreal (City Hall) | 4200 and 0.93 | Not required |
| Quebec City | 5080 and 1.0 | Not required |
| Sainte-Foy | Index 1.1 | Required |
| Percé | Index 1.2 | Required |
Sources: IRC 2021, R703.1; NBC 2020, 9.27.2.2; NBC 2020, Appendix C, Table C-2
Before you tear off or cover: the cautions (reference)
What the sources say, as read.
| Caution | |
|---|---|
| Lead paint | In homes built before 1978, work that disturbs paint is done by certified firms and renovators; exterior jobs disturbing 20 sq ft or less are exempt, demolition of painted surfaces never is |
| Asbestos | It usually cannot be identified by sight: do not saw, sand, scrape or drill old siding; a trained, accredited professional takes the samples |
| Clearances | Wood siding within 6 in of the ground, or 2 in of slabs and steps, must be naturally durable or treated |
Sources: EPA, RRP rule; EPA, asbestos; IRC 2021, R317.1
How it is calculated
Gross area = length x height + length x gable rise / 2 (the gable triangle). Net area = gross - openings deducted. Squares = net area x (1 + waste) / 100 sq ft. Pieces = squares x pieces per square, rounded up to the piece on the total. No waste, deduction or piece count comes filled in: they are yours and the chart's.
The whole job in MesuPro
Siding survey
Four elevations with walls and gables, openings, trim and soffits: squares and pieces per product, housewrap, furring and old siding hazards.
Feet and inches by default
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