How many concrete blocks do you need?
Enter your walls, take out doors and windows, get block count, mortar bags and core fill.
How many concrete blocks do I need?
Multiply the wall's length by its height to get square feet, subtract doors and windows, then multiply by 1.125 — the number of standard 8 × 16 in blocks in a square foot, mortar joints included. A 20 ft by 8 ft wall is 160 square feet, or 180 blocks, before extra for cuts and breakage.
What size is a standard concrete block?
A standard block is sold as 8 × 8 × 16 inches but measures 7⅝ × 7⅝ × 15⅝ inches; the missing ⅜ inch is the mortar joint. With the joint, each block covers 8 × 16 inches, so 1.125 blocks fill a square foot. Widths vary from 4 to 12 inches, but the face, and so the count, stays the same. In the UK the standard block is 440 × 215 mm, about 10 per square meter.
How much mortar do I need for concrete block?
Quikrete says an 80 lb bag of Mortar Mix lays up to 13 standard 8-inch blocks with ⅜-inch joints, so plan on about 8 bags per 100 blocks. In the UK, a 25 kg bag of multipurpose mortar lays about 20 blocks of 440 × 215 mm.
How much concrete does it take to fill block cores?
An 8-inch block's two cores hold about 0.27 cubic feet, so filling every core of 100 blocks takes about 27 cubic feet — one cubic yard. A 6-inch block holds about 0.22 cubic feet and a 12-inch block about 0.40. Many walls are filled only where there is vertical rebar; one core every 48 inches takes a sixth as much.
How many courses of block are in a wall?
Each course of standard block adds 8 inches, so an 8-foot wall is 12 courses high. Along the wall, each 16 inches is one block, so a 20-foot wall is 15 blocks long.
How many extra blocks should I buy?
About 5% covers breakage and a few cut blocks on a simple straight wall. Allow closer to 10% for walls with corners, openings or a lot of cutting.