How to count the materials of a renovation repair

1. The area really redone

Multiply the total surface by the share you redo. Everything that follows is counted on that area.

2. Tiles, plaster, paint

Tiles: the area with waste divided by the area of a tile with its joint, rounded up; adhesive per m²; rubble from the thickness removed. Plaster: the area times the thickness times the consumption per m² per mm, with waste, divided by the weight of a bag. Paint: the area with waste times the coats, divided by the coverage; the primer the same way.

Worked example: 25 % of a tiled floor of 40 m²

Tiles of 40 × 40 cm, 3 mm joints, 10 % waste, adhesive 5 kg/m², 3 cm removed:

• Area redone 40 × 25 % = 10 m².
• Tile with joint 0.403 × 0.403 = 0.162409 m². Tiles: 10 × 1.10 / 0.162409 = 67.7, so 68.
• Adhesive 10 × 5 = 50 kg. Rubble 10 × 0.03 = 0.300 m³.

Plaster and paint

30 % of 50 m² of plaster 15 mm thick at 1.4 kg/m²/mm, 25 kg bags, 10 % waste; then 120 m² repainted with 2 coats at 10 m²/L, 1 primer coat, cans of 10 L:

• Plaster: 15 m², volume 15 × 0.015 = 0.225 m³; 15 × 15 × 1.4 = 315 kg, with waste 346.50 kg, so 14 bags.
• Paint: 132 m² with waste × 2 / 10 = 26.40 L; primer 13.20 L; 3 cans of paint.

What this does not cover

The count does not find the cause of the damage (damp, movement, cracks) or judge the substrate. A repair on a faulty substrate fails again: have the cause identified first.