Finishes
Skimlite calculator
Skimlite is a gypsum skim plaster used across Zimbabwe to give walls and ceilings a smooth finish before painting. This calculator works out how many 20 kg bags you need from the area and the thickness you will apply.
What you need
This calculator works out the figures in your browser, which needs JavaScript switched on. The method below shows how to work it out by hand.
Estimates for planning and budgeting. Real quantities depend on the site and the workmanship, so check with your builder before you order.
Thickness drives everything. A typical application is about 3 mm on plasterboard ceilings and partitions, and 5 to 10 mm on sand and cement plaster, depending on how even the plaster is. A 20 kg bag covers about 12 m² at 3 mm, but only about 4 m² at 10 mm, so a rough wall can need three times the bags of a smooth one.
The coverage figures are per 20 kg bag at each thickness: 3 mm, 12 m²; 4 mm, 10 m²; 5 mm, 8 m²; 6 mm, 6.5 m²; 7 mm, 5.5 m²; 8 mm, 5 m²; 9 mm, 4.5 m²; 10 mm, 4 m².
How it is worked out
- Coverage per 20 kg bag is read from the table for the thickness chosen.
- Bags = area ÷ coverage per bag, plus the waste allowance, rounded up to whole bags.
What it assumes
- Coverage figures are for typical application by a competent plasterer; a first-timer uses more.
- Primers and joint tape for plasterboard are not included.
Common questions
How much does a bag of Skimlite cover?
A 20 kg bag covers about 12 m² at 3 mm, 8 m² at 5 mm and 4 m² at 10 mm.
How thick should skim be on plaster?
Usually 5 to 10 mm on sand and cement plaster, depending on how flat the plaster is. On plasterboard, about 3 mm is typical.
Can I paint straight onto Skimlite?
Once it has dried out fully, apply a suitable primer or sealer first, then paint. Painting too soon traps moisture.
Want exact quantities for your plan?
A calculator works one wall or one slab at a time. A bill of quantities works from your actual drawings and counts everything, which is what builders price against and what stops you buying twice.