Planning to decorate a room

Decorating is cheap compared with most home projects, and the preparation is most of the work. The paint you buy is a small part of the cost of a poor finish. Work out the area, the coats and the trim first, and buy everything together, because tins from different batches can differ in colour.

This planner works for a bedroom or a whole house. Older homes need extra care for lead paint and for crumbling plaster.

Step 1: Measure the walls, ceiling and woodwork

Add up the area of the walls, take off large windows and doors, and measure the ceiling and the woodwork separately. A litre of emulsion covers roughly 12 square metres a coat on a smooth wall, less on rough plaster or a new surface.

Step 2: Work out the whole shopping list

The room calculator gives the paint for the walls, ceiling and woodwork, the primer and undercoat, the filler and caulk, the rollers and the tape. Buy the paint in one go.

Step 3: Prepare the surfaces

Wash, sand and fill, and caulk cracks at the woodwork. New plaster needs a mist coat of thinned emulsion before the first coat. In houses built before the 1960s, old paint may contain lead, so avoid dry sanding and follow safe practice.

Step 4: Wallpaper

Wallpaper is sold in rolls of a stated length, typically 10.05 m, and the number you need depends on the drop and the pattern repeat. Hang the first length plumb, and trim the edges neatly.

Step 5: Skirting boards and finishing

New skirting boards are measured by the perimeter less the doorways and bought in lengths such as 2.4 m. Paint them before fixing, if you can, and fill and caulk the joints afterwards.

Before you start

• The finish you want on walls, ceiling and woodwork.
• Whether any old paint could contain lead.
• Dust sheets and a way to ventilate the room.
• The same batch of paint, with a spare tin.
• Time for two coats and drying between them.

Mistakes that cost people money

• Skipping preparation, so the paint peels or shows every mark.
• Painting new plaster without a mist coat.
• Buying paint for one coat when the change needs two.
• Running out and matching the colour from a different batch.
• Dry sanding old paint in a house that may contain lead.

Frequently asked questions