Preparing walls and ceilings before painting

Preparing walls and ceilings before painting

Preparing walls and ceilings for painting

As with all types of decorating, it is important to spend time in preparing the surface, thorough preparation will make the job easier and ensure a satisfactory finish — paint will highlight rather than disguise any flaws and irregularities in the under surface.

Ideally the walls should be prepared before fitting and finishing any coving, dado rail, frames, skirting board etc, however the walls should be painted only after these have been completed.

Any holes in the walls (including picture hook nails) which are no longer required should be filled during wall preparation, any holes which will be reused (such as for refixing a shelf etc) should be left.

The preparation of the walls will depend upon the existing finish and type of wall.

Existing finishes:

  • Wallpaper:

Some existing wallpapers can be painted without removing, in fact it can save time and avoids exposing the wall surface which may need a lot of work to bring up to a suitable smooth surface. Any loose wallpaper should be stuck down to the wall.

However, vinyl, washable or wipeable wallpapers do need to be removed; if in doubt, try painting a small area and see how well it adheres after allowing it to dry. Removing wallpaper is described on our ‘wallpaper stripping ‘ page. Make sure that all adhesive residue is removed from the wall surface and then treat as below for the type of wall exposed — i.e. old plasterboard or plaster.

  • Paint:

    Check to see if the paint is both non-water soluble and soundly bonded to the wall underneath. In older houses, whitewash or distemper may have been used and these are unsuitable for painting, pay particular attention to ceilings and areas at the top of the walls, near the ceiling where areas above an old picture rail may have been distempered.

    To test if the paint is water soluble, dampen a sponge or cloth and hold it against the paint surface for about 15 to 30 seconds. If then rubbing the sponge on the paint removes a large amount of the wall paint, then the paint will need to be removed, a very slight transfer of the paint colour to the sponge indicates that it should be all right for over painting.

    To remove most water soluble paints just requires cloths, plenty of water, and a lot of effort — it can be messy — don’t over soak the wall as this can damage some plasters and the wall will need to dry out before it will be possible to paint.

    Check if the existing paint is soundly bonded to the wall by looking for signs of flaking paint, all flaking paint needs to be removed.

    Glossy and semi-gloss paint should be lightly sanded to dull the surface so as to provide a key for the new paint.

  • Type of wall:

    • New plasterboard:

    New plasterboard needs little preparation but make sure that any filling of joints has been completed and the filler allowed sufficient time for curing.

    New plasterboard needs to be primed. The type of primer used will depend upon the type of paint to be used. For water-based paints (emulsions etc), apply the first coat using diluted paint (typically 1:4, water:paint — but check the instructions on the container).

  • Old plasterboard:

    Check for. and rectify any cracks, pits and bumps as described on our page for repairing plasterboard.

    Old plasterboard needs to be primed. The type of primer used will depend upon the type of paint to be used. For water-based paints (emulsions etc), apply the first coat using diluted paint (typically 1:4, water:paint — but check the instructions on the container).

  • New plasterwork:

    New plasterwork should always be given time to dry out, typically 4 weeks is a minimum period but depends, among other things, upon the thickness of plaster and the humidity in the room — check with your plasterer for their recommendation.

    Check for any bumps and hollows, generally new plasterwork will be fine but it pays to check. Rub down any high points.

    Once dried and smoothed, new plasterwork should be primed. The type of primer used will depend upon the type of paint to be used. For water-based paints (emulsions etc), apply the first coat using diluted paint (typically 1:4, water:paint — but check the instructions on the container).

  • Old plasterwork:

    Check for, and rectify any cracks, and loose plaster as described on our page for repairing plaster.

    Old plaster can become very powdery (often referred to as ‘blown’), small areas may be overcome by applying a coat of plaster sealer, however when it has become too bad in small areas it can be racked out and replastered. Where a whole wall (or walls) is ‘blown’, it is more time/cost effective to replaster the whole wall.

    Pay special attention to cracks between the plaster and door/ window frames and along the top of skirting boards, rake out any cracks and fill with a flexible decorator’s sealant.

    Once prepared, old plasterwork should be primed. The type of primer used will depend upon the type of paint to be used. For water-based paints (emulsions etc), apply the first coat using diluted paint (typically 1:4, water:paint — but check the instructions on the container).

    If there is any doubt about the suitability of painting a particular type of surface, test it by painting a small area in an inconspicuous place and leaving it to dry for a few days.


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