How To Prepare Your Walls for Painting
How do you prepare a wall for painting?
The temptation is to pick up a brush and start. The finish, though, comes from what happens before that: clean the walls with sugar soap, fill the cracks and holes with Selleys Spakfilla Rapid, fill the gaps between the trim and the wall with Selleys No More Gaps Multipurpose, then paint. Four steps, and the whole job takes an afternoon plus drying time.
The step that most affects how long you wait is filling. Both fillers have drying times that depend on how thick the application is and what kind of paint is going over them — and getting those wrong is what causes paint to crack over a joint or sink into a patch weeks later.
What you need
- Selleys Spakfilla Rapid
- Selleys No More Gaps Multipurpose and a caulking gun
- Sugar Soap Original concentrate
- Flexible filling blade
- Fine sandpaper and a sanding block
- Soft clean cloth
- Drop sheet
- Hammer
Step 1 — Clean the area
Lay the drop sheet down in the area you will be working — worth doing even if you are careful, simply so you are not stopping to wipe the floor.
Use the sandpaper and sanding block to remove uneven surfaces and crumbling paint flakes, and remove any nails or pins from the wall with the hammer.
Dilute half a cup of Selleys Original Sugar Soap into a full bucket (10 L) of water. Soak a soft clean cloth in the solution, wring off the excess and clean the walls. If you have sensitive skin, use gloves — the product has a pH of around 11 and causes serious eye irritation.
Check which sugar soap you have bought before you measure. The 10 litre dilution is the rate given on the data sheet for Original Sugar Soap Super Concentrate (1 L bottle, makes up to 80 litres). If you have bought Selleys Original Sugar Soap (750 mL bottle, makes up to 30 litres), its data sheet calls for half a cup into half a bucket — 5 litres — of water. Getting these the wrong way round leaves you with a solution that is either too weak to shift the grime or stronger than the job needs.
Either product can be used neat on stubborn or in-ground marks with a non-scratch scouring sponge. On walls and ceilings there is no need to rinse. Wipe it off aluminium and brass immediately, and rinse it off glass before it dries.
Step 2 — Fill any cracks or holes
Fill cracks, scratches, dents, and nail or screw holes before you go any further. Apply a small amount of Spakfilla Rapid to your filling blade and draw it across each imperfection. Skim the filled areas lightly in both directions a few times to make sure there are no air bubbles, then remove the excess by drawing the blade down the surface firmly.
Allow the first application to dry for 30 minutes, then sand lightly and remove any dust with a soft clean cloth.
That 30 minutes is the figure for thin applications only. The Spakfilla Rapid data sheet gives 30 minutes for less than 2 mm and 24 hours for more than 2 mm, and asks for 24 hours before oil-based paints. A nail hole is done in half an hour; a deeper dent is an overnight job. Expect longer drying times in cold or humid conditions.
Spakfilla Rapid is virtually non-shrinking, so there is no need to overfill. It is moisture and mould resistant and easy to sand. Before painting, clean off dust and loose filler particles using Selleys Sugar Soap or Selleys Super Kleen.
Its limitations: do not use it on plastic, metal, or exterior timber likely to swell or shrink as it absorbs water. Avoid using it below 5°C or in wet conditions. Do not nail into it, and do not use it for load-bearing applications or anywhere load or compression occurs — behind a door where the knob touches the wall, for instance, the filler may be crushed. Where movement occurs, use No More Gaps.
Step 3 — Fill the gaps
Next, fill the gaps between skirting boards or architraves and the wall with No More Gaps Multipurpose. Use a dry clean cloth to make sure the surface is dry and free of dust.
- Cut the tip of the cartridge, then cut the nozzle at a 45 degree angle.
- Attach the cartridge to the caulking gun and the nozzle to the cartridge.
- Tilting the gun at a 45 degree angle, dispense the product into the gap, making sure enough gap filler is forced into the gap rather than laid across the surface.
- Use a wet finger to smooth over your work, and clean up any excess with a damp cloth.
Then wait before painting — and this is where the page and the technical data sheet differ. The guide says to allow 30 minutes for water-based paint or 2 hours for ceiling or oil-based paints. The No More Gaps Interior Multipurpose data sheet is more conservative: around 30 minutes before water-based paint, but 24 to 48 hours before painting with oil-based paints, with longer drying still required for flat and ceiling paints because they are highly filled, contain less binder, and flex less as the sealant dries. Use the 24–48 hour figure. Painting an oil-based or ceiling paint over a gap filler that has not finished drying is precisely what causes the hairline cracking along a skirting line that people blame on the filler.
To avoid paint cracking, apply the product to gaps no larger than 5 mm deep and 10 mm wide, at temperatures above 10°C, and avoid applying the paint too thickly.
No More Gaps Interior Multipurpose is water-based with a skin time of 20 minutes, a movement capability of ±15% (ISO 9046) and elongation at break of over 300%. It is not suitable for permanent water immersion or constantly damp areas, and it is not for gaps between tongue-and-groove boards or weatherboards — use No More Gaps Exterior for those. Where there is excessive movement or frequent water contact, a silicone sealant is the right choice.
Step 4 — Paint
Paint the wall the colour of your choice. Two coats is ample, but use an undercoat if you are painting a light colour over a dark one.
Handy tips
- Put a drop sheet down, in case you spill anything or simply do not want to risk the floor.
- To minimise sanding and get a perfect finish, tool or spread filler to a feathered edge as you apply it. Feathering with the blade takes seconds; sanding a hard ridge back later takes far longer.
- For a neat, clean finish, tape both sides of the gap before applying gap filler, and pull the tape before the product skins.
- Before you start on the wall with No More Gaps Multipurpose, extrude a small amount onto a piece of scrap material to make sure you have a smooth continuous flow.
Common questions about preparing walls for painting
How much sugar soap goes in the bucket?
Half a cup into a full 10 litre bucket for the Super Concentrate, or half a cup into half a bucket (5 litres) for Original Sugar Soap. Check the bottle you have.
Do I need to rinse the walls after washing?
Not on walls and ceilings. Rinse glass before the product dries and wipe it straight off aluminium and brass.
How long does Spakfilla Rapid take to dry?
Thirty minutes for applications under 2 mm, 24 hours for anything over 2 mm. Longer in cold or humid conditions.
Do I need to overfill the holes?
No. Spakfilla Rapid is virtually non-shrinking, so there is no need to overfill. Press it in firmly and smooth it off.
Can I use Spakfilla Rapid behind a door where the handle hits the wall?
No. It should not be used where load or compression occurs, because it may be crushed. Use Spakfilla Heavy Duty for that hole, and fit a door stop.
How long before I can paint over the gap filler?
Around 30 minutes for water-based paint. For oil-based paints the data sheet asks for 24 to 48 hours, and flat and ceiling paints need longer still.
How big a gap can I fill and paint over?
No larger than 5 mm deep and 10 mm wide, applied at temperatures above 10°C, to avoid the paint cracking.
How do I smooth the gap filler?
A wet finger, then clean up any excess with a damp cloth. Taping both sides of the gap first gives a crisper line.
Do I need an undercoat?
Two coats is ample for most jobs, but use an undercoat if you are painting a light colour over a dark one.
Why does my paint keep cracking along the skirting board?
Usually a gap filler that was painted before it finished drying, or one applied too deep or too wide. Keep the gap within 5 mm deep and 10 mm wide, work above 10°C, and respect the 24–48 hour wait for oil-based and ceiling paints.
Can I use these products outside?
Not these ones. No More Gaps Interior Multipurpose is not for weatherboards or tongue-and-groove boards, and Spakfilla Rapid should not be used on exterior timber likely to swell or shrink with water. Use the exterior products instead.
What do I clean the dust off with before painting?
A soft clean cloth, and for filler dust and loose particles, Selleys Sugar Soap or Selleys Super Kleen.
How much sugar soap goes in the bucket?
Half a cup into a full 10 litre bucket for the Super Concentrate, or half a cup into half a bucket (5 litres) for Original Sugar Soap. Check the bottle you have.
Do I need to rinse the walls after washing?
Not on walls and ceilings. Rinse glass before the product dries and wipe it straight off aluminium and brass.
How long does Spakfilla Rapid take to dry?
Thirty minutes for applications under 2 mm, 24 hours for anything over 2 mm. Longer in cold or humid conditions.
Do I need to overfill the holes?
No. Spakfilla Rapid is virtually non-shrinking, so there is no need to overfill. Press it in firmly and smooth it off.
Can I use Spakfilla Rapid behind a door where the handle hits the wall?
No. It should not be used where load or compression occurs, because it may be crushed. Use Spakfilla Heavy Duty for that hole, and fit a door stop.
How long before I can paint over the gap filler?
Around 30 minutes for water-based paint. For oil-based paints the data sheet asks for 24 to 48 hours, and flat and ceiling paints need longer still.
How big a gap can I fill and paint over?
No larger than 5 mm deep and 10 mm wide, applied at temperatures above 10°C, to avoid the paint cracking.
How do I smooth the gap filler?
A wet finger, then clean up any excess with a damp cloth. Taping both sides of the gap first gives a crisper line.
Do I need an undercoat?
Two coats is ample for most jobs, but use an undercoat if you are painting a light colour over a dark one.
Why does my paint keep cracking along the skirting board?
Usually a gap filler that was painted before it finished drying, or one applied too deep or too wide. Keep the gap within 5 mm deep and 10 mm wide, work above 10°C, and respect the 24–48 hour wait for oil-based and ceiling paints.
Can I use these products outside?
Not these ones. No More Gaps Interior Multipurpose is not for weatherboards or tongue-and-groove boards, and Spakfilla Rapid should not be used on exterior timber likely to swell or shrink with water. Use the exterior products instead.
What do I clean the dust off with before painting?
A soft clean cloth, and for filler dust and loose particles, Selleys Sugar Soap or Selleys Super Kleen.