Preparing walls properly is the part of the project no one sees afterwards — and yet it decides how the wall ultimately looks. Almost everything that bothers you about a paint job happens before the first roller stroke: an unsanded filler patch, dust on the surface, a substrate that soaks up paint unevenly. The good news: all of these mistakes are avoidable, and in a single morning.
What you can no longer fix once it's dry
Unevenness gets bigger under paint, not smaller
A drill hole you overlook before painting is, afterwards, a drill hole with paint in it. Matte wall paint hides little, and raking light shows every edge. Anything you smooth beforehand is something you won't have to explain later.
Adhesion happens at the substrate, not in the paint
Paint holds onto whatever lies beneath it. If there's dust, grease or a chalking old coat of paint underneath, even the best quality won't help. The substrate needs to be clean, dry, load-bearing and free of loose particles — that's the condition re-box sets for the substrate.
Where the time really goes
Most people underestimate the preparation and overestimate the painting itself. Realistically, a room breaks down like this: one morning clearing, taping, patching and sanding — and one afternoon rolling. Cut the first half short, and you'll only lengthen the second.
Why the order is fixed
Clear the room, tape, patch, sand, remove dust, prime — in this order and no other. Fill before you've taped, and you're taping over dust. Prime before you've sanded, and you'll just sand the primer off again. The order isn't a ritual — it's simply the shortest route.
Reading the substrate: four wall types, four answers
Fresh plaster
New plaster absorbs strongly and unevenly. Paint sinks in instantly in some spots and not in others, drying blotchy. Here, priming is almost always worth it: it ensures even drying and noticeably lowers consumption.
Woodchip wallpaper and wallpaper
Firmly attached woodchip wallpaper can be painted over directly. Checking means pressing at the edges and seams with your thumb. Where strips are lifting or bubbles form, the wallpaper has to come off before you continue — how to do that without a mess is covered in Removing wallpaper properly – clean & quick.
Old paintwork
An intact old coat of paint is the best case: wipe clean, patch, paint. It gets tricky when white chalk comes off on the cloth as you wipe. That means the old coat is no longer binding and needs a primer, otherwise the new coat will pull the old layer along with it. The second likely source of trouble is old latex paint in kitchens and bathrooms — glossy, dense and barely absorbent.
Very smooth or patchy surfaces
Smooth concrete ceilings, old oil-based skirtings and water stains all have one thing in common: they take paint differently to the surface next to them. You treat these spots individually beforehand, rather than hoping the second coat will sort it out.
The materials list for one room
For protecting and masking
- Masking film 2 x 25 m for the floor and any furniture staying in the centre of the room
- tesa® Precision Mask – precision masking tape for trim, frames and switches
- Nitrile gloves, because filler and primer will end up on your hands
For repairing and smoothing
- repair filler 1 kg with strong filling power for cracks, drill holes and edges
- double spring filling knife for applying and smoothing with a single tool
- sanding block – grit 120 for dried filler spots
For cleaning and priming
- microfibre cloth 40x42 cm for the final pass before painting
- A bucket of clear water, no additives, so no surfactant residue is left behind
- Primer as needed — what suits which surface is explained in Primer & Preparation
Clear the room and mask up before you touch the wall
1. Empty the room instead of just shifting furniture
Anything that can leave, should leave. The rest moves to the centre and gets covered in film. You need a good metre of clearance all around the wall — otherwise you'll be squeezed into corners and reaching over furniture. Curtain rails and picture rails come down too: painting around them takes longer than mounting them twice.
2. Mask trim, switches and frames
Press the tape firmly onto the edge with your thumb, in short sections and without folds. Every air bubble under the tape is a spot where paint will bleed through later. For clean edges, see Masking correctly without paint bleed – our best tips.
3. Remove nails, wall plugs and hooks
Go over the wall systematically and pull out anything that shouldn't stay. Wall plugs come out best with a screw and a pair of pliers. Leave the holes open — they're dealt with in the next step.
Repairing, sanding, removing dust
4. Fill holes and cracks
Draw the filler in across the direction of the crack, then smooth it off lengthways. Two thin layers are better than one thick one: thick layers shrink as they dry and leave a dip exactly where everything was level a moment ago. For cracks, score them open slightly first so the filler has room to grip.
5. Let it dry, then sand
Only sand once the area is completely dry. Work the edge of the filled spot into the wall with circular motions until you can no longer feel the transition with the flat of your hand. What your hand feels, your eye will see later too.
6. Get rid of the dust — properly
Sanding dust is the mistake you don't spot beforehand: the wall looks clean, yet the paint still rolls on dull and adheres poorly. Sweep it off dry first, then go over it with a damp cloth — from top to bottom, so you don't spread it around again.
Priming: when it's necessary and when it isn't
The wet-finger test
Dab a little water onto the wall. If it's absorbed instantly and the spot turns dark, the surface is highly absorbent. If it beads off, the surface is sealed. In between lies the normal case, where you don't need any primer.
Where it's always worth it
On highly absorbent or fresh plaster, priming isn't a must, but it's the better choice: even drying, less consumption, a calmer finish. The material you save largely makes up for the extra effort.
When you can skip it
On an intact, non-chalking old coat of similar brightness, you don't need any. A clean wipe-down and thorough drying time are enough here. The same goes for firmly bonded woodchip wallpaper that's already been painted once — the benefit is minimal, since the surface already absorbs evenly, and that's exactly what matters.
No substitute for preparation
Primer evens out absorbency. It doesn't fill holes, doesn't smooth edges and doesn't bind dust still sitting on the wall. Use it as a shortcut, and you just push the problem up a layer.
Quantities: how much material a room actually uses
The surface area first, everything else after
Measure the perimeter of the room and multiply it by the ceiling height. A room measuring 4 by 3.5 metres has a perimeter of 15 metres, so at a height of 2.50 metres that's around 37 square metres of wall area. Add another 14 square metres for the ceiling, if it's being painted too.
How much paint that adds up to
Now match that surface area to a container size, always based on two coats: the large 10-litre container covers approx. 30–40 square metres, the medium 5-litre one approx. 15–20 square metres, and the small 2.5-litre one approx. 8–10 square metres. For wall and ceiling combined, our example room comes to 10 litres of re-box base one (matt) plus a medium container on top.
How much filler and tape you'll need
For the usual drill holes and small cracks in a room, the 1 kg container is generally enough. For tape, add up the length of all edges: skirting boards, frames, windows, switches — that quickly comes to 30 running metres, and any leftover roll will come in handy for the next room.
Frequently asked questions about wall preparation
Surface and priming
Do I always need to prime before painting?
No, priming isn't essential. It's worth doing on strongly absorbent or fresh plaster, since it ensures even drying and reduces paint consumption. On a sound existing coat, you can paint directly.
Can I paint over woodchip wallpaper without removing it?
Yes, as long as it's firmly attached and not bubbling. Check the seams and edges beforehand. If strips are coming loose, removing it is the more honest solution than painting over it.
Filling and sanding
How long does filler need to dry before I can sand it?
Until the spot is uniformly light and hard all the way through — the exact time is stated on the packaging. Thicker layers take noticeably longer than thin ones, which is the best reason to work in two passes.
Do I need to sand the entire wall?
No, just the repaired spots and their edges. You only sand the whole surface if the existing coat is rough, textured, or shows the pattern of an old roller.
Ordering and timing
When's the best time to order the paint?
Before you start preparing. Every shade is individually mixed after ordering, and delivery takes 3–5 working days from receipt of payment. That way the paint is ready when the wall is — not the other way round.
When can I use the room normally again?
In most cases after about 24 hours. Until then, keep the furniture in the middle of the room and air it out regularly. re-box wall paints are water-based, low-emission, and made in Germany.
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How to remove wallpaper properly – clean & quick