How to Prepare a Wall for Mural Printing

Almost every enquiry we get asks what the artwork will look like. Very few ask what the surface needs to be like before we turn up - and that is the part that decides whether a mural looks sharp in five years or starts letting go in one. Here is what we actually check, in the order we check it, and the cases where we tell people to fix something first.

It has to be dry, properly dry

UV ink cures under light rather than drying out, so our side of the job is quick. The substrate underneath is the slow part. Fresh plaster and new render hold water long after they look and feel dry, and anything printed onto them is bonded to a surface that is still moving and still releasing moisture. If your room has been skimmed recently, let it dry fully and get a mist coat on it before you book us. How long that takes depends on the thickness, the season and how well the room breathes, so we would rather look at it than guess a date over email.

What the existing paint is doing matters more than its colour

We print onto the coating that is already there, so the ink is only ever as secure as that coating. The things we look for:

• Matt emulsion in sound condition - the easiest case, and most interiors are this.
• Silk, satin or gloss - slick and low-key, so it usually wants a light abrade and a primer coat first.
• Flaking, chalking or powdery paint - if it rubs off on your hand it will take the artwork with it eventually. That needs scraping back and re-priming.
• Old distemper or limewash - common in period London properties and rarely a sound base for anything.

None of that is dramatic work. It is normal decorating, and any decorator can do it. We just would rather it happened before printing day than after.

Texture is welcome; loose material is not

Brick, block, board-marked concrete and rough render are exactly where direct printing earns its keep, because the image follows the surface instead of being stretched over it. The distinction is between texture, which is fine, and material that is not attached, which is not. Sandy mortar joints, efflorescence, spalling brick faces and dusty new blockwork all need brushing down and, on very porous surfaces, sealing. We cover which substrates behave how on our surfaces page.

Worth being straight about the trade-off: on a deeply textured surface the artwork picks up that relief visually. Fine typography and small detail lose crispness in the shadows of the mortar. Bold imagery thrives on it. If your design is text-led, a smooth substrate is the better home for it.

The jobs we turn down

We would rather lose a booking than print onto something that is going to fail. Genuine red flags:

• Damp. Rising, penetrating or condensation-driven - it all ends the same way. Printing over damp seals nothing and hides a problem that is still spreading. Fix the cause, let the surface dry, then call us.
• Salt staining. White crystalline bloom means moisture is moving through the masonry and depositing minerals at the face. That face is not stable.
• Live cracks. A filled hairline crack is fine. A crack that has been filled twice and come back is structural, and no coating solves it.
• Blown or hollow plaster. Tap it. If it sounds drummy, the plaster has parted from the substrate behind and the whole patch will come off in time.

Existing wallpaper: usually strip it

We can print onto sound, flat, well-stuck paper, and occasionally that is the sensible call. But the print then depends entirely on that paper's bond to the substrate, and paper edges lift long before ink does. If the paper is vinyl-faced, embossed or already curling at the seams, take it off and make good. It is the one bit of prep that most often gets skipped and most often causes regret.

How much of the surface we can actually reach

Our printer runs on the floor and works upward, so there is a band at the very bottom and top it cannot reach. In practice that is roughly 36-45cm at the base, around 25cm at the top of its travel, and 23-32cm at either side. Maximum print height is 4.1m, and there is no width limit - the machine indexes along and the image continues seamlessly, with no panel joins.

The base margin sounds like a problem and almost never is: skirting, a dado, a run of desks or a bench seat usually occupies it anyway, and designs get planned around it from the start. What it does mean is that nobody should promise you coverage from skirting to ceiling, and if someone does, ask them how. Our portfolio shows how the reachable area gets composed deliberately rather than apologised for.

What we need on the day

Clear floor space in front of the print area so the ma