Wall crack filling and painting

A professional painter and decorator doesn't just "hide" a crack with paint; they stabilise the area to ensure the repair lasts. This guide covers the costs, timelines, and technical steps involved in restoring your walls to a smooth, seamless finish.

What Does the Work Involve?

• Initial Assessment: Inspecting the crack's width, depth, and pattern to determine if it is a simple cosmetic issue or a sign of structural movement.
• Preparation: Raking out the crack to remove loose debris and widening it slightly to allow the filler to bond effectively.
• Stabilisation: Applying scrim tape (fibreglass mesh) or flexible bridging tape over larger or "live" cracks to prevent future reopening.
• Filling: Applying high-quality interior filler in layers, often using a "two-hit" method with a base coat and a fine finishing coat.
• Sanding & Priming: Sanding the area flush with the wall and applying a primer-sealer to prevent the filler from "sucking" the moisture out of the paint.
• Topcoating: Applying at least two coats of paint to the repaired area, often feathering the edges or repainting the entire wall to ensure an invisible finish.

Typical Costs

Prices for crack repairs vary depending on the extent of the damage and whether you require a local patch or a full-room repaint. The following figures represent realistic 2025/26 UK averages including VAT.

The primary cost drivers are the condition of the existing plaster and the quality of the paint chosen. Repainting a whole wall is usually necessary to avoid "flashing," where the repaired patch is visible under certain lighting.

How Long Does It Take?

• Small Cosmetic Cracks: 3–5 hours of active work, though this is usually spread over two visits to allow for drying.
• Full Room (Prep & Paint): 2–3 days, depending on the number of cracks and the drying time required for the filler.
• Stairwells or High Ceilings: 3–4 days, accounting for the setup of safe access equipment and additional surface area.

DIY or Professional?

Fine hairline cracks (less than 1mm) are well within the reach of a confident DIYer with a steady hand and a sanding block. However, if the cracks are wider than a pound coin’s thickness or appear around door frames and windows, a professional is recommended.

Note: Professional decorators use trade-grade fillers and "dustless" sanding systems, which provide a significantly smoother finish and keep your home cleaner than standard DIY methods.

If you suspect structural issues—such as cracks that are wider at the top than the bottom or diagonal cracks—you must consult a structural engineer before any decorative work begins.

Choosing the Right Tradesperson

• Check Qualifications: Look for NVQ Level 2 or 3 in Painting and Decorating or membership in the Painting and Decorating Association (PDA).
• Insurance: Ensure they hold valid Public Liability Insurance (minimum £1 million).
• References: Ask for photos of previous "before and after" repair work to see how well they blend their patches.
• Red Flags: Avoid tradespeople who suggest filling cracks with silicone (which cannot be painted) or those who don't mention sanding and priming.

Questions to ask:

• "Will you use mesh tape to bridge the cracks, or just filler?"
• "Do you use a dust extraction system while sanding?"
• "Will you repaint the entire wall to ensure the repair is invisible?"

UK Regulations

While standard internal painting and decorating do not usually fall under Building Regulations, there are specific standards to keep in mind:

• Health and Safety: Work at height must comply with the Work at Height Regulations 2005.
• Lead Paint: In homes built before 1960, decorators must follow safe working practices to manage the risk of lead-based paint dust.
• Building Regs (Part A): If cracks are structural, repairs may need to comply with Part A (Structure) of the Building Regulations, involving a surveyor.

Common Problems

• Flashing: This occurs when the repaired area has a different sheen or texture than the rest of the wall. This is avoided by proper priming and repainting the full wall.
• Re-cracking: Using "rigid" filler in a "live" crack (one that moves with the seasons) will cause it to fail. Flexible fillers or mesh tape are the solution.
• Dust Contamination: Sanding filler creates fine white dust that can settle throughout a home. Ensure your decorator uses a HEPA-filtered vacuum sander.
• Paint Peeling: If filler isn't sealed with a "mist coat" or primer, the paint may peel off in strips later.

Frequently Asked Questions

Why do cracks keep appearing in the same place?

This is usually due to structural movement or thermal expansion. If a crack isn't "bridged" with mesh tape or filled with a flexible compound, the natural movement of the building will simply reopen the stiff filler.

Do I need to repaint the whole room if I only have one crack?

Ideally, you should repaint the entire wall where the crack was located. Spot-painting often leaves a visible "patch" because the new paint will be cleaner and have a slightly different texture than the aged paint around it.

Can I just use Polyfilla and paint over it immediately?

No. Most fillers shrink as they dry and are highly absorbent. You must wait for it to dry completely, sand it smooth, and then apply a primer or mist coat before your final paint layers.

What is the difference between a hairline crack and a structural crack?

Hairline cracks are usually less than 1mm wide and are caused by plaster drying. Structural cracks are typically wider than 5mm, often diagonal, and may be visible on both the internal and external faces of the wall.

Is dustless sanding really dust-free?

It is about 95-99% effective. While it significantly reduces the mess compared to hand sanding, a small amount of fine dust is inevitable, so decorators will still use dust sheets to protect your furniture.