Repair vs Replaster: How to Decide What Your Walls Really Need

Plaster problems range from minor hairline cracks to extensive areas of failed material. The right solution depends on the extent of the problem, the likely cause, and how important the room’s appearance is to you.

When Patching is the Right Answer

Patching works well when:

• The problem is genuinely isolated — less than 20% of the room’s surface area
• The cause has been identified and fixed (e.g. a leak that has now been repaired)
• The surrounding plaster is sound, not hollow, and level
• The room will be repainted (minor patching differences become invisible under emulsion)
• The walls will be wallpapered (texture differences become irrelevant)

When Replastering is the Better Value

Go for a full replaster when:

• More than 30–40% of the room has failed or is hollow when tapped
• The existing plaster is very old lime-on-lath that has reached the end of its life
• You are renovating the room anyway — the incremental cost of full replastering over patching is modest
• You want a perfectly flat, quality finish for high-gloss paint or light-reflective surfaces
• Damp has affected large areas of plaster

The 30% Rule

A useful rule of thumb: if more than 30% of a wall or ceiling surface is blown, cracked or damaged, the remaining 70% probably has underlying weaknesses too. At that point, replastering the whole surface is usually more cost-effective than extensive patching.

Costs: Patch vs Replaster

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