How to Repair Cracks in Walls
Often, the initial joy from a fresh renovation is unfortunately overshadowed by defects that only appear some time after all work is completed and the room has been cleaned. Many hidden flaws depend not only on the professional skill of the person who performed the work but also on the quality of materials used.
This article discusses repairing cracks in walls — one of the most common problems found in newly plastered walls. The root cause lies in the fact that plasterers often rush to finish their job and apply cement or gypsum plaster in a thick layer in one or two passes, rather than applying thin layers over several passes.
As a result, uneven evaporation of large volumes of moisture from the plaster mass disrupts adhesion to the wall. Consequently, cracks appear on walls, which may damage the final finishing layer or even tear off wallpaper applied over the plaster.
What to do if you've inherited an apartment with already cracked walls, or if you did the renovation yourself and made a mistake in layer thickness during plaster application? A step-by-step guide is provided below.
Step-by-Step Crack Repair
First, inspect the walls and assess the scale of the problem. With high probability, cracks that are less than 2/3 of the wall’s total height can be reliably repaired. These cracks typically do not recur. Pay special attention to external and internal corners — cracks in these areas are particularly difficult to fix. This is why we begin our solution description exactly with these areas.
Repair starts with cleaning the plaster area around the damaged section. The cleaned area should be slightly larger than the crack itself. For both external and internal corners, create a rectangular protrusion of cleaned plaster.
After cleaning, apply a pre-prepared plaster mix. For best results, use high-strength plaster mixes rather than a simple sand and cement mix. The reason is that construction plaster mixes already contain plasticizers and other additives during production, enhancing resistance to cracking, dynamic loads, and more.
Apply plaster only from bottom to top — never in any other direction. Otherwise, each new layer may detach the previous one. It’s easiest to apply using a special polyurethane trowel. For corner areas, attach a wooden batten or metal profile before application to maintain a clean break line.
For flat wall surfaces (excluding corners), install a small formwork only if the crack length exceeds 2/3 of the wall’s height. Lightly moisten the crack with water before applying plaster — this helps improve adhesion.
As in standard plastering, apply the mix in three stages: first, a thin base coat (since plaster adheres much better to itself than to bare wall); second, a main leveling layer; and third, a final finishing layer, which must be sanded and spackled after drying. Remove formwork only after the plaster has fully dried.
