Oikaisulaasti

Oikaisulaasti is a term used in Finnish construction referring to a leveling or correction plaster layer applied to a substrate to remediate irregularities before finishing plaster, wallpaper, or paint. The purpose is to bring a wall or ceiling to a flat, even plane, improving adhesion and aesthetics.

Typically a cementitious mixture, based on cement and aggregate (sand), sometimes with lime or gypsum to suit substrate and humidity. The exact recipe varies by project and climate, and may include plasticizers or shrinkage-reducing admixtures.

Substrate must be clean, sound, and properly prepared. The surface may be dampened; primer or bonding agent is used where appropriate. The material is mixed to a workable consistency and applied with a plaster trowel or steel rule, in one or more coats. Each coat is smoothed to obtain flatness; typical thickness per coat is small—often a few millimeters; for larger deviations, multiple passes are used. After application, the plaster cures under controlled conditions, avoiding rapid drying, freezing, or exposure to rain.

Used on rough concrete, masonry, or older plaster surfaces, to create a uniform base before final plaster, drywall finishing, or painting. It is not a structural repair and must be compatible with the subsequent finish layer.

Advantages include efficient leveling, improved finish quality, and reduced effort in subsequent finishing. Limitations include potential cracking if the substrate moves, the need for proper substrate preparation, and the requirement that the layer be compatible with the chosen finish.