Haftputz

Haftputz is a term used in German-speaking plastering to describe an adhesion plaster layer. It is a preparatory coat applied to masonry or concrete to improve adhesion of subsequent plaster layers and to provide a mechanical key on rough or smooth substrates. It is not a decorative finish; it serves as a base.

Composition and variants: Traditionally lime-based putty with sand, sometimes cement-lime in modern practice; binder type influences breathability and crack behavior. The mix is chosen to be workable and to achieve a textured surface.

Application: The substrate is cleaned, dampened if necessary; Haftputz is applied in a thin layer, typically a few millimeters thick (roughly 2-6 mm depending on substrate and plaster system). The surface is rubbed, scratched, or combed to create a rough profile to which subsequent coats can adhere. In historic buildings, lime-based Haftputz is preferred to maintain moisture movement; in modern renovations, cementitious Haftputz may be used for rapid setting.

Function: It provides adhesion for subsequent coats (e.g., base render, finishing plasters); it helps to prevent delamination on porous or uneven substrates; it can also help to equalize the substrate.

Historic context: Common in Europe in traditional lime plaster systems; used on brick, stone, or concrete substrates; often part of a multi-coat plaster system.