deklaag

Deklaag, meaning "cover layer" in Dutch, is a term used to describe the uppermost layer that covers an underlying substrate in various disciplines. It can be natural or artificial and serves protective, functional, or aesthetic roles. In geology and soil science, the deklaag denotes the surface layer or a distinct stratigraphic unit that overlies deeper deposits; its composition can range from loose sediments to consolidated soils and can influence moisture retention, temperature, erosion, and vegetation establishment.

In civil engineering and construction, the deklaag is commonly the surface layer of a pavement or road, providing wear resistance, friction, and weather protection. It rests on an onderlaag (subbase or base) that supplies structural support. The material choice—such as asphalt, concrete, or surfacing aggregates—depends on traffic, climate, and maintenance needs.

In environmental engineering and land management, deklaag is used to describe a sealing or insulating top layer, for example a cap on landfills to minimize infiltration and gas migration, or a mulch layer in landscaping to conserve soil moisture and reduce weed growth. In horticulture, a shallow deklaag of mulch or organic matter can protect soil and influence the microclimate.

Originating from dek (cover) and laag (layer), the term is used across disciplines to denote any upper covering layer. Related terms include onderlaag (underlayer) and stratigraphic horizons in geology.