A cover slab is a flat plate placed on top of a wall, column, beam, foundation or sheet pile to spread loads, protect the element or provide a finish. Depending on the application it is made of concrete, natural stone, cast stone, timber or metal and may be structural or purely architectural.
Functions of a cover slab
A cover slab can serve several roles:
- Spreading point loads — for example under a column resting on a foundation
- Capping a wall — protecting masonry from rain and frost
- Tying elements together — joining adjacent beams or piles
- Visual termination — top finishing of a garden wall, chimney or parapet
- Protection — covering sheet piles or retaining walls against water and erosion
Types of cover slab
- Concrete cover slab — cast in situ or precast, on ground beams, pile caps or walls
- Natural-stone cover slab — on garden walls, monumental façades and grave monuments
- Aluminium or zinc cover slab — capping for parapets and attic walls on flat roofs
- Timber cover slab — in timber construction, as a spreading plate under bolts
- Steel cover slab — on sheet pile walls and pier heads
Structural cover slab
In reinforced concrete a cover slab is often used as a pile cap widening: a square concrete block at the top of a pile on which a column or beam rests. The term also describes the top layer of a precast element, such as the structural topping on a half-slab or hollow-core floor.
Architectural cover slab
In classical architecture the abacus above a capital is a particular type of cover slab, separating the architrave from the column. On garden walls a cover slab is both an aesthetic crown and a practical moisture barrier.
Related terms
Want to learn more about construction terms? Visit the knowledge base at Fred’s DIY Plans.