What is a mortar bed?
A layer of semi-dry or wet mortar applied to the sub-base that beds paving slabs in place, either as full coverage or spot applications.
The mortar bed is the adhesive layer between the sub-base and paving slabs. It consists of a mix of sand and cement, typically applied in a semi-dry or wet state depending on site conditions and the paving method chosen. This layer bonds the slabs to the foundation below and provides a level surface for installation.
Two main application methods exist. Full bed mortar spreads across the entire underside of each slab, creating uniform support and load distribution. Dot-and-dab (or spot bed) mortar places small mounds or dabs at key points under the slab, typically at corners and the centre. Full bed generally offers better long-term stability and even weight support, particularly for high-traffic areas. Dot-and-dab uses less material and allows faster installation but requires careful placement to avoid future rocking or cracking.
The thickness and composition of the mortar bed affect drainage, durability, and how well slabs remain level over time. A properly built mortar bed prevents water pooling, movement, and premature failure of the paved surface. Contractors in patio installation and driveways select the bed method based on slab type, expected use, and local ground conditions.