Patio Material Estimator

Layer 1 — MOT Type 1 sub-base

Excavate to the required depth (sub-base + mortar bed + slab thickness + 20–30mm below finished level). Lay MOT Type 1 in layers of no more than 100mm and compact each layer with a wacker plate. A poorly compacted sub-base is the most common cause of sunken, rocking patios. Allow 20% extra material to account for compaction.

Layer 2 — Full mortar bed

Mix sharp sand and cement in a 6:1 ratio (6 parts sharp sand, 1 part cement) to a semi-dry consistency — it should hold its shape when squeezed but crumble if dropped. Spread at 40mm depth across the full area and screed level. Lay slabs immediately and tap down firmly with a rubber mallet. Never use building sand — it is too soft and will produce a weak bed.

Cover the full underside of every slab — no voids. Voids hold water and cause frost damage. Check levels constantly with a spirit level and allow a 1:80 fall away from the house for drainage.

Layer 4 — Jointing

Brush-in compound: Allow the mortar bed to cure for at least 24 hours. Brush dry jointing compound across the surface and into gaps. Add water as directed — usually a light spray — and allow to set. Fast, clean and resilient. Excess wipes off easily. Suitable for most domestic patios.

Traditional mortar pointing: Mix 3:1 sharp sand and cement to a stiff but workable consistency. Press firmly into joints, tool to a neat finish and clean excess promptly. Do not point in frost or if rain is forecast within 24 hours. Do not use on natural stone without a suitable plasticiser — plain cement mortar will stain.