Cut trench mesh to 1590mm lengths. Join using cable ties. Mix concrete and spread in formwork until half full. Put trench mesh in concrete and continue filling until you reach top of formwork. Put a screed on formwork and, slowly moving back in a side-to-side motion, level concrete with top of formwork. Smooth off using wood float. Leave to set for 24 hours, then remove formwork.
Lay out 2 rows of 4 blocks along length of your slab, leaving a 10mm gap between both blocks and rows. Mark outside edge of blocks on slab.
Mix 6 parts brickie’s sand and 1 part cement. Add water until mixture is stiff but workable. Using brickie’s trowel, lay 2 rows of mortar on inside of marked line to suit width of blocks. Lay first block to meet your marked line and make level in both directions.
Butter vertical end of next block with mortar and place against first until you have a 10mm gap between them. Tap down until level with first block and in line along its length. Scrape off excess mortar. Continue in this way until you have laid 4 blocks. Check again that whole row is level and in line. Lay another row next to first, leaving a 10mm gap in-between. Lay a second course on top of first, starting with a block laid across 2 rows at end.
Spread mortar along top of second course and lay block caps across width of bench so they are level. Make sure all mortar joins on bench are filled and there are no gaps.
Mix acrylic render following manufacturer’s instructions. Load onto plasterer’s hawk and use steel float to evenly spread render over blocks to a consistent thickness. Let set for 30 minutes.
When render is firm but not hard, use a fine damp sponge to smooth off surface. Leave render to cure for 7 days.
Apply undercoat and let dry. Apply 2 coats of low sheen exterior acrylic in your selected colour, allowing to dry between coats.