Render Cost Planning Guide
1) Define the scope and measure correctly
Accurate measurement is your first cost control step. Use net wall area and deduct openings such as doors, windows, and large penetrations. If you measure by dimensions, compute length × height × quantity, then subtract openings. Keep one method across drawings and site checks.
2) Thickness, coats, and wastage drive volume
Mortar volume increases directly with total thickness. Extra coats often add time for straightening and finishing, especially on uneven substrates. Add wastage for rebound and handling losses; 5–10% is common, higher for difficult access. Record actual wastage per elevation for future estimates.
3) Convert wet volume to dry ingredients
Wet mortar volume comes from area and thickness, then a dry volume factor converts it to ingredient volume. Apply the mix ratio by parts to split cement and sand. Convert cement volume to bags using bag mass and cement density so purchasing aligns with site packaging.
4) Labor and access costs must match the method
Labor rates must reflect the finish level and crew productivity. Rough substrates, high walls, or tight schedules can reduce output. Treat access and scaffold as an area rate or a lump sum depending on your contract. Include supervision and small tools within labor or fixed costs.
5) Optional items change both materials and time
Options like primer, bonding agents, additives, or reinforcement mesh improve performance but add cost and sometimes waiting time. Include primer for dusty or highly absorbent backgrounds. Use mesh at junctions and crack-prone areas. Dose additives per cubic meter of wet mortar so quantity scales with thickness.
6) Apply overhead, profit, and tax transparently
Separate direct costs from commercial markups. Overhead covers management, QA, and general site support. Profit reflects risk, cash flow, and warranty exposure. Apply tax to the subtotal only where required. Clear separation helps during negotiation and makes later change orders easier to price.
7) Example case with typical inputs
Example: net area 120 m², 12 mm, 1 coat, 8% wastage, mix 1:4, dry factor 1.33. Output is about 1.56 m³ wet mortar, roughly 16–17 cement bags (50 kg), and about 1.16 m³ sand. Update the rates to match your market and crew.
8) Use the output for procurement and control
Use the material quantities to raise purchase orders and plan deliveries. Compare the calculated cost per m² across façades to spot over-thickness, low productivity, or access issues. Export CSV for spreadsheets and PDF for site diaries, approvals, and client reporting.