Mortar quantities for a barbecue are not calculated solely from the surface of its external wall. Brick size, joint length and thickness, and the way elements are laid count. Start with a summary of the working wall, and calculate larger fillings and finishing separately.
Compare compatible usage examples
For Outdoor Oven Cement, the manufacturer gives an example: ten kilograms of material for about fifteen bricks of the 230 × 114 × 64 mm format with a ten-millimetre thick joint. These are specific coverage conditions, not a universal number for every brick and every firebox.
Under the same assumption, sixty bricks require approximately forty kilograms of material before a separate assessment of the spare allowance. If you change the format, thickness, or joint layout, you need to recalculate. Do not treat the example thickness as an automatic design recommendation.
Separate different parts of the order
HPM Heatproof Mortar has different application conditions and coverage example for intended thin joints. Comparing both packages without checking the application and joint geometry gives a misleading saving. First, choose the material according to actual conditions, including weather.
In the summary, describe the wall, arches, cuts, and any fillings with a different product separately. Do not increase the amount of the same mortar to replace a layer with a separate function. Dry-fitting the equipment can reveal additional sections omitted from the initial brick count.
The allowance should have a justification
Add possible losses based on the actual working method and the material allocated for necessary corrections. Do not use a single percentage for all structures, regardless of the number of cuts and the contractor's experience. Separate the calculated quantity from the additional item in the order.
Before purchase, check the packaging sizes and storage conditions. Record the assumptions along with the calculation date. When the project or equipment changes, it will be possible to correct the relevant part of the summary instead of guessing the total amount of mortar again.