How Many Brick Slips Do I Need? Measuring and Wastage

Use metres for area calculations and label every measurement. For a rectangular wall, width × height gives the gross area. Split an irregular wall into simple shapes and add their areas, keeping a sketch so the same section is not included twice. Record sloping tops or steps explicitly rather than assuming the longest height applies everywhere.

Measure before selecting a quantity in the brick slips shop, and recheck after the preparation plan is agreed. Identify where the finish begins and ends: above a worktop, behind a cabinet, at a skirting or at the ceiling. A dimension without those boundaries can produce a surprisingly different order.

Subtract the width × height of each opening that will remain uncovered. Then separately measure any reveal surfaces that will receive slips. For a rectangular window with two clad side reveals and a clad head, those are two height × depth areas and one width × depth area. Add a sill surface only if that is actually part of the approved finish.

Label the opening and its returns together on the sketch. A doorway removed from the front elevation does not remove the need to cover its sides if they are in your specification. Conversely, an opening hidden behind cabinetry should not be counted as clad merely because the gross wall rectangle includes it.

Example: a flat wall is 3m wide × 2.4m high, with a 0.9m × 2m doorway. Assume no clad reveals and no corner units. Gross area is 7.2m²; the opening is 1.8m²; net area is 5.4m².

With a chosen 10% allowance, the quantity to cover is 5.4 × 1.10 = 5.94m². If the chosen box covers 0.5m² under the supplier’s stated joint convention, 5.94 ÷ 0.5 = 11.88 boxes, so order 12 whole boxes. These cover 6m² on that basis. Do not round 11.88 down, and do not apply the 10% again after rounding.

This example demonstrates the method, not a universal waste recommendation. Several small panels, diagonal patterns or many interrupted courses may need a different allowance from one uninterrupted rectangle.

Face dimensions and joints determine a nominal repeating module. For an illustrative 215mm × 65mm face with 10mm joints, the module is 225mm × 75mm, or 0.016875m². One divided by 0.016875 is approximately 59.26 units per square metre in an ideal repeating field, commonly expressed as an approximate 60-unit planning rate.

Real boundaries, cut pieces and the supplier’s box-coverage convention affect the order. A different face height, joint width or pattern changes the calculation. Use published box coverage for buying, and ask the supplier if a piece-count calculation appears inconsistent. Read sizes and thickness to separate face dimensions from the depth of the finished wall.

List corner units independently, then allocate the wall area they cover using the actual format and layout. Remove that area from the flat-slip total. The corner measurement guide explains why buying flats for the entire area and adding corners can count the same surfaces twice.

Agree allowances for flats and corners separately. Keep usable offcuts in mind when planning the bond, but do not assume every small cut can be reused. Discuss the cut layout for herringbone and other patterns with the installer. Any spare pieces you deliberately retain for future repairs should be recorded separately from the cutting allowance.

The brick slip calculator accepts wall dimensions, openings, a waste percentage and total outside-corner height. Its slip mode assumes 0.5m² per box and a 75mm corner course made from a 65mm slip plus a 10mm joint. It estimates adhesive separately using 2.5m² per 20kg bag.

The tool does not know the exact corner return lengths or subtract their facing area from the flat-slip result. Check that adjustment and the product-specific adhesive coverage with your installer. An estimate using these defaults is not a material specification.

Before ordering, save the drawing, selected product, coverage convention, allowance, corner schedule and final rounded quantities. Check available sample options on a shortlisted product such as TBS Birkdale Blend before committing to the quantity. The overview guide connects measuring with the rest of the planning process.