Waste, material costs, and slope

Three settings - waste, material pricing, and (for sloped slabs) the pitch multiplier - decide how the app turns a plan measurement into a quantity you can actually order. Set them on each component once and every quote stays consistent.

Waste

Concrete waste varies by item:

• Ready-mix pour - 3-5% covers overpour, formwork bulge, and load tolerance. 5% is sensible for normal slabs, higher for awkward footings.
• Reinforcing mesh - 5-8% for cuts and overlaps (mesh laps are typically two cells).
• Rebar - 5% for ties and overlaps.
• Formwork timber - 5-10% for cuts and reuse limits.
• Sawn cuts / expansion joints - usually no waste, you cut what you mark.

Set waste against each component so it applies automatically every time you use that component.

Material price and pack sizing

How a product is sold determines how the app converts measurement to order quantity. Get this right and you stop over- or under-ordering trucks.

• Pack by volume - the standard for ready-mix concrete. Priced per m³ with a minimum truck/order quantity. The app converts area × thickness to volume, applies waste, and rounds up to your minimum increment.
• Pack by area - mesh sheets (e.g. SL72 = 14.4 m² per sheet).
• Pack by length - formwork timber, expansion joint material.
• Pack by count - rebar bars, dowels, joint inserts.
• Single unit - per-sheet, per-bar pricing.

For pours, set a realistic minimum order increment. Many suppliers charge a small-load fee under 3 m³ - put that in a Fixed extra component.

Slope / pitch calculation (fall to drainage)

For most slabs the design fall to drainage (typically 1-2%) is small enough to ignore. When the slope is significant - a steep ramp, a drained washdown bay, a sloped car wash pad - turn on the pitch multiplier to convert plan area into actual sloped surface area for mesh, sealer, finishing, and surface coatings.

Only rafter pitch is supported. Valley and hip pitches don't apply to concrete work.

When to use it:

• A drained ramp where the surface area is materially larger than the plan area.
• A sloped equipment pad where finishing area needs to match the slope.

When to leave it off:

• Standard slabs with 1-2% fall to drainage (the maths barely changes - 1% slope = ×1.00005 multiplier).
• Footings, footings, vertical formwork.
• Anything not measured plan-view.

A worked example

A 100mm thick 25 MPa slab over 60 m² of garage floor:

• Plan area: 60 m²
• Slab thickness: 100mm = 0.1 m
• Plan volume: 60 × 0.1 = 6.0 m³
• Waste at 5%: 6.0 × 1.05 = 6.3 m³
• Supplier minimum increment: 0.5 m³ → round up to 6.5 m³ ordered
• Cost: 6.5 × $245/m³ = $1,592 concrete material

The plan area is also driving mesh (one sheet of SL72 = 14.4 m² → 5 sheets after waste) and labor ($48/m² × 60 m² = $2,880 finish).

Related

• Plan vs Actual
• Creating a component