Concrete Estimating Services for Concrete Contractors

Concrete is measured element by element from the structural drawings: spread footings, continuous footings, grade beams, pile caps, piers, slabs on grade, thickened edges, walls, columns, beams and elevated decks. Each element is calculated in cubic feet and converted to cubic yards, since one cubic yard equals 27 cubic feet.

We then add a waste factor for each element type. Footings poured against earth and slabs on uneven subgrade need more allowance than formed walls, so we do not use one percentage for everything. Commonly the allowance falls between 5 and 10 percent, and we show it on its own line so you can adjust it.

Rebar is taken off from the plans, sections and schedules by bar size, length and spacing, including laps, hooks, dowels and corner bars. Lengths are converted to weight using standard bar weights, such as about 0.376 pounds per foot for #3 bar, 0.668 for #4, 1.043 for #5 and 1.502 for #6.

We also list welded wire reinforcement, chairs and supports, and any epoxy-coated or galvanized bar the specs require, because coated bar costs more and needs careful handling.

Formwork is measured in square feet of contact area (SFCA), the surface of concrete that touches the form. Walls, columns, beams, slab edges and elevated decks each have their own form costs, and the number of reuses has a big effect on the price.

• Slab finishes: broom, trowel, burnished or polished
• Curing, sealing and hardeners
• Control joints, construction joints and expansion joints
• Vapor retarder, granular base and under-slab insulation
• Embedded items, anchor bolts and edge angles

How concrete gets into the forms changes the cost as much as the volume does. We consider:

• Pump truck time or crane and bucket placement
• Hot-weather and cold-weather protection, heaters and blankets
• Short-load and after-hours charges from the supplier
• Testing and inspection, when they are in your scope
• Access for trucks and the distance from the street

Some projects use systems that need their own approach. Post-tensioned slabs, common on expansive soils, include tendons, anchors and stressing. Tilt-up walls are cast on the slab and lifted into place, so we include casting beds, bond breaker, lifting inserts, bracing and crane time. Precast elements are usually priced from a supplier quote, and we take off the items around them.

Single-family homes are usually slab on grade or stem wall foundations, sometimes with post-tensioning on expansive soils. Warehouses and distribution centers are driven by large slab areas, joint layouts, flatness requirements and tilt-up walls. Multistory buildings bring elevated slabs, columns, shear walls and shoring, where formwork and reuse drive cost more than concrete volume. Site work adds sidewalks, curbs, paving, dumpster pads and light pole bases.

Because each type puts its cost in a different place, we spend our review time where the money is: joints and flatness on warehouses, formwork cycles on multistory buildings and footing details on homes.

• What concrete strengths and mix requirements do the specs call for in each element?
• Is rebar furnished and installed by you, or by a separate rebar subcontractor?
• Who carries excavation, backfill and the granular base under slabs?
• Are there floor flatness and levelness requirements for slabs?
• Which testing and inspections are in your scope?

Open questions are answered with clear assumptions in the estimate, so nothing is left to guesswork.

Concrete quantities by element help you plan every pour. Cubic yards per footing line, slab section or wall lift become your ready-mix orders, and the formwork areas tell you how many form sets you need and how often they can be reused.

Rebar weights by element support your rebar supplier quotes and detailing, while finishing areas help you schedule finishing crews. The same breakdown gives you a schedule of values for billing by foundation, slab and structure, and lets you price changes from known quantities.

Cubic yard

The standard unit for ordering concrete, equal to 27 cubic feet.

SFCA

Square feet of contact area, used to measure and price formwork.

Slab on grade

A concrete slab poured directly on prepared ground.

Post-tensioning

Steel tendons stressed after the concrete cures to strengthen a slab.

Tilt-up

Wall panels cast flat on site, then lifted into place with a crane.

• Excavation and backfill for foundations, and whether they belong to sitework
• Housekeeping pads for mechanical and electrical equipment
• Stair fill, topping slabs and equipment curbs
• Site concrete such as sidewalks, curbs, dumpster pads and light pole bases
• Patching and finishing at slab penetrations