Construction Cost Estimating

Articles on Cost Estimating

Estimating Concrete

Concrete is one of the most versatile and widely used materials in the construction industry. It can be custom-mixed for compressive strength or color application, placed in almost any shape or form, and finished to resemble masonry, stone, and other surfaces. Concrete is durable and virtually maintenance-free. It is also fairly easy to work with and installs relatively quickly.

Concrete estimating is generally divided into five basic areas:

  • Concrete materials and placement
  • Formwork
  • Reinforcing
  • Finishing
  • Precast concrete

Concrete quantities are usually taken off in measures of cubic yards, as this is how supply companies charge for it. Formwork is taken off in square feet (generally in square feet of area in contact with the concrete as opposed to the actual area of the forms used). Reinforcing is normally taken off in tons of steel. Finishing is taken off in square feet of finished surface. Precast concrete quantities are taken off in either square feet or by the piece, depending on usage and the type of unit being considered.

Green Considerations
Although concrete requires a large amount of energy to produce, there have been recent strides by manufacturers to reduce the environmental impacts of processing and using it. By adding blast furnace slag or coal fly ash (industrial waste products), the cement content of concrete is reduced along with the pollution and greenhouse gasses associated with its production. Using recycled aggregate reduces the amount of material needing to be transported to landfills. Concrete can also be formulated to be very porous; in this form it is useful in reducing pollution due to storm water runoff by allowing the water to seep into the ground where it can be absorbed naturally.

Traditional concrete does not have a high insulating value, but it does have a high mass. This can be used to its advantage. In passive solar spaces, concrete floors can soak up heat during hot summer days and release it during the cooler evenings. When additional insulation value is required for underground structures, permanent insulating formwork works well and saves the additional step of adding insulation after the concrete is cured.

Another green approach is finishing the concrete surface to a higher level of quality, possibly adding color or texture in lieu of adding carpeting or tile and their associated costs, both monetary and environmental.

This article was adapted from RSMeans Estimating Handbook by the RSMeans Engineering Staff & Joseph Macaluso. Click here to read an expanded excerpt.


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Member Comments

Posted by Kevin Smith
02/08/2012
Keep in mind that the newer Post-tensioned concrete estimate will include cable costs by the lineal foot, not by the ton. Your sales personnel with post tensioning products can also give you a better idea of supplemental costs that go into placing the cables such as anchors, wedges, reinforcing steel, chairs and other related products. Keep in mind that post tensioned concrete is an "active" slab, meaning the cable tension is always compressing the slab and both the concrete and the cables are the integral strength of the slab, whereas conventional steel reinforced slabs are "passive" reinforcement, meaning if the slab hydrates and cracks, the strength is in the steel only.
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