Sawing Concrete

Continued

Chainsaw. We also have a hand-held, gas-powered plunge-cutting diamond chainsaw from ICS that provides a handy way to complete corner cuts when overcutting isn't acceptable (Figure 7). The thin bar fits inside the cut made by the circular saw blade. Because the chainsaw is hand-held and has fewer cutting segments than a circular blade, it's harder and more dangerous to handle and control, but it's extremely versatile. We also use this tool to form beam pockets and make other odd cuts that are impractical for the wall-mount saw.

Figure 7. The authors use a gas-powered, plunge-cutting diamond chainsaw for applications where a wall saw is unsuitable, such as completing corner cuts, carving out beam pockets, and sawing through round or irregular concrete.

Heavy Waste

A door-size cutout usually breaks in two when it falls, but the pieces can weigh several hundred pounds and may require further sawing for removal. The average cost for a door cutout is around $400 (our basic 5-hour rate), but we charge $75 per hour for any additional cuts. Getting rid of the debris isn't usually our job — in new construction, the contractor may simply bury the cutout on site in a hole dug for the purpose or add it to the foundation backfill. Whenever possible, schedule concrete sawing to coincide with or precede excavation or backfilling to make disposal convenient. The waste can also be buried under a new floor slab as long as there's no chance of a deep freeze heaving it up through the floor. If the cutout is going to drop on a finished slab, the best way to buffer the considerable impact is to place a few unmounted rubber tires in the drop zone (Figure 8).

Figure 8. Tires break the impact of a solid-filled CMU wall section to prevent damage to the finished slab.

Smaller Jobs

Concrete coring — sawing circular holes from 2 to 12 inches in diameter to accommodate electric, water, and sewer lines through the foundation wall — is also in pretty constant demand (Figure 9). Coring through an 8- to 10-inch-thick wall takes only a few minutes and leaves a neat hole that can be easily sealed around the pipe or cable. If we're already on the job for a wall cut, we charge the hourly rate of $75, which will cover quite a few holes. Otherwise, we charge $250 for a dedicated trip and one or two holes.

Figure 9. Concrete cores, 2 to 12 inches in diameter, are cut with a wet-sawing rig bolted or vacuum-mounted to the surface being cored. The resulting holes can accommodate water or sewer lines, wiring, or ductwork.

Control joints. There are concrete floor saws for scoring and cutting through slabs, and we do a fair amount of this type of work, too. However, the floor tool is big, bulky, and heavy, making it unsuitable for some interior applications. Instead, if we're sawing control joints in an interior slab, for example, we'll simply bolt the wall saw to a short, heavy wooden plank and slide the rig across the floor along a temporary guide strip.

Dennis Smithhas been sawing concrete for CSCC for six years.Peter Zoniis the principal owner of CSCC, in Orleans, Mass., and an expert in all phases of light and heavy concrete construction.