Saw Cutting and Coring Best Practices For Construction

Saw cutting is the controlled cutting of concrete, masonry or asphalt with a diamond-blade saw to make openings, remove sections or form joints, and coring is drilling a clean round hole through a slab or wall with a diamond core bit. Almost every construction project needs some saw cutting and coring, whether it is a new opening for ductwork, a sleeve for a pipe or a control joint in a fresh slab.

The risk involved with these activities can vary depending on the location, phase in the project and scope of the actual work. This article will walk you through some of the best practices for saw cutting and coring in construction that we’ve picked up, from scanning and permits through dust control and clean-up.

Saw Cutting and Coring Terms

As a formality let’s first get you up to speed on the different terminology that we’ll be referencing throughout this article.

Sawcutting – is the act of removing structure or material by way of a mobile saw system.

Coring – the act of drilling out a hole or section of a slab in the structure or building. Holes are typically round in nature.

X-Raying – the use of an X-Ray machine in order to scan underlying or materials within a wall or slab.

Scanning – the act of using a scanner to identify materials inside or underneath of a wall or slab. Most often done with ground penetrating radar (GPR).

Types of Concrete Saws and Coring Equipment

The equipment your contractor brings depends on the thickness of the element, the shape of the opening and whether you are cutting a floor, a wall or a pavement. Knowing the options helps you ask the right questions at the quote stage.

Equipment	Typical use	What to know
Handheld power cutter (cut-off saw)	Small openings, trimming, block, pavers and shallow cuts	Limited depth: a 14-inch blade cuts roughly 5 in (125 mm) deep. Cuts from both sides may be needed on thicker walls.
Walk-behind (flat or slab) saw	Long straight cuts in slabs on grade, pavements and control joints	Horizontal surfaces only. Depth depends on blade size, so confirm slab thickness first.
Wall saw (track saw)	Door, window and duct openings in walls and suspended slabs	Mounted on a track bolted to the element, so it gives clean, square edges with little vibration.
Wire saw	Very thick or reinforced sections, irregular shapes, large removals	A diamond wire is looped through drilled holes, so almost any thickness can be cut. Needs set-up space and guarding.
Ring saw or chain saw	Small, deep openings and corners without overcuts	Useful where overcuts at corners are not acceptable, such as exposed or heritage finishes.
Core drill (rig-mounted or handheld)	Round penetrations for pipe, conduit, drains, anchors and test cores	Rig-mounted drills are anchored or vacuum-mounted. Stitch-drilling a line of cores is another way to make an opening.

Preparing For The Coring and Saw Cutting

There are a number of best practices to follow when preparing for the work.

Identify The Work

The first step you need to take is identifying what exactly is the new opening going to be required for. If the opening is for a duct and is large, you will need to saw cut. If the opening is for a smaller penetration such as conduit or piping coring may be the best approach.

Any new opening in a structural slab, beam, wall or column should be reviewed and approved by the structural engineer before it is cut. The engineer will confirm the size and location, whether reinforcement can be cut and whether the opening needs trimming steel or supplementary framing.

Determine The Location

Once you have the scope of work defined you need to determine the location. When reviewing the location make sure to review it on site and on the drawings. Look for some of the following issues or concerns:

• Access to the space requiring coring and how equipment will be moved into place
• Surrounding interferences that would prevent proper setup
• Mechanical and Electrical services running underneath or nearby
• Other ongoing construction activities nearby
• Structural Interferences
• Location of the core on the under / backside and any surrounding issues (ie is it public space)

Engage a Sawcutting and Coring Contractor

Once you’ve identified what the work is, it’s time to get a professional engaged. You’ll be able to find local saw cutting and coring contractors online or through your trade network. At this point we’d recommend bringing someone out to do an initial review of the site conditions and prepare a quotation for your work.

When you compare quotes, check that each one includes scanning, water and slurry control, dust collection, after-hours work if needed, removal of cut pieces and patching or firestopping, so you are comparing like for like.

Scanning or X-Raying

Your contractor that you engage will likely have the recommendation to scan or X-Ray. We’d recommend doing one or the other but both are very site specific. In general scanning is the “lighter” option of the two. Often times it won’t be able to pick up everything in a slab or structure.

If X-Raying is required there are a number of precautions you should be aware of. X-Raying (concrete radiography) uses ionizing radiation that can be harmful to people’s health, and it needs access to both sides of the slab or wall because the source sits on one side and the film on the other. The radiography contractor will set an exclusion zone around the shot that people must be kept out of, typically on both sides of the element and on the floors above and below. Get the size of that zone in writing from the radiography firm. As you can guess this can be quite challenging to do if there is a lot of work ongoing nearby, so planning this work out well in advance (often for after hours or a weekend) is important.

With either option you need to have this completed before the work commences in order to ensure the work is being performed safely.

Post-Tensioned Slabs Need Extra Care

Post-tensioned (PT) slabs carry steel tendons under very high tension. Cutting or coring through a tendon can release it suddenly, injure people nearby and weaken the slab. Before any cut or core in a PT slab, get the tendon layout from the shop drawings, have the tendons located and marked on the slab by scanning, and get written approval from the structural engineer for the final location. Keep penetrations as small as possible and stay clear of the marked tendons and anchors.

Permits and Sign-Off

Many sites run cutting and coring under a work permit, alongside a hot work permit if sparks are produced. A drilling, coring and cutting work permit is a simple way to record the scan results, the engineer’s approval, isolations, the exclusion zone below and who signed off before the first cut.

Completing the Sawcutting and Coring Work

Once you have a proper plan it’s time to commence the actual work, below are a few rules for you to follow on the day of the cutting.

Rule 1 – Have a Pre-Job Orientation and Safety Meeting

A pre job orientation and safety meeting before the sawcutting and coring will force you to look at some of the hazards surrounding your work area. In your review the site team should be included. Make sure to pay attention to anything that has changed since your initial review. Check out our guide for having an emergency response plan and incorporate it into your safety review.

Rule 2 – Make Sure Nothing Has Changed For the Sawcutting and Coring

Has new conduit been installed in the area, furniture, etc. If something has changed from your previous review no matter what chances are that something was added or adjusted. Check above and below your cuts so you don’t end up hitting anything you don’t expect.

Rule 3 – Clear The Construction Work Zone

After checking above and below for interferences rope off the work area and work areas below your cutting and coring. If material falls you don’t want it hitting someone below. You may want to consider having a spotter if it is practical.

Plan how cut sections will be supported and removed before you start. Large slab or wall pieces can weigh far more than they look, so agree the piece size, rigging or shoring and lifting method with the contractor in advance.

Rule 4 – Remove the Sawcutting and Coring Waste

Leaving waste in your work zone will cause you to slow down your work and inhibit progress. Remove construction debris and material as it is created to keep everything running efficiently.

Rule 5 – Enjoy Yourself You’re Making A Change

Whether it’s for new work, or fixing something you’re doing something that wasn’t originally intended and something that may have a meaningful impact on someone’s life. Enjoy your work and don’t be afraid to show off the finished product.

Dust, Water and Silica Control

Cutting and drilling concrete and masonry creates respirable crystalline silica dust, which causes silicosis and other lung disease. In the United States, OSHA’s construction silica standard (29 CFR 1926.1153) sets a permissible exposure limit of 50 μg/m³ and an action level of 25 μg/m³, both as 8-hour time-weighted averages. Its Table 1 lists accepted controls for common tasks, for example:

• Handheld, walk-behind and drivable saws: use a saw with an integrated water delivery system that continuously feeds water to the blade. Table 1 also calls for a respirator (APF 10) when handheld saws are used indoors or for more than four hours a shift outdoors, and when walk-behind saws are used indoors or in enclosed areas.
• Rig-mounted core drills: use a drill with an integrated water delivery system that supplies water to the cutting surface.
• Handheld and stand-mounted drills (including rotary hammers): use a shroud or cowling connected to a dust collector with a high-efficiency filter, and clean holes with a HEPA-filtered vacuum, not compressed air.

Employers also need a written exposure control plan and a competent person to put it into practice. Download the OSHA silica standard for construction if you need the full table. Outside the US, check your local occupational health and safety regulations, as limits and accepted controls differ.

Wet cutting solves the dust problem but creates slurry. Contain it with dams, wet vacuums or slurry pads, protect finished surfaces and openings below, keep it out of floor drains and storm drains, and dispose of it the way your local authority requires. Keep water away from live electrical equipment and use GFCI-protected power for electric saws and drills.

Saw Cutting Control Joints in New Slabs

Not all saw cutting is about openings. Contraction (control) joints are saw cut into new slabs on grade so that shrinkage cracks form in a straight line under the cut instead of randomly across the slab. Industry guidance from the National Ready Mixed Concrete Association gives these rules of thumb, but your project specification and engineer take precedence:

• Depth: with a conventional saw, cut to at least one quarter of the slab thickness. With an early-entry saw, the minimum is about 1 in for slabs 9 in thick or less.
• Timing: cut as soon as the concrete can take the saw without ravelling or dislodging aggregate. With a conventional saw that is generally within 4 to 12 hours, depending on the weather and the mix. Early-entry saws can cut sooner.
• Layout: follow the joint layout on the drawings. Cutting too late, or too far apart, is the most common cause of random cracking.

After the Cut: Patching, Firestopping and Close-Out

Once the opening is made the job is not finished. Check the following before you sign the work off:

• Exposed reinforcing is treated or covered as the engineer directed, and edges are clean and square.
• Abandoned or oversized cores are patched with an approved repair material.
• Penetrations through fire-rated floors and walls are sealed with a tested firestop system once the services are installed. See our guide to firestopping in construction.
• Openings left open are guarded or covered and labelled until the services go in.
• Scan reports, engineer approvals and permits are filed with the project records.

When was your last sawcutting or coring exercise? Were there any vital lessons learned? Share them with us below in the comments!

Frequently Asked Questions

What is saw cutting in construction?

Saw cutting is the use of diamond-blade saws to cut concrete, masonry or asphalt cleanly and accurately. It is used to make openings for doors, ducts and services, to remove damaged sections, to cut trenches and to form control joints in new slabs.

What is the difference between saw cutting and coring?

Saw cutting makes straight cuts and is used for larger or rectangular openings. Coring uses a hollow diamond bit to drill a round hole, and is used for pipe, conduit and drain penetrations and for taking concrete test samples.

How deep can a concrete saw cut?

It depends on the blade diameter and the machine. A 14-inch handheld power cutter cuts roughly 5 in (125 mm) deep. Walk-behind saws with larger blades cut deeper, and wall saws and wire saws are used for thick walls and slabs. Check the manufacturer’s maximum cutting depth for the exact saw and blade.

Do you need to scan concrete before coring or cutting?

Yes, on almost every job. Scanning locates reinforcing, post-tension tendons, conduit and pipes so they can be avoided. Hitting a live conduit or a tendon is a serious safety risk, and many sites will not issue a cutting permit without a scan report.

Is GPR scanning the same as concrete X-ray?

No. GPR (ground penetrating radar) works from one side and uses no ionizing radiation, so other trades can usually keep working. Concrete X-ray (radiography) gives a more detailed image but needs access to both sides and an exclusion zone around the shot.

When should you saw cut a new concrete slab?

As soon as the surface can be cut without ravelling. With conventional saws that is generally within 4 to 12 hours, depending on the weather, and early-entry saws can cut sooner. Cut to at least a quarter of the slab depth with a conventional saw unless the specification says otherwise.

Related Templates and Guides

• Work Permit – Drilling, Coring and Cutting
• Job Hazard Analysis Form
• OSHA Crystalline Silica Standard for Construction
• Firestopping in Construction and Buildings
• Housekeeping in Construction and Why It’s Important

This guide is general information. Rules for contracts, payment and site safety differ by country, state and province. Check your contract and local regulations, and get professional advice where it matters.

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