Anchors Away

My crew fastens almost everything into concrete, from metal track and staging to 3-ton air conditioners to toilet paper holders. As a result, we deal with a wide range of anchors. To keep my crew moving, I go through a pre-job layout and make a jobsite checklist for each application.

Checklist

First, I take time to choose the right anchors before the job starts. Extra time here saves lots of lost hours and callbacks. It also keeps my foreman off my Nextel screaming at me for different anchors.

Call Outs. I start with the plans. They show what we're setting and where, and they are my first opportunity to find potential problems. The heavier something is, the more attention it requires. If there's any doubt about anchor choice, I call the architect, engineer, or anchor manufacturer, a phone call that could literally save lives and is easily worth the extra time.

Next, I double-check the call-out on longevity. While most of the anchors we set are for permanent connections, sometimes we install temporary anchors for staging and shoring that must be removable and reusable. The best choice for this application is a hardened steel bolt that screws into a predrilled hole.

In putting together an anchor checklist, I consolidate the types of anchors required, trying to use as few different types as possible, which also reduces bit changes to match different products. Also, I buy more anchors and parts than we need in case any anchors fail during installation.

Anchor Holes: Layout and Drilling

Set-Up. To optimize efficiency on site, before work starts we review all of the equipment and accompanying anchors and then locate them around the site, double-checking that we have the correct fasteners, washers, shields, epoxies, applicators, and bits.

Layout. Drilling into concrete is a one-shot deal. Most of the fasteners we use (except epoxies) have precise tolerances: For each anchor to function properly, it must grab the surrounding concrete securely. This means holes must not be too tight or too loose; variances in hole size and location can drastically reduce holding power and may even make a fastener completely ineffective.

If a drilling template isn't provided with the product, we use a framing square and tracing paper to locate the holes. We hold the tracing paper over the equipment to be installed (e.g., a flange or plate). We then mark the perimeter and holes on the paper. Finally, we transfer the paper layout to the concrete to get an accurate layout. A lot of equipment, from A/C units to towel holders, comes with marking templates, so check the box carefully before you discard it.

We also use lasers for marking holes, especially overhead for a run of conduit or surface-mounted lighting. We lay out on the floor first using chalk lines and black Sharpie pens to mark the centers or specific hole locations, then use the laser to plumb up to the ceiling and transfer the marks.

Drilling. Once the layout is established and double-checked, it's a matter of drilling the right size hole to the correct depth. Here are some tips:

• Match the drill bit with the anchor; it's critical.
• Use the right drill: A hammerdrill works for small stuff, but anything over 1/2 inch requires a rotary hammer.
• Let the tool do the work: jamming the bit into the hole can cause the bit to wobble, affecting the size and location of the hole.
• Drill straight: Drill at a right angle to the work to ensure proper hole alignment.
• Use a depth gauge. A gauge provides consistent hole depth and easy repetition.
• Big holes: For holes 1 inch and up, pre-drill a 1/4-inch pilot hole. This ensures that the bigger bit won't wander and makes the second hole easier to drill.
• Don't beat on the anchor during installation: If it doesn't fit, re-drill the hole or clean it out. Pounding on anchors can weaken or destroy them. If you manage to jam it in the hole and break it, you've got two problems.

Setting and Tightening

An anchor holds only as well as it is installed. Make sure it's tightened properly – but avoid over-tightening; over-tightening can break the anchor or cause it to rise out of the hole, weakening the connection. To avoid this, I tighten with a socket wrench, not a cordless drill or impact driver. Tightening by hand lets you feel the anchor grab. Blow or brush any debris out of the hole so the anchor is biting into hardened concrete instead of loose dust.

Epoxy: A two-part chemical mixture that hardens in a pre-drilled hole. It's great for grabbing rebar, threaded rod, or other non-anchor material. It creates a strong connection, but application is time consuming, expensive, and potentially messy (especially overhead). Epoxy is versatile, though, because it handles a variety of applications – including stone and underwater tasks.

Mechanical: The heaviest duty fastener, it has its own cutterhead. The unit is inserted into a predrilled hole where the cutterhead then creates a pocket in the bottom of the hole. Wrenching the bolt head secures the unit. This is an extremely strong but expensive and time-consuming anchor method, and is generally limited to holding bolts.

Expansion: We use this type of anchor for the vast majority of our work. A sleeve slips inside a pre-drilled hole; the sleeve then accepts a bolt. Tightening the bolt expands the device, creating a strong connection relatively quickly and easily.

Heavy-duty shields: Lead anchors inserted into a hole accept a screw or lag bolt – tightening the screw expands the shield, wedging it in the hole; this is ideal for lag screws and is an easy, economical, and fairly strong device.

Light-duty anchors: Generally plastic or lead, these anchors are ideal for installation of electrical and bathroom fittings. They have very limited strength and are ideal for screws.

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Erik Elwell is a custom residential and light commercial contractor in New York City.