Attaching wood to concrete floors and walls
Attaching wood to concrete is one of the most basic, time-consuming and iffy tasks in construction. Whether you're anchoring wall sill plates or attaching furring strips to concrete walls, you'll find yourself engaged in an exacting task, working with seemingly incompatible materials and wondering if everything will stay attached.
If you have a dozen or more permanent connections to make, save time and money by using powder-actuated tools (PATs). With safety as the highest priority, we'll show you the most popular tasks this tool can do around your house.
Also called stud drivers, stud guns and rem guns, these are heavy-duty tools that fire gunpowder cartridges. This “power load” pushes a piston inside the tool that slams a special heat-treated and hardened steel nail (a “drive pin”) through wood and into concrete. It takes only seconds to load and fire a stud gun, so you can drive dozens of fasteners quickly.
Uses and costs
PATs became available in the early '60s and have grown increasingly popular for fastening wood sills to concrete floors and wood furring strips to poured and block concrete walls.
To finish off a whole basement with scores of wall furring strips and/or floor sill plates, you can spend as little as $20 for the hammer-activated gun or $70 for the trigger-activated type. For occasional use, rent a heavier-duty tool for about $25 a day. Either way, it will cost a combined 50¢ to 75¢ for one power load and a standard drive pin.
NOTE: Before you work with stud guns, check with your local building officials. The use of power fasteners is sometimes restricted with certain construction techniques and situations.
Not suitable for all concrete
PATs have the power to shoot a projectile more than 300 ft. per second and drive a fastener into concrete with such force that it sometimes takes a ton of leverage to extract it. But PATs don't work in every situation. Never attempt to use power fasteners in very hard concrete or stone—or brittle materials like glass, tile or brick. Before using a stud gun, test the hardness of your concrete by conducting a “center punch test.”
Apply these basic rules for power fasteners:
- Follow the spacings shown for placing drive pins and for working near the edges of concrete slabs (Fig. A).
- For best results, use power fasteners in concrete aged more than 28 days. “Fresh” concrete fewer than seven days old can't exert a compression bond sufficient to permanently secure a drive pin.
- Follow the results of the center punch test. Concrete that is either too weak or too strong won't hold power fasteners. Instead, use specialty wedge anchors or expansion shield–type concrete anchors. These are also the right choice if you have only a few furring strips to attach to a wall, if the strongest connection is a must, or if someday you may want to take the project apart.
- If you use power fasteners, consider the installation permanent. Extracting drive pins wrecks the wood and damages the concrete base.
- Improve the holding power for permanent installations by using construction adhesives on sill plates and wall framing.
- “Overdriving” power fasteners occurs when too powerful a powder load pushes the gun piston partially out of the muzzle and drives the fastener too deep into the wood. Overdriving is a sure way to damage a PAT. Find the proper power load by using the weakest power load first (Level 1, gray) and working toward the most powerful (Level 4, yellow)—until you get the proper drive pin penetration. If drive pin heads consistently go below the top of the board or split your wood, use washered power fasteners.
Drive pins only need to penetrate 1 in. into the concrete.
Figure A: Why Drive Pins Work, and Why They Fail
Know the rules for fastening into concrete. The drive pins should penetrate 1 in. to 1-1/4 in. into the concrete, but never protrude through it. Drive pins displace the concrete, which tries to return to its original form, resulting in a compression bond. Follow the spacing rules shown, and only shoot fasteners into concrete that's more than three times as thick as the fastener's intended penetration.
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Follow basic safety procedures
Using a PAT has been described as “an intense experience” and I agree. The first time I used a PAT, I couldn't believe my anxiety anticipating the force, the noise and the recoil. I've always respected the tool, have been well served by it and, best of all, have no personal-injury horror stories.
Learning the proper use of a PAT not only improves your efficiency and speeds up tasks but also directly affects safety. A lot of it is common sense, but follow these additional guidelines:
- Keep the tool and unspent powder loads locked up and away from kids. Injuries and deaths have occurred when ricocheting projectiles have struck bystanders, or when people have tried to use common nails in stud guns.
- Use safety goggles (not safety glasses) and hearing protection when working with stud guns.
- If the tool is dropped, check for damage to the barrel and other moving parts and don't use the PAT until it's repaired.
Clean and Maintain the Tool
Simple maintenance will help you avoid problems like a sticky barrel slide and spent power load casings that won't eject (which is also caused by using drive pins longer than 2-1/2 in.).
Each day, after regular use, inspect the unloaded tool for damage and then take a rag and clean out the chamber and around the barrel. Buy barrel brushes from your PAT tool distributor and clean the gunpowder residue out of the inner working parts. Spray a little WD-40 lubricant on the inside and all over the outside of the tool and then wipe those areas clean and dry.