How to Fasten an Interior Wall to Concrete
We'll walk you through the different types of fasteners used for attaching framing to concrete, plus point out a few best practices.
Not sure which type of wall fastener to use? We've laid out all the options to help you decide. Each method has it's own set of tools and difficulty level, but most fasteners can be attached in a few minutes time.
If you're looking for speed, it's impossible to beat powder-actuated fasteners. But unless you've already invested in this tool, you'll have to factor in the time involved in two round trips to the rental center and filling out the paperwork. If you're finishing an entire basement, you'll save enough time to make the rental process worthwhile. But it's a questionable call for installing a single wall.
No matter which fastener you choose, consider 1 inch of concrete penetration as the minimum. To increase holding power, choose a fastener that burrows deeper into the concrete or has a larger diameter. For example, a screw with a diameter of 1/4 inch has more than twice the pullout resistance of a 3/16-inch screw when both are driven 1 inch deep into concrete. Driving the fasteners 1-3/4 deep more than triples the pullout resistance for the 3/16-inch screw, and the 1/4-incher is nearly three times stronger. In shear (perpendicular to the long axis of the fastener), the 1/4-inch screw is nearly twice as strong as the 3/16-inch version.
With steel track, you can install a fastener as short as 20 mm, but a 27 mm length produces the better penetration and superior strength. Choose a 72 mm fastener length when working with 2x stock. The boosters (powder cartridges) are available in a variety of color-coded strengths to match the fastener to the density of your concrete. A yellow booster is about midway on the power range and is usually a good starting point.
Hardened Concrete Nails
If the concrete is less than a year old, you may be able to drive special hardened concrete nails. Some concrete nails are the cut-nail design, shown in the photo, with a thick flat shank and a tapering V-profile. Other nails have a thick shank that sometimes has spiral ridges for improved holding power. Choose a length that will penetrate the concrete at least 1 inch. Be sure to wear safety goggles when hammering masonry nails into concrete.
Drill with Two Different Bits
A carbide-tipped bit is ideal for drilling concrete, and it does an acceptable job of punching through steel runner, but it drills poorly through wood. So it's a good idea to drill holes in the sole plate with an ordinary wood bit before you tip the wall into place. Then you can switch to your carbide bit, and use the holes through the wood to guide the carbide bit.
Masonry screws are an easy solution to concrete fastening chores. When you buy the screws, you'll also need to get a special bit that makes a pilot hole matched to the fastener. Drill at least 1/4 inch deeper into the concrete than the fastener's embedment, and suck dust out of the hole with a shop vac. The hex-head style has an integral washer to spread the bearing pressure for a firm grip.
There are several different styles of drop-in anchors. The style shown is called a sleeve anchor, and it installs easily through identical-size holes in both the sole plate and concrete. Tightening the hex nut pulls on the bolt and expands the slotted metal sleeve within the hole.
Lag shields produce strong joints, but they involve more installation steps than most fasteners. Drill holes through the wood sole plate with a wood bit and mark the floor. Move the sole plate, drill the floor, suck out the dust, and tap the shield into place. Replace the sole plate and drive lag screws with washers into the shields.
A hammer-drive anchor requires only a small pilot hole; the one shown requires only a 1/4-inch hole. Drill the hole at least 1/4 inch deeper than the length of the lower portion, and vacuum or blow out the hole. Drop in the anchor, and hammer on the pin to expand the bottom of the shield against the wall of the hole.
Bonus: Use Adhesive to Boost Holding Power
Construction adhesive offers additional strength when combined with mechanical fasteners, but don't rely on adhesive alone to anchor the wall. A single wavy bead of adhesive is adequate; dual strips spread over a larger area and produce a stronger bond.