7 Ways to Fasten an Interior Wall to Concrete for a Secure Hold
We'll walk you through the different types of fasteners used for attaching framing to concrete, plus point out a few best practices.
Concrete makes a tough, durable surface, and securing anything to it typically requires special tools. If you're planning to build a wall on top of a concrete slab, you'll need to use a specific type of fastener to anchor the wall in place. To help you decide which wall fastener to use on concrete, we've outlined all the options that can help you successfully secure wall framing to the slab. Each method has its own set of tools and difficulty level, but most fasteners can be attached in just a few minutes.
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 1/4-inch diameter 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 inches deep more than triples the pullout resistance for the 3/16-inch screw, and the 1/4-inch one is nearly three times stronger. In shear strength (its ability to resist forces perpendicular to the long axis of the fastener), the 1/4-inch screw is nearly twice as strong as the 3/16-inch version.
If you're looking for the quickest way to fasten walls to concrete, powder-actuated fasteners ($199, The Home Depot) offer the most speed. But unless you've already invested in this tool, you'll have to factor in the time involved in two trips to the rental center or home improvement store, as using this tool requires filling out paperwork for a license. If you're finishing an entire basement, you'll save enough time to make the rental or purchase process worthwhile, but it's a questionable call for installing a single wall. In that case, consider the following types of fasteners to securely attach a wall to concrete.
1. Steel Track
With steel track, you can install a fastener as short as 20 mm, but a 27 mm length produces 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.
2. Hardened Concrete Nails
If the concrete is less than a year old, you might be able to drive special hardened concrete nails. Some concrete nails feature the cut-nail design, shown above, 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.
3. Drill with Two Different Bits
A carbide-tipped bit is ideal for drilling concrete. Although this bit does an acceptable job of punching through steel runner, it drills poorly through wood. 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.
4. Masonry Screws
Masonry screws ($5, The Home Depot) are an easy solution for fastening a wall to concrete. 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.
5. Drop-In Anchors
There are several different styles of drop-in anchors that can be used to fasten a wall to concrete. The style shown above 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.
6. Lag Shields
Lag shields produce strong joints, but they involve more installation steps than most fasteners. First, 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.
7. Hammer-Drive Anchor
A hammer-drive anchor ($18, The Home Depot) 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.
Tips for Using Adhesive to Boost Holding Power
When attaching a wall to concrete, construction adhesive ($8, The Home Depot) offers additional strength when combined with mechanical fasteners. However, you shouldn't rely on adhesive alone to anchor the wall. A single wavy bead of adhesive is adequate to boost the holding power. For a stronger bond, apply dual strips of adhesive to cover a larger area.