Your Complete Guide to Choosing and Using Concrete Screws
Wherever there’s the need to attach metal or wood fixtures to concrete, screws seem to offer the best strength, the highest holding power, and the most versatility. Screws come in varied designs, sizes, and materials, and can easily be installed (or removed) in different types of concrete.
Their versatility also extends to other masonry materials, and you’ll see that they also work perfectly fine in stone and brick as well as wood. Another plus point making them extremely popular (when compared to other concrete-specific fasteners like anchors and plugs) is that they’re downright cheap, so they can lower building costs in larger projects.
What are Concrete Masonry Screws?
There’s quite a bit of confusing lingo in the fastener world. Just like you’ll find wood screws used primarily in wood, the sturdy concrete screws are used to attach anything to concrete. But they may also go by different names, such as masonry screws, concrete bolts, and concrete screw anchors, or can be branded, such as the widely popular Tapcon screws. This is more down to the design differences than anything else, but the purpose is generally the same.
All screws used in concrete have a unique thread that easily burrows its way into a pre-drilled hole, and unlike expanding anchors, doesn’t expand into the surrounding substrate. This means there’s a lower likelihood of damage or cracking, and there’s the ability to add fixtures in some unique places, like in overhead applications or near edges.
Where and How They’re Used
The good news is that concrete screws are used in all kinds of masonry but work best in concrete. They’re the go-to fastener for solid concrete, and they work perfectly fine in both cracked and uncracked concrete. They’re also safe to use in hollow concrete blocks.
Screws are more forgiving than expanding anchors and won’t cause or contribute to changes in the substrate due to temperature variations, pronounced fatigue, or when holding fixtures requiring high-weight loadings. This means they’re good for all applications in terms of holding power, but especially so in medium and heavy-duty uses.
Typical instances where these screws can be found are in HVAC and ventilation systems, electrical installations (like mains boards and enclosures) when attaching heavy steel structures, in overhead and ceiling applications when affixing railings and handles, and for supporting fences and clamped items. As mentioned, they’re also chosen in close-edge anchoring and when fixtures need to be attached close to edges.
Installing this type of screws is a fairly straightforward process. The first thing to do is to drill a hole in the same diameter as the screw and to a depth slightly longer than the overall length of the fastener. This can be done with a hammer drill. The hole is then cleaned for any debris, either with a wired brush or air tool, and the fixture and screw are then inserted into the hole. Here basic tools like impact drivers are needed. For better results also observe the torque to ensure that the screw isn’t too tight or too loose and that the fixture stays put. Simple.
Choosing the Right Concrete Screw for the Job
There’s so much variation that choosing the right screws for your project can soon become a headache. Screws differ in head designs, the type of thread, whether they meet building standards and regulations, and the materials and finish they come in.
Screws with hex heads are some of the more common types and include an integrated washer just below the head. They are suitable for uses where the head and washer can protrude from the item being fastened. A hex head offers easy installation in things like railings and steel structures.
Pan and flat-head concrete masonry screws offer flush finishes in varied applications, particularly in countersinking. The design though means lower holding strength than a comparable hex head. You’ll find these used in items like electrical enclosures and channelling.
Go with screws that have connecting threads for fixing things like pipe clamps and railing, especially in overhead applications like ceilings. Items will definitely be easier and quicker to install, without forgoing holding strength. Choose screws with internal threading as a good alternative to drop-in anchors, and fixtures like pipe routing or ventilation ducts. Or use types with external threads in common applications. such as cable routing or attaching lights.
Industry Regulations and Materials
Screws need to abide by guidelines and regulations to ensure they work with the intended fixture and the environment they’re used in. This means they have the correct strength, won’t cause structural decay or damage, and most importantly aren’t a safety risk. All concrete fasteners sold in Australia must abide by rules set out by the European Technical Approval (or ETA) both in terms of specifications and when used in areas prone to fires, flooding, and earthquakes.
As for materials, different steel grades and types are used. Carbon steel is the most common material, but higher-grade 410 steel, treated with silver or corrosion-resistant zinc galvanised coatings is common as well.
Lengths and Diameters
Lastly, choose screws in the right size. Lengths generally range between 30 and 150mm, and diameters (including the thread) range from 4 to 16 mm. Most screws are sold in metric units, but for specialised uses, you’ll also find imperial sizes.