Baffled by the sheer variety of masonry anchors? No doubt you’ve wanted to add wooden or steel fixtures into concrete, block or brick, but didn’t know which type of anchor to use. For light to medium tasks, say handrails, wall brackets or junction boxes, this will definitely have to be a sleeve anchor.
What are Sleeve Anchors?
Sleeve anchors are some of the most versatile masonry anchors out there. They are a type of mechanical expansion anchor, that get their name from the metal sleeve that expands into the surrounding material when tightened. This allows for high holding strength, so the attached fixtures into concrete and other masonry will stay put no matter what. One of the most recognisable names among Aussie tradies and DIYers are the Dynabolt sleeve anchors.
Parts of a Sleeve Anchor
Sleeve anchors consist of several parts. The sleeve sits atop a threaded bolt or stud that flairs outward towards the end. At the tightening end, there is the head, which puts pressure on the sleeve with each turn. When at maximum torque the sleeve presses on the bolt end to fully extend the sleeve into the substrate. Depending on the type of sleeve anchor, there can also be a nut and washer, and these are found in hex head sleeve anchors.
Types of Heads
The type of head determines the holding strength of Dynabolt sleeve anchors, and the finish required. The most common are hex-bolt sleeve anchors and these allow for the most torque to be asserted on the bolt and sleeve. This means they also have the highest holding force. Next up are headless anchors, that are threaded to the top, and require a hex nut and washer to be installed. Similar to hex heads are acorn head sleeve anchors. For finishes that sit flush with the masonry surface, look to countersunk and flatheads. They provide pleasing looks, and are often used for decorative purposes. There are also round head sleeve anchors used in similar finishes. Hex head sleeve anchors are tightened using a spanner or socket wrench, while flathead and countersunk anchors can be tightened with a Phillips screwdriver.
For attaching overhead fixtures into concrete ceilings and walls, look for eye bolt, hook bolt or tie wire sleeve anchors. These allow you to hang or suspend larger and heavier items safely.
To achieve that high holding strength, sleeve anchors need to be built tough. High grades of stainless steel, as well as carbon steel, are used for heavier loads. These can be hot-dip galvanised if they’re intended for outdoor use. They’ll stand up to the weather and won’t rust. For lighter applications indoors, there are zinc-plated steel sleeve anchors. The different types are recognised by the colour. Galvanised anchors are dull grey, stainless-steel anchors are silver(y), while zinc-plated anchors have a shiny hue bordering on yellow.
Sleeve anchors are used for a variety of wood and steel fixtures into different types of masonry. They can be used in softer concrete variants, hollow concrete, concrete blocks and mortar joints and brick. Typical applications include affixing door and window frames, handrails, pallet racking, bottom plates, brackets, machinery and equipment mounts and more. Depending on the type of sleeve anchor, and the materials, they can be used both indoors and outdoors for light to medium applications.
Overall strength depends on the size of the anchor. Dynabolt sleeve anchors are measured as the width of the threaded bolt and sleeve combination, given as a metric number in millimetres. There are M4.5, 6, 8, 10, 12,16 and 20mm. The overall length of the anchor varies, from 27mm to 157mm, with dozens of lengths within that range.
Using Sleeve Anchors
Sleeve anchors are inserted in the mounting points of the fixtures and fit in a pre-drilled hole in the masonry. For concrete, holes are drilled with a hammer drill to an adequate depth of roughly 10 to 20mm more than the overall length of the sleeve anchor, using a carbide-tipped bit. The width of the hole should be equal to that of the anchor to ensure a snug, secure fit. The hole is cleaned of any dust using an air tool or steel brush. The fixture is positioned and the sleeve anchor inserted by hand. Tap the anchor lightly with a hammer until the nut and washer are flush with the surface. Tighten by hand and continue with a spanner for hex head anchors and the right screwdriver for countersunk and flat head anchors. Torque levels, or how much the anchors needs to be tightened, are critical in that they determine optimal holding strength without deforming.
Since these are expansion anchors, there is also the need for proper spacing. As a rule, sleeve anchors shouldn’t be installed closer than 10 widths of each, to avoid the concrete or concrete block from rupturing.
Benefits of Sleeve Anchors
Sleeve anchors are cheap to buy, quick to install and used for a range of different fixtures in different concrete types as well as brick. All parts are pre-assembled to speed things up. When installed they fill any gaps or fissures in the substrate, thus ensuring higher overall strength. They can be used for both light and heavier fixtures both in and outdoors. And come in different sizes and heads for a range of finishes and applications.