Anchor Bolts Resource


Lag Shields, Bolts And Screws

Lag screws or bolts provide heavy-duty fastening for attaching two thick pieces of lumber. When combined with lag shields, these fasteners are enhanced, making it possible to attach items to hard surfaces, like concrete, concrete block, brick, and stone. 

Lag shields look like thick metal tubes, and they serve as anchors within the hard material that will accept and hold the screws. Zinc alloys comprise most shields, and some contain lead. Stainless steel types are also available for application areas with high concerns about corrosion. Threads inside the tube accept and secure the lag screw.

Two halves that click together form the shield tube. When a screw descends through the female threading inside the tube, the pressure expands the shield halves against the exterior material. The expansion creates a firm hold that permanently attaches the lag screw. 

This fastening system provides secure solutions in a variety of applications. When building a deck against a block foundation wall lag bolts combined with shields can be used to attach the ledger board for the deck's joists to the foundation. The fastening of smaller things, like shelving or a hose rack, to block or brick walls would also call for these fasteners. Their advantages include widespread availability and durability. Except for requiring a hammer drill to install them, no other specialized tools are needed. 

Lag shields come in both long and short sizes. Material depth and hardness determine the proper length. Builders select long lag shields for relatively softer materials or thick materials, as this extra length creates more surface area connection to hold a load. Short lag shields are appropriate for the hardest materials. The hardness of the material reduces concerns about the connection failing. Additionally, short lag shields naturally require shallower holes, which means less drilling into the tough material. 

Both professional builders and do-it-yourselfers can readily obtain these shields for their projects. Multiple fastener manufacturers serve the market and many provide a selection online. Big box home building supply retailers will stock lag screws and shields in all common sizes. Large retailers typically package screws and shields in specific quantities. Smaller neighborhood hardware stores sell these items as well and frequently sell them by the individual piece, which is useful for small projects. 

What Are Lag Shields Used For?

Lag shields enable the fastening of lumber, shelves, racks, or other items to concrete and brick surfaces. They form a sheath around the screw that expands and grips the hard surrounding material with a permanent connection. 

How Are Lag Shields Attached For Lag Screws?

A hammer drill, sometimes called a percussion drill, is needed to drill the holes in the hard material. The drill bit needs a carbide tip and a diameter that matches the exterior diameter of the shield. The depth gauge on the hammer drill assists with making the hole the proper depth to accommodate the shield. In the absence of a depth gauge, masking tape can be wrapped around the bit to indicate where drilling should cease. 

After the hole is drilled, the debris must be removed to ensure a good connection. A round wire brush is useful for clearing dust and chunks, and a shop vac can be used to suck out any remaining debris. 

The closed end of the shield goes into the hole first. It should be tapped with a hammer until it is flush with the surface. At this point, the shield is now ready to accept the screw. Care should be taken to avoid over-tightening the lag screw or bolt, as the application of excessive torque could disrupt a shield’s connection. 

Are Lag Shields The Same As Anchor Bolts?

Although lag shields can be called concrete anchors, anchor bolts typically describe bolts embedded in concrete when the material is poured. The concrete hardens around the bolts while leaving the threaded ends exposed. The threaded ends are then used in the process of attaching steel structural elements. 

Can Lag Screws Be Used In Concrete?

When combined with lag shields, which serve as anchors, lag screws are an appropriate choice for connecting things to hard masonry materials. Lag screws provide superior fastening strength compared to wood screws and are ideal when a connection needs to hold a heavy load. 

What Is An Expansion Shield?

Shields for lag screws sometimes go by the name expansion shield. The term arises from the fact that the screw applies pressure within the shield that causes it to expand and grip the hard material.