A User’s Guide to Construction Lag Bolts

A lag bolt is also referred to as a lag screw. The most common use of a lag bolt is in heavy construction when wood needs fastening to another piece of wood or other type of material. Because it’s capable of supporting heavy loads, a lag bolt is often used in residential construction projects such as building decks, wooden staircases and outdoor swing sets.

The Strength of a Lag Bolt
A typical lag bolt is capable of supporting loads much greater than the weight of construction materials. When the bolt is comprised of steel, lag bolt strength is usually 35,000 psi for shear strength and up to 85,000 psi for tensile strength.

Lag Bolt Fastener Size Options
Common lag bolt sizes include diameters of 0.500 to 0.750 inches and lengths of up to 18 inches. Lag bolt dimensions include a standard thread length of 0.500 inches to 6 inches, with 3 to 7 threads per inch. The typical tolerance in our lag bolts is +/- 0.005 inches.

Lag bolts

Tips for Placing a Lag Bolt
In order to place a lag bolt into a piece of wood, you must first drill a pilot hole. Making a lag bolt pilot hole and using a screw anchor ensures that the head of the screw does not break before the entire length of the lag bolt is pushed into the wood. Whether the lag bolt has a gimlet, semi-conical or conical end, a pilot hole ensures optimal placement and durability of the bolt.

Lag Bolt Types
A lag bolt fastener is available in several different options. A concrete lag bolt features coarse threads that are ideal for fastening wood to concrete or masonry structures. These bolts feature flat bases and lengths of up to 14 inches to maximize both tensile and sheer strength of the structure.

Applications for Lag Bolt Fasteners
A lag bolt can be used in many different residential and commercial construction applications. Construction crews use these lag fasteners when building wooden decks or when attaching a wooden frame to a concrete basement floor slab or a masonry foundation wall. Home improvement specialists and do-it-yourself folks could use these bolts to build a swing, deck or even a tree house.

Advantages of Using a Lag Bolt
The main advantage of a lag bolt is that it can be placed into concrete after it has already set. This is ideal for finishing a basement years after a home has been built. It also allows a homeowner to hang a television set or place shelving on a concrete wall.

A lag bolt is important for residential and commercial construction, improvement and remodeling projects. We have a wide variety of lag bolt size options in stock. Our tool and die room also has the capability to produce custom lag bolt fasteners in the diameter, thread and length that your project requires.

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