Typical Length Measurements for Building Fasteners
Just as buildings come in all shapes and sizes, Building Fasteners and even Marine Fasteners or Line Fasteners are also manufactured in many different shapes and sizes. There are standard measurements used in common applications as well as the ability to create customized fasteners for almost any application.
How Is Fastener Length Calculated?
The length of a fastener is measured from the tip to the where the surface material is assumed to be. That means that a building fastener that is meant to be countersunk will be measured from the top (which will be flush with the surface) to the tip.
In contrast, the length of screws with a head that will sit above the surface are measured from the bottom of the head to the tip of the screw or bolt. Some common building fasteners measured in this way are:
pan head screws
round head screws
carriage bolts
lag bolts
truss head sheet metal screws
hex head bolts
socket head caps
How Do You Know Which Length to Order?
The length and design of the fastener ordered will depend largely on the material being ordered and the application. When building wood framing for a structure or flooring the screws and bolts needed will probably be specified by the building codes. A good rule of thumb is to be sure the fastener will penetrate the wood at least 1 to 1 1/2 inches (assuming that this length won’t penetrate through the wood).
If the fastener is too long it could result in split wood and if they are too short the project will not hold together.
When dealing with steel the length of the fastener will often be determined by the thickness of the steel and the nut required to complete the attachment. In many applications a good rule of thumb is to ensure that only one thread touches the steel. There also needs to be enough thread extending past the steel to hold on the nut and possibly a washer.
If you are in doubt about the length required and the applicable building codes don’t help, contact a fastener distributor or manufacturer for some guidance. Remember that the total length is based on where the surface of the material is and be sure to account for a nut and washer when working with steel.
