A lag shield
is a type of concrete anchor that is used in a variety of base
materials including concrete, brick and block. A standard lag screw is
used to expand the lag shield anchor once it is placed in the hole in
the base material. The length of the lag shield is designated as either
short or long. The short lag shield anchors are most commonly used in
hard, dense base materials while the long lag shield is used in softer,
less dense base material. The lag shield anchor is referred to by the
inside diameter of the anchor or by the size of the lag screw that gets
inserted into the anchor. The lag shield anchor is available in 5
different diameters in both the short and long versions. These diameters
include: 1/4", 3/8", 1/2", 5/8" and 3/4". The diameter of the hole to
be drilled is larger than the designated size of the lag shield. For
example, the 1/4" lag shield requires a 1/2" hole and a 3/4" lag shield
will require a 1" hole. Calculating the length of lag screw needed for a
job involves adding the thickness of the material to be fastened to the
length of the anchor and also adding space for the washers that are
used.
When spacing lag shields in the base material, it is important to
consider that the expansion forces which are created when the lag
shield is set are transferred to the base material. If the lag shields
are placed too close together, an interaction occurs between the
expansion forces of the lag shields. This may decrease the holding
values of both anchors. The industry standard for minimum spacing for
any type of expansion anchor is that they should be placed a minimum of
10 anchor diameters from each other and a minimum of 5 anchor diameters
away from any unsupported edge. If lag shields are used in applications
where the possibility exists for sudden impact or vibratory loads, then
the anchor spacing should be increased.
The installation process for a lag shield into concrete, brick or block includes four steps:
1. Drill a hole into the base material using a hammer drill and
masonry bit that is carbide tipped. The bit diameter should be the one
recommended for the lag shield diameter being used. Drill the hole the
length of the lag shield plus 1/2" in order to allow space for any
debris or dust created during the installation process.
2. Clear all debris and dust from the hole using compressed air, vacuum, or a wire brush.
3. Insert the ribbed part of the lag shield into the hole that
was drilled in the base material. Tap the lag shield with a hammer until
it is level with the surface of the base material.
4. Place the fixture over the lag shield making sure the hole in
the fixture lines up with the lag shield. Insert the lag screw through
the fixture and into the lag shield, turning the screw clockwise until
the head of the bolt meets the surface of the fixture. It is important
that the lag screw is not over-torqued because this can cause the lag
shield to spin in the hole.
Note: In some applications, the lag screw will begin to
tighten or torque-up before the lag screw head meets up with the
fixture. Should this happen, take a hammer and tap the head of the lag
screw back into the hole until it is flush with the fixture being
fastened. Use a wrench to retighten the lag screw into the lag shield
to complete the expansion process.
The installation of a handrail is a very critical application and
must be done with great care to make sure that it is erected safely and
properly. Contact the department of your city and/or state that would
be in charge of building codes. It is imperative that you find out what
the codes are and make sure that all codes are understood and followed.
These different codes may include allowable height distance from the
floor or stairs, the distance from the wall and/or the distance away
from the first stair. All of these codes have been placed on the books
for a reason and they are there for the purpose of protecting people
based on past experience.
If the lag shield is used for attaching a handrail to brick, it
can be placed into the brick or the mortar joint. The quality and
quantity of the mortar in the joint, the strength of the brick and the
quality of the installation determine the holding values of the lag
shield. Make sure that when the handrail is fully installed that the lag
shields are anchored fully and provide the holding values needed for
the particular application.
Lag shields
are good anchors to use when attaching a hand rail to brick or other
base materials. However it is important to follow all building codes to
ensure proper and safe installation of these lag shields. In this
specific application, proper installation is very critical because
people's safety can be at risk if installation is not correct.
As with any anchoring project, it is important to keep safety in mind and follow instructions carefully. Always remember to wear safety goggles, handle all tools with extra care and follow all technical specifications. This article is meant to serve only as a basic explanation of concrete fasteners. Always refer to manufacturer's instructions or consult a contracting expert during any anchoring project.
Article Written By:
Bob Carlisle, President of Concrete Fasteners
Concrete Fasteners, Inc. has over 40 years of experience selling concrete fasteners. We can ship out one box or a whole pallet of concrete anchors. Our products are of the highest quality... "your satisfaction is guaranteed". We ship all orders the same day the order is received.