JulianConstruction.com: Common Types of Anchor Bolts Used in House Bolting
by Julian De La Torre Julian ConstructionOver the years we have learned the effect seismic
activity has on a building and how to minimize the impact of a quake.
Earthquakes can cause a building to slide, shift
off of its foundation and overturn. They can also buckle cripple walls, causing
them to collapse.
House bolting is also called foundation bolting, anchor
bolting, or seismic retrofitting. The purpose of house bolting is to make the
structure safer and prevent damage during an earthquake. The bolts strengthen
the wood frame by connecting it securely to the foundation. The two types of
bolts commonly used in house bolting are epoxy foundation bolts and expansion
foundation bolts.
If you live in an older home, an epoxy-set
foundation bolt will be your best option. Older homes tend to have weaker
concrete. Epoxy bolts are longer than expansion foundation bolts, which means
they must be inserted deeper into the concrete. The deeper insertion improves
the bolt’s performance.
Epoxy bolts are also a good choice in locations
where the motion of a quake can lift up the structure. Because of the length of
the bold, the chances of the wood frame pulling away from the concrete
foundation is reduced.
Expansion foundation bolts are best used with
foundation concrete that is in good shape, such as concrete in a new home or a
new foundation in an older home. This is because the bolt requires “strong
concrete” to be effective. The bolts can be used as long as they don’t crack
the concrete.
Anchor bolts need to be installed with square plate
washers. The washers create a sturdier and more secure connection to the
foundation. Before square plate washers came into use, the bolts were secured
with round washers. However, round washers did not have enough holding
strength.
Sometimes other types of anchors may be necessary,
depending on whether or not the home has cripple walls. Homes can also have a
combination of cripple walls and places where the floor rests on the
foundation.
To find out if your house needs bolting, go down
into your home’s crawl space. The crawl space is the area between the
foundation and the first floor. Find the sill plate, which is the board located
on top of the foundation. Most but not all sill plates are made of lumber. The
board runs horizontal to the vertical wall.
Inspect the sill plate for the head of anchor
bolts. In most cases they will appear
every four to six feet.
Many homes built during and after the late 1930’s
will have some form of house bolting (Los Angeles and other earthquake-prone
cities especially). Check to see if any existing bolts have become weak, or are
set to far apart to provide the support needed in a quake.
Any work that gets done to strengthen the structure
of your home needs to meet current standards. A foundation repair expert or
foundation contractor should be consulted to determine if any existing bolting
needs to be replaced, and the extent of any new bolting that may be necessary.
Julian De La Torre, expert in Los Angeles foundation inspection, repair & house bolting and founder of Julian Construction (http://www.julianconstruction.com) in Los Angeles, has inspected over 15,000 structures for building & safety and done more home foundation repair than anyone else (http://julianconstruction.com/about/ ). See their video: https://www.youtube.com/watch?v=6I8j7dXzpj4
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Created on Dec 31st 1969 18:00. Viewed 0 times.