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Feeling Strapped And Going Nowhere?
By George Porter
This is exactly the feeling you want if you happen to be a
person inside a HUD code home. Unfortunately, that is not always
the case. As a matter of fact, in my experience, it very seldom
is the case. Having been in the business more than thirty years,
and having installed hundreds and hundreds of homes, all of them
in a hurricane zone, at least from '76 to '94, I thought I knew
a little something about anchoring. Then I met two people who
caused little beads of sweat to break out all over my forehead.
About eleven years ago, I attended a meeting in which Robert Fuller
(then Director of Manufactured Housing, at HUD) gave a talk about
installation. At the time, he was in charge of compliance and
he said HUD had conducted a survey of one hundred homes across
the country and all one hundred homes were found to be incorrectly
installed. Furthermore, the most common mistake is that the homes
are improperly anchored. He then asked the audience of several
hundred if they ever used concrete collars. We all looked at each
other with the puzzled expression of "concrete what?"
It seems these little items have been required in certain circumstances
by HUD since 1976. It sure was news to me and everyone else there
too. Mr. Fuller made a very big impression on me that day. The
meeting was held in Delaware and all of that state as well as
the entire Eastern Shore of Maryland and Virginia are located
squarely in the middle of the hurricane zone. You must realize
this was using the pre _94 Wind Zone map. On July 13, 1994, HUD
issued a new Wind Zone map and this area was de-rated to Wind
Zone 1. (apparently we are not going to have any more hurricanes???)
According to what we heard, very few of the homes were properly
anchored.
I think everyone there was kind of hoping that what Mr. Fuller
was talking about didn't really apply to them and he was discussing
some strange condition in say, Kansas. Unfortunately he was not,
there's nothing quite as discomforting as when a government official
is right, you're wrong, and he is talking to you.
This was just about the time I decided to start giving seminars
on installation and I needed to go find an expert. That's when
I met a fine fellow named Locke Jones from Minuteman Anchors.
Locke was a very big help in writing the section on anchoring
in my book. I could not have done it without him. He told me more
about anchoring than I ever dreamed anybody needed to know. Locke
was giving seminars for Minuteman on the proper anchoring of manufactured
housing in the very early '70's, long before the HUD code ever
existed. He, in fact, was promoting the standards that HUD eventually
adopted. Locke has since gone on to other areas of the industry
but I am still grateful for his help. So how in the world did
most of us in this industry get so far off the mark?
If you think your homes are properly anchored, here's a little
test for you. I've done it hundreds of times and actions speak
much louder than words. If the anchors were installed after the
home was blocked, they run in at an angle underneath the edge
of the home. The steel straps from the tops of the anchors go
to the frame of the home. Keep in mind that there are criteria
for anchoring systems. The entire system must be rated at a working
load of 3,150 lbs. and withstand a 50% overload or a momentary
surge of 4,725 lbs. Reach under the home with your foot and step
on the strap somewhere about half way between the top of the anchor
and the steel frame of the home and stand on it. If this anchor
does not have the concrete collar Mr. Fuller talked about, or
a stabilizer plate, which is much more commonly used, the head
of the anchor will probably move 3" to 6" through the
top of the ground. Now if your foot weights more than 4,725 lbs.,
maybe this home was anchored.
Earth anchors are all rated according to their holding capacity,
but that rating is tested by pulling them straight out in exactly
the same direction that they went in. The metal plate or helix
at the bottom of the anchor is what does the holding, not the
rod. The rod can easily slice sideways through softer ground and
allow the home to come off of its foundation. If the entire anchor
was pointed in the direction of the steel frame it was tied to,
it would be an entirely different story. But you can't put it
in that way once the home is already there, unless the home is
high enough off the ground. Additionally, at a 45 degree angle,
the anchor must be 1/3 longer to be the same depth as if it were
straight into the ground. This is important because it is the
dirt above the anchor that keeps it in the ground and if it is
not deep enough it will not work as intended.
I see many people use a post hole digger to install anchors.
They dig the hole, throw the anchor in the hole and put the dirt
back in. After some rain runs into this hole does anybody out
there think it would be hard to pull out? Even if the ground is
heavily tamped as the dirt is replaced in the hole, I really don't
think it is as good as the helix screwing itself into the ground.
When you screw an anchor into the soil you leave about 3 inches
of undisturbed soil between each cut of the helix as it goes down.
This is what makes the anchors work from the moment it is installed.
Some people put anchors in the wet concrete when they pour
the footings, runners, or slabs. This can pose several problems.
In many cases, the anchor strap goes straight up to the I-beam.
This definitely holds the home on the ground and resists any upward
forces, however lateral forces, or the wind blowing on the side
of the house, are a major factor. You need some kind of lateral
resistance in order to keep the home on the piers. This can be
accomplished by having an additional anchor strap from the same
anchor head run to the opposite I-beam of the same chassis and
one over there coming back, creating an "X" between
the two frame members. These lateral straps in addition to the
original vertical strap from each beam down will cover both loads.
A single strap could be used if the angle between the anchor and
frame is 45 degrees _ five degrees. If the angle exceeds this
and the straps start becoming more vertical, the anchor will have
to be moved away from the frame to achieve the 45 degrees. If
the home is very close to the ground and the angle is far less
than 45 degrees, it is not achieving its vertical component. So...
you have two loads on the anchor, one vertical and one horizontal.
At 45 degrees of strap angle from the beam to the outside of the
home, you take care of both loads. If you can't get the 45 degrees
then divide the load between two straps per anchor, one vertical
and one horizontal.
But even with all that, we have to talk about what the anchor
is sitting in. If you have installed a concrete anchor of about
8" long with a little hook at the bottom that you imbedded
in wet concrete you may have a problem. Remember each strap has
to be able to resist a working load of 3,150 lbs. and a momentary
50% overload. The only thing holding this anchor is the concrete
footing, and the weight of the footing is the only thing that's
keeping the footing on the ground. It is not locked there in any
measurable way. Consequently, if you figure how many pounds of
concrete it takes to resist the load, you will find that it takes
a little more than 1.17 cubic yards. Unfortunately all of its
resistance is a function of its weight and not many footings are
that big.
There are so many engineering principles and calculations that
come to bear with anchoring it is unbelievable. There are many
kinds of anchors for use in many kinds of soil. There are devices
for solid rock, coral, sand, and wet concrete and all things in
between. If you put the wrong kind of anchor in the wrong kind
of soil, (you test the soil with a 5 foot rod called a soil probe)
you have done little more than waste your money and create a false
sense of security with the homeowner.
Anchoring is a lot more complicated than I ever thought it was,
and it certainly is something that should be done right. Anchoring
is a perfect example of an attitude that's fairly common in the
industry. "I've been installing homes for years and I know
what I am doing." I'm sure these guys mean well and maybe
they really do know what they are doing, but I think it would
be good if every once in a while we all did a severe self-examination
and ask ourselves how much of this stuff that we "know"
could be verified by a qualified engineer. I can assure you of
one thing, if there is ever a problem with wind damage due to
a home that you have installed and an engineer comes to inspect
it, he won't care how long you've been doing this work. The local
customs of anchoring may find themselves in deep trouble when
they are compared to the Federal Emergency Management Agency publications
on anchoring and installation. The factory whose homes you are
installing has a few ideas about anchoring as well as all manufacturers
of anchoring equipment, and then there's HUD, and they've got
a lot of ideas about anchoring.
There are at least a dozen ways to make an anchor not work
and still have it look like the home is anchored. You might not
have the strap going to the top of the beam or you might not have
4+ wraps around the split bolt or the strap might not be certified,
and perhaps the anchor is the wrong class for the soil type, lateral
angle from the beam to the anchor might not be 90 degrees and
the beam cuts the strap...and much more.
Anchors do work, but they must be done with lots of attention
to detail. Close counts in horseshoes but not in anchoring.
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