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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
HUD code home with people in it. 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 twenty years,
and having installed hundreds and hundreds of homes C all of them
in a hurricane zone C 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 four years ago, I attended a meeting in which Robert
Fuller (now Director of Manufactured Housing, at Housing &
Urban Development) 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 found was that the homes were 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 under 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 being held in Delaware and all of Delaware as well as the
entire Eastern Shore of Maryland and Virginia are located squarely
in the middle of the hurricane zone. According to what we had
just 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.
When I decided to write my textbook on the installation of
manufactured housing, 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 would need to know.
Locke was giving seminars for Minuteman on the proper anchoring
of manufactured housing in the early '70's, long before the HUD
code ever existed. He in fact was promoting the standards that
HUD and NCSBCS promote today. 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 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. Bear in mind that there are criteria
for anchoring systems. The entire system must be rated at a working
load of 3,150 lbs. with no more than 2% stretch C and should withstand
a brief 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, it will probably move
3" to 6" through the top of the ground. Now if you weight
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,
as in the illustration, 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.
I have seen 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 in the hole they put the anchor
in, does anybody out there think it would be hard to pull out?
Even if the ground was heavily tamped as the dirt was replaced
in the hole, I really don't think it would be as good as the helix
screwing itself into the ground.
Some people put anchors in the wet concrete when they pour
the footings. This can pose several problems. In many cases, the
anchor strap goes straight up to the I-beam. while this definitely
holds the home on the ground and resists any upward forces, lateral
forces, or the wind blowing on the side of the house, are a major
problem here, and you have to have a lateral resistance in order
to keep the home on the blocks. This could be accomplished by
having the anchor strap run to the opposite I-beam and one over
there coming back, creating an "X" between the two frame
members. Uplift is a factor and can be accounted for by keeping
the angle between the bottom of the homes and the strap going
to the opposite anchor at 45 degrees " five degrees. If the
angle exceeds this and the straps start becoming more vertical,
the anchor will have to be moved 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 and
it is necessary that you also install a vertical anchor strap
to the beam directly above the anchor in the footing.
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 on the bottom that you imbed in
wet concrete you may have a problem. Remember each strap has to
be able to withstand a load of 3,150 lbs. and an occasional momentary
50% overload. So that means if you put two straps on one anchor,
you have to resist a sustained load of 6,300 lbs., and an overload
of 8,450 lbs! The only thing holding this anchor is the footing
that is poured in the ground, and very nearly the weight of the
footing is the only thing that's keeping it in the ground. It
is not locked there in any way unless it is pretty deep. Consequently,
if you figure how many pounds of concrete it takes to resist each
strap, you will find that it takes a littler over 1.5 cubic yards.
Obviously the dirts offers some resistance. However, nearly 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 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 awhile 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, some law firm like "Dewey,
Ripum, and Howe" will come calling with their engineer, and
he won't care how long you've been doing it. 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 home you are
setting up also has a few ideas about anchoring and then, there's
HUD, and they've got a lot of ideas about anchoring.
Next month, we'll talk more about flood hazard areas and buoyancy,
other kinds of anchors and "does a home really need anchors
anyway?" Any comments or suggestions, please contact George
Porter, Manufactured Housing Resources, P.O. Box 9, Nassau, DE