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This Place Is A Site
By George Porter
For the first twenty years of so in this business, I thought
site preparation meant removing things on the ground that would
cause the tires to go flat as you backed the home on the lot.
Few things are more frustrating than having to put on some new
tires so the home can go another five feet to its final destination.
How many times have you put a home on a lot and before you
were through, you wished you had done a few things to the site
that would have made the job a little easier. If we could turn
our hindsight into foresight, we would all be a darn sight better
In the last year or so, I have come to believe that site preparation
is one of the absolutely most important and most overlooked steps
in the installation of a home. Improper site preparation can adversely
affect (and this is only a partial list):
- The ability of the anchors to hold;
- The depth of the frost penetration;
- The amount of frost heave in the area of the home;
- The stability of the footings;
- The ability to skirt the home;
- The ability for the home to resist moisture and the subsequent
rotting and mildew;
- The resale value of the home five to ten years down the road;
- The ability of the home to remain structurally sound and
livable on that location;
- The health of the people inside the home;
- The amount of energy needed to heat and cool the home;
- The ability to ever put additions on the home;
- And, possibly in the future, the ability to finance or insure
What do you have to do to avoid all these problems? It's simple.
The home should be located in an area that's higher than its immediate
surroundings and free of vegetation. How much higher is determined
by the topography of the ground in the area it's located. In an
area that has large amounts of rain, it should be able to flow
around and away from your home by at least ten feet. If you are
in an area that doesn't get much rain, and you are on fairly well
drained land, your site can be as little as four to six inches
above its surroundings. On very flat land that is not well-drained,
you may want the site to be a foot or higher above the surrounding
The idea is to keep the area under the home as dry as possible.
Water is the enemy here and we have to do our best to be sure
that it does not get under the home and stay there. Moisture drastically
affects the load-bearing capacity of soil. It acts as a lubricant,
and the grains of sand, silt and other particles in the dirt will
part more easily. In other words, if the ground beneath your footings
turns to mud, the mud will part and the footings will sink. If
the ground around your anchors turns to mud, the anchors will
easily pull out. Consider what could happen when a hurricane visits
a site like this. You have strong winds and lots of water. Improper
site preparation will cause the anchors not to hold, the footings
to sink and away goes the house.
Unfortunately site preparation can usually only be accomplished
at one point during the installation, it has to be done before
the home gets there. If you decide to re-grade after the home
is already installed, how do you get the ground under the home
higher? Conceivably you would skirt the home and bank the dirt
up against the ground enclosure and slope it away from the house.
What you end up with is a somewhat shallow, to maybe fairly deep
dirt basement that will fill with water and stay there. The ideal
situation is that if you threw buckets of water under the home
before it was skirted, it would drain away to an area at least
ten feet away from the site.
An improperly prepared site is one of those problems that you
start putting band-aids on. The customer may have high humidity
due to water under the home, so you then advise the customer to
get a de-humidifier. The customer begins to de-humidify inside
the house, but the moisture in the underside of the home causes
the frame to rust out prematurely and the floor joists to warp,
crack and grow mildew. If the home has paneling, it will begin
to delaminate. In the north in winter, when you have excess dampness
under the home, water vapor will find its way to the roof cavity,
freeze on the underside of whatever kind of roof you have, be
it metal or wood, and form fairly large sheets of ice. When the
sun comes out, it will melt these areas of ice, water will then
run down the underside of the roof and create stains in your ceiling,
giving the impression of a roof leak. Unfortunately it is a roof
leak that no amount of patching on the roof can fix.
Site preparation is one of the cheapest and most effective
ways to preserve the quality of the home, and the comfort of the
people residing therein. Damp insulation in the belly board below
the floor suffers a drastic reduction in R value. If it becomes
so laden with moisture that it actually falls through a rotting
belly board, your heat bill can skyrocket. The humidity that forms
on the inside of the windows of the home due to the dampness underneath
the home can cause a lot of damage to the windowsills and in worse
cases, even rot away the framing that surrounds the window. Proper
grading of the lot prior to the installation of the home should
eliminate nearly all the moisture caused problems we face in our
All vegetation should be removed in the area under the home.
Once the perimeter of the home is enclosed, the grass and weeds
die and become an enormous fire hazard. The least little spark
from a heat tape, or any place else can set it off and it will
completely engulf the underside of the home in less than a minute.
Another reason for removing the vegetation is that it harbors
all sorts of vermin. I have personally found myself face to face
with raccoons, rats, and reptiles in an area with very little
room to maneuver. As a result, I have had to repair and/or replace
three and four foot sections of skirting on customer's houses
where I felt the need for a quick exit.
Attention should be given to things that may eventually come
to reside under the home, like the roots of nearby trees. Even
under the best of site preparations, the area under the home is
an ideal environment for tree roots. Over the years, they will
seek it out and the roots that were already there and were not
removed during the site preparation will grow larger. Once these
roots have expanded and shifted the footings, you have no choice
but to redo the foundation. If you cut the tree root, it will
rot and create a soft spot where it once was, and if you don't
cut the tree root, it will continue to grow. If you remove a big
enough root on a tree that's very close to the home, you could
very well kill that portion the tree that is hanging over the
home. If the tree is large enough, the dead limbs could eventually
fall onto or into the roof.
These considerations merit some discussion with the homeowner
as to exactly how he wants to take care of the tree problem. You
can't set the home on the roots, and if you cut the roots, you
will probably damage the tree. Whatever the homeowner's decision
is, make sure you have a short letter describing the problem,
his decision and have him sign it. Keep the letter in a file for
as long as you have a place to store it. Sometimes, many years
down the road, homeowners have a way of forgetting details when
they have a large tree limb in their living room.
As a sales person of manufactured housing, I would be very
concerned about what lot this home was going on. Site preparation
is very important and I would certainly want to know how much
of it my company had to do when I told them that set-up was included
in the price of the home. If you simply roll it on to a field
with poor drainage and no site preparation, the customer will
always have complaints caused by moisture. The dealership will
never be able to correct these complaints short of re-installation
after a proper site preparation of the home and the industry as
a whole will have suffered because the customer will be absolutely
sure his problems are caused by the fact he bought a "trailer".
If I were a lender making fifteen to twenty year loans on homes,
it would be extremely important for me to know the site was properly
prepared. It would be so important to me that I would allow customers
additional financing for site preparation. It is one of the most
important ingredients in the preservation of their collateral.
Banks really should take a much larger interest in these things.
All the installation manuals I have ever read require you to
put at least six millimeter plastic down under the home to help
retard the moisture. If the site is improperly prepared and water
runs under the home and gets under the plastic, there is no way
for it to evaporate. The plastic is good and necessary, but only
on a site that is graded for drainage away from the home. If you
leave the vegetation on the ground and put the plastic down, you
are creating an enormous mushroom and slug farm-the odors of which
will be most unpleasant to the occupants of the home, particularly
people with allergies.
All of the things talked about here are the reasons you should
do the right thing-grade the lot and keep it free of vegetation.
Having completed that, you will then be able to say, "This
place is a site".