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How Level is Level?
By George Porter
How can you tell when a home is out of level? There are some
regulators that say that you have to be within an inch all over
the home and there are others that say that if everything is working,
doors, windows, etc., then it's level enough. There should be
a way to absolutely say when the home is too bent on the frame
or in the roof. How about when the tail ends of the main beam
are hanging above the supports at the rear of the home because
of the camber? How much is too much there?
These and many other questions have been coming up over the
last 30+ years for me and I guess I thought no one really knew.
I certainly never asked anyone who gave me an answer other than
"well, when I look at a problem like that, this is what I
do" and then they proceed to tell me what they believe to
be the facts. Guess what, all this is written down and has been
available to everyone for over twenty years. It is somewhat embarrassing
for me to tell you where I found this wealth of information. It
has been right under my nose and I never thought of looking there.
All about this question and thousands more besides are found in
a government document called Part 3280; you might know it better
as the HUD Code. This is so typical, where is the last place you
always look for help when you can't figure something out and all
the stuff you have been dreaming up doesn't seem to work? Well
it's the instructions of course! Somehow I've got to get it into
my head that getting caught with instructions in your hand doesn't
prove to the world that you are too dumb to figure this out by
yourself. There is always room for improvement I guess.
Back to the question of level! According to Part 3280, subsection
3280.305 (d) it clearly states the formula for allowable deflection
(bending) of girders (main beams) is L/180. "L" is defined
by the clear span between supports or two times the length of
a cantilever. So.. If you support your homes eight feet apart
under the beams then "L" is eight feet in your case.
A cantilever is a projection supported only on one end, like a
diving board, or in our case, the distance between the beams and
the sidewall of the home. What you do is divide that length (eight
feet) by 180 and you get the maximum deflection allowed under
the HUD Code. It is easier to do this in inches so let's use 96
inches instead of 8 feet. 96 divided by 180 ' .53 inches
or a little over 2 inch.
The sidewalls can be measured the same way but they are not
beams, they are floor, and the floor has a different standard
L/240. If the floor extends out from the beams 48 inches then
you must use the rule for cantilever and double the distance.
This makes sense because if you cut a span between two supports
in half you would have two cantilevers pointing at each other.
It is assumed that each cantilever is half-way to the next imaginary
support so you double its length to keep the deflection ratio
equal. To get the number you take the 48 inches multiply times
2 (this gets you "L") and divide by 240. The answer
is .4 inches or about 3/8 of an inch.
That's the way you prove you are right and it is in the federal
code, and yes, I have called several different industry engineers
about this and they all agree that this is correct but, they also
all said there is more to it than that. And then I learned one
more thing that I always knew but didn't realize it. The HUD Code
is a performance code. What this means is that in addition to
the "L over whatever thing" the home must also fit and
For instance, if you were within the tolerances of the HUD
Code but the doors did not work right then you would have to do
whatever would be the corrective measures for them to close as
they should. Another example would be if the frame camber was
holding up the tail of the home a half inch above perfect level
and everything inside fit and functioned correctly then you could
just wedge it tight and leave it there.
One last example, if the home is perfectly dead level but the
doors don't work and the marriage walls have a two inch gap between
them you still are not done. In order to complete the assembly
of the home so it complies with the HUD Code these problems will
have to be addressed. The solution might be to actually take it
out of level, but within the HUD tolerances for the floor and
For all these years I have been referring to whether the home
was level or not. What I should have been doing was asking if
the home fit and function correctly. Level is important, but there
is more to good installation than that. Whether or not the home
meets the performance criteria for the HUD Code is the measure
whether the home is correctly installed or not.