February 2001
Should You Worry About Sloping Floors?
If you're buying an old house with
sloped floors, here's what you're getting:
-
Extra charm at no additional
expense (the owner's perspective)
-
A structurally-unsound home
(the inexperienced home inspector's perspective)
-
An ability to hose down your
dining room floor (the practical homeowner's perspective)
In most cases, none of these
choices is quite accurate. Sloped floors are common in older homes,
and even in homes as new as 15 to 30 years.
Sloping floors are most often
caused by normal and acceptable deflection (bend) in the wood joists, which
comprise the floor structure. In some cases, the slope is caused or
aggravated by similar deflection in the girder (main bearing beam) that
supports one end of the joist sets. But, even in this scenario, there
is usually not a problem that needs repair.
As an organic material, wood
joists are prone to deflection under load. However, the amount of bend
or deflection allowed by most building codes (typically, joist length
divided by 360) does not address the nature of lumber to
"creep." Creep, in this sense, means to normally bend over a
prolonged period of time.
A new floor design that satisfies
code requirements for bearing capacity and rigidity (resistance to bend) may
still be appreciably sloped after many years of service. The
likelihood a given floor has for bending is affected by many factors, but
the most common primary cause is simply old age. Pronounced floor
slopes can, however, be an indication of a structural problem that needs
attention. If you are considering a purchase of any home with
noticeably sloped floors, consider these four factors:
-
Age of the Home
Expect to find more slopes in an older home. Even a slope as great
as an eighth-inch per foot in an 80-year-old home may be no problem,
while any readily discernible slope in a 5-year-old house would be
reason for concern.
-
Direction and Shape of
the Slope
Floors that dip in the middle are usually caused by non-structurally
significant joist deflection, but sloped or tilted floors that are
straight (i.e. slope in one direction) may indicate a more serious
foundation or bearing wall problem.
-
Joist Sizes, Spans and
Spacing
Assessing the design of a floor system usually requires a
professional engineer, but as a gross general guide, joists that are 2
inches by 8 inches, and are set 16 inches apart (standard), are suitable
for spans of up to about 12 feet. Joists that are 2 inches by 10
inches at the same spacing are suitable for spans of up to about 16
feet.
If you have sloped floors with 2-inch by 10-inch joists that run 18 feet
between the end supports, you probably have, or will have, a problem.
the species and grading of the lumber also impacts its span
ability. The Western Wood Products Association has an easy-to-use
online span table, which can be accessed at www.wwpa.org/techguide/pdf/floor.pdf.
(Adobe reader is needed to view this table).
-
Wall Crack Patterns
Some wall cracks can indicate evidence of an ongoing problem. Look
carefully at the interior door frames set in partition walls parallel to
the joist runs. Look for diagonal crack patterns extending from
the top corners of the doorway. Hairline cracks, or cracks that
have been sealed, indicate stability (assuming the house has not
recently been painted). Larger, newer cracks indicate a possible
problem. If the house has a bathroom next to the sloped floor
room(s), look at the wall tiles.
Ceramic tiles are non-resilient and will crack readily, so they are
often good indicators of movement. For example, in a 100-year-old
house we may not pay much attention to moderate floor slopes, but if the
same house has a new bathroom with large cracks in the wall tiles, we
know that the movement has recurred or worsened since the new bathroom
installation. This may be a problem.
Most importantly, if in doubt,
consult an experienced home inspector or engineer. While most sloped
floors are simply "charming," such slopes may also indicate a
serious problem.
Contributed by Andrew
Kleeman
National General Manager for Commercial Real Estate
U.S. Inspect
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