C&O Investigations: Buckled, Crowned or Cupped Hardwood
FLOOR Claims
By
Metropolitan Engineering, Consulting & Forensics
https://sites.google.com/site/metropolitanforensics/c-o-investigations-buckled-crowned-or-cupped-hardwood-floor-claims
This past winter we had a
lot of assignments dealing with damaged hardwood floors. The insureds claimed that water from the
winter storms caused the damages to the wooden floors. Cupping, buckling, and
crowning are three common problems encountered in wood flooring damage claims.
They are all caused by moisture changes in the wooden floor and the subfloor,
assuming the floor was properly installed.
Incorrect expansion gaps and lack of vapor barrier are also very common
reasons of hardwood floor buckling.
Wood will lose or gain moisture
until it is in balance with this surrounding environment. Higher relative
humidity (RH) usually causes the expansion of wood, because the wood absorbs
the increased water moisture vapors from the air; lower RH usually causes wood
to shrink as it releases the excessive water moisture vapors back into the air.
Acclimation
of hardwood floors to the jobsite, proper testing and control, before, during,
and after the installation plays a very important role in the behavior of the
hardwood floor. Many hardwood manufacturers suggest keeping the relative humidity
of the home in the range of 40-55% after the installation to maintain the
floor's original appearance. Not doing so will cause shrinkage, swelling
(buckling) or other unpleasant surprises.
Cupping occurs when the edges of a board are higher
than its center. See schematic below.
Assuming the
flooring has been properly installed, cupping can occur due to excessive
moisture which causes the wood flooring to swell, crushing the boards together
and deforming them at the edges. The board edges then “cup” due to excessive moisture
content (MC) in the flooring. Once the cause of the moisture is identified and
controlled, cupping can possibly be reversed.
Crowning is the opposite; the center of a board is
higher than its edges. See sketch below.
This can
occur when the surface of the floor encounters moisture or is left in wet or
humid conditions for an extended period of time. Crowning may also occur due to
previous floor cupping problems. If the floor is cupped, the floor should be
given ample time to dry. If the floor is sanded while the boards remain cupped
and moisture is still present, the sanding process can sand off the top edges
of the board and thus, the edges are lower than the rest of the board when it
returns to a normal MC.
Buckling occurs when wood flooring actually pulls
away from its sub-floor, lifting up to several inches in one or more places.
Figure 1.
Buckled floor. Here, our C&O
investigation discovered significant moisture issues in the basement, mold
growth throughout the basement and past water impacts. We also determined that no vapor barrier was installed
between the concrete floor and wooden floor and that the expansion gaps were
insufficient for the size of the hardwood flooring, causing it buckle in
several areas. We opined that the recent
winter storms did not cause the floors to buckle.
In addition
to incorrect installation (e.g., inadequate expansion gaps), the most common
reason that buckling occurs is excessive moisture or after a floor has been
flooded for a period of time. Other causes on nailed floors might be
insufficient nailing, incorrect nails or incorrect subfloor construction. On
glued floors, use of incorrect or insufficient mastics to an inadequate mastic
transfer, a subfloor separation or a subfloor contamination can cause buckling.
Improper Installation
Often times we see improper
expansion gaps in hardwood floors. Many
installers use one quarter inch gaps for expansion at the walls; the 1/4"
recommendation can sometimes cause problems for both hardwood and laminate
floors. Expansion gaps are spaces left around the perimeter of rooms, against
fixed objects such as columns, thresholds, hearths, baseboard, and other
stationary items built or secured into the framing structure of the home. Even
though wood flooring used is no longer living and breathing, it still reacts to
moisture changes in the environment. The cells in the hardwood will take on or
absorb moisture when the relative humidity is high, or when exposed to water.
Expansion takes place across the grain or width of the plank. Conversely, when
air moisture levels decrease, moisture content evaporates, shrinkage occurs.
Solid
hardwoods by far, will expand and contract more than engineered products. How
much will depend on the layout involved, seasonal change in relative humidity,
specie selection, and type of hardwood cut. For smaller areas such as 10' x 12' rooms,
leaving 3/8" expansion would be satisfactory. However getting into larger
layouts over a few thousand square feet it would be wise to stay within the age
old guideline of at least 3/4" on the perimeter. At other times we see no vapor retarder between
a concrete slab and wood flooring, as is recommended by the National Wood
Flooring Association. See NWFA Technical Publication No. C200,
Problems, Causes and Cures of Hardwood Floors, 2002.
Based on the
above discussion, there are quite a few causes of wooden floor damage: The home
owner turning the air conditioning off and the RH rises to greater than 55%; the
floor supplier delivering wet wood. The contractor / sub-contractor / installer
not checking the concrete slab or the sub floor, contractor not acclimating the
floor long enough, not installing the floor properly, and so on.
The C&O Investigation
After determining the facts
regarding the history of the hardwood floor installation and maintenance, the next
step of a C&O investigation is to identify the moisture source: high indoor
RH, site drainage issues, crawlspace or basement moisture issues, a water
spill, a leak from a dishwasher hose or a plumbing leak, etc. Most insureds fail to recognize the importance
of the moisture content in the actual subfloor. Without paying attention to it,
an imbalance between the subfloor and wood flooring can cause unsightly effects
with the most common being cupping. Both wood and concrete subfloors should not
be exposed to excessive moisture. However, this is easier said than done, as we
always observe significant issues with the moisture management around the
building. The main moisture “culprits”
are listed below:
Culprit #1: Rain Gutters and Downspouts Discharging
next to the Building Foundation
Improperly constructed and maintained
rain gutters and downspouts are one of the leading problems of moisture intrusion
into the building. Clogged gutters and downspouts from leaves and disconnected
downspouts, are all factors that could allow water to discharge immediately
next to the foundation. A downspout extension that delivers water away from the
perimeter of the home is a simple form of moisture prevention.
Figure 2. View
of the rain gutter discharging immediately next to the crawl space,
contributing to the moisture problem.
Culprit #2: Unventilated Crawl Spaces and Basements
A crawl space is an area
below a wood subfloor or below the floor joists. The crawl spaces and high
humidity basements account for a large number of wood floor problems. Proper water
drainage and air ventilation must be available and the area be protected with
thick plastic film to minimize air vapor affecting the sub base. Covering is
one requirement, keeping moisture from collecting or forming in puddles on top
is another. Excessive moisture in this area can also lead to mold growth on
surrounding framing members. Poor drainage has been known to seep into crawl
spaces as well. Another problem area with the crawl spaces is that many leaking
utilities exist there, with the insured almost never inspecting the crawl space
(out of sight, out of mind). On many occasions, the insured improperly
discharges the dryer vent into this space, causing significant moisture problems
(See Figure 3).
Figure
3: View of an unventilated crawl space
and the dryer vent pipe running through it.
Note the lack of a vapor barrier.
Also note the moisture impacts on the walls and bottom of the crawl space. The damaged wooden floor is located
immediately above this high moisture area.
Culprit #3: Improper Drainage
Many homes that are built
on sloping surface face drainage issues, as the upgradient water is moving
towards their home. Most modern homes and their developments take drainage into
account when they are built. The problem arises when the insureds expand their
homes, without taking site drainage into account. On some occasions, the subsurface drains have
been damaged by new construction or are clogged, and so on. Thus, diversion of the water away from the
building is not possible, leading into moisture problems inside the home.
Lack of diverting ground
water away from the foundation creates a wick effect. Any standing or subsurface
water has to go somewhere. If you find your home falls into this category after
heavy rains or major snow melt, corrective measures should be taken. Depending
on the circumstances it may be as simple as digging a few trenches or more
complex, by installing a drain system.
Figure 4.
View of a rainwater accumulation area immediately outside the crawl
space. Note the settlement gap that also
allowed rainwater to enter the crawlspace. This and several other areas around
the building contributed to the moisture problem inside the crawlspace.
Many
other areas of moisture intrusion into the building exist: sprinklers that
deliver too much water close to the building, window wells receiving rain
water, unsealed foundation walls, settlement around the building, and so on. Unless these moisture sources are checked,
they can enter the building basement or crawlspace and adversely affect the subfloor
and the wooden floor.
Metropolitan Engineering, Consulting &
Forensics (MECF)
Providing Competent, Expert and Objective
Investigative Engineering and Consulting Services
P.O. Box 520
Tenafly, NJ 07670-0520
Tel.: (973) 897-8162
Fax: (973) 810-0440
E-mail: metroforensics@gmail.com
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