1475 IMPERIAL WAY, THOROFARE, NJ 08086
(P) 877-950-3667 (F) 877-950-2123 WWW.USAWOODDOOR.COM
Date: ______________________________________
Company: __________________________________
Attn: ______________________________________
Job: _______________________________________
Order #: ___________________________________
We are in receipt of your correspondence concerning the warpage of door(s) at the above
referenced job and have the following response.
Warpage may occur during the first year door(s) have been hung, this will be more
prevalent during the heating season. The door(s) must become conditioned to the humidity and
the temperature of the building. Hollow core doors are much more prone to warp than a solid
core door. Ninety-five percent (95%) of all warped doors will become straight after they go
through a complete heating and air conditioning cycle. Under the terms of the standard door
warranty, USA Wood Door reserves the right to defer replacement for one (1) year from the date
of USA’s invoice. If after one (1) year, warpage exceeds ¼” in the plane of the door itself, this
door would be considered to be defective and would warrant replacement. For the reasons stated
above, USA must request the door(s) to hang for the one (1) year time period specified.
This letter, along with your correspondence will be placed on file for future reference if
required. If you have any additional questions concerning USA’s position on warped doors,
please feel free to call.
Sincerely,
USA WOOD DOOR, INC.
WARP OF WOOD DOORS
This paper provides some information regarding the issue of door warp. First, it would be useful
to clarify the Wood Industry’s position regarding this subject and then provide some discussion
on specific issues which may arise on a project. The following is the exact verbiage taken from
the Architectural Woodwork Quality Standards Illustrated 7th Edition Version 1.2 199 which
addresses the issue of warp. There are several illustrations that you may review in this
publication should you wish to do so. Please note that this information is published by the Wood
Door Industry, not any specific door manufacturer.
Architectural Woodwork Quality Standards Illustrated 7th Edition Version 1.2 1999
Section 100-G-8 Dimensional Stability, Relative Humidity and Moisture Content.
All woods are affected significantly by moisture and to a lesser degree by heat. Lumber
Swells and shrinks primarily in two directions: thickness and width. There is insignificant
change in length. The changes in dimension due to moisture vary with different species,
thus influencing the selection of lumber to use and the design elements.
Prevention of dimensional problems in architectural woodwork products as a result of
uncontrolled relative humidity is possible. Wood products perform, as they have for
centuries, with complete satisfaction when correctly designed and used. Problems
directly or indirectly attributed to dimensional change of the wood are usually, in fact, the
result of faulty design or improper humidity conditions during site storage, installation or
use.
Wood is a hygroscopic material, and under normal conditions all wood products contain
some moisture. Wood readily exchanges this molecular moisture with the water vapor in
the surrounding atmosphere according to the existing relative humidity. In high
humidity, wood picks up moisture and swells. In low humidity, wood releases moisture
and shrinks. As normal minor fluctuations in humidity occur, the resulting dimensional
response in properly designed construction will be insignificant. To avoid problems, it is
recommended that relative humidity be maintained within the range of 25% to 55%.
Uncontrolled extremes – below 20% or above 80% relative humidity - are likely to cause
problems.
Together with the proper design, fabrication and installation, humidity control is
obviously the important factor in preventing dimensional change problems.
Wood is anisotropic in its shrinkage characteristics. It shrinks most in the direction of the
annual rings when it loses moisture from the cell walls. This illustration from the USDA
Wood Handbook shows the typical distortion of cuts from various parts of a log (Picture
is in the publication, but not this letter).
For additional data on relative humidity refer to the AWI publication A Guide to Wood
Species.
End of Section
Determination of existence of warp
Typically, we are informed about a “warped door” when someone notices a gap between
the face of the door and the stop of the frame. This gap can seem quite large and the
owner invariably refers to the size of this gap as the amount of warp – it is not. The flaw
of this method is that the visible gap is a reflection of the quality of the entire opening –
not just the door – plumbness of the door frame and how the door was hung and/or
shimmed are reflected in this observation as well. The only accurate way to measure
warp is to isolate the door so that only the door is being checked. To do this, one places
either a straight edge or a string on the concave face of a door that tis warped. See AWI
Quality Standards, 7th Edition 199 Section 1300-T (page 421). The maximum distance
from the door face to the straight edge or near side of the string is then determined. Only
if this distance exceeds ¼” is the door warped. In addition, the maximum dimensions
which can be checked for warp are 3/6 x 7/0. That is, if you are checking a 4/0 x 8/0
door, then only3/0 x 7/0 sections can be checked according to AWI standards.
What is warp in a flush door and why does it occur?
Simply put, warp is one door face shrinking faster than the other. Seasonal changes,
Particularly during the winter and spring of the first year, may cause some doors to warp.
The problem arises because of radical fluctuations in the amount of water in the air of the
building, particularly during these two seasons. Some HVAC systems delay the
acclimation process either by injecting moist outside air in to the environ or using energy
saving timers that allow humidity to fluctuate dramatically when temperatures are
lowered at night and on the weekends. The temperature variation in some offices due to
direct sunlight though glass and heating system fluctuations, can also affect the time for
acclimation.
Wood is a natural material that can move with daily changing humidity conditions until
the door’s components and the surrounding air reach equilibrium. These multiple
components of interior doors will shrink and swell at different rates until they reach the
equilibrium moisture content of the building. In almost all cases, doors will straighten
when the interior moisture conditions stabilize and the doors reach the equilibrium point.
To replace or not replace
All wood door manufacturers resist any request to replace doors prior to them hanging for
a full year. There are several reasons for this. First, per the information above, warp is
generally not caused by any problem in the manufacturing process – rather it is a result of
field conditions over which the manufacturer has no control. (This is especially true for
field finished doors which are rarely sealed or properly prepared for finishing.) More
importantly, once doors have hung through the acclimation period, they will straighten
and, barring conditions as outlined in the next paragraph, will not warp again. To
compound this point, consider that, when we replace a door, we are replacing it with
another door which is similar in fashion and may also warp as it goes through its
acclimation period.
Exclusions
Warp may continue to manifest itself in cases where temperature and humidity variations
on two different sides of a door are common. Examples of those types of doors are
computer rooms (generally kept very cold), nursing home patient doors (generally very
warm and by far the most common door we inspect; hollow core doors used as bathroom
doors are a particular problem), tenant entry doors (where a tenant keeps temperature
different from corridors), and offices with a lot of glass (wide variations in temperature
on a daily basis – cold at night because of the glass and warm during the days when it is
sunny). These are cases where we will strongly resist any insistence that warp is a
reflection of the performance of the door.
Summary
Remember, when there is a gap between the door and the frame, the easiest blame and the
best solution for the contractor is that the door be warped. It is extremely difficult to
reset a frame in a completed building or to have to call their HVAC supplied to make
adjustments to the system. Further, they can try to charge the wood door supplier for
their time to hang the replacement doors. As such, some contractors will go to great
lengths to attempt to convince you that the problem is with the doors.
To summarize, manufacturers want every distributor, contractor, and end user to be
satisfied with every wood door they sell, however, they cannot guarantee that a door will
not warp unless conditions in the field are “wood door friendly”. Too often, customers
buy wood doors for their natural beauty, but forget that with that beauty, they also get
natural products that can react to their environs. Because wood “lives and breathes” it
will eventually acclimate to its environs to provide the privacy, security or life/safety for
which it was intended.