Installing Patterned
Carpet
A
successful patterned carpet installation requires a thorough understanding
of patterned carpet characteristics by designers, specifiers,
and all others involved with the carpet selection and installation
process. Carpet is a textile fabric subject to inevitable processing
variations. These variations are more critical when patterns are
introduced. Most manufacturers provide established tolerances
and specific installation instructions for their patterned goods,
although most do not guarantee an exact pattern match. Skilled,
responsible, and competent craftsmen experienced in the installation
of patterned carpet can effectively make adjustments within the
manufacturer. s tolerances to provide a successful installation.
To assist this process, the manufacturer. s tolerances should
be clearly understood, communicated, and agreed upon by all parties
prior to the specification, bid, purchase, and installation. There
should also be an understanding about the additional carpet that
must be allowed for pattern match.
Factors affecting an acceptable pattern match on the job site
include, but are not limited to, the method of installation, the
condition and levelness of the subfloor, and the type carpet backing
system selected. It is imperative that realistic levels of expectation
be clearly agreed upon between all parties before the carpet is
installed.
Installation of patterned carpet requires more time and expertise,
often requiring the use of power stretchers and additional staffing,
thus affecting the cost of installation.
Understanding
Patterned Carpet
The following
overview describes how patterns in carpet are created.
Using
pre-colored or pre-dyed yarns, patterns may be created in any
of the following construction methods:
- Woven -
Axminster Weave, Wilton Weave, Velvet Weave
- Knitted
- Tufted
- graphics or various computer controlled techniques
Patterns
can also be produced after the carpet is woven or tufted using
undyed yarns and the pattern applied afterwards - a post-dyeing
method. Commonly used are:
- Screen
Printing - flat and rotary
- Injection
Dyed - computer controlled processes whereby colorant is injected
into the carpet pile
Regardless
of the method of construction, slight variations in yarn tensions,
yarn feed, etc. can create changes in pattern configuration.
Patterns
created by the tufting process, tufted graphics, as well as screen
printed and injection dyed carpet, require processing and finishing
after the pattern is created. All of the subsequent finishing
processes affect the size, straightness, and squareness of the
pattern.
Pattern
Variations
Pattern
variation can be characterized by four conditions that may be
found on any patterned carpet. The possible existence of all these
variations must be considered when specifying and bidding any
project where broadloom patterned carpet is to be installed. These
conditions are 1) pattern bow, 2) bias, 3) repeat variation, and
4) trueness of edge. All patterned carpets are subject to these
conditions.
Variations
in pattern are normally described by the measurement of these
four conditions, performed on a single uninstalled breadth of
carpet, as described below:
Pattern
Bow - To measure, stretch a string across the width of the
carpet from match point on one side to the corresponding match
point on the opposite side. These reference points, illustrated
as Point A and B in Diagram 1, should be as close to the selvage
as possible. Measure the distance of greatest separation between
the string and the pattern line. Uncorrected pattern bow is visible
on the floor as wavy or crooked pattern lines when viewed across
seams.
Diagram
1
Measurement of pattern bow (width) and trueness of edge (length).
Isolate points
A & B as directed in the document. Connect these points with
tightly stretched string as indicated by the pattern at the point
of greatest separation. This is indicated here by the white dot.
Trueness
of Edge Measurement
The same general
procedure is used to measure trueness of edge. For that measurement,
select the same points on the same lengthwise pattern line near
the selvage edge at least 40 ft. apart. Edge trueness is the greatest
separation between the string and the pattern.
Bias
or "Skew" - This describes the squareness of the pattern.
This condition is measured using one of the methods described
below.
Diagonal
Difference Method
Step
1 - Take the same two pattern points previously identified
in the pattern bow measurement and mark with masking tape or white
chalk as A and B.
Step 2 - Using a steel tape, measure exactly 9 feet from
these points parallel to the selvage, allowing the steel tape
to follow the same length pattern line. These points should also
be marked with tape or white chalk as C and D.
Step 3 - Measure diagonally from A to C and from B to D
as indicated in the diagram. If diagonals are equal, the pattern
is perfectly square. The degree of inequality indicates severity
of bias. See Diagram 2.
Diagram
2
Measurement of Pattern Bias
Isolate points
A and B as directed previously. Note that these are points lying
on the same widthwise pattern line as close to the two selvages
as possible. In this example they are the same point within the
pattern. Points C and D are established by measuring exactly 9"
up the edge of the carpet along the lengthwise pattern lines containing
points A and B.
Measure distance
between A and C and B and D as shown. The difference between these
measurements is reported as "diagonal difference". Another method,
using a T-square, is explained below.
T-Square
Method
Step
1 - Using a 4 foot T-square or long carpenter square, align
the short edge of the square along one selvage edge.
Step 2 - Making sure the square. s short side is perfectly
parallel to the carpet pattern, place one end of a white chalk
line at the corner of the square.
Step 3 - Pull the chalk line tight and make sure it stays
parallel to the long side of the square.
Step 4 - Follow the pattern and line across the carpet
width. The difference between the pattern and line will be the
amount of skew or bias. On a job site, uncorrected bias is visible
as the pattern running parallel with two opposing walls and running
into or away from the other two walls.
Repeat
Variation (Length) - This variation is sometimes referred
to as "pattern run off" and is determined by a direct measurement
method as follows.
Step
1 - Determine specified length pattern repeat in inches.
Step 2 - Divide this number into 144 inches. This usually
results in a whole number. Example, if a carpet is specified as
having an 18 inch match, determine the number of repeats in 12
ft (144 inches) by dividing 144 by 18, which equals 8. Use this
number (in this example "8") and go to step 3.
Step 3 - Measure the distance covered by this number of
repeats in numerous places through the dyelot. See Diagram 3.
Diagram
3
Measurement of Pattern Repeat Variation (length or width) 18"
x 18" set match in this example.
Measure the
specified number of exact repeats, 8 for this example, and record.
Use this measurement as a sequencing guide.
Step
4 - Use these numbers to sequence cuts working from longest
repeat (largest number) gradually down to the shortest repeat
within the dye lot. Uncorrected pattern variation (width or length)
is visible on a job site as seam mismatch.
Width
pattern repeat variation can be determined in the same manner.
From an installation standpoint, this is important only on end-to-end
or "cross" seams.
Trueness
of Edge - To measure, stretch a string or white chalk line,
at least 40 feet long if possible or as specified by manufacturer,
near the selvage of the carpet. Both ends of the tightly stretched
string should be on the same point in the pattern. Trueness of
edge is the maximum separation or distance between the string
and the pattern line. See Diagram 1.
Uncorrected
variation in edge trueness is visible on the job site as wavy
or serpentine pattern lines when looking down the length of the
carpet.
Is There
an Industry Standard?
Because there
are no "industry standards" for pattern variation, the carpet
manufacturer should be responsible for providing, before the installation,
written specifications as to the degree of variations expected,
the degree of installed mis-match (if any) considered acceptable,
and any guarantees or warranties of pattern match offered.
When
selecting patterns, remember:
- Large patterns
tend to decrease the apparent size of an area.
- Large expanses
of floor space generally require larger and bolder patterns.
When placed in a large room, such as a ballroom, smaller patterns
tend to lose definition and will have the appearance of a tweed.
Smaller patterns are best used in smaller areas and where there
are fewer seams.
- The larger
the pattern, the easier to match and install.
- Patterns
with high degree of linearity, such as plaids or stripes, present
more difficult installation challenges.
When
planning the installation, remember:
- Although
exact pattern match is usually not guaranteed, manufacturers
will provide tolerances and specific installation instructions.
- The installation
method selected may influence the degree of pattern adjustment
that can be realistically expected. The amount of adjustment
possible will vary with the backing system selected.
- Pattern
adjustment during installation is possible and expected.
- Relaxing
carpet by unrolling in a room for 24 hours under controlled
conditions as directed by CRI-104, Standard for Installation
of Commercial Carpet will help facilitate adjustment for
pattern variations.
- Power stretchers
and stay nailing are commonly required even in glue-down installations.
- Time requirements,
thus labor costs, will not be the same as for installation costs
of plain goods.
