Carpet Construction

Carpet Construction

How well a carpet will “perform” (e.g. stand up to regular wear and tear, including daily traffic, spills and pets) is determined primarily by the following criteria:

  • Carpet Fibre - The material used to make yarn (and how it is treated to fight stains);
  • Construction – How the carpet is made (Twist, Gauge Rate, Density, etc.);
  • Backing – The material through which the yarn is sewn; and
  • Underlay – The underlay installed under a new carpet, which can make a big difference in the look, feel and wear of your carpet.

Carpet Fibre

The type of carpet fibre, along with the method by which the fibre is turned into yarn, significantly impacts both the price and performance of a carpet.

Carpet fibre is turned into yarn using one of two common methods: Staple or Bulk Continuous Filament (BCF).

Staple is a short strand of fibre (usually around 6 inches long) that is twisted together with other similar pieces of fibre to create a tuft of yarn. BCF is one long continuous strand of fibre that is used to create the yarn.

Because carpets made with staple fibre use many small pieces of fibre, they tend to shed, or “pill”, significantly more than carpets made with BCF. As more fibre comes off the carpet’s surface over time (through foot traffic, vacuuming, etc.), the carpet literally “wears” away.

Better quality carpets are typically made with BCF. The only benefit of staple fibre is its lower cost, which is why lesser quality carpets are often made with staple fibres.

Carpet fibre represents about 75% of the cost of making carpet, so it has a significant impact on carpet price. But the type of fiber also impacts how the carpet will perform in the home.

Most carpet today is manufactured from synthetic, or man-made, fibres, such as olefin, polyester or nylon. Each fibre has different performance characteristics affecting the look, feel and performance of the carpet.

Olefin

Olefin is a relatively inexpensive synthetic fibre that is extremely resistant to stains and moisture.

Olefin is a solution-dyed fibre, which means the colour is added during the production process rather than after the yarn is produced. The colour is in the fiber through and through, not just on the surface. Think of solution-dyed fibre like a carrot: when you slice it, it’s orange all the way through. Fibres dyed through more traditional topical applications are like radishes: red on the outside, but white on the inside.

More importantly, the colour is “locked-in” and only extreme heat will cause the dye sites to reopen. This makes olefin and other solution-dyed fibres “colorfast” (e.g. highly resistant to staining and fading).

While it is relatively inexpensive, there are some disadvantages to olefin:

Olefin is NOT “resilient”

  • If you step on cut pile carpet made from olefin, it crushes and mattes (i.e., doesn’t return to its original position). This lack of “cellular memory” explains why cut pile carpets are NOT made from olefin.
  • The natural shape of a loop pile carpet, however, creates added stability that makes up for any lack of “cellular memory” in the yarn. Consequently, loop carpets CAN be made from olefin.

Because it is solution-dyed, Olefin can NOT be made in bolder, vibrant colours.

  • This is not generally an issue because customers tend to prefer neutral coloured berbers.

Olefin tends to have an oily residue on its surface so when dirt comes into contact with olefin, it adheres to the yarn, accumulating over time and causing the carpet to appear soiled.

Olefin’s low cost, combined with its increased stability when made in “loop” form and its resistance to stains and fading, make it the fibre of choice for less expensive Berbers (as well as for the majority of commercial carpets).

Polyester

Polyester is the most widely used fiber for residential carpets.

Polyester offers a number of benefits:

  • More resilient than olefin (so it can be used to make cut pile carpet);
  • Can be made in bright, rich colours (unlike olefin, which can only be made in lighter, more neutral colours);
  • Available in specialized fibres offering increased softness;
  • Highly resistant to staining and fading; and
  • More affordable than nylon.

Polyester fibre is dyed after the yarn is extruded. Because of the chemical structure of polyester fibre, a tremendous amount of heat is required to open the dye sites. This characteristic makes polyester inherently resistant to fading and highly stain resistant, even to water-soluble stains (because, unless extreme heat is applied to the carpet fibre, the dye sites remain closed, blocking the staining agents from getting in).

Buyer’s Tip: There is a wide range of polyester fibres used to make carpet, from staple polyester to bulk continuous filament polyester made from virgin polyester to premium polyester made with advanced engineering to increase softness and durability. The differences impact both price AND performance. Make sure you know which polyester you are buying.

Nylon

Nylon is the most expensive synthetic fibre. It is an incredibly soft, durable and resilient fibre. Combined with its ability to hide soil and stains, nylon is the ideal fibre for carpet used in the most highly trafficked areas.

The benefits of nylon can be summarized as follows:

  • Softer to the touch than other synthetic fibres;
  • More resilient than polyester and olefin, so it springs back under traffic;
  • More resistant to wear and traffic, so it retains its original appearance longer;
  • Treated to resist stains and soiling better than other fibres;
  • Available in a wide array of colors and resists fading in sunlight; and
  • More affordable than wool.

Special, branded nylon fibres have been developed, using state-of-the-art technology in chemistry and engineering to produce softer, yet more durable and stain resistant fibres. Branded fibres, such as Dupont’s STAINMASTER Tactesse Nylon, have the added benefit of quality assurance: they are manufactured to strict parameters and subjected to specialized testing.

Although nylon is not inherently stain resistant like polyester, nylon can be solution-dyed, a process that makes the fibre as stain resistant as polyester. And because nylon does not have an oily-residue, dirt does not adhere to nylon the way it adheres to olefin.

As described above, solution-dyed fibres can not be made in bold, bright colours. However, there are nylon fibers which are NOT solution-dyed, such as STAINMASTER Tactesse Nylon. These nylons CAN be made in vibrant, bold colours. Since nylon is not naturally stain resistant, nylon fibres that are not solution-dyed must be treated with a topical stain treatment, such as STAINMASTER.

Buyer’s Tip: Not all stain treatments are equal. Lesser quality carpets use generic treatments that wear off after only a few cleanings. Even Scotch Guard, a recognized brand, wears off relatively quickly. It’s best to go with a carpet fibre that is inherently stain resistant or treated with a premium applicant, like STAINMASTER, which does not wear off.

Wool

Wool is the pre-eminent natural fibre used to make carpet, noted for its luxurious appearance, natural softness and high performance (e.g., natural resilience, good texture retention and good resistance to soil).

Wool is shorn from sheep and the natural shape of wool fibre keeps dust and dirt near the surface of the carpet pile, making it easier to clean. However, wool is not naturally stain resistant (although stain treatment can be applied).

On the downside, carpets made from wool are significantly more expensive than carpets made from synthetic fibres, which explains why wool carpets account for less than 1% of the total market.

Acrylic

Acrylic is a synthetic material first created by the Dupont Corporation in 1941 but has gone through various changes since it was first introduced. In the past acrylic used to fuzz or pill easily. This happened when the fibres degraded over time and short strands broke away with contact or friction. Over the years acrylics have been developed to alleviate some of these problems although the issues have not been completely removed. Acrylic is fairly difficult to dye but is colourfast, washable, and has the feel and appearance of wool, making it an ideal rug fabric.

Carpet Construction

In addition to the “type” of fibre used to make the yarn, carpet performance (or how well a carpet will wear and how long it will last) also depends on the manner in which the yarn is constructed.

The problem is to build a pile which can maintain its initial pile height for a reasonable length of time without premature flattening. As a general rule, the higher the pile, the greater the number of stitches and density necessary.

When considering pile height, it is important to consider the pile weight and to analyse how this weight is distributed between the height, the gauge and the number of stitches. Pile height must work in conjunction with the gauge and the number of stitches.

TwistTwist refers to how tightly the yarns in each tuft are twisted together. It is measured in terms of the number of twists per inch of yarn (TPI).

The twist level of a fibre significantly impacts how a carpet will stand up to wear. Generally speaking, the tighter the twist, the better the performance.

Twist LevelA tighter twist level will generally produce a carpet with more consistency in appearance and greater resistance to matting and traffic marks (because the yarn is more likely to bounce back to its original position after being walked on). A carpet with a low twist level will likely become unravelled with regular use and the ends will fray over time.

Some lesser expensive olefin berbers are made using a method called “Air Entanglement” (AE), rather than the standard method of twisting the yarn together. Air entanglement is a suitable method to make berber carpets because of the added stability created by tight loop construction. It is not suitable for cut pile carpet.

Buyer’s Tip: Some carpet dealers promote lower priced carpet that is made with high pile height but “low” twist, creating the appearance of a fuller yarn. Unfortunately, the yarn will unravel, or “flower”, over time.

Gauge rate is measured in two ways: across the width and along the length of the carpet.

Across the width: On tufting machines the space between the needles is defined by precise standards. The space between needles is given in fractions of an inch (1 inch = 25.4 mm). This is called the GAUGE.

If the gauge is known, the number of needles per metre can be calculated using the following formula:

1,000/g x 25.4 = no. of needles/metre

example: gauge = g = 5/32nds
1 metre = 1000 mm

(1O00 x 32) / (5 x 25.4) = 252

Depending on the gauge, tufting machines comprise a number of needles in a range from 126 to 630 in a 1 metre width, and from 504 to 2520 in a 4 metre width.

Each needle inserts a tuft which corresponds to one stitch. This means that, with a 1/10th gauge, for example, for every metre there will be 394 needles so 394 tufts inserted.

Changing the gauge allows the number of tufts to be varied to produce highly differing structures, from the finest to the coarsest, in varying densities, depending on the appearance and the quality required.

The foregoing introduces the notion of yarn count, as it is impossible to dissociate gauge and yarn count. Yarn count should increase as the space between the needles increases. If the yarn is too fine for the gauge, the number of rows will be insufficient, resulting in an open, weak pile, with low resilience and an unattractive appearance.

Along the length: Tufts along the length are expressed as the number of stitches per linear metre or decimeter. Stitches are determined by the rate at which the backing, in which the rows of tufts are inserted, is fed through the tufting machine.

Generally, stitch rates should be the same longitudinally as laterally. If the gauge is, for instance, 1/8th", this means 315 tufts per metre; the longitudinal stitch rate should be approximately the same. If it is lower, the pile will be excessively open and will appear furrowed. Frequently, however, it is higher as this gives a higher pile density.

Pile density stems from the number of tufts per metre and is calculated by multiplying the number of rows (gauge) by the stitch rate. Whilst the gauge is normally given, the number of stitches is frequently not supplied, although it is an important item of information.

To calculate the stitch rate, divide the total number of tufts per metre by the number of rows. For example, a 100 000 tufts/m' floorcovering with a 1/8" gauge has 315 rows. 100 000 divided by 315 = 317 stitches/meter – giving an appropriate construction.

Pile Height

Pile height is the thickness of the pile above the primary backing. It is measured in millimetres. In some structures, particularly cut pile, the pile height may be substantial, 10 to 20 mm, or more. Obtaining pile thickness is technically easy as it is merely a question of putting more material into the pile height.

Pile weight is the total weight of the material used to form the pile itself. In other words it is the weight of the yarns in the carpet.

The weight of the yarn itself is not all you should be concerned with. What is more important is how that yarn is composed into the carpet face. This can be understood better by comparing 4 factors – yarn count, height, gauge and stitch rate.

Luxury carpets with a high, very dense cut pile use more yarn than low pile height, loop carpets with medium gauge and stitch rates.

Pile weight is expressed in two ways, and measured in grams per square metre.

  • TOTAL weight: the mass of material in the pile including the part within the backing.
  • USABLE weight: the mass of material located above the primary backing, and which can be measured by shearing.

DensityDensity refers to the thickness of the yarn and how close the tufts of yarn are spaced together (which is a factor of the gauge and stitch rate).

Carpets with higher density (i.e., the tufts are closer together) will generally perform better. You can measure density by pressing down on the carpet pile with one finger and seeing how easy or difficult it is to penetrate to the backing. Better, denser carpets are more difficult to penetrate.

Buyer’s Tip: Beware of lower priced carpets that feature relatively high weight in ounces but low density. As stated above, density is a more critical measure of how a carpet will perform. Carpets with high pile height and low density tend to matte and crush very easily, causing the carpet to wear very quickly (with the exception of Frieze, which has added stability due to high twist levels).

Carpet Backing

As stated above, yarn is stitched through a backing material to create “tufts”. The carpet backing holds the yarn in place, impacting the carpet’s durability, seam strength and overall appearance, including pattern straightness and the ability to keep its shape and not wrinkle.

Carpet backing is NOT all the same. Standard backing is made from woven polypropylene. Lower quality carpets use backing made from cheaper chemicals that make the backing tough and brittle. Over time, the backing loosens up, causing the carpet to sag and wrinkle.

Premium backing made from fibre offers many benefits over standard backing:

  • Greater comfort under foot - Not only is the carpet itself more pliable, the backing is actually softer to the touch, making it more comfortable to walk on.
  • Stronger and less visible seams - The carpet cuts very clean, making for cleaner seams that are less vulnerable to peaking.
  • Improved dimensional stability to prevent wrinkling and buckling – Carpets with premium backing often come with “No Wrinkle” warranties.
  • Improved cleanability – Premium backing keeps spills above the pad longer, so there is more time to clean up the spill.
  • Softer and more flexible - Easier for installers to carry into the home and less likely to damage walls and baseboards during installation.

Buyer’s Tip: Beaulieu is the only major carpet manufacturer that uses premium backing made from fibre as the secondary backing. Other mills apply premium backing on top of the secondary backing (as stated above, typically made from woven polypropylene), which defeats the purpose of having premium backing – which is Beaulieu is the only company that offers a No Wrinkle warranty for carpets using its premium backing.

Carpet Underlay

Carpet underlay is as important as the carpet itself in terms of a carpet’s performance.
In addition, not using an underlay, or using an underlay that does not meet manufacturer specifications for the particular carpet, can void product warranties.

Carpet underlay helps increase comfort and maintain the carpet’s original appearance by absorbing foot traffic. When you walk on carpet, you put pressure on it. Carpet underlay helps to alleviate that pressure, which makes the carpet feel softer, thicker and richer.

Carpet underlay improves the efficiency of vacuuming. A quality underlay makes cleaning more efficient because it raises carpet off the sub-floor and provides air space underneath, allowing the carpet to “breathe.” When you vacuum, that space allows more air to come up through the carpet, picking up more dirt.

Selecting the “correct” underlay (as specified by the manufacturer) helps minimize matting and crushing, as well as soiling and staining. A quality underlay can increase the useful life of carpet as much as 50%. Pile crushing can make carpet “look” worn out before the fiber is actually worn out. A quality underlay helps decrease pile crushing, allowing the carpet to maintain its pile height and stay looking new much longer.

The latest advancements in carpet underlays are stain and odour fighting capabilities. A special moisture barrier on the surface of premium underlay prevents spills or pet accidents from saturating the underlay or soaking into the sub-floor, causing mold. This barrier gives the homeowner time to blot up the spill and prevent it from wicking back to the surface causing recurring stains.

Some premium underlays have a special enzyme that helps eliminate offensive odours.

Underlay

Most carpet underlay is made from foam or rubber, with foam underlay accounting for approximately 75% of the market.

Bonded polyurethane, referred to as re-bond, is the most common form of foam underlay. It is formed by combining chopped and shredded pieces of recycled foam, in different sizes and usually different colours, into one solid piece. The re-bond foam that is produced is itself recyclable.

Premium re-bond underlay features:

  • Heavier weight (typically 8 lbs vs. 6 lbs), compacted to make smaller air pockets, creating a denser, firmer underlay that will perform better;
  • Moisture barrier to prevent spills or pet accidents from saturating the underlay; and
  • Anti-microbial enzymes to help break down odours.

Product warranties typically specify the minimum type and grade of underlay to be used with a specific carpet. The “grade” of underlay is determined primarily by weight and thickness.

Note: A thinner underlay is used for Berber carpets because a thicker, less dense underlay would produce too much “give”, pulling on the seams.

Buyer’s Tip: Many contractors lower the cost of new carpet by reusing the existing underlay or using a less expensive underlay that does not meet manufacturer specifications for thickness and weight. In addition to causing wrinkling and buckling and separation of carpet seams, reusing the existing underlay or using a non-specified underlay will likely void the product warranty.

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