Carpet Construction and Styles
Woven Carpet: Woven refers to a rug or carpet that is made with a loom by a weaving process. In woven carpets, the face and back are formed at the same time, by interweaving warp, weft, and other yarns. Woven carpets consist of face yarns, backing yarns and in some cases adhesives (or back coatings). The face yarns are intertwined with the warp and weft yarns. While slower and more expensive to make, they can usually withstand far greater traffic in a conventional installation when compared to tufted carpet.
a. Face yarns: consist of a broad range of fibers. i.e., nylon, polyester, wool, acrylic, olefin, etc., and form the pile of the carpet.
b. Backing yarns: Fibers used in backing yarns can be synthetic, however more commonly seen would be cotton and jute which are cellulosic fibers.
c. Warp Yarns: run lenghtwise.
d. Weft Yarns: run widthwise.
Included in woven carpets are the hand made " orientals " as well as American Indian flat woven. In addition there are various specialized machine woven carpets which carry proprietary names such as Karaloc from Karastan. Knitted, hooked and braided rugs are also considered woven. In this section we've included three of the major machine wove processes.
Velvet: The velvet weave is usually used to produce extremely dense plush velvet piles. It is a relatively simple weave and used to produce solid colors.
Wilton: The wilton weave is a more complex weave. Wilton goods are produced on a Jacquard loom. The Jacquard loom is capable of producing mulitcolored patterned goods. Wilton carpets are normally very expensive and long wearing carpets.
Axminster: Axminster carpets are very easily identified by their ability to be rolled in a length wise direction only. Axminster carpets are noted for their intricate colors and designs. Cleaning technicians should be extremely cautious not to overwet axminster carpets due to the fact the widthwise shrinkage is virtually impossible to restretch. Newer versions may have synthetic warp and weft yarns which will help this problem. Always pre-inspect the seams of axminster carpets. They should be sew or bonded with specialized hot melt tapes capable of holding up to the stress when the carpet is cleaned. They can be identified from the back due to their ribbed appearance and no secondary backing.
Tufted Carpet: Most carpets manufactured today are tufted carpets. Here, the face yarns are essentially "sewn" or stitched into the carpet by a giant multi-needle sewing machine. If the yarns are undyed this is referred to as "greige goods". A layer of adhesive is added to the back to lock in the tufts and usually a secondary back is adhered to that. A tufted carpet is constructed much like a sandwich consisting of face yarns and primary backing adhesive, and secondary backing. The publications from the Carpet & Rug Institute (CRI) Number 104, Commercial give the guidelines for Installation of Tufted Carpet.
a. Face yarns: consist of a broad range of fibers. ie., nylon, polyester, wool acrylic, olefin, etc., in various pile constructions.
b. Primary backings: A component of tufted carpet consisting of woven or nonwoven fabric into which pile yarns tufts are inserted by the tufting needles. Most primary backings is either woven or nonwoven polypropylene, although woven jute is sometimes still used.
Adhesive: A layer of latex, hot melt adhesive, or in some cases a vinyl or a foam product.
Secondary Backings: Woven or nonwoven fabric reinforcement laminated to the back of tufted carpet, usually with latex adhesive, to enhance dimensional stability (maintain its size and shape), strength, stretch resistance, lay flat stiffness, and hand. Most secondary backings are woven jute, wove polypropylene, or nonwoven polypropylene.
Unitary Backed: In this construction there is no secondary back applied, but a special latex compound gives very high tuft bind (20lbs. or more). These carpets are designed for direct glue down applications.
Cushion Backed: Here in place of a secondary backing a layer of aerated foam or urethane creates a carpet with an attached cushion. (Caution: older cushion backed carpets may have decayed and will lump during cleaning.)
Delamination: Separation of the primary and the secondary backing (or cushion) or tufted carpet. In newer carpet most delamination is caused by improper formulation or application of adhesives, or improper specification carpet or cushion. In older carpet the cause of delamination usually can be traced to age and oxidation of latex, or simply to excessive traffic (especially that which rolls over the carpet). Localized delamination may be caused by excessive use of dry solvent spotters, or by fuel oil spills. The on location technician should give special consideration to the fact that the backings materials and latex bonds must be in sound condition before attempting to clean the carpet. Weaknesses, such as backing separations, (delamination) or weak dry rotted conditions, will surely become apparent when exposed to the moisture necessary for carpet cleaning to improper flood restoration techniques. These conditions are not caused by the cleaning process when proper procedures are followed. However, dry solvent overuse will also cause delamination. The most common cause of backing delamination on newer carpet is improper formulation or application of adhesive.
Ripples or Wavy Carpet: This is the phenomenon that occasionally occurs when the type of latex that holds the tufted primary and the secondary backing together swells in the presence of moisture. This swelling is caused by the latex absorbing mositure through exposure to cleaning or increases in building humidity and accelerated by temperature increases. This expansion causes the polypropylene primary to push against the polypropylene secondary forcing a rolling or wavy appearance to show up in the carpet. This phenomenon is sometimes called differential expansion. The forces involved are strong enough to break loose glued down carpet if it is not well installed. Although it looks bad, the carpet returns to its normal appearance as it dries. Inform the customer of the cause and ask them to wait for the carpet to dry.
Tufting: Tufted carpet accounts for about 95% of all carpet produced in the U.S. today. It is a relatively simple process. Yarn is fed to the needles and they punch the yarn through the primary backings where the looper forms the pile. The tufted carpet with the pile on the underside is raised up so that it can be inspected and mended if needed. The finished product is greige goods-a term for undyed face yarns that have been tufted into a primary backing material ready for dyeing or backing.
Plastic/Fusion Bonded Carpets: Fusion bonded carpets are produced by implanting the face yarns directly into liquid vinyl or rubber adhesive that fastens them directly to the backings. It allows the yarns to be more closely packed than either weaving or tufting, resulting in extreme density. The weight of the adhesive usually precludes twelve foot goods, but helps hold it down when constructed as "modular" carpet squares. Fusion bonding is gaining popularity and is commonly found in commercial installations. Fusion bonded carpet is common in recreational areas, airports or other areas where extreme wear occurs. Fusion bonded carpets may be cut or looped pile depending on the manufacturing system used.
Needle Punched Carpets: Needle punched carpets are produced by evenly distributing loose fibers on the top and bottom of a prewoven material to form a sandwich. This is then run through a needle punching machine where barbed needles interlock the loose fiber to the pre-woven material. A backcoating is then usually applied to improve dimensional stability. Needle punched carpet is commonly found in indoor/outdoor carpet and carpet squares.
Carpet Cushion: Carpet Cushion is also an important part of many installed carpet systems. When the proper cushion is installed it can help the carpet resist matting and crushing. It certainly adds greatly to the comfort of walking on the carept. There is considerable debate about what constitutes "proper" cushion. Many commercial installations are installed without cushion to avoid problems of back separation or seam fatique, but these are usually very low pile and not particularly prone to appear- ance distortion. The only other negative is that theya re not very soft under foot.
It has been assumed for many years that a good cushion adds to the life of the carpet and tests are being performed to verify this:
Carpet Installation: The actual techniques of carpet installation are quite detailed and are convered in the Carpet and Rug Institute publications CRI 104 Commercial Carpet Installation and Carpet Installation Standard and CRI 105 Residential Carpet Installation Standard. In addition, the IICRC has a two-day Repair and Reinstallation course for technicians. As a cleaner, you should be familiar with the principal methods of installations since they can affect the equipment or system you use.
Direct Gluedown: Carpet is adhered with adhesive directly to subfloors/substrate.
Advantages:
1. Relatively simple procedure
2. No stretching required
3. Avoids delamination
4. Avoids buckling and rippling
5. Avoids seam separation
Disadvantage:
1. Hard under foot
2. Pile crush more likely
3. Adhesive must be applied properly
4. Seams must be "sealed" with seam adhesive
Double Glue-down: Cushion is adhered to subfloor/substrate and carpet is then adhered to cushion.
Advantages:
1. No stretching required
2. Softer underfoot than direct glue
3. Avoids crushing
Disadvantage:
1. Adhesive must be applied properly or ripples and separation will occur
Attached Cushion: Carpet with attached during manufacture is adhered to subfloor/substrate.
Advantages:
1. No stretching required
2. Softer underfoot than direct glue
3. Avoids crushing
4. Avoids separation ripples
Disadvantage:
1. Performance is dependent on durability of attached cushion
Stretch-In Utilizing Tackless Strip: A carpet installation term for carpet when it is stretched over pad onto tackless strip. According to CRI 104, cushion thickness in a commercial stretched-in installation should not exceed 3/8 inch and according to CRI 105 cushion thickness in a residential stretched-in installation should not exceed 7/16 inch. In astretched-in installation, to prevent shifting of cushion during and after installation, cushion should be securely fastened to the subfloor with cushion adhesive and/or staples. To ensure proper stretching a "power stretcher" must be used.
Advantages:
1. Soft underfoot
2. Carpet can be replaced over existing cushion
3. Cushion may be varied-softer or thicker
4. Reduces subfloor preparation, hides sublfoor flaws
Disadvantage:
1. May loosen over time and traffic
2. Pieces must be joined with seam tape or sewn
3. Seams may separate with delamination on tufted carpet
Other Systems:
Carpet Modules - Squares: Loose carpet or self adhesive backed squares of carpet. Also referred to as carpet tiles.
Tacfast: Like attached cushion with a velcro type backing. Attached at perimeter and seams with velcro strips adhered to subfloor/substrate.
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