Carpeting can be either glued directly to the sub-floor or installed over padding. Either way, rippling can appear. When ripples appear on carpeting that has been glued down, the cause is almost certainly that insufficient glue was applied to the sub-floor. Since the cost of the adhesive is the installer’s expense, some apply it too sparingly. The result is that, in time, the carpet detaches and ripples or humps appear.
To understand why rippling appears on carpeting installed over padding, one must understand a bit more about installation procedure: First, tack-strip is nailed to the sub-floor around the perimeter of the room at the baseboards. Next, the pad is laid. Then, the carpet is hooked on the tack-strip along one wall then stretched and hooked on the tack-strip along the opposite and lateral walls. When ripples appear on carpeting so installed, the reason may be attributed 1) to the thickness of the pad, or 2) to improper stretching.
Pad thickness: If the thickness of the pad raises the carpet too much above the level of the tack-strip, the carpet can slip off the strip. Detached, tension is lost and, eventually, ripples appear. One can avoid this problem by selecting a pad that is no thicker than one-half inch.
Stretching carpet: A carpet layer, properly equipped, has two tools for stretching carpeting-a knee-kicker and a power-stretcher. The power-stretcher is an adjustable, tubular device that runs the length of a room. At one end is a pad that braces against the baseboard or wall. At the other, a rectangular device with prongs or teeth that sink through the pile into the carpet backing. The rectangular head stretches the carpet by applying leverage.
A knee-kicker is only about 2.5 feet in length. While its head grips the carpeting with prongs as a power-stretcher does, the opposite end is equipped with a cushion. The carpet is stretched as the installer pounds his knee against the cushion.
However, the rigidity of carpet backing makes it virtually impossible to stretch carpet properly with a knee-kicker in a standard size room. In this instance, the use of a knee-kicker is more to position the carpet than to stretch it. However, in small areas-closets, small bathrooms-where a power stretcher cannot be used, the knee-kicker is used as a stretching tool.
After years of use, carpeting can lose tension simply because the backing has relaxed. However, save for exceptions, if rippling appears within two years of installation (and the under-padding is not too thick) it is most probable that the carpeting was not stretched properly in the first place. In many service industries, profits are of greater concern than quality workmanship; and, so it is with many carpet installers.
How many yards of carpeting an installer lays in a day determines how much he earns – a circumstance that encourages shortcuts and installation flaws. And, a common shortcut is to use a knee-kicker instead of a power-stretcher, because it takes less time. The job goes quicker. Immediately after completion, the carpeting may look great, but, in time, for lack of proper tension, rippling appears.
It may also be that ripples only appear on humid days, which is still indicative of insufficient carpet tension. It’s just that the lack of tension is not as great.
Correlation between humidity and rippling: The most common carpet construction consists of two layers of backing material. The carpet pile is attached to the primary backing-the backing one sees in separating the pile. The secondary backing-the backing one sees in turning the carpet face down-adds stability to the structure and is glued to the primary through the use of an adhesive.
Backing adhesive will absorb moisture, even out of the air. And, the absorbed moisture causes the glue to expand. This expansion can cause ripples. If ripples are already apparent, they may appear worse on humid days. If not, they are usually slight.
Rippling after cleaning: Because of moisture absorption by the carpet backing adhesive, it is not uncommon for ripples to appear after hot water extraction cleaning (steam cleaning). However, the service having been performed by a competent professional constitutes no threat to the carpeting. In fact, more and more carpet mills are coming to recommend hot water extraction cleaning only.
If carpeting stays wet too long, according to the Institute of Inspections, Cleaning and Restoration Certification (IICRC)-backing separation can result. Such also fosters the proliferation of bacterial contamination. So, in selecting a professional carpet cleaner, qualification is far more important than price-considering that one’s financial investment and his family’s health are both at stake.