There are four different installation types for carpet.
1) Direct Stick
This method is predominately used in commercial installation. You don’t require an underlay with this method. This results in a direct saving in overall cost. You would use this method in offices, shops, demountable buildings, entertainment areas or to convert a garage into a room.
This is a method used in almost every residential home around the world. The term conventional is the procedure of stretching the carpet to the smooth edge (which is positioned around the walls) and the use of a cushioned underlay. The reason for this choice of installation in a residential home is the use of the underlay. In this method the sole purpose of the underlay is comfort; this is achieved with various qualities and thicknesses of underlay, maintaining softness under foot and insulation properties as well.
3) Double Bond or Double Stick
Essentially the same as direct stick but in the double bond system we use a specific double bond underlay that is adhered to the floor first and then the carpet is glued to the underlay. As we have spoke about underlay before you can see that once again the role here for the underlay in a double bond installation is comfort and insulation and in some cases it can also reduce ambient noise. Again this is predominately used in commercial installations.
4) Loose Lay
This method is exactly as it sounds, the carpet just laid loose to the floor with no glue or anything else holding the carpet down other than the weight of the carpet and the furniture you place on top of it. Ideal for a temporary fix, DIY or something to cover up an access point.