Cotton is used for both warp and weft in most rugs, however, some tribal rugs use wool in their foundation and intricate silk rugs often use silk as a foundation as well as pile.  

Pile refers to the material or fibre used in weaving the rug. The main materials used in Persian rugs are wool, silk and cotton. Sometimes camel or goat wool is used by tribal weavers.

Wool is the most commonly used material in weaving handmade Persian rugs, mainly because it is soft and durable but also due to the availability of the natural resource to the people of Iran. Although camel or goat hair is sometimes used, in excess it is undesirable. While they may add sheen to a carpet they are very difficult to dye and the rug may lose its colour faster than if woven with sheep wool.

The best wool generally comes from colder climates, higher altitudes and the mountainous topography in parts of Iran is well suited to producing excellent quality. Other wool is imported from Australia and New Zealand who also produce excellent materials. Kork or Kurk wool is regarded as the best type of wool, this is high quality wool which is extremely soft yet durable. The wool is shaven from the shoulders and under-belly of a lamb on its virgin cut. This is when the wool is at its finest and is often used in conjunction with silk.