The tent contains 2 separate layers, which are placed one on top of the other on its roof or upper part.

Usually, the first layer has waterproofing, while the second is a layer that allows air passage and offers better ventilation in the tent.

The waterproofing of a tent indicates how much water the outer fabric can repel. It is measured in millimeters (mm) and refers to how many millimeters of a vertical water column (and therefore pressure) a square centimeter of fabric can withstand without being penetrated by water.

The higher the degree of waterproofing, the less breathable the fabric is, and thus the warmer the tent. Common waterproofing values range from 500mm to 10000mm. Theoretically, any fabric with waterproofing >1000mm is considered waterproof. For example, a summer tent may have waterproofing from 500 to 1500mm.