How waterproof are tarpaulins?
How waterproof are tarpaulins?
Many tarpaulins will be marketed as being waterproof. However, some of the materials used to make these tarpaulins are not actually waterproof (such as canvas and jute). Rather, these tarpaulins will be given a coating (e.g. a wax coating), to give them water-resistant properties.
Hydrostatic Head Rating
Some tarpaulins (such as the camping tarpaulin pictured) may be subject to a hydrostatic head rating.
This indicates how much water can be applied to a fabric before it starts leaking.
This is measured by attaching the fabric to a transparent tube which is then filled with water. For a fabric to be considered fully waterproof, it must hold a hydrostatic head rating of 1000 (measured in millimetres to indicate how high the water in the tube is). However, the Ministry of Defence accepts a rating of 800mm to be the minimum.
Does the waterproof coating degrade?
The wax coating on a canvas tarpaulin will degrade over time after prolonged contact with water, and you may notice that the tarpaulin begins to stay wet after use. This may also extend to the back of the tarpaulin.
In addition, the canvas may begin to feel different, as it starts to lose the wax layer and dry out. However, it is possible to buy products that restore the tarpaulin’s water-resistant properties.
Are cheaper tarpaulins less waterproof?
How effective a tarpaulin is at keeping the water out varies depending on the type of material used to create it, rather than the price. For more information, see our section: What are tarpaulins made of?
