A leaky tent can quickly turn your dream camping trip into a nightmare. That’s why you often see brands highlighting the waterproofing capabilities of their tents in terms of mmHH. What does that mean, though? Is water resistance the same as waterproof? Which materials will best protect you from rain or moisture?
A waterproof tent is made of fabric that repels water to a certain degree. It’s rarely a permanent ability though because waterproofing can degrade due to exposure to environmental factors or regular wear-and-tear.
Manufacturers describe the tent’s ability to repel water through Hydrostatic Head (HH). This measure indicates how many millimetres (mm) of a water column the fabric can resist from above. The higher the rating is, the more protected you will be.
Engineering a waterproof tent involves the polyurethane (PU) or silicone coatings, taped seams, covered zippers, groundsheets, and a durable water-repellent (DWR) finish.
Why is it important to waterproof a tent properly:
A tent must be waterproofed to:
- Keep yourself and your valuables dry;
- Minimise the potential damage from the sun’s UV rays; and
- Prolong its life and useability.
Most modern tents are waterproof, but the cheaper variants tend to be water-resistant only. That means the tent only has a water-resistant finish that can protect you from light rains only. Therefore, if you’re not confident the weather will be fine during the trip, we suggest going for waterproof tents of at least 2,000 mmHH.
Another option is to waterproof a tent by yourself. This will also be handy in ensuring the longevity of your camping gear. The tent’s protective layers can erode when exposed to the elements. Packing it without letting it dry first will also lead to damage due to moulds and mildew.
Waterproofing a tent can be done in 3 ways:
- Re-apply PU or silicone coating on the tent fabric.
- Spray DWR finish all over the tent.
- Repair and seal the seams.
By going through the effort of waterproofing your tent, you will also save money since you won’t have to buy a new one whenever you have an upcoming camping trip. The supplies needed for DIY waterproofing are affordable and accessible for most people, too.
Buying a waterproof tent and learning to maintain it can be your contributions to protecting the environment, too. If we invest in high-quality camping gear, there is a low chance that you will throw away the tent after a single use.
The properties of hydrostatic head explained
When a company is creating a waterproof item, such as a tent, they need to consider these 5 key factors:
- Waterproof – How much the item repels rain. This is obviously the reason why you buy a tent with a high waterproof rating to begin with.
- Breathability – How much the material allows for airflow to pass through the material. It’s important for tents to be breathable or heavy condensation would be building up inside the tent and this essentially renders waterproofing useless.
- Durability – How strong is your material in regards to force. Without a durable material, your tent would rip and tear with ease in harsh weather such as torrential rain or hail stones which will leave you and your valuable items soaking wet.
- Weight – How light a tent will be can be a considerable factor especially if you will be trekking a reasonable distance before setting up your tent.
- Price – Usually, the better a tent performs in the above categories, the more expensive it will be.
It can be difficult for manufacturers to balance these key factors and that is why there is so much variation between the rating of tents because as one factor’s rating goes up, there will inevitably be sacrifice in another category. The high-quality and well regarded tents will naturally be more expensive due to the fact that they consistently perform well in each of these categories.
How are materials made waterproof?
The key to a good waterproofing material is one that allows perspiration and heat to escape through it without allowing water to get into it. Sort of like a one way system.
There are two major ways of making a tents material both waterproof and breathable and this is achieved through either lamination or coating:
Lamination:
This way of waterproofing tends to be the more expensive option of the two as it usually leads to a better result of being both highly durable and breathable. It is usually constructed by layering three materials on top of each other. These layers include:
- Pre-treated external material – Hydrophobic materials that do not absorb water such as Polyester or nylon are used here which have been treated with a Durable Water Repellency (DWR) spray.
- Fabric membrane – A thin material with miscopic pores that allow vapour droplets to pass through whilst simultaneously preventing larger water molecules from entering through the fabric.
- Protective internal lining – A sheet of fabric that is either laminated to the membrane or is loosely attached which prevents the membrane from collecting oils and dirt which could block up the porous holes and prevent it from doing its job.
Coating:
This way of waterproofing with a Polyurethane coating (PU) is much cheaper and quicker to produce than lamination and is much more common. The process of coating is much more simpler and can come in many formats:
- Direct coating
- Transfer coating
- Foamed and crushed foam coating
- Hot melt extrusion coating
- Calender coating
- Rotary screen coating
Lets dive deeper into some of these processes and how they help to make tents waterproof:
1) Direct coating
One of the most simplistic coating methods where the material has the coating applied directly to the material. This method is sometimes referred to as the ‘knife over air’ or the ‘floating knife’ technique and involves the material being stretched flat to allow a smooth surface.
The material is then passed under a stationary knife where it gets scraped by the blade and a polymer resin gets applied in an even manner across the surface.
2) Transfer coating
This method works in a similar fashion as laminating in which the polymer gets spreaded onto release paper forming a film and is then laminated onto the fabric. The process usually follows a few short steps:
- Coating the resin or top layer on the transfer paper to which the solvent is evaporated.
- The second layer is then coated on top turning this into the base layer. This is the layer that acts as an adhesive which joins the top layer to the fabric.
- The fabric is then laid on top of the coating to join the two parts together.
- The coated fabric is then peeled off of the release paper.
3) Foamed and crushed foam coating
This method is best used with fabrics that cannot be directly coated such as woven or knitted fabrics. The foam is able to better coat the fabric as it sits on top. Crush foam coating reduces the penetration of resin into the fabric allowing for a smoother and softer finish
3) Hot melt extrusion coating
This method is usually used by passing granules of thermoplastic polymers through heated rollers which melts, smooths and applies the material. This method of application allows resin to be applied to fabrics at a much faster rate than that which can be applied by transfer coating or direct coating. This method is more common with tarps.
4) Calendar Coating
This process utilises a series of hard pressure rollers to flatten polymer dough into a uniform sheet material that can then be applied directly to fabric. The rollers are set with a gap that allows them to generate a pre-defined thickness.
Usually, the more rollers that are used, the more accurate the sheets will be when they are created. Some rollers also generate a level of heat allowing them to be directly applied to the fabric as it is brought into contact.
6) Rotary Screen Coating
This technique works by applying a compound to a fabric by forcing it through a cylindrical screen. The resin is pushed through a screen onto the fabric causing an array of docs which form together to create a continuous coating.
The properties of hydrostatic head explained
Seasoned campers know how essential a waterproof tent is for an enjoyable and worry-free outdoor experience. We suggest inspecting a model’s waterproofing rating and features before proceeding with the purchase. Make sure that it has a rating of at least 2,000 mmHH, but to be on the safe side, consider higher ratings for maximum protection.
Read the tent’s description to find out more about its water-repellant layers and materials. Taped seams, covered zippers, and groundsheets will also minimise water seepage or leakage inside the tent.
Don’t expect the waterproofing of your tent to last forever, though. Verify its integrity before heading to your destination by pouring water directly on the fabric. Inspect for holes or tears, too. Taking these precautionary measures and correcting them before the trip will save you from headaches and chilly nights later on.
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