Which Types of Tents are Waterproof? Sealing Tips and Pitfalls


If you’ve slept in a good tent in a rainstorm, you’ve likely experienced the wonder that it is to have rain pouring down on your tent without getting wet. It might be easy to think that because most tents made out of vinyl are made of the same materials, that they should all be waterproof, but is that the case?

Are all tents waterproof? Although tents are not truly waterproof, tents vary widely in degrees of water resistance. Fabric type, the density and thickness of the fabric weave have some impact on water-resistance, but the quality of the waterproof coating is what really makes a tent water-resistant.

Doing research for this makes me realize how much goes into weatherproofing a tent! There are a lot of factors that impact the water-resistance of a tent, and so good research is required to find a tent that will keep you dry.

Are Nylon or Polyester Tents Waterproof?

If you have ever used nylons, or worn a polyester shirt, you probably have spilled water on them before (unless you’re one of those amazingly coordinated people who know how to drink water properly… I guess maybe I’m admitting too much here). Anyway, Nylon and polyester fabrics are not naturally water-resistant.

Polyester fibers don’t absorb water like nylon fibers do, but fabrics are just fibers woven close together, and water can seep or be pulled through to the other side of a fabric, polyester or nylon.

The weave of the polyester and nylon does impact how much water can get through, and denser fabrics will generally stop water better than thinner fabrics of the same type.

One big problem interrupts a weave, however: seams. No matter how tight a weave is, two pieces of fabric are joined with seams, which means a needle and thread passes through the fabric, tying them together. Seams are an entry point for water.

How are Nylon or Polyester Tents Waterproofed?

Just like in chocolate dipped ice cream, the secret about waterproofing synthetic materials is all about the coating.

Tent fabrics, in order to be “waterproofed”, they have to be coated with either polyurethane, silicone, or a DWR (Durable Water Repellant), or even a combination of several of these.

All of these coatings will erode over time, and so even a very expensive tent with all the waterproofing treatment will need re-treatment if you want to continue to benefit from a dry tent.

DWR is the most lightweight treatment of all of these sprays (and therefore will erode), Teflon being a recognizable type. The use of DWR is controversial as to its environmental impacts and its overall effectiveness.

Polyurethane is a plastic material which is commonly used for waterproofing fabrics (including tents). Typically the type of polyurethane are either polyester urethane (PU) or polyether urethane (PE), which have similar attributes with PE having some advantages of longevity and lack of water absorbency over PU.

Silicone is an inert substance known for its nonstick capabilities. It is incredibly water-resistant and lasts a long time.

Tents are coated with some form of polyurethane or silicone, and many times both.

If you want an explanation of the different waterproof coatings as well as a breakdown of advantages and disadvantages, look at this blog post from slingfin.com.

Why Is it So Many Tents Leak?

As I was researching the process in how nylon and polyester tents are waterproofed, it turns out that adding the coating is a tricky and delicate process. As it is common for a tent to be coated with PU and with Silicone, the different types of coatings must be added separately as they are not compatible to be applied together. In fact, if too much silicone is added, the PU won’t adhere to the tent properly!

Coupled with that, sealing the tent seams is a tricky and tedious business, and if rushed or done offhandedly, the seams will inevitable allow water in.

Buying an inexpensive tent means you are at risk of buying a tent that doesn’t pass quality control standards, and you may get a tent with very poor waterproofing.

If you are in the market for a tent and want to see what the prices of a budget tent vs. a high quality tent, check out my tent prices guide where I compare tons of different tents so you can find which one works for your situation.

How Can I Tell How Waterproof a Nylon or Polyester Tent is?

This is a difficult question to answer, as the technical specs don’t tell the whole story. Even a tent with good “specs” might not be very weather-resistant. The design of the tent as well as other attributes all play a part. Here are a couple things to look for in any case:

Waterproof Rating, or HH

Tent fabrics have a waterproof rating. This rating called HH (or Hydrostatic Head), is expressed in millimeters (mm). The higher the mm, the better the waterproof rating.

If you are planning on significant rainy weather, then a HH rating at or higher than 1000mm will give you enough protection.

Taped Seams

One attribute you should look for when trying to get a waterproof tent are “taped seams“. Taped seams just means a waterproof tape made of silicone or polyurethane is covering the seams. This doesn’t mean that the seams are taped well, though, so you might have to inspect to ensure there’s no peeling or other defect with the taped seams.

Heat-Sealed Seams

Some seam tapes seal to the seams with heat and will penetrate the holes thus creating a tight seal.

Waterproof Thread

MSR tents advertise a stitching technology that uses precision stitches with waterproof thread that swells to seal the hole created by the needle.

Inverted Seams

This just means that the fabric is folded inside the tent, so the seams are sewed inside the tent rather than on the outside of the tent. This is just one technique out of many to try and not expose the seams to water.

4-Season

4-season is definitely a marketing term, and doesn’t necessarily mean anything. Many tent manufacturers use the term 4-season to mean a tent with higher weatherproof capabilities. Don’t count on this term to be what you need, as 4-season tents are often designed to withstand cold, and not wet, so you have to look at the other capabilities of the tent to make a decision.

Which is Better for Rain? Polyester or Nylon?

This is somewhat of a holy war kind of topic where there is no right side and opinions abound!

However, one aspect of nylon that can’t be denied is that it does absorb a small amount of water. If a nylon rainfly gets wet, then the rainfly will sag slightly. Tentlabs did a pretty in-depth comparison here if you want to see examples of how much sag can happen.

Why is sag a big deal? Maybe it doesn’t look as nice, but does it cause any issues?

A huge part of the water-resistant capabilities of a tent is gravity.

The roofs of our houses are sloped in such a way to make rain run off. If water was allowed to collect on top of our roofs, then water would eventually make its way into our houses. This is true of tents. Tent walls are sloped downward, so the water takes the path of least resistance down to the earth.

Any bunching or folds in the tent means a stopping place for water. Any place on a tent where water collects is where water will soak through.

Polyester is superior in this point because it doesn’t absorb nearly as much water, and so after a long rainy night, the tent will still be as taut as it was when you set it up.

Are Cotton Tents Waterproof?

Cotton tents, more commonly known as canvas tents, are not as common, nowadays, but they are an old technology that’s been around for a long while.

Canvas tents do have a natural waterproofing ability, but it requires some preparation.

Cotton is a very breathable fabric, which is part of the reason of its huge popularity in textiles. You’d think that this would make it not-so-awesome in rainy weather.

Cotton, however, absorbs water like crazy, and will actually swell up when wet, sealing the pores of the tent, effectively creating a water-barrier. It’s the “can’t beat ’em, join ’em” kind of approach where the water itself is used as a way to redirect the water to the ground.

To make a canvas tent more waterproof, it needs a little bit of water to swell up the canvas fibers. You can do this yourself with a hose, and if you want you can put a smelly friend inside “to supervise” while you’re doing this so that they get a much needed bath.

A problem with this is that the walls of your canvas tent are swollen with water, which means that if you, or anything else you have touches the walls of the tent, capillary action will send the water into the tent.

Some canvas tents are blends of synthetic and cotton to get the best of both worlds, while others are completely made from polyester.

As always, there is a trade-off for each material.

How to Waterproof your Canvas Tent

Many different methods are out there to do your own waterproofing of canvas:

Some swear by applying a DWR (durable water resistant) spray to the canvas (make sure to avoid silicone as this will gum up the pores of the cotton canvas), on a yearly basis, but as I’ve mentioned, there is some controversy in this method.

Still others use wax, or linseed oil or other substances to create a waterproof barrier on a canvas tent. Be very careful about any of these methods, especially oil-based methods, as oil and canvas can create a gigantic fire-hazard. (even creating the potential for spontaneous combustion)

The absolute best and foolproof way to waterproof your canvas tent is to suspend a tarp over your tent. Admittingly this isn’t the easiest thing to do sometimes, but it is by far the most effective, and won’t impact the fire-retardant or breathable capabilities of your canvas tent.

If you’d like to see more details about why you possibly would want a canvas tent, I found several compelling reasons and put them in this article.

How to Waterproof Your Own Nylon/Polyester Tent

Before you embark on this journey, remember that it’s not the fabric that creates the waterproofing as much as the coating. Although polyurethane and/or silicone have decent longevity, if the the tent was stored wet (storing a wet tent can destroy a tent much more quickly. Check out my article on drying your tent to see how to dry your tent and why)

If the protective PU or silicon coating is peeling off the tent walls or rain-fly, then your tent is not salvageable, at least in terms of its waterproof abilities. You can always get a replacement fly–but if your tent floor loses its waterproof power, then you might want to start shopping around for a new tent.

Where you CAN waterproof your own tent is at the seams and by repairing small holes.

Tents can accumulate small holes over time (our tent right now has a couple in the tent floor), and these holes can let in water. Using patch kits matching the fabric of the tent can extend the life of your tent and keep water from coming in.

A very common way for a tent’s weatherproofing to deteriorate is at the seams. Even if they’ve been factory taped, heat sealed, reinforced with adamantium (just kidding on the adamantium), these seams will eventually deteriorate. Fortunately, you can apply your own seam sealer to keep water out and make your tent last longer.

Gear Aid makes the definitive seam sealer that is super popular. You can see it on Amazon if you’d like by clicking here.

Step 1: Find problem areas in your tent by hosing down the tent in your backyard and watching carefully for areas where the water is soaking through.

Step 2: Apply the seam sealer using a syringe or a brush applicator to the inside of the seams (inside the tent)

Step 3: Ensure no beads or drops form, wipe away with a sponge you won’t use again (you may have to use mineral spirits on the sponge to be able to work with the seam sealer)

Waterproof vs. Water-Resistance

I’ve used waterproof and water-resistance interchangeably in this article, but to ease my mind about being correct, I wanted to mention that no tent is waterproof. A waterproof tent would be a tent that you could submerge in a swimming pool and it wouldn’t allow water to pass through.

Tents are at best water-resistant. Getting this water resistance is really a combination of several different techniques which should all be explored if you’re wanting to stay dry.

Water Resistance vs. Air Breathability

Another conundrum to think about while researching a tent is that if your tent fabric is breathable, you will have less moisture build-up inside your tent. If your tent fabric is less breathable, it is likely more water-resistant.

It’s a trade-off! Even if your tent is super water-resistant, you may find water condensing on the inside of your tent from the air you breath and from general humidity.

I’ve experienced this many times. Even if it doesn’t rain, if it gets chilly outside, water will condense on the wall of the tent, making everything damp and clammy.

So what do you do?

Remember that to keep the inside of your tent dry, it’s just as important to ensure your tent has adequate ventilation. Guying out the vents on your tent and ensuring your rainfly is taut will make a big difference on the inside of your tent in the morning.

Peter

Peter is a software developer who loves to take every opportunity to go outside that he can get. Peter grew up going on long backpacking excursions with his family every Summer and now enjoys staying at the beautiful Texas State Parks and swimming in the amazing Texas Rivers.

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