Frequently Asked Questions


Waterproof means that all external fabric has been coated with our durable polyurethane coatings and the seams have been factory-taped, making that area of the tent impermeable to water. "mm" refers to millimeters and is paired with a number to represent a standardized measurement of how “waterproofness”. For instance, a 1500mm coating will withstand a 1500mm (5') column of water before water might appear through the fabric. That's strong enough to prevent rain from leaking into a tent in a hurricane-force storm.
We recommend that you use a footprint underneath your tent. Customized to fit each specific model, it will not only keep your tent floor clean and dry, but it will also protect it from rocks that can cause punctures and excessive abrasion, prolonging the life of the tent. In addition, all of our tents can be set up with just the footprint and fly, creating a minimalist alternative to a full tent.
We voluntarily follow ASTM International F 1934-98 standards around these two tent industry terms. In accordance with this standard, packaged weight includes the total weight of the packaged contents off the shelf. Minimum weight, by comparison, refers to the combined weight of the tent body, rainfly (if applicable) and tent poles, but not any of the other items that may appear in the package, such as tent stakes, guy cords, stuff sack, etc.
Superior fabrics and construction make Therm-a-Rest tents extremely waterproof. The rainfly and floor are factory seam taped, so seam sealing is not necessary. If any problems develop over time, seam seal the specific area only, on the inner, shiny side of the area. Follow the instructions on the seam sealant tube. Use a syringe for accuracy. Allow the seam sealant to dry, then apply a light dusting of baby or talc powder to prevent it from sticking to the rest of the tent when stuffed or folded.
Condensation is the build-up of moisture inside your tent due to differences between the inside and outside temperatures. There are three main sources:
  • Weather Conditions: High humidity, low temperatures, and rainy conditions create the most condensation.
  • People: We produce about 1 - 2 pints of moisture per night through breathing and skin evaporation.
  • Wet Environment: Wet ground or wet gear stored inside the tent.
While no tent design can eliminate condensation, the key to reducing it is ventilation. Cooler, drier air has to flow into your tent and warm, moist air must escape. We have designed a variety of ways to do this.

To start, the tent body and ceiling are made of breathable and mesh fabrics. This allows moisture to escape the interior of your tent. However, it must also be able to escape the waterproof fly, and every Therm-a-Rest rainfly has a peak vent that provides protection from the outside, while still allowing essential, free-flowing fresh air to move through your tent. You can also leave a door open in good weather, or take advantage of the double sliders on the doors to vent from the top where warm and moist air tends to accumulate. Make sure to leave at least two vents open if possible, allowing any breeze to provide cross-flow ventilation for maximum circulation. Guying out your rainfly will also increase ventilation in hot or humid conditions.

Video: What causes condensation in a tent
"D" stands for Denier. It's a numbering system for fibers, filaments and yarns, in which the lower numbers are lighter/finer and the higher numbers heavier/coarser. "T" stands for Thread Count – specifically the number of warp and fill threads in a square inch. The lower numbers represent a loosely woven fabric and the higher number a tightly woven fabric. These two numbers together help indicate the strength and feel of a piece of fabric.
Never pack or store your tent if it is wet, damp or dirty. Although we use the best polyurethane waterproofing available, prolonged exposure to moisture causes hydrolysis which, in turn, causes the waterproof layer to break down, becoming soft, sticky and no longer waterproof. Storing a wet tent for as little as 24 hours in warm weather is also likely to start the process of mildew forming on the fabric. Mildew will cause your tent to stain, smell and will also lead to the premature breakdown of the waterproof coating. Mildew and moisture damage are not covered under the Limited Warranty. For long-term storage, keep your tent in a dry and cool area, out of direct sunlight. Store it outside of its stuff sack, as you would a sleeping bag, in a breathable, over-sized cotton or mesh duffel for protection. On the cheap, an old pillowcase is ideal.
A tent's lifespan is directly connected to the amount you use it. A tent's biggest enemy is UV radiation (just like your skin). A tent that lives in extreme conditions at high altitude, such as Everest Base Camp, may only last a few months, while a well taken care of tent, used occasionally under normal conditions, can last for many years.
One of the easiest ways to damage your tent is by not drying it as quickly as possible after it gets wet. Storing a wet tent for as little as 24 hours in warm weather is likely to start the process of mildew formation. Mildew can permanently damage the waterproof coatings by causing them to separate from the fabric, but mild to severe staining is more common. Mildew stains are permanent. They cannot be removed without potential harm to the fabric coatings and are not covered by warranty. Even when your tent appears to be dry after use, it is always best to assure it is completely dry before storing. Hang it outside or pile it loosely in your house for a few days, turning it inside and out to assure it has dried everywhere. Never machine dry your tent as the heat can melt the fabric.
Cleaning your tent is not necessary unless it has an offensive odor or becomes heavily soiled. If heavily soiled, the pressure from a regular garden hose will remove most loose dirt. For more severe cleaning, set up your tent and hand wash it with warm water, a sponge and mild, non-detergent soap. Do not use dishwashing liquid, detergent, bleach, pre-soaking solutions, or spot removers. Rinse well. Dry your tent by pitching it or line-drying it. Never dry clean, machine- wash or machine-dry your tent. Any of these methods can remove all the waterproof coatings from the tent.
You can do minor repairs in the field using one of several alternatives. We recommend waterproof, self-adhesive patches for all of the fabrics and mesh on your tent. Seam sealants are also a good alternative for small holes, or use duct tape for minor, temporary field repairs. If you use duct tape, be sure to remove it as soon as you are through with your trip. The adhesive will eventually eat away at the fabric and you will end up needing a larger patch. We recommend carrying at least one of these as a precaution. If you have a large tear, our Product Service Center can also fix your tent after you return from your trip.
If a tent pole breaks, you can make a temporary splint with the pole repair sleeve. Slide the repair sleeve over the broken section and tape or wedge in place with a stick to hold it secure. Once you get home, send the pole in and we will repair it at no charge.