Every year we get a few calls from unhappy campers who have ruined their wall tents. They put them away the season prior, only to unroll them and find that the tent is stained with black mildew, or worse yet that the tent is completely rotten. "I thought my tent was supposed to be mildew proof" is the comment we frequently receive.
Most canvas wall tents are treated with chemicals to make them both water resistant and mildew resistant. The key word is "resistant". No canvas is 100% water proof or rot proof. Canvas is a natural fiber and under the right conditions can become infected with mildew. So although a treated canvas will not mildew as quickly or readily as an untreated canvas, all cotton canvas must be cared for properly to ensure that it won't mildew.
Proper storage of your cotton canvas tent is the most critical way to ensure that your tent is not ruined by mildew. Before you roll your tent up for the winter, you'll need to find a place to completely dry it out. A cold garage may not be the best place to do this, as the tent may not dry completely. Although not popular with your wife, you may need to bring the tent inside your warm, dry house, spread it out, and let it dry completely. You may need to turn it over a couple of times, and be sure there are no pockets of moisture anywhere. Even a small area of moisture can ruin your entire tent.
Once your tent is completely dry, you will need to store it in a place that will remain dry and have low humidity. If you live in an area that is humid, you will want to find a dry place to store your tent. A garage or storage shed may turn out to be a bad place to store your tent if there are times when it will be quite humid. In addition to protecting from humidity, you will want to ensure that no rodents are able to get into your tent. Mice love to make their homes in cotton canvas products and they will chew on them as well as defecate/urinate in them. Be sure to store your tent in a rodent-proof box, but one that has some ventilation.
A little extra care when storing your tent will ensure you have a great product that will last you a lifetime!