A lot of thru-hikers use closed-cell foam sleeping pads because they are lightweight and easy to attach to the outside (bottom) of the backpack. This is the most preferred way and it works fine in most conditions. There are straps on the bottom of almost every backpack that you can strap onto your sleeping pad and it doesn’t affect your balance, which is a great thing. Now, if you don’t like this method or if you’ve got an inflatable pad, there are some other ways around. There are four other possibilities to carry or attach the pad to your backpack.
Attach it to the outside – Bottom
As I mentioned earlier, this is what most people do. It is easy, effective, and doesn’t occupy space in your pack. But you need to consider a few things before you attach it that way. Are you planning to hike through dense foliage? If so, there is a high chance that your attached sleeping pad would catch on branches and be damaged or pulled off. Also, in many cases, it will prevent you from getting between trees or it will catch on vines. If this is the case, you need to consider packing it inside the pack. If not, attaching it to the outside of the pack is perfectly fine.
Attach it to the outside – Top
It is not very uncommon for a pad to be attached to the top of the backpack. You can do it easily and then cinch it down with the top closing straps. This is similar to the above-mentioned method except the position is different. Pros and cons are also the same.
Vertically using side compression straps
Most backpacks come with side compression straps that can be used for attaching a sleeping pad. Although this is not the most practical way as it adds weight to one side, which affects your balance. If your pad is super lightweight (as most foam pads are ultralight these days), you shouldn’t be worried about the balance. Also, if your backpack has side stretch pockets, put it into one of the side stretch pockets and cinch down the top with a side strap. Some people will avoid attaching anything to the outside because they say anything attached to the outside of the pack are more likely to damage, get wet, or lost. So, in the case of a foam pad, it doesn’t matter if it gets wet or gets a hole or tear.
Packing it inside
Most ultralight pads (probably inflatable) are so compact that you can fit them inside a regular backpacking pack. I haven’t seen many people carrying pads inside the pack just because it’s hard to see inside someone’s pack. Personally, I am not a big fan of this method because it just takes too much space in my pack and I end up with very little space for other gear. Also, it makes my pack too rigid, and I like using my pad for rests and breaks. I need my pad frequently on the trail. So people avoid putting it inside because they think it may not fit or may get squashed. Or if you’ve got a foam pad, packing it inside may not be an option for you.
Packing it in the large back mesh pocket
Some backpacks feature a large mesh back pocket that can be used to carry a sleeping pad. It is a large stretch pocket that most people use to store extra backpacking clothes for easy access. If your pack has this packet and your pad is a foam pad, I’d suggest that you use this method. Foam pads are easy to store there and you can easily access them for rests and breaks without unloading your pack. Also, it won’t affect your balance and center of gravity as foam pads are super lightweight.
In conclusion, if you’ve got an inexpensive and lightweight foam pad and you won’ be hiking in dense foliage, attach it to the outside. For this, you have three options, bottom (most preferred), top, and side. On the other hand, if you’ve got an inflatable (probably expensive) sleeping pad or you’ll be hiking mostly through dense bush and you’re afraid it can get damaged, pack it inside of your backpack.