Saturday, December 26, 2009

Re-waterproofing a backpack

Do you have a trusty backpack? Because I do. It goes everywhere with me. Work, travel, play, outdoors. It holds my computer, or it holds my passport, or it holds a light jacket when I'm out on a day hike. It's a North Face Hot Shot, and it's about 8 years old.

Soon after some heavy traveling, I noticed white flakes appearing on all of my gear I stuffed inside the bag. Upon further inspection, I noticed that the waterproof coating on the inside of the packcloth was actually peeling off, making the bag pretty much useless in any sort of drizzle or downpour. But I couldn't give up this pack, it meant too much to me.

After some research, a local REI sales rep recommended McNett's Tent Floor Sealant, a water-based urethane coating that you paint on with a foam brush. I have no idea why it's called "Tent Floor Sealant" when it has so many applications, but it did the trick. Here's a short description on how to apply it, just in case you run into the same problem.

1) Peel off excess waterproofing (this part take forever). Tip: it helps if you wet the surface of the pack. Let the pack dry completely.

2) Lay down a work surface, since the sealant is quite liquidy, and it tends to drip when applying. I cut up a paper grocery bag and laid it down on the floor.

3) Liberally squeeze the sealant onto the included foam brush and paint onto INSIDE of the pack fabric. Make sure to coat underneath the zipper flaps.

4) Hang and let the coating dry for a day or two. Reapply if you want an extra level of protection.

Available on McNett's website and at REI for $10.

Update 1/24/10: I've noticed some very slight darkening on the top section (it looks like faint rubbed-in dirt) of my backpack after re-waterproofing. This is probably due to the amount of sealant I coated the inside with; I put enough on to the point of saturation. If you have a light colored pack and don't want this to happen, don't quadruple coat when you're waterproofing. :)


  1. I'm in the same boat as you - I have a great pack that's just the way I like it, but getting a bit elderly. The waterproofing has long since shredded, but despite looking for at least two years now I've yet to find one quite up to my standards. I was looking for some way to refurbish it, and found this site. MEC in Ottawa says they have the sealant too, so combined with some patches I can hopefully bring my beloved pack back to life. Thanks!

  2. did you use anything to help scrap off the excess waterproof material besides water?

  3. @Anonymous

    Unfortunately, no. I used a small, rough green scrubber sponge to help loosen some of the waterproofing at first, but found that doing it with my fingers was by far the fastest (only relative speaking). If the waterproofing is on a ripstop material, you may find it easier to peel it off following the ripstop lines in a vertical direction. Good luck!


    Glad to hear you found some sealant nearby! McNett's is a pretty big brand so it actually should be available at quite a few outdoor stores and online retailers.

  4. Just great!! I have a great northern face pack that has been to Europe and the middle east and my lining was shedding over everything and I haven't found a pack that is exactly what I want...almost broke down today and bought another one from REI until I decided to look online one more time. Sure glad I did!! Thanks again

  5. how well did this waterproofing method work out for you? I might do this to my backpack too...

  6. @Anonymous

    It worked very well for me. I've never had to endure extended rainstorms after the waterproofing, but it has been through a few showers and protected all the contents. It will basically return it to its factory-style water resistance, but for downpours, I might suggest additional rain protection.

  7. I am in exactly the same situation, have a pack that I love but its shedding on everything in my pack. I have noticed on one of the flaps that only the top two inches is peeling but the rest appears to be intact, the bottom of the pack is what is really falling apart. I plan on stripping and applying new sealent to the bottom of the pack. Is it better to strip the whole thing or can I apply the waterproofing over top the two inches that are peeling and leave the rest?

    Thanks for your post I almost despaired and went out and bought a new backpack

  8. @Barry

    Glad to hear that you get to hang onto your faithful pack. I would suggest probably stripping the entire thing, because the waterproofing will usually come off in clumps or strips, and once you remove one, it usually loosens the edges of the next area. If you'd like to give it a try and simply strip and apply sealant to the top two inches, go for it. If later on, the rest of the waterproofing starts flaking, you can always reapply to the rest.

  9. How well has this lasted? I'm looking to do the same thing to repair an old Dana pack I love. Any thoughts?

  10. @Chris

    It has lost a little of its water-resistance in the two years it has been since I applied the coating, but still remains much more protective than uncoated fabric. Obviously a brand-new pack made of cordura or coated oxford would be more waterproof, but if you're looking to breathe a little life into an old, loved pack, then this is a good option. Additionally, I haven't noticed ANY flaking of the new coating.

    Like I suggested above, if you're looking to face some downpours, I would definitely suggest a pack cover or something similar, but if you're just looking to keep it somewhat water resistant until you can get your pack cover on, or until you're under cover, this will be up your alley.

  11. Thanks a ton!! The membrane isn't peeling but it's clearly degrading and getting tacky/sticky. Any recommendations on how to clean this prior to waterproofing?

  12. @Chris

    It depends on how bad the coating is getting. Try scraping it off with your fingers and see if if gives and starts peeling. There is no good way to get the stuff off really, and unless it's peeling, you might just want to coat over it.