How to Waterproof a Canvas Tarp

How to Waterproof a Canvas Tarp

Water damage is one of the most aggravating things in the world.

It comes out of nowhere, it’s often impossible to spot an issue when it occurs, and then you find out what happened after hundreds (or thousands) of dollars in repairs are needed.

But there’s a way to avoid all of that when you know how to waterproof canvas tarps. These inexpensive tarps can be used to cover windows, roofs and sheds when hurricanes or storms roll in, so if you can waterproof them, you’ll essentially make a rain shield for whatever it is that you’re covering.

Dealing with water damage is terrible, but with a little ingenuity and a good chunk of time, you can waterproof a canvas tarp on your own to be ready for the next storm.


Is It Possible to Waterproof a Canvas Tarp?

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It’s possible, it just takes a little bit of involvement. With some time, you can get it done and make it as strong as possible. Whether you want to use a canvas tarp as a canopy, or use it to prepare for the next hurricane, it’s completely possible.

Just as a word of caution, I do mean that it takes a fair amount of time. Waterproofing it will take you less than an hour, but curing it is another beast entirely.

When you’re done curing it, you still have to inspect it, and it may not be done a few days later. Make sure you have a space where you can cure this for at least three days before you start the project.

What Do You Need to Do It?

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Water-Resistant Coating

This is the first thing you’re going to need. This is sold all over the place for shoes and work gear, and just about any waterproofing spray will do.

This is something you have to do every single year no matter what, so you don’t have to go crazy with the cost on this one.

Adhesive Spray

Consider this like a primer before you put anything else on. This is going to help the water resistant coating stick to the canvas tarp a little bit better, and add that extra layer of protection.

Since we have human error on our plate here, this acts like a check and balance system that covers potentially missed areas with the waterproofing spray. We can be thorough, but we can’t be perfect.

Clean Surface

You need a nice clean and clear surface to do all of this on. Your tarp has to be laid out as much as possible without wrinkling on the corners or having creases running through it.

The best place to do this is in a garage, because it still gives you enough time to walk around the edges and actually perform all of these tasks as you go.

Breathing Mask

Your respiratory system is fragile, and on a day-to-day basis, we’re already inhaling far too many fumes and chemicals in this country.

This task is going to put you in with some concentrated chemical fumes, and we want to avoid damage, potential cancer, and the risk of a trip to the emergency room.

Canopy Cover

Which canvas tarp are you going to use?

Get it ready, and spread it out so that you can prepare it in the next phase of this guide. Be sure to inspect your tarp before you bother spending time and materials on this.

If there are tears, cuts, or it’s just in generally bad condition, pack it up and do this another day. Waterproofing a tarp is meant to protect it so those things don’t happen as easily.

Single-Use Gloves

These are just to protect you against harmful chemicals. Your skin absorbs a lot more than you think it does, and we want to prevent that from happening at all costs.

Do not skip any safety recommendations or procedures when you’re dealing with harsh chemicals like this. Single-use gloves should be non-powdered, and fit nice and snug so you aren’t swapping out utility and grip for safety. You can have the best of both worlds.

General Cleaning Supplies

Bucket, cotton rags, hot water, dishwashing detergent. Most of us already have these items lying around our home, so get them ready, because you’ll be using them first.

How to Waterproof Your Canvas Tarp

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1. Scrub Your  Tarp

Once you have all of your protective gear on, it’s time to scrub your tarp down. Even if you just unwrapped this from its package, you still need to wipe it down.

Tarps can build up dust in warehouses and get trace elements of debris on them, which will absolutely mess with the chemical bonding process.

Use a solution of hot water and dishwashing detergent to scrub this tarp down from front to back, even in areas that don’t look like they need it. Be sure to pay attention to the grommets.

2. Air Dry and Check Grommets

Run a rinse to get all that soap off. Now it’s time to wipe the whole thing down with a cotton rag to soak up most of the liquid. Even after you do this, you have to hang this up so that it has ventilation and can air dry.

Run your rags over the grommets to make sure there’s no trapped water anywhere. If you dry the tarp off sufficiently, you should only have to let it air dry for about thirty minutes at most. This is the only stage in this process where you can use a fan to dry things off and ventilate it.

3. Apply Adhesive Spray

Adhesive spray acts like a primer, so we need to apply it in a nice even coat so that the water resistant coating has something to stick to. Stand about six to eight inches away from the tarp, and move as you spray it.

If you spray in one concentrated spot for more than one second, it could create a bubble of the chemical that will dry awkwardly. It’s important to be confident when you’re doing this, otherwise you have to wipe this off before it dries, and then start from step one all over again.

4. Apply Water Resistant Coating

The moment you’ve all been waiting for – actually applying the waterproof coating. After your adhesive spray has dried completely, do the same motions with your water resistant coating.

While we don’t have to make this look perfectly aesthetic, we want a nice clean, smooth coating on this to prevent water from getting trapped in the grooves of dried chemicals.

While this is unlikely to happen and cause problems, if you’re going to do something, it’s best to do it the right way. Be sure that your area is nice and ventilated without the use of fans so you aren’t breathing the runoff spray in or getting it in your eyes.

5. Give Three Days to Cure (or More)

Give this all the time in the world and then some to cure. You have to let all the materials combine on a chemical bonding level, and that’s not something you can rush.

Do not use fans to try and expedite the process in any capacity; just let it run. Make sure your space is well ventilated to get rid of all those chemical fumes we’ve been using.

What Happens if You Don’t Waterproof a Canvas Tarp?

What Happens if You Don’t Waterproof a Canvas Tarp?

Canvas is either made of cotton or polyester, and while both of these materials are fantastic, they’re able to rot out. These fabrics are not inherently mildew resistant, so you have to really ensure that your waterproofing method sticks to the tarp.

This helps repel stagnant water, which can cause problems of its own, and keep your actual tarp material protected. With cotton and polyester canvas, you don’t have the same level of natural resistance that polyethylene does.

When mildew gets in, it eats through cotton and polyester at an accelerated rate. You would find shreds of your canvas tarp with holes throughout it, and a nasty odor that wouldn’t go away.

If you only use your tarp for indoor use where it’s not near water, this isn’t going to be a problem that you’ll face. However, most people get a tarp because it needs to protect them from the rain and wind, so it’s definitely a good idea to waterproof your canvas tarp if it isn’t already.

It’s Easy, if You Have the Time

It doesn’t take a lot of effort, but it does take some time for everything to cure on your canvas tarp.

If you’re willing to wait and waterproof these properly, they’ll last for years before you need to revisit these steps, effectively saving whatever you’re covering from serious, long-lasting water damage.

Whether it’s a hole in the roof, or you’re tying down your lawnmower to keep it from rusting, a waterproof tarp is an investment.