How to waterproof a tent: reproof, seal and refresh

Waterproofing a tent is three separate jobs done on one dry day: reproof the outside of the flysheet with a spray-on proofer, seal the seams from the inside with seam sealant, and refresh the coating on the groundsheet. Do all three on a clean tent that is pitched and bone dry, let everything cure fully, and a tent that had started letting water in will keep you dry again.

You do not need a new tent when the old one leaks. Almost every leak is a worn coating, not damaged fabric, and worn coatings are cheap and quick to put right at home. This guide is part of the complete UK camping gear guide from Camping Sites in Britain, where you can also find and compare campsites across the country once your kit is sorted.

Why tents stop being waterproof

Tents lose their waterproofing because the coatings wear out, not because the fabric fails. A new flysheet has two things working for it: a durable water repellent (DWR) treatment on the outside that makes rain bead and roll off, and a polyurethane or silicone coating that stops water passing through. Both degrade with time, sunlight, dirt, packing damp and simple use.

When the DWR wears off, the flysheet "wets out". Instead of beading, rain soaks into the outer fabric and the whole panel goes dark and heavy. A wetted-out flysheet feels damp to the touch on the inside even when no water is technically getting through, and in a downpour it will eventually let water in. UV from the sun is the biggest culprit in the UK, which is why south-facing panels and the tops of family tents fail first.

The seams are the other weak point. Every seam is a line of needle holes, and the factory tape or sealant over them peels and lifts after a few seasons. Water finds those holes long before the main fabric gives up.

The three jobs at a glance

Waterproofing splits into three tasks, each fixing a different part of the tent. You can do one or all three depending on where the water is getting in, but doing all three at once is the sensible move because the tent is already up and the day is already set aside.

Job	What it fixes	What you use
Reproof the flysheet	Rain soaking in instead of beading off (wetting out)	Spray-on proofer such as Nikwax Tent & Gear SolarProof
Seal the seams	Water through needle holes where panels are stitched	Seam sealant matched to your coating (PU or silicone)
Refresh the groundsheet	Damp coming up through the floor	A tent floor sealant brushed onto the inner surface

Do it on a dry, clean, pitched tent

Pitch the tent and make sure it is clean and completely dry before you start. Every one of these jobs fails on a dirty or damp surface, because proofer and sealant will not bond to grime or trapped moisture. Pick a warm, dry, still day and give yourself a few hours plus curing time.

Brush off all mud, grass and bird mess, then wipe the flysheet down with clean water and a soft sponge. If the fabric is genuinely grubby, use a technical cleaner such as Nikwax Tent & Gear SolarWash rather than washing-up liquid or detergent, which strip coatings and leave residues that stop new proofer taking. Let it dry, or work on damp fabric only where the product specifically allows it.

Job one: reproof the flysheet

Reproofing restores the DWR so rain beads and runs off again. For tents you want a spray-on proofer, applied to the outside of the pitched flysheet. Wash-in proofers are for jackets and small items, not something the size of a tent.

1. Pitch the tent and clean the flysheet as above. Nikwax Tent & Gear SolarProof goes on clean, damp fabric, so you can proof straight after rinsing.
2. Shake the bottle. Spray the proofer evenly across the outside of the flysheet from around 15cm away, covering every panel including the ones you cannot easily see.
3. Leave it for two minutes, then wipe off any excess with a clean damp cloth so it does not dry into patches.
4. Let the flysheet air dry completely, ideally in the sun, before you pack it away. Give heavy-weather panels a second coat once the first is dry.

A 500ml bottle covers a small tent and costs roughly £10 to £15 in UK outdoor shops. Larger family tents need more, so buy the concentrate or a bigger bottle. Follow the maker's own instructions, which you can check on the Nikwax Tent & Gear SolarProof page.

The one rule that matters most in the field: never touch the inside of a wet single-skin flysheet. Pressing a finger, a sleeping bag or a stray elbow against damp fabric breaks the surface tension and draws water straight through at that spot, turning a dry night into a drip. Keep bedding and bodies off the flysheet when it is raining, and this is far less of a problem on a tent with a separate inner.

Job two: seal the seams

Sealing the seams closes the needle holes where panels are stitched together, which is where most tents leak first. The trick is to match the sealant to your fabric, because the two main coatings need different products.

1. Pitch the tent so you can reach the seams, and leave the inner out so you can work on the flysheet seams. Many people pitch the flysheet inside out for easier access.
2. Clean each seam with a cloth and a little rubbing alcohol, and gently peel away any old tape or sealant that is already lifting.
3. Work out your coating. Polyurethane-coated nylon or polyester takes a PU seam sealant such as Gear Aid Seam Grip; silicone-treated (silnylon) fabric needs a silicone sealant such as SilNet. Using the wrong one means it will not stick.
4. Brush a thin, even line of sealant along the inside of each seam, following the instructions on the tube. Do the whole seam, not just the visibly damaged bit, because the rest is usually next to fail.
5. Leave it to cure fully before you touch or pack the tent. Most seam sealants need a good number of hours and are best left overnight.

The method is set out in the Gear Aid guide to waterproofing and seam-sealing a tent. If a seam is coming apart at the stitching rather than just leaking, that is a repair job, covered in our guide to how to fix common camping equipment issues.

Job three: refresh the groundsheet

Refreshing the groundsheet stops damp rising through the floor where you sleep. The inner surface of a sewn-in groundsheet carries the same PU coating as the flysheet, and it flakes with age and abrasion.

1. With the tent pitched, look across the inside of the groundsheet for flaking, peeling or shiny worn patches.
2. Scrub off any loose, flaking coating and wipe the area clean, then let it dry.
3. Brush a thin, even coat of tent floor sealant over the worn areas, or the whole floor if it is going generally.
4. Leave it to cure for at least 24 hours before packing. A groundsheet sealant needs to be properly hard or it will stick to itself in the bag.

Also brush the mud off the underside before every pack-down. Grit ground into the outer face is what wears the coating through from below in the first place.

Dry it fully, then store it dry

Let every treated surface dry and cure completely before the tent goes in its bag. Packing a tent even slightly damp is the fastest way to ruin it: mould and mildew bloom within days, they smell, and they eat coatings, which undoes the work you just did. If you had to strike camp wet, get the tent back up in the garden or over a bannister at home and dry it properly before storage.

When to waterproof your tent

Reproof once a year for a tent in regular use, or as soon as it starts letting water through, whichever comes first. A brand-new tent needs nothing for the first few seasons because the factory coatings are fresh. After that, three signs tell you it is time.

• Rain soaks in and the flysheet goes dark instead of beading and running off.
• You find flaking or peeling on the inside of the flysheet or groundsheet.
• Water actually comes through during a trip, usually at a seam or a worn panel first.

You can test at home before a trip: pitch the tent, spray it with a hose, and watch whether the water beads and runs or soaks in. Sort it in the garden rather than discovering the problem on a wet weekend away. Once your tent is holding water out again, browse campsites across Britain and put it to use.

Frequently asked questions

Can you waterproof a tent while it is up?

Yes, and you should. Spray-on proofers and seam sealants are designed to be applied to a pitched tent so you can reach every panel and seam evenly. Pitch it, clean it, treat it, and leave it standing until everything has dried and cured.

What can I use to waterproof a tent?

Use a purpose-made tent proofer such as Nikwax Tent & Gear SolarProof for the flysheet, a seam sealant matched to your coating for the seams, and a floor sealant for the groundsheet. Avoid household sprays and detergents, which do not bond and can strip existing coatings.

How often should you reproof a tent?

About once a year for a tent used through a normal UK camping season, and sooner if you camp a lot or store it in strong sun. The real trigger is behaviour: reproof the moment rain stops beading and starts soaking in.

Why does my tent leak when I touch it?

Touching the inside of a wet single-skin flysheet breaks the surface tension of the water sitting on the fabric and pulls it through at that point. Keep bedding, kit and elbows off the flysheet in the rain, and reproof if the whole panel is wetting out.

Can you make an old canvas or polycotton tent waterproof?

Yes. Canvas and polycotton tents are weathered rather than sprayed: pitch the new tent and wet it down so the fibres swell and close the needle holes. After that they take specific canvas proofers, not the sprays used on nylon flysheets.

Is it worth waterproofing a cheap tent?

If the fabric and poles are sound, yes. A £15 tin of proofer and an afternoon is far cheaper than a new tent, and it works as well on a budget tent as an expensive one. Replace the tent only when seams are tearing or fabric is perishing.

The short version

Reproof the flysheet, seal the seams and refresh the groundsheet, all on a clean, dry, pitched tent, then dry it fully before it goes away. Do it once a year or the moment rain stops beading, and never touch the inside of a wet flysheet. For everything else that keeps you dry and comfortable outdoors, see the complete UK camping gear guide, our pick of the best waterproof jackets for campers and the best waterproof camping bags.