Does Tarpaulin allow water to pass through or not? Tests, facts and tips for choosing

When it comes to protecting your car from rain, snow or dust, the first thing that comes to mind is Tarpaulina - a universal blanket that is used to cover cars, cargo and even construction sites. But in practice, many car owners are faced with an unpleasant surprise: moisture still appears under the cover. So why tarpaulin allows water to pass through, if manufacturers claim that it is waterproof?

The fact is that not all types of tarpaulin are equally resistant to moisture. It all depends on the material, the density of the fabric, the quality of the seams and even how you lay it. In this article we will look at:

• 🔍 What types of tarpaulin exist? and how they behave in the rain
• 💧 Why even “waterproof” material can get wet — physics of the process
• 🚗 How to choose the right car coverto avoid corrosion and mold
• ⚠️ Common mistakes, due to which tarpaulin loses its properties

Spoiler: Even the most expensive tarpaulin labeled "100% waterproof" can leak moisture if used incorrectly - and we'll tell you how to avoid this.

1. Types of tarpaulin: which material really does not allow water to pass through?

There are more than 10 varieties of tarpaulin on the market, but only 3-4 types are usually used for cars. Their key difference is base and impregnation, which determine the degree of protection against moisture.

Tarpaulin type	Material	Waterproof	Service life	Price (per 1 m²)
Polyethylene (PE)	Dense polyethylene with reinforcement	⭐⭐⭐⭐⭐ (100% with integrity)	2-4 years	from 150 ₽
Polypropylene (PP)	PVC coated woven base	⭐⭐⭐⭐ (90-95%, may “sweat”)	3-5 years	from 250 ₽
Canvas	Cotton/synthetic with water-repellent impregnation	⭐⭐⭐ (70-80%, requires re-processing)	5+ years	from 400 ₽
PVC (vinyl)	Laminated vinyl with reinforcement	⭐⭐⭐⭐⭐ (100%, but heavy)	5-7 years	from 600 ₽

Cheapest options - polyethylene covers - actually do not allow water to pass through, but only if they are new and undamaged. However, they have a disadvantage: when temperature changes, condensation forms under the film, which settles on the car. Polypropylene Tarpaulin is more breathable, but in heavy rain it can get wet at the seams.

Best choice for long term protection - PVC-taprpaulin. It is not only waterproof, but also UV resistant, which is important for outdoor parking. However, its weight (from 300 g/m²) can create problems in strong winds - additional fastenings will be required.

2. Why tarpaulin allows water to pass through: 5 physical reasons

Even if you bought a case marked "waterproof", this does not guarantee 100% protection. Here are the key factors that cause moisture to penetrate under the shelter:

• 🌧️ Capillary effect: water seeps through microscopic pores into the fabric (especially true for tarpaulin and cheap polypropylene).
• 🔥 Thermal "breathing": when heated by the sun, the air under the cover expands, and when cooled, it draws in moisture from outside.
• 🧵 Leaky seams: If the cover is sewn with threads without heat sealing, water will seep through the stitches.
• 💨 Wind and mechanical stress: when there are gusts, the material stretches, allowing moisture to enter.
• 🕳️ Microdamage: scratches, punctures or cracks from frost (relevant for PVC at -20°C).

Particularly insidious condensate. If you cover a wet car with tarpaulin, the moisture evaporates and settles on the inside of the cover, and then flows back onto the body. This is one of the main causes of corrosion during long-term storage of a car under cover.

⚠️ Attention: If water accumulates under the tarpaulin after rain, check it for hydrostatic pressure. Cheap materials can withstand only 300-500 mm of water. Art., while high-quality - from 2000 mm.

How to check your case? Pour water into a glass and place it on the stretched tarpaulin. If after 10 minutes drops appear from below, the material not suitable for protection from rain.

3. How to choose the right tarpaulin for a car: checklist

To avoid the problem of “tarpaulin leaking water,” when purchasing, pay attention to the following parameters:

Material density ≥ 200 g/m² (optimally 250-300 g/m²)

Availability heat welded seams (not stitched!)

Marking PU-coated (polyurethane coating) or PVC-coated

UV stabilization (important for long-term parking under the sun)

Availability ventilation valves (to combat condensation) -->

For short term protection (for example, for a trip out of town) a polyethylene cover with a thickness of 120-150 microns is suitable. For long-term storage (car winterization) needed PVC-taprpaulin with a density of 300 g/m² and always with ventilation holes.

Please note size: the cover must cover the car with a margin of 30-50 cm on the sides, otherwise the wind will tear it off, exposing the body. For fastening use rubber bands or straps with carabiners - they will not damage the paintwork.

4. Typical mistakes when using tarpaulin

Even the most expensive case will lose its properties if the operating rules are violated. That's what can't do:

• 🚫 Covering a wet car: moisture will remain under the cover and cause corrosion. Always dry your car before covering it.
• 🚫 Use a case with holes: Even a small hole will eventually turn into a large crack due to the wind.
• 🚫 Keep tarpaulin wet: Dry it before folding, otherwise mold will appear.
• 🚫 Attach the cover to sharp elements (antenna, mirrors): this leads to punctures.
• 🚫 Use household tape for repairs: It does not adhere to PVC and polyethylene. Need special repair tapes.

Another common mistake is buying a back-to-back cover. If the tarpaulin fits tightly around the car, it will rub the paintwork in the wind, leaving micro-scratches. It is optimal when there is a gap of 10-15 cm between the body and the material.

⚠️ Attention: If you store your car under a tarpaulin in winter, shake off the snow once a month from the case. A snow cap creates additional stress on the material and can tear the seams.

5. How to eliminate leaks: repair and care of tarpaulin

If your case begins to leak water, do not rush to throw it away. In most cases it can be restore:

For small punctures (up to 5 mm):

1. Clean the damaged area with alcohol.
2. Paste repair tape (for example, Tesa 51608 or 3M Scotch-Weld).
3. Warm up the repair area with a hairdryer (temperature 50-60°C).

For large gaps:

• Use liquid rubber (for example, Mastix) for sealing.
• Suitable for PVC tarpaulin cold welding (for example, Loctite).
• If a seam is torn, glue it hot melt glue from the inside.

For prevention, treat the cover once a season water repellent spray (for example, Nikwax TX.Direct). This will restore the hydrophobic properties of the material. Store tarpaulin in dry place, folded, but not squeezed (so that creases do not form).

Why is condensation under tarpaulin dangerous?

Condensation is the main cause of a “wet” cover, even if there is no rain outside. Moisture settles on the body and creates ideal conditions for:

- Metal corrosion (especially in places where the paintwork is chipped)

- Mold development on seals and interior

- Oxidation of electrical contacts (for example, in headlights)

To avoid this, use covers with ventilation valves or periodically ventilate the space under the tarpaulin.

6. Alternatives to tarpaulin: which is better for car protection?

If you're disappointed with tarpaulin because it leaks water, consider these alternatives:

Option	Pros	Cons	Price (from)
Car cover from Oxford	Lightweight, breathable, UV protection	Not for heavy rainfall	3 000 ₽
Pneumatic frame box	100% protection from moisture, snow, dust	Dear, needs space	20 000 ₽
Garage awning	Durable, wind resistant	Difficult to install alone	8 000 ₽
Liquid glass + wax	Protects paintwork from moisture	Does not protect from dust and birds	1 500 ₽

For long-term storage (for example, for winter) is optimal pneumatic frame box. It creates a sealed space around the machine and prevents condensation. If your budget is limited, combine tarpaulin with silicone body treatment - this will reduce the risk of corrosion.

💡

Tarpaulin is a temporary solution. To reliably protect your car from moisture for more than 3 months, consider alternatives: a garage awning, an air box or specialized covers made of membrane fabrics.

FAQ: Frequently asked questions about tarpaulin and water

❓ Is it possible to wash tarpaulin in a washing machine?

❌ No! Tarpaulin cannot be washed in a machine - this destroys the water-repellent coating. The maximum that is allowed: hand wash warm water (up to 40°C) with a mild detergent (e.g. Kärcher RM 519). After washing, be sure to dry the cover in the open air, but not in direct sunlight.

❓ Why does water accumulate under the tarpaulin, even if there was no rain?

This condensate, which is formed due to the difference in temperatures inside and outside the cover. To avoid the problem:

• Use cases with ventilation holes.
• Periodically lift the tarpaulin for ventilation.
• Cover only dry car.

❓ Which tarpaulin is better for protecting a motorcycle?

Optimal for motorcycles polyethylene cover with a density of 180-200 g/m² or PVC-taprpaulin with ears for fastening. It is important that the case has:

• 🔹 Reinforced seams (motorcycles are often stored outside where the wind is stronger).
• 🔹 Hole for steering wheel (so as not to rub the plastic).
• 🔹 UV protection (if the motorcycle is standing under the sun).

Brands we recommend Dowco or Nelson-Rigg.

❓ Is it possible to use tarpaulin to cover a car in winter?

⚠️ You can, but with reservations:

• 🔸 Choose frost-resistant materials (PVC or polypropylene marked "Winter").
• 🔸 Shake off snow regularlyto avoid sagging and tearing.
• 🔸 Use fleece lining under the cover to reduce condensation.

If the temperature drops below -25°C, it is better to use garage awning or pneumatic box.

❓ How to check tarpaulin for water resistance before purchasing?

In the store you can spend express test:

1. Ask the seller for a sample of the material.
2. Pour water on it and wait 5 minutes.
3. Turn the fabric over - if the back side is dry, the material is waterproof.

Also pay attention to:

• 🔹 Seams: They should be glued, not stitched.
• 🔹 Marking: look for inscriptions Waterproof, PU 2000mm or similar.