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Can You Lay Tarmac in the Rain? [Hot & Cold Laying Guide]

Laying asphalt or tarmac can be a big job that requires a fair amount of preparation; for a sizeable tarmac driveway, you can be looking at a few days of prep time. So, what are the ideal conditions to lay asphalt? And can the job be completed in rainy weather and cooler temperatures?

Let’s take a look at the differences between asphalt mixtures and find out can you lay tarmac in the rain.

Can Tarmac be Laid in the Rain?

In short, yes, but only if other conditions are met and the rain isn’t too heavy. Light rain shouldn’t cause too much trouble to your installation, but rainy weather of any kind isn’t ideal.

Laying tarmac in the rain will halt any asphalt paving project, as too much water present can wash away the tarmac before it has a chance to set and bond.

Cold mix asphalt, in particular, must be kept away from heavy rain, as the asphalt mixture already has water present. Too much added moisture will ruin the project, so even light rain should be avoided where possible.

How Weather Dependent is Laying Tarmac?

Laying asphalt of any kind is pretty weather dependant. Whilst rainy weather should always be avoided where possible, there are also several other considerations to consider when laying asphalt of any kind.

Dry temperatures are ideal to allow asphalt and tarmac to set into a durable surface. Mist and humidity should be avoided and freezing temperatures will cause hot mix asphalt to cool rapidly, ruining any asphalt pavement.

Whilst conditions can be worked around if necessary; you’ll want to lay asphalt in high temperatures with low humidity to ensure a smooth surface and faster curing time.

Does Temperature Affect The Process?

Temperature greatly affects the quality and curing time of any asphalt paving project. Whether you’re using cold mix asphalt or hot mix asphalt, the temperature at which it’s installed will affect both the quality of the finish and the time it takes to cure.

Dry temperatures of at least 15°C and rising are recommended for any type of asphalt, but ideally, you should look for weather conditions of up to 30°C with high temperatures on the ground.

This allows the asphalt to properly dry and create a durable bond between the ground and the walkable surface. The longer asphalt or tarmac sits, the more likely it is to form cracks or wash away, causing unintended results in your project.

Laying Asphalt & Different Types

Cold Mix Asphalt

The base materials of cold mix asphalt are gravel aggregate and oil-based binder with some water present to aid the bonding process. Because heat is not needed during its preparation, cold mix asphalt can be applied in cooler temperatures and even freezing temperatures if necessary.

The faster preparation time for cold mix asphalt means it’s commonly used as a quick-fix repair for the potholes and cracks that you might find in car parks or asphalt pavement. Generally, cold mix asphalt is used as a cost-effective, temporary solution until a hot mix asphalt can be acquired and used.

This is why you’re unlikely to see cold mix asphalt used in large projects like a tarmac driveway or full asphalt paving. Though a cold mix can be installed in light rain, you should avoid heavy rain and excess water.

Hot Mix Asphalt

The base materials of hot mix asphalt are gravel aggregate and an oil-based binder, though this type of asphalt contains no water. The hot mix must be heated prior to application and cannot be laid on wet surfaces or standing water, as the oils repel water and will result in the asphalt washing away.

Most professionals and contractors use hot mix asphalt for large jobs, like driveways and block paving, as its strong seal protects the driveway beneath. Hot mix should not be applied when it’s actively raining.

Water means this asphalt will wash away and ruin the installation of your driveway; contractors will advise that you don’t pave in the rain and instead wait for optimal conditions before the tarmac is laid. The labour costs of preparing and installing hot mix asphalt are far greater than cold mix, so under normal circumstances, this asphalt will be used on a large job site rather than for personal projects.

FAQ’s

Can you apply tarmac to frozen ground?

We don’t recommend tarmac to be laid on frozen surfaces or concrete as the frozen moisture present will melt and cause issues with the asphalt once applied.

When is the best time to lay asphalt?

The spring and summer months are ideal, with warm, dry weather and no chance of rain for 12-24 hours after laying the tarmac.

Will water react with curing tarmac?

Yes, if freshly laid asphalt comes into contact with water before its 12-24 hour setting time is complete, you will run the risk of the oils separating from the aggregate. The tarmac can come loose from the concrete or paved surface and ruin a job.

What Happens if it Rains on Fresh Tarmac?

If it’s raining when you install fresh tarmac, you risk the oil being forced out of the asphalt as the oil repels water. Though asphalt can be weather-resistant when fully cured, asphalt will not adhere to the ground, concrete or block paving if exposed to rain before it’s set.

We advise that you check your weather forecast before laying asphalt and, if there’s any chance of rain in the 12-24 hours after it’s been laid, try to avoid applying asphalt of any kind.

Can you Lay Cold Mix Asphalt Paving in Wet Weather?

Generally, no, it’s not advised that you lay cold mix in wet conditions. The water already present in the cold mix means applying this tarmac to potholes and cracks whilst it’s raining can cause serious issues with the bonding of the material and will result in a poor finish.

Light rain is permissible if absolutely necessary, but you must make sure that the surface itself is dry and that the showers aren’t expected to worsen as the asphalt is curing.

Does Rain Affect Driveway Maintenance?

Once laid and dry, any type of weather won’t have too much of a bearing on your drive. Although, see our how to maintain a tarmac driveway guide to ensure that you correctly look after yours in the years to come. By doing this your investment gets plenty of use and still looks great in 10 years time!

Last Word

To summarise, we recommend that you wait until the weather is warm and dry before attempting to lay asphalt of any kind. Although asphalt can be applied in mild rain if necessary, it’s usually worth your while to wait for a window of optimal conditions.

Cold mix can be great as cheap alternative asphalt for small jobs and can be used in cold weather, but be aware of its limitations when it comes to water exposure. Hot mix is preferred for larger jobs and longevity but requires a longer prep time and warmer weather to be correctly applied.

If in doubt, consult a professional, but generally, you should avoid rain of any kind when applying asphalt to a surface.