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How to Thin Roofing Tar

how to thin roofing tar

Roofing tar is a thick substance that has many uses. It’s important to know how to use roofing tar properly and get the desired result.

The first thing you need before applying roofing tar is a bucket, some water, and a sponge or brush for spreading the material evenly.

There are two basic ways of thinning out your roofing tar: adding water and adding thinner (which can be either paint thinner or mineral spirits).

The process is simple: add a little bit of one or the other, mix thoroughly and apply.

What is Roofing Tar?

Roofing tar is the resin product found in asphalt shingles. It’s designed to bond to shingles and protect them from water damage, making it easier for them to last longer. 

In some cases, you need more than just a simple water barrier—for example, if you live in an area where the temperature swings between extremes, you might want to add some insulation.

Roofing tar comes in two different textures, determined by how it’s mixed: hot-pour roofing tar is harder and more pliable; cold-pour roofing tar is softer.

  • Hot-pour is what most people think of when they picture roofing tar; it’s used as a protective layer and as an adhesive.
  • Cold-pour roofing tar is used to fill cracks or holes in your roof.
Worker repairs the roof with molten tar from a bucket with a broom. Roof repair tar.

Why Do You Need to Thin Roofing Tar?

Roofing tar is pretty viscous on its own, which means you can’t spread it very easily. This isn’t always the case, but when in doubt, take a look at the label.

If your roofing tar needs to be thinned, there’s usually a good reason for that.

In some cases, you can use it as-is—but this is only okay if you’re just using it as an adhesive or protective layer. The thicker the tar, the less effective it is as adhesive.

As for using roofing tar as insulation, you need to thin it down until it’s almost watery—and even then, its insulating quality isn’t optimal.

When Should You Thin Roofing Tar?

  • If your roof needs more than just a water barrier, you’ll need to figure out how to thin your roofing tar.

For example, if you’re using hot-pour roofing tar and you want to add insulation: most people recommend heating it until it’s boiling [careful] and mixing in chopped fiberglass [wear gloves].

Keep in mind that this will not provide effective insulation—it’ll just be a little better than the original tar.

  • If you want to use roofing tar as an adhesive, you’ll need to thin it down until it’s almost watery. Even then, using waterproof cement is recommended.

You should also consider thinning your roofing tar if your bags are too hard for you to open or if they’re not dispensing properly.

Be careful—manufacturers usually add extra hardeners to make sure the tar stays in place while it’s shipped and stored, which means that you could end up with a clumpy mess if you try to use it as-is.

How Do You Thin Roofing Tar?

Roofing tar is a petroleum-base product used for waterproofing roofs.

It’s sticky, so you have to be patient when applying it — but even when you’ve done everything right, it might still be too thick in some places and leave certain spots untouched.

To solve this problem, you can thin out the roofing tar instead of trying to apply more.

Before you start, make sure the product is roofing tar and not asphalt paint. If it is asphalt paint, there’s no need to thin it out; you can simply use a roller like usual.

If the tar has hardened too much and feels like a rock or brick instead of a paste, that means it needs to be thinned out.

To do this, you’ll need mineral spirits mixed with an oil-based product like diesel fuel or roof coating solvent.

If the tar is just too thick in places, then follow these steps:

  • Soak a rag in your oil mixture and wipe down the object until you have covered all of it.
  • Repeat the process if the tar is still too thick in some places. This might take a while, so keep wiping it down until it’s completely covered and thin enough to spread.
  • After you get all of the roofing tar off of your hands, wash them thoroughly with soap and water, then grab a cold beer from the fridge to celebrate a day well done.
tar texture

Benefits of Tar Roofing

A roofing tar has many benefits. It protects a house’s exterior from water damage, as well as preventing insects from entering the house and rotting away the attic. 

When a roof is sealed with tar, it also protects the house from fire damage. Tar is waterproof and will prevent water from burning through the shingles or wood of a home.

Some people prefer to use this type of roof due to its affordability and lasting durability.  Tar provides a long lifespan; tar roofs can last as long as 40 years.

Tar roofing is weather-resistant and strong. This type of material holds up well in stormy conditions, which makes it perfect for hurricane areas.

Disadvantages to Using Tar Roofing

There are disadvantages to using tar roofing depending on your lifestyle and how often the dwelling is used.  Tar roofs are not for everyone.

One of the disadvantages is its weight. It weighs around eleven pounds per square foot, which means tar roofs weigh more than most other types of homes.

Another disadvantage is that it can be difficult to maintain or repair since tar is an organic compound made from petroleum products. Tar roofs are also difficult to clean, which leaves the roof susceptible to leaks.

Tar Roofing Materials

Roofs made from tar are composed mainly of bitumen. Bitumen is a black or brownish-black sticky material that has been used as an adhesive since ancient times. 

It is obtained from the distillation of petroleum and can be used in roofing because it has properties that make it a good base for adhesives, coatings and surface treatments:

  • Waterproof – Bitumen prevents water from penetrating the roofing material, which inhibits damage caused by moisture.
  • Fire resistant – When bitumen is mixed with other ingredients, this compound becomes less flammable and more fire-resistant.
  • Flexible – Bitumen can be used to form durable elastic coatings that are able to stretch and recover their original shape.
  • Sound insulator – Its excellent sound absorbing qualities allow for quieter homes.
  • Insulating properties – Tar roofs are often used to reduce energy consumption by reducing heating costs in winter and maintaining cool temperatures in summer.
    • Additionally, they are an inexpensive way of creating a barrier between the exterior elements and the interior of the home.
  • Resistant to chemical and weather agents  –  Bitumen is resistant to rust and corrosion. It is just as durable as steel but much lighter, making it ideal for roofing purposes.
  • Durable –  Bitumen is suitable for the creation of long-lasting roofs that can withstand harsh weather conditions.
  • Maintenance – Tar roofs are low maintenance and usually only require an annual inspection to maintain their characteristics.
    • The number of times it will be necessary to perform repairs or undertake replacement work on a tar roof will depend on the materials used, local climate, layout of the structure and other conditions.
tar, roof insulator

Final Note

Tar roofs are the best option in terms of lifespan and durability.

This makes them an excellent investment for homeowners who want to make sure that their roof will be there for many years to come.

There are instances when tar can lose its adhesion or become brittle leading to cracks on the surface.

These are signs that the material needs to be reapplied. The hardest part about applying tar is thinning the material for better penetrability to promote strong adhesion.

You can seek professional help or repair your roof yourself if you want to save money.

But sometimes it may be safer and more practical to hire a contractor for this type of project as high temperatures, fumes and slippery surfaces make working with tar quite dangerous.

Tar roofs with two levels in Potsdam