When not to repair a flat roof – Hot Tar and Gravel Roof

There is a point when not to repair a flat roof (Hot Tar and Gravel) but rather replace

We have been installing and repairing flat roofs in Connecticut for over 30 years. We claim that we can fix almost any roof. But when it comes to Hot Tar and Gravel Roofs, we draw the line. Hot Tar Build-up Roofs gets too brittle and start blistering. These blisters can pop open anytime and cause a significant leak.

Watch this video to see when a roof is beyond repair.

This video shows the reason why it is not wise to make any repairs

The Age of Hot Tar and Gravel Roof is Critical

Anytime when a “hot tar and gravel roof” is over a certain age, it is not advisable to make any repairs. It is hard to tell how long such a roof should last. It all depends on how many layers of tar and paper was put on at the time of installation.

Tell-tale signs when a Tar and Gravel Roof is beyond repair

  1. Blisters pop up that causes the gravel to heave.
  2. When black streaks appear through the stone, it is a sign to replace. The roof will bubble up and cause air pockets in some areas. When the roof starts leaking in the middle where there are no other obvious reasons, the hardest part of replacing an old roof is to clean and repair the existing drains. It is difficult to remove the tar build up of numerous repairs over the years. The rule of thumb is 20  to 25 years is the life expectancy. The hardest part of replacing an old roof is to clean and repair the existing drains. It is difficult to remove the tar build up of numerous repairs over the years.

Installing a Modified Bitumen Torch Down Rubber Membrane over a Hot Tar and Gravel Roof

It is not necessary to remove an old Hot Tar and Gravel Roof to install a Torch Down Rubber Roof. You can easily install a Rubber membrane over a Tar and Gravel roof by using the technique in this video.

This video demonstrates how to install a Torch down Rubber Membrane over a Tar and Gravel Roof
Tar and Gravel roof that is beyond repair
This the same roof as in the video above before installing a Torch Down Rubber Roof over it. The black blisters and streaks were a sign that this roof was beyond repair.

The image below shows blisters pushing the gravel up.

One of the tell tale signs when a Tar and Gravel Roof is beyond repair, is when blisters forms. These blisters are formed from water seeping in the layers of the hot tar asphalt, and when it heats up during the day, the steam will swell these pockets causing blisters.

Hot Tar Gravel Flat Roof
Hot Tar Gravel Flat Roof – If you look carefully, you will notice the stone heaving up slightly in a few spots. These are the blisters formed in the Tar layers and water is trapped inside these blisters. When it gets hot the steam make them swell up.

We have a technique that we can install a rubber roof over such a gravel roof at a relatively low cost provided the flashing is in good shape. Most of the time flashing is made of copper and is in excellent condition.

The other factors would be skylights and other obstacles on the roof that could make it hard to reach the flashing.

The old roofs are fast being replaced by rubber roofs. There are several ways to go about replacing such a roof.

Most roofing companies would recommend to remove the old roofing material to the deck, which could be tongue and groove boards or plywood, and then install a new rubber roof.

That is the preferred way to do it, but the cost rise considerably due to more people are involved in stripping the roof and removing the debris. — Dumpster costs. Then the possibility of damaging existing flashing while removing the old roof is also a factor.

Most of the time we will recommend to install a rubber roof over an existing gravel roof. We have done this with most of our projects and it is perfectly alright to do so. The problem sometimes is if there are many skylights on the flat roof. Anytime you go over an existing flat roof, you need also to tie into the flashing of the old existing roof. That flashing is buried under the old roof surface and has to be exposed to adhere to the new rubber roof to that.

The most time consuming part of a roof are the drains, air conditioners and flashing.
Removing the old Tar and Gravel roof to install a ne rubber Roof
The roof is ready to receive the final membrane. Notice that the base sheet is under the flashing.
This is what the roof looks like after the old roof have been removed. This is the base membrane in this image.

Conclusion about Hot tar and Gravel Roofs

Hot Tar and Gravel Roofs used to be the industry standard for all flat roofs. These Hot Tar and Gravel roofs came in different thicknesses and therefore varied in life expectancy. As in any other roof system, it depends on the experience of the technicians, how many asphalt paper layers, and complication of the roof surface to judge the quality of such a roof.

From our experience, it is never necessary to remove an Old Tar and Gravel Roof, but instead, install a new Torch Down Rubber Roof over it. The life expectancy of a Torch Down Roof over a Tar and Gravel Roof if installed correctly, will last beyond 40 years

Questions about Hot Tar and Gravel Roofs

What is the life expectancy of a Tar and Gravel Roof?

The life of a Tar and Gravel Roof depends on how many layers of tar and paper is there. The more sheets of asphalt paper, the thicker the roof is and the longer it would last. The consensus is that a Hot tar and Gravel roof can last between 15 and 60 years.

Can a Hot tar and Gravel roof be Repaired?

Yes, it can be repaired if it has no signs of blistering or cracking.

How do I repair a Tar and Gravel Roof?

The best way is to remove the stone or gravel first. Then use a propane torch with a spade. Heating the hot tar you can then scrape the top layer of the Tar Roof to get a smooth surface. Once you have a flat surface, then you can use Karmak 81 to make repairs.

Can I repair a Tar and Gravel Roof as a homeowner?

You can do it yourself if you buy a Roofers Propane Torch and follow the videos I have made on how to do it.

More Articles on Flat Roof repairs:

About The Author

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.