Usually, when a tar and gravel roof begins to leak, it is not considered ‘repairable’. Thus this guide is aimed to home owners and facility managers for a temporary patching of the roof and stopping the leaks, until complete roof replacement can be done.

Complete roof replacement is highly recommended to avoid / prevent the ’sunk cost’ – costs that have been incurred and which cannot be recovered to any significant degree (or simply – waste your money). An analogy can be drawn with an old car, where you keep on fixing small thing, one after another, until something major breaks, and all the money put into fixing it, are lost.

Before you begin – getting tools, supplies and materials

These can be purchased at your local roofer’s supply warehouse, lumber yard, Home Depot or Lowe’s. Roofer’s warehouse is a preferred place to buy your supplies, as they’ll have the best selection and knowledge of products you’ll need.

Try Bradco Supply, ABC roofing supply, Beacon supply or Harvey Industries (in New England only). These are all either regional or national roofing supply warehouse, and they usually stock everything you may need, and also have somewhat knowledgeable staff, to answer some of your question.

These are the places where most roofing contractors shop, so you should be able to find what you need!

Tools you will need:

1. Utility knife with a few spare blades
2. A bucket (or two) of tar
3. Asphalt saturated fabric (cotton or fiberglass, it doesn’t matter too much)
4. Plastic trowel for spreading the tar
5. Few dry towels / rags.

Finding the leak

This is the essential step in patching of the roof. The nature of flat roof leaks makes it difficult to identify the spot where the water is coming in, since it may ‘travel’ under the roofing membrane until it finds the lowest spot, and only then you see the stains on your ceilings.

Easiest way to find a leak is to start at the lowest spot, where the water may be collecting and sitting for days after each rain – this is called ponding water, and it is one of the most common leak spots. You will need to shovel off the loose gravel to the high spot and clear at least about 100 sq. ft of roof area. If you have ponding water under gravel, you can use old clothes / rags and a dust pan to put it in a bucket and get it off the roof.

Now it’s time to do some repairs – a 10 steps process:

1 ) Once the area is clear of water and dry, look for blisters, cracks and openings in the tar, or other signs of water entering spots.

2 ) Cut out the blisters with the utility knife – make a large ‘X’ cut & pull it back a little. Let it dry out, then open up the cracks and let them dry out also.

3 ) When everything is dry, use a plastic trowel to apply a thick layer of tar under the area you cut and set the sliced portions of the roof back in the tar.

4 ) Use the towels to clean up the area under the X. Sweep away all dust and dirt under, over and around the cut area. This will greatly improve the quality of your repair.

5 ) Now spread an even coat of tar over the patched area approx 1/8 inch thick or a little more, so that it goes at least 6 inches beyond the repair area.

6 ) Cut out a piece of fabric that would be enough to cover the repair area and place the piece of fabric in the tar. Use the trowel to set it in, so that the fabric gets saturated with the tar until you see it coming through the fabric.

7 ) Apply another thin and smooth coat of tar over the fabric and beyond its edges.

8 ) Feather the edges into the old roof.

9 ) Put back the gravel with your hands, over the repaired area – make sure you do not use a push-broom, as that will disturb your new patch. This gravel will protect the repair from the devastating sun light.

10 ) This is a 3 course tar and fabric patch. Add another layer of fabric then tar and it is a 5 course.

Afterwards: Roof Repair or Replacement

Bear in mind that this repair will last you about 3-6 months, after which another repair in the same spot will be required, and at the same time more leaks will probably appear elsewhere. The purpose of such repairs is not to get rid of leaks all together, but a temporary stop of leaks, while you gather resources and information to install new roofing systems. Due to nature of tar and gravel roofs, there is no permanent cure for roof leaks, as tar dries up it turns in a ‘dust compound’ which helps de-lamination of the patch from existing tar roof. Therefore, unless you are willing to take the continuous roof leak and repair cycle, which not only have direct repair costs, but also does hidden damage to the structure of your home or building, which in effect will increase your out of pocket costs when you go with full roof replacement.

Also, if you do not feel comfortable performing these repairs yourself, we recommend that you hire a professional roofer specializing in flat roofing – not Joe the shingler that your friend knows. Flat roofs are completely different from regular shingle roofs, and require special training/experience when dealing with them.