DIY: Flat Roof Repair

We recently moved into a new (to us) house.  It is a quirky 60s thing with lots of neat design features, but it also has several issues- such as a flat roof.

We moved in as winter was upon us, and although the roof gave every indication it was in good shape, it did not do well over the winter.  So when spring rolled around we started looking into how we might repair it.

We did hire a company to come out and repair some trouble spots- several hundred dollars later we had several small spots patched, no guarantee (we couldn’t find any roofers willing to guarantee patches to a tar and gravel flat roof), and we still had leaks.

So we did some research and found some products that we could use to patch larger areas and hopefully address the issues.  Dry, hot, summer time is the time to do these repairs so, in almost 100 degree weather, I decided to try my hand at being a roofer.

Our roof is a “flat tar and gravel” roof (which is really called low-slope built-up roofing).  We decided to patch 2 trouble spots to see how things went.

Step One: Sweep away all the loose gravel in the area you are working:

Step One: flat roof repair

Step Two: Wash the area really, really well- preferably with a pressure washer but a hose and gentle scrub brush may also work- we have a pressure washer so that is what I used.

Step Three: Using asphalt emulsion and a roofing brush, apply the asphalt emulsion to the area to be patched- this needs to be done when the roofing is dry (although a fine mist can be applied to help with adhesion) and preferably during hot weather:

Step Three: flat roof repair

Two coats of asphalt emulsion should be applied, and should be applied in opposite directions (for example, one coat parallel to the roof’s edge, the other perpendicular to it).  Also, depending on how smooth or rough the roof surface is, you may need more asphalt emulsion than you think- I needed twice as much as I initially calculated based on the approximate coverage listed on the product- this is because our roof is old, had a lot of embedded gravel, and needed more product to even out some sagging spots.  However, asphalt emulsion is one of the cheaper roofing products for this type of roof so it is better to use more of it and less of the more expensive top coats.

Step Three: flat roof repair

Step Four: At this point, you have a choice: asphalt emulsion is a great water-proofer but it does not hold up against sun damage- it MUST be covered with something.  After the emulsion has cured for a minimum of 24 hours, you can choose to sweep the gravel back onto the newly patched area, or it can be coated with a cool roof coating.  Since we wanted to be able to monitor these trouble areas, we decided to use a cool roof coating instead of replacing the gravel- a very simple process that simply requires a paint roller:

Step Four: flat roof repair

 Just like the asphalt emulsion, it is best two do two perpendicular coats of the cool roof coating.  Hopefully, however, enough emulsion has been used to even out the roof area meaning less cool roof coating has to be used.  Based on my roof and it’s specific conditions, I ended up using (4) 5-gallon buckets of emulsion and half a 5-gallon bucket of the cool roof coating.

As a final step, I swept the gravel onto the edge of the cool roof coating so there was a couple of inches in overlap and the “seam” was not exposed.

The best part?  After a few rain storms this fall these patches appear to be holding up!  It is not a final solution but it looks like these patches may have bought us a few years before we will need to consider a roof replacement- phew!