Introduction: Crack Repair in Concrete Roof

About: Loving Husband, Professional problem solver, Electronics master degree student, Technology geek. Electronic Engineer. Clean energy promoter.

Hi, thanks for reading this Instructable.

This time, i'll describe how to find, seal and repair a crack on a concrete roof.

I needed:

-Electric extension


-Full Body harness

-Eye protection

-Good Rope


-Round wire brush (for the drill).

-Paint Brush

-Polyurethane sealant

-Silicone gun

This is where i live (left); it's a house that used to have a waterproof asphalt coating. It kept the water away, but absorbed a lot of heat (really), and that's a problem living in a tropical weather in the Mexican Coast.

The difference of temperature between the first and the second floor was so remarcable, that you could feel the termal shock just a half way on the stairs. The main room felt like the inside of an oven; the bed was hot, and you couldn't rest before 10 p.m., or at least 40 minutes of air conditioner. This of course had an effect on the electricity bill.

So i decided to remove it, and use a waterproofing with thermal insulation. Worked fine, the heat reduced a lot, just like it did my bill, but the roof had a surprise for me.

Step 1: Reveal the Problem.

The fun in this problem was this.

On heavy rain there was no problem, but with a light drizzle, i had a constant drip and couldn't find the source.

After a while, i came with the idea of using a red flannel, and it worked like magic. The shape of the drip was revealed and i had a clear view of what to look for on the roof.

When rain stoped, i searched for a diagonal crack, and it was very easy to find once i had a clear shape in mind.

I used a gray spray paint (it was the only in my house, the color is unrelevant) to mark the working site.

WARNING: Make sure to NOT let spray paint it on direct sunlight, especially if you live in a hot weather zone.

Step 2: Preparation.

The crack was located on a tilted roof, a complicated position that require special security measures. So i tried to work the safest posible.

I bought a full body harness and a life line (not seen in picture).

I tied myself to the base of a water tank (where i live have very poor water pressure, so we need to lift it and use gravity). It was the strongest fixed point available.

I got a truck rope (Home Depot); i considered it enough because on an incident, i wouldn't be hanging my full weight on the rope, just in case of a slip, i would need the rope to endure to not roll over to the edge.

Also, i left very little rope, so i was far away to the edge.

Step 3: Work Itself.

Once located the crack, and safety measures taken, i got to work.

I foolish man, tried to use a hand wire brush, on noon, on a tropical weather, over a roof with no shadow.

The heat beated me. I had to stop and rethink my strategy.

I came back with a power tool, and a pair of round wire brush. I advanced more in 5 minutes than in the previous half hour.

So, i found many layers of coating.

The first was white, the waterproofing with thermal insulation.

Then i found the remainings of the asphalt coating.

For some reason, after removing the asphalt and after a while of brushing, it turned a SILVER color.

After that, i had to move around the wire brush to remove the remainings from the inside of the crack.

Finally, the raw concrete has to be in a dark gray color, and clean view of the crack.

Step 4: Sealing Crack.

After a while, i had the entire crack clean, and used a Polyurethane sealant.

I aplied it in the secuence of the image, to make sure water not have a chance to leak.

In the step 3 of the secuence, i used a spatula to flat the product.

And that's it.

I forgot to repaint with a coat of waterproofing with thermal insulation, and even so, there hasn't been another leak.

Hope you can find this method usefull.