patching crack in flagstone patio

My flagstone patio is developing cracks at the joints. I would like to know how to patch/seal them to avoid water from sipping excessively into the ground. I understand patching is not a water proof method.

What product can be used? How do match the color of the "grout"?

 

I've had the same problem with mortar joints in a grey flagstone pool deck (pictured below) and a slate walk, stair treads and porch.

I don't think anything is going to last many years, especially with big temperature changes, but I found that using a high-quality outdoor grade grout mix for pool decking was the best product to use and it made cleanup fairly easy too.

I would not recommend using a flowable product from a tube because it will probably have latex or silicone as part of the product which will most likely make a mess of what the joints look like...though it may help seal the water out.

 

The instability of the base that the stone is set on is the problem, as the ground moves the grout joints crack. That's why paver patios use sand to fill the joints, they have more give.

Your going to have a constant choir if digging out those mortar joints and repai=ring, might want to consider using plyometric sand instead.

 

thanks Marq1, I think you are absolutely right. I also live in an earthquake zone so not surprised w/ the cracks.
Although given my patio is 25 years old, I would say it has held up well so far. But as you said, cracks will keep coming.

How can I match the color w/ polymeric sand?

 

BBS sell just a couple basic colors but any of the concrete/stone centers will have a much larger sellection.

Not bad for 25 years!