I have a mortared brick patio attached to the back of my house, and the patio has developed a large diagonal crack over the past two years. We noticed that water pooled along this crack when it rained, and this water seeped through a brick wall and caused some foundation issues. As part of the foundation repair, our contractor recommended taking out two rows of the brick patio and putting in a French drain to fix the drainage problem.

When removing the rows of brick, another problem became clear. The soil under the patio has eroded away for several feet under the patio. The underlying concrete has been solid enough to keep the patio from cracking and sinking further, but I am at a loss of how to fix this.

Is it possible to fill the gap left by the erosion without tearing out the whole patio? What other methods are there to fix this problem?

Thanks for any help!