In Minnesota flagstone (or limestone) can be used to make beautiful, naturalistic retaining walls. The only thing is, the wall can break apart if the limestone is not the right kind for building walls. Different quarries have different grades of limestone, and they can vary greatly greatly in quality. This limestone wall was built by a previous homeowner out of a “local” limestone from a quarry nearby. He probably got the stone for the right price (free)! After a few years, it began to crumble and fall apart and it had lost its structural integrity and was starting to collapse. The reason is that it is a soft limestone, which absorbs moisture. Because of that, the freezing (expansion) and thawing (contraction) action of the ice crystals in the limestone due to our our Minnesota winters caused it to break apart, crumble, and eventually start to collapse.The best material for flagstone walls is found in Wisconsin. Because of shipping costs and the extra labor it takes it to make a good limestone wall, the cost of replacing a wall of this size can be a stretch on the budget.
After we explored different alternatives, the client decided on a block wall with a weathered look, and colored to match the brick on the house. Because of the location, we had to bring in a backhoe to remove the old wall and excavate for the new wall and step system. Because the wall was located next to a well head, the excavator had to be extra careful not to hit the main water line going in to the house.
There is more to building this wall than just stacking the blocks. We had to install an anchoring system behind each wall to prevent the wall from getting pushed out by water pressure (officially called hydrostatic pressure), along with gravel and tile for drainage.
We added steps along the house, along with some planters. A small landing gives an opportunity to change the direction of the steps to lead up to the back yard, and also gives it a more restful look.
Written and posted by Doug Grove, Grove Landscaping, Northfield, MN