Over the years I have renovated a lot of deteriorating landscapes (which is how I started landscaping-fixing other people's mistakes) mostly in the form of lockstone concrete pavers and retaining systems. Heaving, discoloured, and disintegrating due to poor installations by both DIY and contractor and even thou manufactured to a new state-of-the-art technology these early pavers have not all stood the test of time, but times changed!
Landscaping in the 1970s witnessed a new era of affordable landscaping with the introduction of modular concrete products in large due to a very progressive company called Unilock. They pioneered a very good product at a very attractive price in comparison to natural stone. And so began a tsunami of homeowners installing without any understanding other than affordability. Contractors came out of the woodwork and the gold rush began. The number of failures is staggering.
Here is a sample of a multitude of mistakes and hard to believe that this failure took place so quickly given the wood staircase installed at the same time looks like it has barely aged by comparison. The obvious selection of different materials is mind-boggling was there a fire sale at three different suppliers? The lack of base preparation ie. compaction, and sediment control of base aggregates leads to shifting and settling. However, the biggest mistake of all was no attention to groundwater and surface drainage. At the top of the failed garden behind the retaining wall where the deck skirt meets the ground an eaves trough discharges water so the installer placed riverstone in an attempt to control and disperse the energy spilling out.. The soil behind the retaining wall soaked it up like a sponge, the plants rotted and disappeared, water seeped into the garage through the concrete block wall, and then began the cycle of freeze and thaw of our Canadian climate, shifting everything. Water collects at the base of the retaining walls and is absorbed by the permeable nature of concrete and freezes and disintegrates the steps, algae slime flourishes in the corner where water collects creating the most dangerous landscape entranceways I have ever seen. Ice can move mountains!!
The solution:
1st remove all the old concrete and send it to recycling, excavate the area to a depth 16" below the final grade because the entire area is pure sand. Add 3/4" crusher run gravel in 2-3" layers and compact 6" of sub-base for dry footings. Begin with the main retention L-wall and line with geodesic fabric for sediment trap.
The concrete block wall was exposed, scrapped down to the area of the original water-sealed basement, and applied water-proofing to the future elevation of the required retaining area. The deck skirt was removed and the eavestrough was given an extension under the deck stairs to be extended once the retaining wall is in place.
As the wallstone rises the areas are checked for level and compacted aggregates every two inches.
Each step/landing is retained, sediment trap and compaction to a precise 6" rise before installing the coping. Once the coping and step pavers were installed we extended the big-O pipe with sediment cloth along the side to discharge the excess water to the lower lawn area. After the wall had completely dried it was painted to match the siding and strapped.
The wall was covered with Cedar lath panels for the vines to grow on, and geodesic cloth was placed before the riverstone was re-purposed for low maintenance. Dwarf trees and shade-loving shrubs with hosta under-plantings to enhance the space.
Polymeric joining sand was watered in to ensure a good seal and proper surface drainage. Once dry the excess joining sand will be swept away. The transformation is complete and the lawn area was graded to suit, topdressed, and seeded for a stellar result.