Details Landscape Art, a Novato design-build landscape contractor, was called in the spring of 2020 to build a new redwood retaining wall for a hillside residence in Novato, CA.
The existing retaining wall had been built some twenty-five years ago, and was badly rotting and falling apart.
It had been poorly constructed, with no allowance for drainage or other protection from hillside rain and irrigation. When water or dirt is in contact with redwood it accelerated the decomposition and deterioration of the wood.
We agreed to build a new redwood retaining wall of almost the exact dimensions as the old wall, but about twelve inches forward of the hillside to allow for drainage behind the wall. 
We also allowed one to two inches clearance from the ground so there would be no earth to wood contact. It was a difficult construction project due to the various return angles of the wall (which were not 45 degrees), and because of the intense heat in the mid-nineties, even reaching one hundred degrees.
Once the wall was completed, we stapled plastic sheeting onto the backside of the wall, and backfilled partway with ¾” crushed drain rock. A 3” perforated drainpipe wrapped in filter fabric was then laid the entire length of the wall, about mid way up the height of the wall, gently sloping in the downhill direction of the property.
A few months later, we returned to relandscape the hillside above the wall, replace the lawn in front of the wall, and replace the lawn and drip irrigation systems. The lady of the house is a real garden aficionado, and loved plants and flowers, and relished the maintenance associated with perennials, There was high deer traffic on the hillside, with bucks, does and fawns brazenly walking past us as we worked at all hours of the day.
As an accomplished Novato design-build landscape contractor, we were very familiar with hillside deer property. We worked closely with the homeowners in developing a list of colorful yet deer resistant plants that would yield the look of an English garden they wanted. Unfortunately we had to reject some plants they asked for such as roses and hydrangeas, since the deer would have eaten them immediately.
After the demolition of the old dead and tired plantings, we noticed several gopher tunnels on the hillside, so we recommended that each plant be wrapped in pre-made gopher baskets. The additional cost was justified as insurance against the little creatures nibbling the tender juicy roots of the new plantings. The slope was severe in areas, so we began the landscaping by installed jute netting as an erosion control technique. We purchased a truckload of plants and began placing them with the assistance of the homeowner, spacing them according to their eventual mature size.
The old lawn in front of the retaining wall was mostly dead, and we set a bendaboard lawn edging about twelve inches in front of the retaining wall, and installed a new lawn sprinkler system so that the sprinklers did not reach the redwood, yet just covered the new sod.
The key to a successful landscape is a versatile irrigation controller, so this Novato design-build landscape contractor connected a new Raindial indoor controller to the new valves.