One of the less glamorous, yet essential, elements of a garden installation is drainage. A landscape must be graded in order to direct water away from a residence or else a drainage system must be installed to redirect the water.
There is an often-used acronym in landscaping: WWW – water will win. Left to it’s own devices, the accumulation of water can cause damage in a number of ways. The collection of water under a house can cause dry rot, and can result in mold and the infestation of insects and rodents. Excess water around plant material can cause root rot and instant plant death. Water in continuous contact with wood, such as siding, fences, and decks, will cause dry rot. Puddles on concrete steps and patios will lead to mold and discoloration, and undermine grout in flagstone, brick and tile applications. The collection of water on hardscape materials leads to slippery surfaces which are a safety hazard.
A note about grading…many homeowners ask for mounds in their garden, because they like the look of rolling terrain. Mounding, however, creates valleys. And valleys collect water. So creating mounds usually requires some sort of drainage solution to carry water from the valleys away toward a more desirable location, such as the street or another drainage facility.
Details Landscape Art, one of Sonoma County’s premier landscape contractors, is diligent about ensuring that the grading of its hardscape surfaces and of the garden itself directs and diverts water properly. Techniques we use are as follows:
- Surface drainage. Simply grading the property so that water flows away from the home or building and toward the street or available storm drains is the most basic and least expensive method.
- Solid drains carry water from one place to another, and are useful to connect gutters and downspouts, and also catch basins, directing water to a desired destination using solid drainpipe. The pipe must slope slightly down towards the destination.
- French drains. When 1.and 2. Above are insufficient, we may dig a trench twelve inches deep and twelve inches wide, sloping this trench in the desired direction at a rate of at least one inch per eight feet feet (one and one half inches is better, if possible). A thin layer of three quarter inch crushed drain rock at the bottom of the trench keeps the perforated drainpipe a little off the ground. This drainpipe is wrapped in a filter fabric to keep dirt out of the pipe.(Drainpipe already wrapped is available at contractor irrigation suppliers). When the drainpipe is laid in the trench and connected to downspouts or other lateral branches of the French drain, the trench is then filled with crushed drain rock. This French drain collects water along its entire length and carries it to its destination.
- Channel drains: there are certain situations where there is an unavoidable valley in a concrete pour, or where concrete slopes away from the house to a retaining wall or seat wall. In these situations it is appropriate to use a channel drain. A long narrow trough is buried in the concrete or at the edge of the concrete (always sloping in the desired direction). The trough is then covered with a grate that snaps into place.