Drainage Systems

If you’re a homeowner in Alameda, Berkeley, Oakland, El Cerrito, and Piedmont, CA.

Common Drainage Questions

Drainage is capturing all of the water coming from above and around and below your home that may affect the structure. People may not know this, but there are different types of drainage systems and problems that may need to be addressed.

The first is what we refer to as surface drainage, which is basically anything not underground. You need to capture the roof water to go through your downspouts. This also includes any water gathering on surfaces like patios, walkways, or driveways, posing a risk to your structure that must be channeled away from your building.

The second aspect of drainage, which is often more complex and insidious, is the subterranean (or underground) water. This water is handled by french drains, which are deep drainage systems backfilled by gravel below the elevations of your affected areas in your crawl spaces or basements.

Why do you need proper drainage?

Without proper drainage, your home is at risk of settling, leading to foundation deterioration and interior damage. In the Bay Area, a significant number of homes are built on sloped properties, and there is substantial subterranean water which can be exaggerated by underground creeks, streams, water directed from utility piping, trees, and any other penetrations in the ground that can channel water to your home. This issue is heightened in sloped homes but can impact level properties as well.

In either scenario, homes can be affected by rising water tables that occur through the course of a rainy season. Various factors, including atmospheric rivers, large-scale rain events, adjacent property work, utility projects, and your property’s location in relation to others, influence your drainage needs. The direction of rain events, whether from the north or south, also plays a role.

Most older homes either have no french drains or older, clogged up clay systems that don’t work, causing flooding or damage to basements or crawl spaces. To safeguard your home from these risks, investing in modern drainage solutions is essential.

How do we do your drainage job?

For comprehensive drainage, we need to address both surface and underground water. We do it in the following steps:

First, we address the surface water:

Trench digging – Dig shallow trenches and install solid plastic piping connected to your downspouts.
Additional solutions – If needed, we control other surface water issues with either area or channel drains.
Proper sloping – Properly slope all piping and direct it to either the street, a sump pump system leading to the street, or a drain field at the back of your property. This step is going to be dependent on the slope and layout of your property.

Second, is addressing underground water. This is a more difficult and complex endeavor. It goes as follows:

Trench excavation – We dig trenches around affected areas, reaching a minimum depth of 12 inches below the lowest affected elevation. Depths may vary based on property slope, ranging from 3 feet to as much as 10 feet for full basements on sloped properties.
Membrane installation – We then install a membrane system adjacent to the foundation with perforated and plastic piping at the bottom of the trench.
Backfilling – The trench is then backfilled with gravel and wrapped in filter fabric, usually topped with soil or concrete.
Integrate drainage system – These pipes are then routed to the same location(s) as the surface drainage, tied into the solid piping beyond the house.

Why Older Drainage Systems Fail

Most foundations, basement, patios, etc. lack proper drainage, and a majority have no drainage at all. At a minimum they require proper surface drainage, and in sloped conditions or in excavated conditions most will require separate French Drains as well. Trenching, piping, membranes and pumps where needed make up the backbone of proper drainage work.

The Proper Depth is Critical

Basement spaces, garages, and other below grade area need French Drains. Unfortunately, these can be big projects if those spaces are deep below the outside grade. Proper subsurface drainage is dug below the floor level, and for full height basements can often be 8’ or 9’ deep or more. When drains aren’t deep enough they can actually make your drainage problems worse, or re-route the problem to a new area of your home. What seems like a good deal at the time can turn into a disaster if your minor problem becomes a major one, especially in a finished basement, garage, or below-grade lower level of your home.

Shoring is Required for Safety

Deep drainage jobs require a stable trench to provide safety for the excavators. Below 5’ we use plywood and aluminum hydraulic shoring and cribbing to ensure that the trenches don’t collapse during the digging process.

We Utilize Conveyors to Help Us Move Soil and Gravel

On large drainage jobs we can easily end up moving 100 cubic yards, or 200,000 pounds or more of soil, and then replacing it with a similar amount of gravel! We have various sizes of conveyors we use to help get materials in and out of our truck or trailers on sites with poor accessibility.

Downspout Drainage is Made Up of Solid 4” PVC Piping

The bulk of the water affecting most homes comes from the high-volume roof water coming through the downspouts when it rains. Many properties drain their downspouts directly into the ground next to the house, leading to settlement and foundation problems. We connect solid piping to all of the downspouts, and these pipes all slope to the street. Where the proper slope is not present we install a sump pump which will pump the water to the street. Except on large properties where we can create a large gravel pit in the rear yard and can be sure potential water won’t spill into the neighbors property, most cities require the water to go to the storm drain system at the street.

French Drains (aka Subdrains) Consist of Gravel, Perforated Pipe and Membranes

The downspout drainage and French drains are separate systems, with water transmitted through perforated piping at the base of the foundations or interior lower elevations. French drains are designed to handle the passive low volume underground water that can often be an issue year-round. Trenches are backfilled with gravel and then wrapped with filter fabric to keep dirt out. We use a dual membrane system at the foundation as secondary protection against any water. It is crucial that these systems work every time, as any future leak would be difficult to trace and might require extensive and expensive repairs.

Cast Iron Piping Goes Under the Sidewalk

The sidewalk needs to get removed and replaced at the location where water is brought to the street. Sometimes the curbs are shallow, which requires us to reduce the 4” pipe down to several smaller pipes. Cast Iron piping is required here to handle any potential heavy traffic in this area.