By JCP Geologists

Why is Water A Problem?

Many of the problems homes can have are caused or aggravated by water. Running water erodes gullies. Water can saturate soils and trigger landslides or mudslides. Water causes the clays in expansive soils to swell and foundations can be damaged. Too much water can result in flooding.

All of this can damage homes. Engineers design structures to minimize the potentially damaging forces of water. However, homeowners themselves must maintain their homes, landscaping and drainage for the same reason. Water that collects under houses is a common problem for California homeowners.

Why Does Water Collect Under a House?

The common California construction method of building a crawl space under the floor lower than the ground outside can create the perfect water trap.

Discovering if there is water under a home can be as easy as taking a flashlight and looking under the house. A musty, moldy smell when the heat is turned on could also signal moisture or water under a house.

Once water gets under a house, it evaporates slowly because there is minimal air circulation. Such water can cause problems - wood rot, mildew, insulation deterioration, electrical problems, warped wood floors and raised humidity in the home. These conditions are an invitation for termite infestation too. Minor amounts of water might seem to just be a nuisance, but the damage it can cause can be expensive to correct.

What Are the Possible Sources?

Some common sources of water under a house are:

• A plumbing or sprinkler system leak. This is the potential cause to eliminate first. Repairing the leak should eliminate the problem once the water under the house has evaporated or been pumped out.
• Inadequate drainage control. Water that flows or ponds next to the foundation often seeps under the house. This includes water from rain gutters, leaky sprinklers, or heavy landscape watering.
• Subsurface water or springs. However, this is a relatively uncommon source in California.

What Can Be Done?

Here are some easy and inexpensive ways to help keep water from ponding under a house:

• If the water comes from roof drainage or surface drainage collecting next to the foundation, it is necessary to direct the water away from the house. Don't let roof drains and gutter pipes terminate next to the foundation. Make sure water is directed away from the house to a suitable drainage facility by some method such as closed pipes.
• Don't let water pond or flow next to the foundation. Make sure that all soils and walkways next to the foundation slope so that rainwater will flow away from the foundation.
• Plan your landscape watering to give just the ideal quantity of water. Overwatering can cause sub-surface water problems or the excess water can simply flow into crawlspaces via vents in the foundation. A drip irrigation system is ideal in many cases.

It is not always possible to make enough improvements to keep water from getting under a house because of swimming pools, patio decks, or landscaping. Sometimes the only reasonable solution in these cases is to install a sump pump at the lowest place under the house.

If groundwater is causing the problem, a deep sub-drain can sometimes be built to intercept the groundwater and keep it from rising to the surface. This is usually not a practical remedy, however, because it can be very expensive.

Take time to inspect your roof gutters and drains and clear out leaves and other debris. Clear your surface and buried drains to make them ready to carry water. Don't wait for the next rainstorm to check the system. Prevention is preferable to repair.