house drainage

Drainage Inspections

Why is Water A Problem?

Musty odors, soil erosion, lingering damp spots and damage to a home’s foundation could create a homeowner’s nightmare. However, costly repairs for patio, pool and home foundation damage caused by poor drainage can be prevented. Many of the problems homes can have are caused or aggravated by water. 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 Washington state homeowners. Pacific Crest Inspections can help you identify the issues and make recommendations on the most cost effective ways to solve the your drainage issues, call us today!

Why Does Water Collect Under a House?

The common Washington  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 dampwood 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?

Identifying causes of poor drainage can be difficult. Surface runoff is the most common cause of drainage problems and includes runoff from rain, sprinklers, supersaturated soil, underground springs or a high water table. Runoff also carries polluting materials toward a home or into streets, where they creep into water supplies through gutters and storm drains.

Sources can be steady, seasonal or sporadic. Paved surfaces, bare soil, slope of the yard, lack of vegetation, soil type and house design could be helping water cause problems. many times drainage systems are overwhelmed by heavy rains and the problem is a short term issue. Other times you may want to look at the properties around you for changes. If a neighbor added a lot parking areas that adjacent to your yard that may be directing water into your yard. In most cities one owner may not direct their runoff into another’s yard.

Some problems can be fixed easily and inexpensively:

  • Watch how quickly rainwater soaks into the ground. It should not puddle or create runoff. Consider adding dirt or improving clay or silt soil with organic matter.
  • Examine the yard’s slope. It should drop six inches in the first 10 feet from a structure and at least one foot per 100 feet beyond that. The slope should be gentle enough to allow gravity to move excess rain toward the street while letting some water be absorbed into the soil.
  • Watch for runoff from the street, other homes, hills, patios and play areas. It should not drain toward a home. A yard should effectively divert water at least 20 feet from the house.
  • If basement window wells collect water, install covers. The fill soil next to the foundation should not sink or settle, causing water to collect near the house.
  • Gutters should be free of debris, in good condition and should slope toward a downspout. Downspouts should carry water at least 10 feet from a home. A splash guard might be needed where water exits to absorb forceful energy used to create gullies in the yard.
  • A basement, even with a footing-level drain tile system, should not remain damp or leak clear subsurface water.
drainage slopes diagram

Maintenance is the Key

downspout drainage pipes in yard

The first step in correction of many drainage troubles is routine maintenance. Make sure that gutters are kept clean and that the downspouts pipe the water to a driveway, drainage easement or practical lower spot in the yard. This may require that extra fittings or pipes be added to your gutter system. It is well worth the money, so that the foundation and surrounding areas will not be compromised.

Also remember the laws of gravity, and that water will flow to the lowest point available. With that said, you must ensure that water flowing over the ground flows away from your house and does not pool or puddle around the foundation. Make sure that the ground slopes away from the house and the foundation, so that surface water runs away from the building. Take a look at the earth around your house, and if it doesn’t appear to be sloping at least slightly away, fix it.

Often, this basic routine maintenance will solve your drainage problem. If you’ve still got puddling in the yard (away from the foundation), improving soil structure alone may help solve the problem. As mentioned before, our heavy clay soil holds water and does not allow good drainage. Tilling the soil and adding organic material can be helpful, additionally providing a better environment for plant growth. For low spots in the lawn, leveling the area with additional topsoil may be the answer.


Examine your property carefully the next time it rains. Watch for runoff water from the roof, gutters and hardscape areas (driveways, patios, sidewalks), as well as the flow from your neighbors’ yards. Does the water follow a neat pathway from the gutter downspout, along the driveway to the street and into the storm sewer? Or does a sudden downpour create a reservoir in your front yard that takes days to drain? Make note of your observations so you can make modifications to your property before you begin landscaping.


If you have significant drainage dilemmas, soil improvement or leveling may not be enough. A diversion, such as a swale, could be constructed to channel the water to a more desirable spot and prevent pooling in the yard. A popular solution is to create a dry creek bed, which provides an interesting focal point to the landscape during dry weather and serves a useful purpose when the rainy season arrives. Both swales and dry creek beds also help significantly with erosion.

If neither of these options is feasible in your landscape, subsurface drainage might be the answer. Underground collection pipes, catch basins and channel drains can be installed to remove large amounts of potentially damaging water. French drains are another alternative, particularly around the foundation and in raised beds or planting areas. These drains collect water and allow it to slowly seep back into the ground.

In some situations, drain fields can be dug and filled with crushed rock to enable water to seep into the earth. While handy homeowners can install simple drainage systems, larger or more complicated jobs might be better suited to a landscape professional who is an expert in grading and drainage work.

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 were you want to consult with drainage experts to determine the most cost effective solution

footer drainage diagram


What about erosion caused by drainage problems? Planting vegetation often is the best solution, since the plants’ roots will help to hold soil in place. Turf and ground cover are excellent remedies for eroding soil, particularly on a gradual slope. For more steeply graded areas, terraces may be built to slow the water flow. Terraces also can provide wonderful planting areas for the landscape. If there is a great deal of erosion present, we recommend a drainage expert who can look at ways to stabilize the area and put a drainage system in.

A watchful eye, careful planning, routine maintenance and renovation in the landscape will help protect your property, add beauty to the landscape and help our natural environment stay healthy and clean.