Homeowners who have a crawl space know the problem: you look under the house after a storm and there is standing water. It happens to people in older neighborhoods and in new builds. In El Cajon it usually happens after heavy rain, when water runs toward the house from the yard, the roof or a downspout and collects in the low spot under the floor.
Many owners see water under the house after heavy rain and simply give up on the space. Others take it more seriously and prepare the house for what the weather can do. First of all, rain has to be kept away from the foundation. You also need a way to carry water away. And if, in spite of everything, the crawl space flooded anyway, the goal is to make sure the water stands there as short a time as possible.
Dampness under a house usually comes from outside, from rain that the grading and gutters send toward the walls; a leaking pipe under the floor is the other common source. Dehumidifiers and interior waterproofing give a temporary effect if the outside source of moisture is not removed. Below we go through what to do when a crawl space floods when it rains, step by step.
Is a Flooded Crawl Space Dangerous?
Yes, and in more than one way. Water is a very good conductor of electricity. Before anything else, the power has to be dealt with.
If the water has reached outlets, junction boxes or wiring under the house, shut off the power at the main panel first. If you cannot do that safely, do not go in - call an electrician or your utility. Tools and equipment may be switched on again only after the electrical system has been checked and has dried completely.
The second danger is the water itself. A rotten-egg smell under the house can mean a natural gas leak, since gas lines often run there. Don't go in and don't switch anything on or off: leave the house and call the gas company or 911 from outside. Only once a gas leak is ruled out can the smell be put down to stagnant water. Water from a broken drain line can carry sewage; in that case it is no longer just a puddle to pump out - stay out of it and call a pro.
A third danger is slower. Mold, the Aspergillus fungus among others, does not only spoil surfaces but also affects people's health. Moisture control is the key to mold control; see the EPA's guide to mold, moisture and your home.
Crawl Space Flooded: What to Do First
After the power is off, assess how high the water is and find where it comes from. If it keeps coming in through a drain, the storm sewer, cracks or an access opening, remove the cause first. Pumping water out of a space that is still filling is wasted work.
- Shut off the electricity. At the main panel, before you touch the water.
- Find the source. Drain, storm sewer, cracks in the foundation, an access opening, or a leaking pipe.
- Stop the inflow. Only then start crawl space water removal.
- Document the damage. Take photos of the water and of what it reached before cleanup starts.
If you are not sure where to begin, our page on water damage restoration in El Cajon describes how this work is usually done.
Pumping the Water Out
With a small volume, water can be removed by hand or with a shop vacuum that picks up liquids. Bailing it out with buckets is possible but very inconvenient. With serious flooding you need a drainage pump.
Choosing a crawl space water pump
The choice of pump depends on how dirty the water is. For clean or slightly dirty water most household models will do. If there is a lot of sand, silt, fibers or other large particles, you need a pump for heavily contaminated water, a sewage pump.
- Ordinary drainage pump: handles water with particles up to about 1/4 inch.
- Sewage pump: copes with particles of about 2 inches.
Place the discharge hose as far from the house as possible, so the water does not run straight back to the foundation.
A pit with an automatic pump
If the house is old and for some reason all the recommended repair work cannot be done, there is a simpler option. A plumber or a waterproofing contractor can set a plastic sump basin into a pit at the lowest point under the house. The basin holds a sump pump with a float switch. As soon as the water reaches a set level, the pump sends it out. Again, the discharge hose should go as far from the house as possible.
Why speed matters for the floors above is covered in our article on why fast water extraction saves floors.
Drying the Crawl Space
Next comes drying. You can simply air the space out, or use forced drying with fans and a dehumidifier. Fans speed up the evaporation of moisture and lower the risk that water spreads through materials by capillary action. A dehumidifier helps take water out of the air. The foundation walls can be cleaned with detergent and water, wearing gloves and an N-95 respirator, with the space aired out.
Tools and power equipment may be used only after the electrical system has been checked and has dried out completely.
Vapor Barrier and Insulation
Most crawl spaces have a dirt floor covered with a vapor barrier, a sheet of heavy plastic that keeps ground moisture from rising into the space. After a flood, check it: if water is trapped on top of the sheet or under it, the sheet has to be pulled back, the soil dried, and the barrier relaid or replaced, with the seams overlapped and taped and the edges run a few inches up the foundation walls.
Then look up at the floor above. Fiberglass batts between the floor joists soak up water, sag and hold it against the wood. Wet insulation is pulled out, and new insulation goes in only after the joists and the subfloor are dry.
Find the Source: Grading, Gutters, Plumbing
The fight with water begins with finding the cause. Only after the source of the trouble is known can you talk about getting rid of moisture under the house. Pros name two factors.
- Rain water. The most common cause. A missing or poorly built system of gutters, downspouts and drainage lets water collect at the foundation and then get inside.
- Failed plumbing. Pipes in bad condition. This is the easiest source of moisture to fix.
Grading around the house
The soil next to the house should slope away from the foundation, so rain runs off instead of under the house. Flower beds built up against the wall, a patio that tilts toward the house or a low spot by the foundation send water straight underneath. Regrading is usually the cheapest and fastest first step.
If water stands on the lot after rains, solve the drainage of the whole lot first, otherwise the drain along the foundation will be overloaded.
Gutters and drains
Drainage laid around the perimeter of the building carries storm water away quickly. Gutters and catch basins reduce how much water gets in. Such a system serves to carry water off; it is not used as the only protection against moisture. It works together with good grading, not instead of it.
A perimeter drain is a perforated pipe in a gravel bed around the foundation at the level of the footing. It takes water away from the building before it can press on the walls. If water shows up every rainy season, put in a perimeter drain before the next one. Such drains can be built around a house after construction is finished.
Mold and Wood Rot
Under a raised floor, the wood takes the damage: the sill plate on top of the foundation, the floor joists, the posts and the underside of the subfloor. Wood that stays wet for weeks grows mold and then starts to rot. Probe suspect spots with a screwdriver: sound wood resists, rotted wood is soft and breaks off in short pieces.
Some signs mean you cannot wait:
- Horizontal cracks in the foundation walls. A sign of soil pressure greater than the wall can carry. This is not cosmetic. It needs an urgent structural assessment.
- Water standing on the floor under the house. Each time it happens, the wood above stays wet longer, and until the source is fixed it gets worse every rainy season.
- A rotten-egg smell. Treat it as a possible gas leak first: leave and call the gas company or 911 from outside.
Ventilation deserves a lot of attention as well. Its job is to bring the humidity of the air back to normal. It prevents mold and removes the musty smell of dampness. When mold has already spread, it is a separate job - see our page on mold remediation for homes. If belongings stored under the house or in the rooms above need to be moved out while work goes on, there are pack-out services for damaged contents.
Is Crawl Space Flooding Covered by Insurance?
It depends on the policy and on where the water came from, so take photos of the water and the damage before cleanup and check the terms with your insurer.
Three Steps to Remember
- Find the source. Rain from the yard and downspouts or a leaking pipe: the fix depends on which it is.
- Check the grading and the downspouts. The soil should slope away from the house, and downspouts should empty away from it.
- If water comes in every rainy season, put in a perimeter drain. This helps protect the foundation and the space under the house.
It is always easier to prevent a problem than to solve it. To learn who we are, visit about our El Cajon restoration team, read what homeowners say in reviews, browse more water damage articles or go back to the water damage restoration home page.