Outhouse Inspection

by Nick Gromicko, CMI®

An outhouse is a small, stand-alone structure that contains a waterless toilet that does not flush or empty into a sewer or septic system. These cost-effective, decentralized waste-management structures are primarily used in low-income urban communities and rural areas, especially in the developing world. Modern outhouse with ventilation and lighting

Outhouses function differently than septic systems partly because its waste pit is not filled with standing water, although urine provides small amounts of moisture. The aerobic environment of an outhouse pit (in contrast to the anaerobic environment of a sewer) allows for insects, amoebas, molds and earthworms to flourish, turning waste matter into ecologically safe compost. Decomposition is generally effective as long as the input of new waste does not exceed the capacity for it to be consumed and decontaminated, although the process is typically slow due to the layering of waste material.

Odor Control

The decomposition of waste naturally leads to the emission of odorous gasses, such as methane and hydrogen sulfide. The odor will be minimized if these gasses are allowed to escape through a vertical vent tube, which is typically installed in the corner of the outhouse structure. Ventilation of the outhouse also helps prevent overheating during the summer months. During the day, the sun’s heat forces a convection cycle whereby fresh air enters the outhouse and expels warm pit gasses out the vent tube. Vents can be constructed of a 4-inch or larger metal or plastic pipe, or 1x6 boards framed into a rectangle.

Homeowners can reduce outhouse gasses by adding the following materials:

  • lime, which has long been used to neutralize outhouse odors, as well as ward away flies. Do not get lime on the seat, as it will cause skin burns;
  • sawdust. A thin layer of sawdust can be sprinkled after use. Cedar and other aromatic woods are preferable. Do not use thick wood chips because they will decompose slowly and reduce the life of the outhouse pit;
  • wood ash;
  • straw or peat moss. These materials encourage the formation of a crust atop the waste, which also reduces the proliferation of flies; and
  • kitchen waste. Vegetable waste (but never meat or other animal products) will accelerate the composting action in the waste pit.


InterNACHI inspectors may check for the following outhouse hazards:

In cold climates, outhouse waste pits should be dug below the frost line
  • insects and parasites. Houseflies are attracted to decaying organic material, which they will use to feed their offspring and as a place to lay their eggs. Mosquitoes, too, are attracted to any standing water in the pit. Flies can be controlled with an insect screen that covers the vent opening. Flytraps may also be installed. The waste pit should be dug at least 6 feet deep to prevent hookworms from traveling to the soil's surface;
  • splinters;
  • fire and explosion. Methane and other gasses created by decomposing waste are flammable and even explosive. Keep open flames out of the outhouse and ensure that there is adequate ventilation;
  • groundwater pollution. In an unlined pit, waste materials can easily enter neighboring sandy soil and underlying gravel and fractured stone. An organic lining, such as a thick mat of grass clippings, can be added to waste pits to prevent this seepage and allow time for bacteria and other organisms to decontaminate the waste.  Also, outhouses should not be located where they may contaminate a nearby well, stream or lake. For instance, outhouses in Vermont may not be within 200 feet of a well. Homeowners should check with their local authority having jurisdiction’s groundwater contamination guidelines before erecting an outhouse.

Additional Precautions

  • In cold climates, the waste pit needs to be dug below the frostline. Frozen waste does not decay.
  • Ensure that the outhouse's components will not allow a small child or small animals to enter or fall into the pit.
  • Provide lighting inside and outside the outhouse if it's used at night.
  • Never pour bleach or any other chlorine product into an outhouse toilet, or any other type of dry toilet, as it may mix with urine and form toxic chloride gas.
  • Never pour deodorizing chemicals intended for chemical toilets into outhouse toilets. 
In summary, outhouses can be ecologically sound waste-management facilities if they are constructed and maintained properly.