Due to the potential risk of damaging a septic field, building a garage over one is not recommended. It is possible to compact the soil over the septic field due to the weight of the garage and vehicles.
There may be potential consequences for the system and the environment, as well as potential health risks.
The feasibility of such construction and its possible impact on the septic system should be assessed by a qualified professional, such as a structural engineer. OK, so the answer is “No.” However, a few details are missed.
Reasons Why You Can’t Build A Garage Over A Septic Field
Drain fields must remain free of impervious surfaces (such as concrete floor slabs) because their main purpose is to diffuse septic tank effluent into the soil.
Two methods are used to accomplish this:
(1) infiltration into the surrounding soil (also known as absorption), and
(2) evaporation-transpiration (also known as evaporation).
The movement of moisture upward through soil is fundamental to modern on-site sewage disposal systems (“Septic Systems”).
Similarly, surface vegetation releases airborne pollutants into the atmosphere, and effluent absorbs into the soil where it is treated by bacteria and other organisms and is filtered until it reaches the water table.
You lose both actions if you cover the top of the drainfield. So, the Codes require structures to be set back. Moisture absorption of the soil is dramatically decreased when the soil is covered.
Furthermore, this is because soil voids need somewhere for the displaced air to go when moisture is present. As a result, both absorption and evaporation are diminished.
How Close To A Septic Drain Field Can You Build A Garage?
To ensure proper drainage, a foundation must be placed 10 feet away from a septic tank and 20 feet away from a leaching area.
Garage slab foundations must be 10 feet away from a septic tank and 10 feet away from a leaching area.
It is required that concrete columns for decks be located at least five feet from the septic system and not disturb it.
Building Near and Over Septic Tanks
Construction of an initial house cannot be permitted over any point of a septic system due to setback requirements established by the Texas Commission on Environmental Equality (TCEQ).
Among these setback requirements are distances from foundations, swimming pools, property lines and wells from the septic tank and drainfield.
The extension of a patio deck or the building of a home extension over a home’s sewage system is an issue faced by some homeowners, whether accidentally or intentionally. When the system is found and serviced, this can cause higher expenses.
Building Over Drainfields
Water is absorbed by the solids in the drainfield along with some evapotranspiration. Drainfield effluent must be treated by microbes in the soil beneath the drainfield in order to keep the soil healthy.
Nevertheless, if a permanent structure is built over a drainfield, the oxygen flow and evapotranspiration processes can be restricted.
Building over the drainfield poses a significant risk of collapsing the lines. It is also possible for the soil surrounding trenches to compact, which prevents water from percolating.
According to your local authority’s regulations and the age of your system, you may need a completely new drainfield system if you want to repair or move it.
Building Over Septic Tanks
Septic systems should never be covered with structures. We see most problems when someone wants to pump out their septic tank but does not know where it is.
In many cases, tanks can be found underneath wooden decks, pool patios, driveways, or even room additions.
Homeowners rarely plan for future maintenance on their tanks because they are unaware of their location.
There are times when homeowners make removable boards or trap doors that lead under a deck to their septic tank lid for pumping.
Although the homeowner might not be able to pump out their septic tank, no permanent structures should be built over any portion of the septic system.
What are the risks of building over a septic tank if the sewer system has been converted to the city system?
I love this question. The septic tank at your residence should have been abandoned (crushed and filled in) if you are now connected to the city sewer system.
Building over the tank should not be a problem if the tank was properly abandoned. You should crush and fill in your tank if it hasn’t already been done.
Final Words
So, can a garage be built over a septic field? You cannot do that. No construction should be built over the septic field. This will cause it to stop working.
Building a new septic leach field would allow you to build the garage where the septic leach field used to be.
The septic tank shouldn’t be built over; what happens if there is a problem, and you need to dig it out? There is more to it than just pumping access.
