Can You Build A Deck Over A Septic Tank? Step By Step Guide

Decks make excellent entertainment corners while not causing you to compromise your existing house space. You might be thinking of constructing a deck in your lawn/backyard area. However, if a septic tank and field occupy that space, you might ask, can you build a deck over a septic tank?

It is safe to build a deck over a septic tank if you have no other option; however, it is recommended not to do so. While making the deck, if you damage the tank accidentally, you’ll be posing a significant threat to your health and environment due to contaminated water and gases contained in the tank. Moreover, it is forbidden to build a deck this way in some areas due to the safety risks.

Do you want to learn more about why building a deck over a septic tank is not recommended? What are the dangers of building a deck this way, and what to do with the space instead? Keep reading.

Can I Build A Deck Over A Septic Tank?

If allowed in your area, you can safely build a deck over the septic system on your lawn. However, it is not something I would recommend to you due to the safety risks.

Can I Build a Deck Over a Septic Tank

Septic tanks need enough soil for the effluent released from the tank to be absorbed by the earth. Letting the effluent sink into the ground is the best way to get rid of it, so you should avoid covering the soil atop these tanks with a deck, let alone a patio or some other concrete-made structure.

Also Read: Deck VS Terrace

Another reason to bypass building a deck over a septic tank is that these tanks release carbon monoxide alongside the effluent. Carbon monoxide is very poisonous and proves fatal if exhaled. So, it will not be safe to build a deck where all this harmful material meets the environment.

In addition, wooden decks built on top of septic tanks might rot sooner due to the humidity and carbon monoxide trapped under the deck. It might cause you to get the deck repaired frequently. So, if you must, building a stainless-steel deck over the septic tank is a much better option.

Building a deck over a septic tank is against the rules in some areas due to the safety risks. So, before you even start planning, you need to ensure that the local building code approves of this setting.

Can I Build A Floating Deck Over A Septic Tank?

It is not safe to build a floating deck over a septic tank for several reasons. Moreover, in many cities, states, counties, and countries, it is unlawful to construct any structure more than 5-10 feet closer to the septic tank. Since a floating deck is usually only 2.5-3 feet above the ground level, you might want to dodge this option.

Can I Build a Floating Deck Over a Septic Tank

Secondly, floating decks are wooden decks made with wooden beams and flooring. If you install a wooden floating deck over a septic tank, you’ll notice that the wood has started to deform and crack due to the excessive moisture and humidity.

You’ll also see the wooden frames and sheets expanding due to absorbing the extra moisture. As a result, some parts of the deck might expand and result in the breakage of the deck. Moreover, the wood also becomes soggy when it comes in contact with the water, further lowering the wooden deck’s stability.

Also Read: How to Prepare the Ground Under Deck in 7 Steps?

Can I Pour Concrete Over The Septic Tank For A Solid Deck Floor?

You must refrain from covering the earth over an active septic tank with anything that restricts the water and gases released from the tank from being absorbed by the earth.

Because concrete and gravel harden once dry, they’ll prohibit the water and gases from escaping like they are supposed to. It might cause the ground to start sinking and emitting a foul odor. So, it is best to avoid covering the ground over the septic tank with concrete, cement, gravel, etc.

However, if the septic tank is empty and is no longer in use, it is considered safe to pour concrete or even gravel on the ground over a septic tank.

Things To Consider When Building A Deck Over A Septic Tank

If you must build a deck over a septic tank, I have a few tips and tricks to help you ensure you are not putting yourself at any sort of risk. These include:


Ensure It Is Not Illegal

Most building codes have prohibited building anything within 5-10 feet reach of the septic system. So, check-in with the local building guides and build the deck at an appropriate distance from the septic tank/field.

Locating The Area Covering Septic System

Before you get workers to start building the deck, I highly suggest you clearly mark the area covering the septic system. This way, the workers will be more careful around the marked area, and it will save the pipes and tank from getting damaged.

Also Read: Deck VS Balcony: Differences, Costs, Pros and Cons

Leave Enough Space Under The Deck To Quickly Clean The Tank

Septic tanks need to be cleaned thoroughly after every 3- 5 years. So, you should leave enough space for the tank’s routine maintenance to take place effortlessly. Moreover, pre-planning and building the deck a bit higher will also save you from destroying it when it’s time for maintenance.

Ensure The Area Over The Tank Is Not Fully Covered:

As discussed earlier, septic tanks release effluent and carbon monoxide. So, it would be best not to entrap the tank entirely, or else the water and gases present inside might make your deck area smell like a gutter.

Sun Exposure

If you are building a deck, make sure the deck is built in a direction that ensures some sunlight can reach the area beneath the deck. Or else you’ll have to experience a slough-like situation.

Build A Stainless-Steel Deck

If you are building a deck atop your septic tank/field, it is better to avoid using wood for constructing the deck. A wooden deck built over so much moisture might break within a few years. So, using stainless steel instead of wood to build a deck over the septic system is wiser.

Alternatives For A Deck Over Septic Tank?

If building a deck on top of a septic tank now seems off to you, you might be thinking, what else can you do with that piece of land now. Here is an excellent option for safely using the area over the septic tank and giving it a more aesthetic look.

Alternatives For a Deck Over Septic Tank

You can plant small shrubs, grass, and flowers on top of the septic system area. However, make sure not to use any deep-rooted plants as the deeper roots might mess with septic system pipes.

Also, it is best to avoid planting any vegetables or fruits atop the septic system as the water released is not completely clean. The fruits/vegetables grown from this water might not be safe for consumption.


Building a deck over the septic tank is a highly complex thing. Even if constructing any such structure is allowed in your area, you’ll have to face difficulty in achieving this setting. So it is best to steer clear of this option.

However, if you don’t have much choice and a deck over a septic tank is the only way to go around, you can do so, but be careful, or else you might end up wasting your money and effort.

Also Read: Deck VS Porch

To avoid any bad situation from happening, you can check out the crucial factors mentioned in this article to ensure your deck does not turn out to be a disaster. Moreover, I have also mentioned how you can use the area above the septic system if a deck is not possible.

Leave a Comment