Pavers Decks and Patios Over a Septic Tank

Can You Put Pavers, Decks, or Patios Over a Septic Tank?

In Home Exterior, Tips by Jamie

A septic tank is a mysterious part of many people’s homes. They know its there, but they don’t understand how to take care of it, or exactly where it is. When landscaping, the placement of the septic tank needs to be taken into consideration, but what can you put over your septic tank? Your best option will always be plants with shallow roots, but if you take adequate precautions other things can work.

Septic tanks cannot bear much weight without damage, avoid weight on the ground where your septic tank is located. Concrete patios are too much weight, a small deck might be okay if you build it without adding weight directly over the tank area, pavers and other stones should be avoided as they can become heavy.

Below we’ll talk about each of the common structures people seek to put over their septic tank, and the things you need to keep in mind.

Can Your Put Pavers Over a Septic Tank?

Pavers may seem like an ideal landscaping structure over a septic tank, because the pavers can be lifted and moved to access the tank. However, many tanks are not rated for any significant amount of weight, and the pavers may be too heavy. Newer tanks are a little more robust, so ask your contractor or consult the house plans to see what kind of tank your property has.

Even if your tank won’t be damaged by pavers, I would advise against them because pavers tend to be a high-traffic area in a yard, which isn’t ideal. They can place pressure on the ground over time potentially putting your septic tank and patio at risk.

Can You Put a Deck Over a Septic Tank?

Can You Put a Deck Over a Septic Tank

A deck is any structure which is raised above the ground and supported by support beams set into the ground at specific intervals. Most decks exceed the size of the septic tank, and the support beams can be placed away from the tank, so it does not take the weight of the structure. This means that a deck can be a safe landscaping solution over your septic tank, although this is to be built with consideration of where the tank is. 

A deck can make accessing the septic tank more labor intensive, especially if there is less than five feet of clearance between the ground and the bottom of the deck. As a result, you can expect maintaining the system to be a bit more expensive if an issue arises. If your deck is not a permanent structure, it can be removed for maintenance and bypass this problem. However, most decks are permanent structures, so keep this in mind.

Can You Put a Concrete Patio Over a Septic Tank?

While a concrete patio won’t have cars going over it, it is still very heavy. This means it has the potential to damage your septic tank. Not only this, but any poured concrete structure will make maintenance a nightmare. Finally, concrete doesn’t ventilate which means that any gas buildup in your tank (a common problem) won’t be able to vent out as it normally would.

This can cause an increase in pressure which may result in your drains spewing sewage or your tank exploding. Poured concrete is, in my opinion, the worst possible thing your can put over your tank. Avoid doing so at all costs. 

Can You Put Pavement Over a Septic Tank?

I would strongly advise against paving over your septic tank. This will make it a nightmare to preform maintenance, and – especially in the case of a driveway – expose your tank to loadbearing which it cannot handle. Similar to concrete you put risk of an increase in pressure to the system.

It won’t ventilate well, and the gases produced by the septic tank can reach a catastrophic pressure. This can cause damage all over your property from raw sewage backup, or even an explosion. In all, any contractor encouraging or suggesting a driveway over a septic tank would make me suspicious.

How Much Weight Can You Put Over a Septic Tank?

The fragility of your septic tank cannot be overstated – it is often made of fiberglass and not meant to withstand much more than the pressure of the soil on top of it. Anything heavier than a full wheelbarrow or push lawnmower risks damaging the tank, an expensive repair which can cost more than 3,000 U.S. dollars.

In theory, a fortified lid and pipe system can increase the loadbearing capacity of your septic tank, but rarely is this worth the trouble. A fortified lid makes routine maintenance much more expensive and labor intensive, not to mention the presence of whatever heavy structure you installed over it.

Additionally, while the lid is fortified, the rest of the tank can experience material fatigue over time – this is where microcracks form from extended periods of strain. These microcracks prime your system to fail at the slightest provocation, which again, is a very expensive mistake.

What Are the Safest Landscaping Ideas Over a Septic Tank?

What Are the Safest Landscaping Ideas Over a Septic Tank

Your safest bet for landscaping over a septic tank is grasses and perennial flowers. This is because they do not place significant weight on the tank, and their root systems are shallow enough not to reach the tank.

Additionally, grass is easily replaceable after maintenance, and perennial flowers can be removed and placed back. This makes your septic system easily accessible. This solution is not only beautiful, but practical.

Can You Put Anything Over Septic Lines?

Septic lines are buried deeper than the tank itself but are still generally fragile. Flowerbeds are usually safe to put over septic lines, if you avoid plants and trees with deep root systems. The septic lines also rarely need to be accessed, meaning that you don’t need to worry about tearing up perennial plants to do maintenance.

Where is your Septic Tank and What does it Need?

Your septic tank is buried underground in your yard and made of fiberglass. Ideally, it was placed in a remote area of the property free from heavy traffic. This is a fragile structure, so its’ ability to bear weight is poor.

Additionally, septic tanks should have the sludge pumped out of them every three to five years, so it needs to remain accessible. In some places, it is illegal to put a permanent structure such as a patio or deck over your septic tank.

To keep your tank accessible, install only lightweight temporary structures over it, and leave at least three feet of clearance above and on each side of the tank. To best decide how large of a space you need to leave, I’ll discuss average tank depth and size.

How Deep are Septic Tanks and Lines?

The depth of your pipes and tank varies based on soil conditions and location, but generally the tank is between four inches to 2 feet under the surface. The pipes will be an additional foot to two feet below the top of the septic tank.

How Wide Are Septic Tanks? 

Septic tanks are usually 5×8 feet. If building or placing anything nearby, make sure to leave a couple feet clearance on each side to keep the tank accessible for maintenance.

Final Thoughts

Your septic tank is a frequently forgotten but integral piece of your home. It needs to be treated with care, so make sure your landscaping doesn’t damage it! Newer tanks might be able to handle pavers, and a well-constructed deck will probably be fine (if a little inconvenient for anyone preforming maintenance), but please do not pour concrete over your septic tank, and never drive a car or heavy machinery on top of it.

If you want to make the safest choice, flowerbeds of perennial flowers or grass are ideal over your septic tank. These will keep your yard beautiful without risking a hefty repair bill.

About the Author

Jamie

Jamie is the founder of The Backyard Pros. When he was 15 years old he started working at a garden centre helping people buy plants, gardening products, and lawn care products. He has real estate experience and he is a home owner. Jamie loves backyard projects, refinishing furniture, and enjoys sharing his knowledge online.