How to Build a Retaining Wall Over Tree Roots?

How to Build a Retaining Wall Over Tree Roots

To provide extra support to the plants and yard soil, walls over the roots are a “must.” So, if you have planned to go for one, know that you can create it on your own. Yes, without any professional help and spending bucks! Are you excited to learn how to build a retaining wall over tree roots? 

Building layers of stones and gravel in a circular or square pattern is the base for the retaining wall. And to construct in a way to prevent root damage, follow the safety tips I listed here.

What Material Do You Need for Building A Retaining Wall?

It takes fewer tools to build any kind of retaining wall over the tree roots. All you have to gather is –

How to Build a Retaining Wall Over Tree Roots?
  • Gravels, stones, cement, and water for the wall layers.
  • A shovel, spirit level, spatula, nails, and threads to get into the building process.
  • Safety gloves for protecting your skin from the cement. 

How to Build a Retaining Wall Over Tree Roots

How to Build a Retaining Wall Over Tree Roots?

As much as building a retaining wall is easy, a wrong step can cause havoc to the tree roots. So, to avoid that, follow these guidelines –

Step 1: Determine the Distance for the Wall

First, you decide how far from the tree trunk and root the retaining wall should be. It is a must step to prevent the tree roots from pushing the retaining wall.

For that, take a long string, tie one end of it to the base, and attach another end to the nail. Then, pull the nail taut and nail it to the location where you will start constructing the wall.

Step 2: Prepare A Circle

Using a shovel or trowel, start removing the soil around the tree to dig a leveled ring. The circle should be 3 to 6 feet deep. While digging, try to avoid cutting the roots. If you want square retaining walls, dig a square instead.

Note that if the ground is already level, you can dig 4 to 6 inches for the ring. But making the ring leveled in the sloppy ground requires digging deeper. The pit should be wider enough to place the paves and stones properly.

Step 3: Install the First Layer of the Wall

Add one-inch deep gravel in the ring, and with a mini compactor or 4×4 lumber, ensure to level or tamp down the layer. Place and align the stones on top of the gravel. With a carpenter’s level, make them straight. 

Step 4: Apply Cement

Go through the manufacturer’s instructions to mix the cement with water. The consistency should not be runny. Try to mix masonry cement. Do not leave it in the air for more than a few hours. Here, you should wear gloves while working with the mix for your safety. 

With a spatula or putty knife, apply a thin layer of the mix over the first layer of stones without any gap. Spread the mix evenly. 

Step 5: Make the Second Stone Layer

After applying cement, add stones on top of that in a way that the joint of the second layer meets the middle point of the first one. Then, keep spreading cement and building layers until the wall reaches a preferable height.

But do not make the wall too high that you cannot properly fertilize and water the roots. 

Step 6: Let the Wall Dry 

As per the cement manufacturer’s guide, let the wall dry. It should not take more than two days to cure and dry. After that, refill the ring with the soil you have removed. And you are done with the retaining wall. 

Safety Measures to Follow While Building Retaining Wall Around Existing Tree 

How to Build a Retaining Wall Over Tree Roots?

Nobody goes through tree retaining wall ideas only to find out that if the walls are not installed properly, they can stress the roots. As a result, the tree can die prematurely. But proper planning and safety measures described below are the way out –

1. Avoid Critical Root Zone

Tree roots grow in each direction, and they require an unbothered zone to thrive. And in this zone, most of their major root systems begin and access nutrients. This is the critical root zone or CRZ, which you must avoid while building the wall.

To measure the CRZ, notice where the dripline ends. If it seems confusing, build a wall outside the canopy line. Only then, the stones will not block the roots from growing.

On a side note, do not choose small trees for retaining walls. In case you have to, do not add too many layers of gravel and rocks. Because these trees are prone to constructional damage.

2. Contact an Arborist 

An arborist is a tree doctor to help you with basic guidelines, assisting the trees in withstanding any type of retaining wall. They know your tree needs more than you.

So, feel free to contact them and know what impacts the roots might have due to the construction. The plus side is they can share tips to save the decaying roots around the build-up.

Frequently Asked Questions (F.A.Q’s):

Do I Need Government Permission to Build a Retaining Wall?

Some countries require written permission to build a retaining wall around trees, especially if the plants are in the city yard. It is better to contact a local arborist to know the exact answer. 

Can Tree Roots Damage The Retaining Wall?

If you construct the wall away from the growing zone of the roots, they will not damage the wall. Otherwise, they can weaken the stone layers. 

Do I Need to Cut Roots to Build Wall Over Them?

No, you should not. Otherwise, the retaining wall can stress the whole tree easily. It is better to keep the roots untouched, especially in the critical zone. 


Building a tree retaining wall is a fun yet tricky process. This is because a lack of guidelines can make the wall a threat to your plants. So, you ask how to build a retaining wall over tree roots without any issues? Find out the best place to create one and follow the safety measures given above. 

I’d suggest you avoid making a wall around too old or young trees. They are more vulnerable to constructional impacts. 

Md Biajid

Meet Mia Biajid, a passionate nature lover. Particularly, he has a deep-rooted connection to the plant. Mia loves to spend time exploring forests and uncovering the secrets held within trees. He always inspires others to appreciate and protect our precious part of the ecosystem.

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