FAQ about Retaining Walls

Does a retaining wall sound like something you and your landscaping might need? Here are the answers to some general questions you might have.

What is the cheapest type of retaining wall?

The cheapest types of retaining walls are ones made of wood and concrete blocks. It is the cost of the material that makes building one inexpensive or expensive. The cheapest design to DIY is one made of treated pine.

What is the easiest retaining wall to build?

Short walls under three feet high and constructed of concrete blocks or masonry blocks are the easiest type of wall for DIYers to build. They are ideal landscape solutions for a front yard or raised flower bed.

What is the strongest type of retaining wall?

The strongest and most durable type of retaining wall is a poured concrete wall.

How do you make a strong retaining wall?

Soil shifts. Take into account topsoil and soil weights. Build the wall in proportion to the amount of material that needs to be retained. To make a wall strong use well-compacted base material, calculate the required slope, and include a step-back design in the construction plan to “push” the wall against the soil.

Do you need drainage behind a retaining wall?

Yes, proper drainage is essential for all retaining wall designs. Groundwater needs to be directed away from the wall to avoid soil from swelling and putting pressure on the wall itself.

Do I need a concrete footing for a retaining wall?

No, a concrete footing isn’t necessary for a retaining wall. However, you do need a base or footing, but use a porous material such as a course stone aggregate or gravel to allow the wall to naturally shift with the ground.

How long do retaining walls last?

The longevity of retaining walls depends on several factors including the microclimate of the outdoor space, soil, and the quality of the wall materials used. Properly designed and constructed masonry walls, including a natural stone wall, can last for 100 or more years. Treated timber walls have a lifespan of up to 40 years. Walls made of concrete blocks or poured concrete walls have been known to last anywhere from 50 to 100 years.

What slope requires a retaining wall?

For a yard with common types of soil including granular and soil with low clay content, a slope over 35 degrees will need some sort of wall.

At what height does a retaining wall need to be engineered?

You will need to consult an engineer for a wall that is higher than four feet.

What do you use to backfill a retaining wall?

The best material to backfill a retaining wall is crushed stone or gravel. Start with the stone or gravel for the first foot of the wall, then use compacted soil for the remainder of the wall.

How do you landscape a retaining wall?

To landscape it without risk of damage to it, select low growing plants, small bushes, and medium height flowering plants. The root systems of tall trees and larger shrubs might push against stone walls or a concrete block wall, allowing water seepage and/or shifting soil to break through.

How can I make my retaining wall look better?

Improve the appearance of existing concrete retaining walls by applying a layer of stucco – for a color such as light blue, pale lemon, or peach, add oxide pigment to the stucco mix before applying it to the wall.

Grow a row of shrubs or a hedge the same height as the wall.

For a finished, professional look create a cap by attaching small slabs of flat, natural stone to the top of a wall made of stone, brick, or concrete. To add visual interest to a wood retaining install the cap made from a different wood or stained with another color.

Do you need landscape fabric behind a retaining wall?

Landscape fabric behind a retaining wall, whether the wall is made of concrete, brick, stone, or wood, creates a barrier between the soil and the blocks/wood. It is constructed of woven fibers that let water through, helping to extend the lifespan of the wall.

Why do retaining walls fail?

The number one cause of retaining wall failure is poor drainage. The second most common cause is improper construction methods. Miscalculations during the design process and the age of the wall are other top reasons.

What is the best retaining wall block?

Interlocking concrete block is ideal for DIY retaining walls. Since they come in a number of colors, sizes, and shapes, they are exceptionally versatile.

When should you build a retaining wall?

Build a retaining wall when:

  • Your yard is on a hill and you want a flat area for a garden, patio, or some other type of outdoor living space
  • The ground is uneven
  • A part of the front yard or backyard is too low to do anything with unless it is elevated
  • Soil erosion is subtracting from your curb appeal

Can retaining walls be built into other landscaping features?

Yes, wall designs with water features or with steps can be built to create a stunning outdoor space.

Do retaining walls require mortar to hold them together?

No, they don’t. There are many concrete and stone (interlocking blocks) products at an affordable price specifically designed for DIY projects that don’t require mortar to hold them together.

How high can my retaining wall be?

Without a permit or a licensed engineer, a retaining wall can be just under 4 feet. A wall higher than 4 feet typically requires a permit and adherence to local restrictions, regulations, and/or guidelines.

When should I call a professional?

When building a retaining wall is over four feet, you should call a professional. In most local regions and municipalities, a permit is required, and before one is issued, you’ll need to consult a licensed engineer for any wall designs that are four feet and taller.


If you live in Portland, Oregon, and are in need of professional assistance considering all your retaining wall options then give Sound Retaining Walls of Portland a call! We would be happy to help. (503) 213-9422

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