Retaining Wall Steps: Layouts and How to Build Them Into a Block Wall

Retaining wall steps are built one riser at a time on compacted stone, usually as part of the wall, with each riser sitting on at least 6 inches of base that runs 6 inches past the back of the block. Decide the layout and count the risers before you dig, because the steps share the wall’s base, its drain pipe and often its courses.

Three ways to put steps in a retaining wall

Allan Block’s stair design guide sorts retaining wall stairs into three layouts. Which one fits depends on how much room you have in front of the wall and how steep the climb is.

Layout	What it is	Good for	Watch for
Recessed	Stairs cut straight into the wall, with wall sidewalls on both sides	Tight yards; works with all wall types; tread depth is flexible	Sidewalls need corners or curves
Protruding	Stairs built out in front of the wall face	Short walls and spots with room for landings	Takes up yard in front of the wall
Parallel	Stairs climb along the face of the wall	A gentler climb; least block cutting	Needs a long run of wall

Curved sidewalls give a softer, natural look. Straight sidewalls with square corners look crisp but, in Allan Block’s system, need corner blocks and more custom cutting and time.

You can also build the steps separate from the wall. Allan Block notes that freestanding steps make it easier to add landings and tune riser and tread sizes to your local code, though some block cutting may be needed. If you’re adding steps beside an existing wall, don’t mortar the steps to it.

How many steps the wall needs

Start with the total rise: the height difference between the bottom and top of the stairs. In a block wall the block sets the riser, so Allan Block’s rule is to divide the rise by the block height, about 8 inches for its full-size units. A 48-inch rise gets 6 steps.

On a steep slope, set the risers tight together. With Allan Block, that gives an 8-inch rise and a 12-inch run per step. On a gentler slope, add pavers or other tread material behind each riser to make the treads deeper and stretch the stairs out. A landing breaks up a long flight.

For the rest of the sizing (equal risers, comfortable treads and when you need a landing), our free outdoor step calculator works it out from your drop and run.

Check the code before you pick a block

For stairs serving a house, the 2021 IRC caps risers at 7 3/4 inches and requires a handrail on at least one side of any flight with four or more risers. Allan Block’s stair guide notes that riser limits can affect step design, since its blocks are nominally 8 inches tall. That’s a quarter inch over the IRC limit.

Whether your town applies those rules to steps out in the yard is a local question, and Allan Block says to check local code before building any stair. If code applies, plan a shorter step unit or riser before you order block.

Related: which interlocking retaining wall block to choose

A tall wall beside the stairs can also trigger guard rules. Our guide to putting a fence on a retaining wall covers when a guard is required.

How to build steps into a retaining wall

This is Allan Block’s method from its residential installation manual, with notes from its commercial stair guide. Other systems differ in the details, so read your block maker’s instructions too.

1. Lay out the risers. Mark the center of the stairway and the first riser, then the rest of the risers from your rise and run. Excavate for every riser’s base at once.
2. Fix the soil. Dig out organic or wet soil and replace it with granular material. If you over-dig, fill back with wall rock and compact it. The commercial guide compacts the excavation to 95% Standard Proctor.
3. Build the base. Compact the trench with at least two passes of a plate compactor, place 6 inches of wall rock, compact it with two more passes and check level. Our guide to retaining wall base depth covers the wall itself.
4. Run the drain pipe through. Continue the wall’s drain pipe behind the stairs at the lowest elevation. Don’t stop it at the stairs. Our retaining wall drainage guide explains why it matters.
5. Set the base course. In Allan Block’s example, the first riser is a continuation of the wall’s base course. Level each block side to side and front to back, and check the backs against a string line. Like the wall, the first course gets buried, 4 or 6 inches depending on the standard install. Adjust so the first riser stands no more than 8 inches high once the tread and final grade are in.
6. Fill and compact. Fill the block cores and at least 12 inches behind the blocks with wall rock, more if the next riser needs it. The tread area has to come up level with the top of the course. Compact in lifts of 8 inches or less; the commercial guide uses 4-inch lifts where possible, because stairs need extra compaction to avoid settling later.
7. Set the next riser. Place it on the compacted tread area, parallel to the course in front, with room for 6 inches of wall rock behind it. Level it off a reference block set on the wall, so the risers stay level with the wall.
8. Repeat, then add treads. Backfill and compact behind each new riser the same way. Once all the risers are in, install the tread material.

Belgard’s step unit instructions set a different order for its one-piece step units: when the stairs go into a wall, build the steps first and then build the walls up beside them.

Geogrid and taller walls

Allan Block calls it a good idea to reinforce stairs, and when they’re built into the wall, to keep the same geogrid spacing and strength in the steps as in the wall. On a protruding stair, grid can go in on the same courses as the wall.

A stair recessed into a geogrid wall sits in the soil the grid would normally reinforce. If the wall was engineered, the stairs belong on the engineer’s drawings. Our geogrid retaining wall guide covers how grid works.

Treads, finish and winter care

Allan Block’s front lip works as a built-in edge for many tread materials: its capstones, pavers, poured concrete, crushed rock, mulch or flagstone. With rigid treads like caps or pavers, plan the stair dimensions around the tread size to cut down on cutting.

Allan Block says to glue rigid treads in place with a high-strength construction adhesive. Read the data sheet before you buy. The Loctite PL 500 Landscape data sheet, an adhesive made for capstones and block walls, says it isn’t recommended for landscape step or stair construction, for safety reasons, so pick a product rated for the job.

Belgard allows its step units a slight pitch toward the front, no more than 1/4 inch, to shed water. When the units sit next to a retaining wall, though, Belgard keeps them level front to back.

Allan Block warns that in colder climates, salt can’t be used on its blocks or capstones because it will cause them to deteriorate. Use sand on the treads instead.

When to call a pro

Short garden steps through a low wall are a reasonable DIY project if you’re already comfortable building the wall. Call a pro, or at least get a design, when:

• The wall is engineered or uses geogrid. The stair opening has to be part of that design.
• The steps serve a door or a main walk. That’s where code limits on risers, treads and handrails are most likely to apply.
• The units are heavy. Belgard’s step units are moved with skid-steer forks, a clamp, straps or a cart, with a second person guiding each one into place.
• The slope is long or steep. Landings, sidewalls and riser spacing take real layout work.

Planning the wall around the steps? Every wall article we’ve written, from caps to walls over 4 feet, is on our retaining wall guide, and our retaining wall calculator counts the block for the wall itself.

Frequently Asked Questions

How many steps do I need in a retaining wall?

Divide the total rise in inches by the block height. With Allan Block’s roughly 8-inch blocks, a 48-inch rise needs 6 steps.

Do retaining wall steps need geogrid?

Allan Block says it’s always a good idea to reinforce stairs, and in stairs built into a wall it keeps the same grid spacing in the steps as in the wall. If the wall was engineered, the stair opening belongs on the engineer’s drawings.

Should you build the steps before or after the wall?

Build them with the wall or first. Belgard says to build the steps first and the walls beside them, and Allan Block builds the risers into the wall courses as the wall goes up.

Can you add steps to an existing retaining wall?

Yes. Allan Block suggests building the steps separate from the wall, which also makes it easier to add landings and set riser and tread sizes to your local code. Don’t mortar the steps to the existing wall, and expect to cut some block.

Sources: Allan Block, Residential Installation Manual: Retaining Walls Steps and Stairs (pp. 42 to 45); Allan Block, Commercial Installation: Stair Construction; Allan Block Tech Sheet #1022, Design Guidelines for Stairs; Belgard Product Installation Guide, Landings Step Unit Installation (Technical Resource Guide p. 79); Belgard Product Installation Guide, Landings Step Unit Handling (Technical Resource Guide p. 80); 2021 International Residential Code, R311.7 Stairways (R311.7.5.1 risers, R311.7.8 handrails); Loctite PL 500 Landscape Construction Adhesive, Technical Data Sheet

Written and reviewed by Thayne Muthler, owner of Muthler Landscaping & Construction (PA HIC #PA212584). How we check facts: editorial policy.