Why Your DIY Garden Steps Will Slide Away (And How to Fix Them)

The Dilemma

A homeowner recently asked:

We built garden steps by placing terracotta tiles directly on the soil, hoping grass roots would lock them in place over time. Will this hold up, or do we need to lift them and add a gravel base?

The GardenOwl Diagnosis

The Scenario

This is a textbook case of The Migratory Riser Syndrome. You have a slope, you have gravity, and you have rigid materials (tiles) floating on a fluid medium (topsoil). The homeowner here has done what many DIYers do: they dug out little shelves in the dirt and dropped pavers in, hoping that "nature" (grass roots and sediment) would eventually glue everything together.

It looks rustic and charming for about three weeks. But looking closely at the photo, you can already see the physics fighting back. The front edges of the tiles are unsupported, and the soil is visibly soft. This isn't just a stability issue; it's a safety hazard waiting for the first heavy rainstorm.

The Trap

The trap here is the "Settling Myth". There is a common misconception in DIY landscaping that soil "settles" into a concrete-like hardness over time. While soil does compact, it never stops moving. Topsoil is active—it swells when it gets wet, shrinks when it dries, and heaves when it freezes.

If you place a rigid object (a tile) on a moving object (dirt), the rigid object will move. Without a mechanical anchor or a non-reactive base, those steps will slowly slide downhill, tilt forward (dumping you on your nose), or crack as the soil beneath them erodes. Relying on grass roots to hold structural weight against gravity is a gamble you will lose.

The Solution (Deep Dive)

To fix this, you have to stop thinking of these as "pads" and start thinking of them as "structures". You need to decouple the walking surface from the living soil.

1. Excavation and The "Box" Concept A step on a slope needs a face (riser) and a top (tread). You cannot just have a tread. You need to cut a 90-degree notch into the hill.

• The Riser: You need a physical barrier to hold the soil back. This could be a 6x6 timber, a large natural stone, or a row of wall blocks. This riser must be anchored (using rebar for timber) into the subsoil.

2. The Sub-Base (Crucial) Once you have your "box" cut out, do not put the tile back on the dirt. You need to excavate down another 3-4 inches.

• Fill with Aggregate: Fill this void with crushed angular stone (often called 3/4" clean or road base).
• Why Angular? As noted by the Portland Cement Association, irregular, jagged stones lock together when tamped. Round stones (pea gravel) or sand act like ball bearings—they roll. You want a base that locks.

3. Compaction Tamp the stone base until it is rock hard. This creates a non-reactive layer. Water flows through it, not under it, which prevents frost heave and washout.

4. Resetting the Finish Now, place your terracotta tiles on top of this compacted stone base. They will stay level because they are sitting on a friction-locked pad, not on squishy biological matter.

The Diagnostic and Visualizing Safety Net

Hardscaping on a slope is mathematically unforgiving. If your "Rise" (height) and "Run" (depth) are inconsistent, people will trip. Before you start digging trenches or buying timber, you can use GardenDream to act as a blueprint check.

Upload a photo to our Exterior Design App to visualize how different materials—like timber ties versus stone blocks—will look on your specific gradient. It helps you see if your steps will look like a graceful ascent or a steep ladder before you break ground.