Almost always hydrostatic pressure. Water saturating the soil behind the wall makes it far heavier and pushes outward, and if there is no drainage layer or weep to relieve that pressure it accumulates every wet season until the wall deflects. Frost adds to it: saturated soil expands when it freezes, driving the wall further out each winter, and the movement does not reverse in spring. A leaning wall has already lost its structural geometry, so the repair is rebuilding the affected section with proper drainage rather than pushing it back or facing over it.

Occasionally, if movement is minor, confined to a small area, and the cause has been corrected — but honestly, not often. Once a wall has rotated or bellied, the courses no longer bear on each other the way they were built to, and cosmetic repair leaves the failure mechanism fully intact. What usually makes sense is rebuilding the affected section, reusing the original stone or block where it is sound, and installing the drainage that was missing. We will tell you plainly which situation you have rather than quoting a patch that will not hold.

Low garden walls are straightforward masonry. Above roughly three to four feet, the soil loads increase enough that engineering, reinforcement, and often a permit come into play, and the exact threshold varies by municipality across Delaware County. Taller walls may also need geogrid reinforcement extending back into the slope, or to be built as two terraced walls rather than one tall one. If you are considering something in that range it is worth raising it early, because it changes the design rather than just the price.

Three parts working together. Free-draining crushed stone directly behind the wall so water moves down rather than pressing against the face; filter fabric separating that stone from the soil so it does not silt up and stop draining; and an outlet — weep holes through the wall or a perforated pipe carrying water to daylight. Leave any one of the three out and the system stops working: a stone backfill with no outlet just becomes a reservoir. This is the single most skipped element on retaining walls and the most common reason they fail.

Natural stone, brick, and block are all workable, and the right choice depends on wall height, the look you want, and what the rest of the property is built from. Natural stone suits older Delco properties and can be dry-laid or mortared. Segmental block is engineered for retaining loads and is often the practical choice for taller walls. Brick reads well against brick houses but is generally better suited to lower walls. In each case the structural work behind the wall is the same — the material choice changes the face, not the requirements.

K&S Masonry Restoration is based in Brookhaven, PA and works throughout Delaware County and the Philadelphia suburbs, including Philadelphia, Havertown, Springfield, Drexel Hill, Chester, Wayne, Radnor, and Ardmore, plus Montgomery and Chester Counties. If you are unsure whether your address is in range, call (610) 990-1379 and ask — it is a quick answer.