Whether you need to seal retaining wall blocks depends entirely on the type of block you are using and your aesthetic preferences.
Sealing Concrete to Protect It
Using concrete blocks for foundation walls or above-grade walls on some structures has a lot of advantages. Because concrete blocks are much more permeable than poured concrete, however, and because they have more mortar joints than concrete, concrete blocks must be treated and sealed.
Seven common mistakes when installing retaining wall blocks include poor base preparation, inadequate drainage, not using proper backfill, failing to compact soil, improper alignment of blocks, ignoring wall height limits, and neglecting to use geogrid reinforcement when needed.
The 1/3 rule is a general guideline for stability: About 1/3 of the wall's total height should be buried below ground. This helps the wall resist the pressure from soil and moisture behind it.
Yes, you should fill hollow retaining wall blocks with gravel. This process is known as core filling.
For masonry cores over 4 inches wide, QUIKRETE Core Fill Grout – Coarse should be poured around the rebar; for masonry cores under 4 inches wide, QUIKRETE Core Fill Grout-Fine should be used.
The best backfill for a retaining wall is a compacted, angular, open-graded crushed stone or gravel (such as ASTM #57 or #78). This "free-draining" material prevents the buildup of hydrostatic pressure—the leading cause of wall failure—by allowing water to pass through and drain away harmlessly.
Yes, a 3-foot retaining wall absolutely needs drainage. While it is a relatively short wall, trapping water behind it creates immense hydrostatic pressure. Without proper drainage, this pressure, combined with heavy saturated soil, can cause the wall to bulge, crack, or collapse.
If between 1.5-2 metres from boundary, maximum wall height 2 metres. If greater than 2 metres from boundary, maximum wall height 3 metres. If more than 600mm above or below ground level, are contained by a structural support.
Our professional building inspectors often find that retaining wall failures boil down to poor planning, poor installation, and, most commonly, poor drainage.
Yes, a retaining wall should always be built true level horizontally, regardless of the slope of your yard. Failing to level the blocks or stones can cause structural failure, as gravity will constantly push the weight downhill.
Most policies provide coverage for retaining wall damage caused by covered perils, which typically include fire, lightning strikes, windstorms, hail damage, vandalism, theft, and damage from vehicles.
Apply sealer liberally by spray, lambswool applicator, roller or brush. Leave for 5-20 minutes then reapply a second coat whilst still wet. Wipe off excess sealer on top with a clean cloth after 10 mins. Allow to dry, water repellency will be evident immediately the surface appears dry, full curing will take 24 hours.
Coca-Cola does three main things to concrete: it slows down the curing process (acts as a retarder), etches the surface to expose decorative aggregate, and removes tough stains. This happens because of the soda's high sugar content and phosphoric acid.
Concrete block retaining walls typically last 50 to 100 years. However, reaching this upper limit depends heavily on having a well-prepared gravel base, proper drainage to prevent water pressure, and correctly angled (battered) stacking.
Foundation bearing (gravity case)
For the following simplified procedure, the “middle third rule” is applied, whereby the wall foundation is dimensioned so that the resultant vertical force acts through the “middle third” of the footing.
The best base for retaining wall blocks is a 4 to 8-inch layer of compacted crushed gravel (often called 3/4-minus, crusher run, or ABC stone). This material contains both angular stones and rock dust, locking together to create a solid, stable foundation that allows proper drainage and resists settling.
Yes, a 2-foot retaining wall generally needs a footing. However, "footing" means different things depending on how the wall is built. Instead of a deep, poured-concrete foundation, shorter walls usually rely on a compacted aggregate base or a single buried row of blocks.
The International Building Code (IBC) requires engineering design for any retaining wall 4 ft (1.21 m) or taller retaining soil and any retaining wall 2 ft (0.60 m) or greater retaining lateral loads (like buildings, streets, parking, etc.) in addition to soil.
It is recommended retaining walls be inspected four times a year, that is, before or after each season. Heavy rains or soil frost movement can have a significant effect on a retaining wall in a short time. At the very least, someone should perform an annual inspection and compare those findings with the year before.
Drainage is one of the most important factors in ensuring the longevity and stability of a retaining wall. When water builds up behind a retaining wall with no way to escape, it increases pressure on the structure, leading to bulging, deterioration, and even collapse.
Yes, you can dig a hole and fill it with gravel to create a drainage system (often called a dry well or a vertical French drain). However, to ensure it works and doesn't quickly clog or fill with mud, you need to follow a few specific steps.
Inadequate Drainage
One of the most common mistakes is inadequate drainage. Water can accumulate behind the wall, exerting pressure that leads to bulging or even collapse. Ensuring proper drainage is critical for a long-lasting retaining wall. To avoid this mistake, install a proper drainage system.