Above a certain height, a retaining wall stops being a stack of blocks and becomes a reinforced soil structure.
What geogrid does
Sheets of high-strength polymer mesh laid between courses and extending back into the soil. The wall and the soil mass behind it become one unit, which is far heavier and far harder to push over than the blocks alone.
When it is required
Height above grade, slope above the wall, and any surcharge — a driveway, a pool, a structure — near the top all push the threshold lower. Manufacturer tables give the starting point and an engineer confirms it.
Why it cannot be added later
Grid goes in as the wall is built, layer by layer, with compacted backfill over each sheet. Retrofitting means taking the wall apart.
What to ask
If a quote for a tall wall does not mention grid or engineering, ask why. The answer should be specific, not reassuring.
Read next
Terracing a sloped backyard: two low walls beat one tall one
Why splitting a slope is usually cheaper, safer and better looking than holding it all at once.
ReadWhat goes behind a retaining wall, layer by layer
Clear stone, fabric, pipe and compacted backfill — and what happens when one is missing.
ReadGarden steps that people actually use safely
Riser height, tread depth, landings and the drainage detail everyone forgets.
ReadFree estimate
Planning something like this?
Send the address and a photo, or call or text 647-621-8592.