Segmented Retaining Wall Contractor in Seattle

The geogrid. A segmental retaining wall system uses dry-stacked concrete units with layers of polymer grid extending back from the face into the retained soil, so the wall and the ground behind it behave as a single reinforced mass rather than a face resisting a push. Visually the finished wall can look identical to a gravity wall of the same block — the difference is entirely in what was buried behind it and at what spacing. That is also why you cannot tell by looking whether an existing tall wall was built correctly, and why the drawings matter at resale.

There is a threshold and it varies by jurisdiction across this service area, with several cities measuring the height from a different datum than homeowners assume. Surcharge changes it too: a wall below the trigger height can still need engineering if it is holding up a driveway, a pool or a neighbour's slope. We establish the position for your specific parcel and put it in writing before quoting, rather than quoting a number here that would be wrong for someone reading it in the wrong city.

Rarely, and it is worth being blunt about why. Geogrid has to be laid between courses as the wall is built, extending back into the fill — there is no way to introduce it into a standing wall without taking the wall down. What can sometimes be done is reducing the load instead: regrading to cut the retained height, removing a surcharge, or building a second wall above with sufficient setback. Where a wall has already rotated, the honest answer is almost always a rebuild, and we would rather say that at the estimate than discover it halfway through.

Because the structure is not the wall face, it is the reinforced soil mass behind it, and the grid has to reach back far enough to be anchored in ground that is not moving. On a six-foot wall that reach is typically measured in feet, not inches, and every layer needs the fill above it compacted in a controlled lift. This is the single most common place a cheap quote saves money, because once the backfill is in, nobody can see how far the grid went or whether it went in at all. If you are comparing quotes on a tall wall, the embedment length on the drawing is the number to compare.

Sometimes, and it is always worth pricing both. Two shorter walls can fall below an engineering threshold individually, use lighter blocks, and look better on a long slope than one tall face. But the upper wall applies a surcharge to the lower one unless it is set back far enough, and "far enough" is a calculation rather than a guess — set them too close and you have built one tall wall with a decorative step in it, carrying loads neither was designed for. We model both options where the slope allows a genuine choice.