Segmental retaining wall blocks do not use mortar. They are simply stacked one upon another. Sometimes there are grooves, or lips, or pins or clips that align the blocks. However, the blocks always rest one upon another.
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When blocks are "out of tolerance" it means that one side of the block is higher or lower than the other side. You can see that this can cause big problems for these reasons:
- Adjacent blocks are not at the same elevation. The next block you place will rock back and forth;
- The next block you place will have its weight pushing on one point. It's weight is not distributed evenly, so that block is likely to crack; and,
- If there is a separation, then the geogrid layers have no friction holding them to the face!
Take a look at these blocks and you can see what problems arise when tolerances are not met.
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