Hardscaping in South Seattle

Because the area covers two ridges and a valley, and because parts of it have been worked over for more than a century. The ridges carry glacial till like the rest of the city. The Rainier Valley floor has genuinely poor-draining low ground. And there are pockets of historic fill where land has been made up at some point, which behaves differently from undisturbed ground. The three need different base and drainage specifications, which is why we test rather than assume.

Fill was placed rather than deposited, so it has not consolidated the way natural ground has and it can hold and move water unpredictably. A retaining wall footing on fill may need to go deeper to reach something competent, and a patio base may need more depth and better compaction. It is not a reason not to build; it is a reason to know first.

Usually, and on the valley floor it is the most common thing we are called about. The answer is a designed water route rather than a bigger patio fall — where the water arrives, where it currently pools, and where it can legitimately go. Sometimes that is a French drain to an approved discharge; sometimes it is regrading plus a dry well. What it is never is paving over the problem and hoping.

Often, because Beacon Hill and the Mount Baker side both fall substantially and usable flat ground has to be made. The four-foot exemption applies measured from the bottom of the footing, and terracing into two shorter walls frequently avoids a permit while producing more usable ground. Where a parcel sits inside a landslide-designated area the exemption stops applying, so we check first.