Retaining wall repair, and when leaning means rebuild

It depends on where the movement is and why. A wall bulging in one section between a sound top and base can often be taken down to below the bulge, drained properly and rebuilt from there — a partial rebuild at a fraction of the full cost. A wall that is rotating at the base along its whole length has lost its foundation, and resetting the face without fixing that buys a couple of years at best. The honest test is whether the drainage can be made to work without taking the whole wall down. We look at the back of the wall before giving an answer, and we quote both routes where both are real.

Water, in the overwhelming majority of cases. Soil behind a wall saturates over a Seattle winter, saturated soil is dramatically heavier and pushes dramatically harder, and a wall with no drainage has nothing to relieve that pressure. The wall moves a little each season until it is visible. Secondary causes are a base that was too shallow or never compacted, and backfill dumped in one go rather than compacted in lifts so it settled later. What it is almost never is the blocks themselves.

A partial rebuild with drainage retrofit — taking down a failing section, putting proper drainage behind it and rebuilding that section — typically runs $1,500 to $6,000 depending on length and access. A full rebuild is priced as a new wall, $5 to $45 per square foot of face, plus demolition and disposal of the old one. The reason the repair figure is a range rather than a number is that nobody can price it properly from a photograph; the cost depends on what is behind the wall.

Possibly, and it is worth checking before you start rather than after. Rebuilding is new construction, so the exemption rules apply fresh: a wall is exempt only if it is four feet or lower measured from the bottom of the footing, outside an Environmentally Critical Area, and causing no damage to adjoining property. An old wall that predates current rules does not carry its exemption over to its replacement. A repair that leaves the structure in place is a different matter and usually does not trigger a permit.

Less urgent than one that is still moving, but worth measuring rather than assuming. A wall that rotated once during an exceptional winter and then stabilised can stand for a long time. A wall that moves a little every wet season is on a trajectory, and the cost of dealing with it goes up as the movement does — partial rebuild now, full rebuild later. The thing to watch is whether the lean changes year to year. If you have a photograph from a few years ago, compare it against the same angle today.

This needs sorting out before work starts, not during. Whose wall it is determines who pays, and a wall causing damage to adjoining property loses its permit exemption regardless of height. We have done enough of these to say that the conversation with the neighbour goes better early, with a diagnosis in hand, than it does once a contractor is on site. We will put the assessment in writing so you have something to show them.