A surcharge load is any additional weight placed on the ground above or behind a retaining wall, beyond the weight of the soil itself, such as a driveway, patio, parked vehicle, or slope of imported fill.
Retaining walls are designed around the pressure of the soil they're holding back, but that calculation changes fast once something else adds weight on top of that soil. A driveway or parking pad above a wall, a patio, a hot tub, even stacked topsoil from another part of a landscaping project, all add surcharge load that increases the lateral pressure the wall has to resist beyond what the bare hillside alone would produce. A wall sized correctly for bare soil can be undersized the moment a homeowner parks a vehicle or builds a patio on the ground above it, which is why surcharge has to be part of the design from the start, not something added or noticed later.
This comes up often on the properties we work on in Carroll and Grayson County, where driveways and parking areas are frequently cut into a slope right above a retaining wall to make use of the grade. When we design a wall for that kind of site, we account for the surcharge the driveway will add, not just the soil behind the wall on its own, so the finished wall is actually built for the load it's going to carry for the life of the property, not just the load it faces on day one.
More masonry vocabulary from the glossary.
The services where this term comes up.
Chelo's Brick & Stone serves Hillsville, Galax, Wytheville, Fancy Gap, and Independence, VA. Call for a straight answer and a free on-site estimate.
