Des Moines, IA

801 Grand Avenue


The plaza at 801 Grand Avenue, originally constructed in the 1980s, suffered from water leakage into the underground parking garage, paver movement, and paver deterioration. The 31,000 sq ft plaza is a concrete slab with waterproofing covered primarily with granite pavers on a mortar setting bed. The plaza also featured planters, concrete drive ramps, and concrete sidewalks. SGH investigated the causes of leakage and paver deterioration, recommended a remedial program, and designed repairs.

Our investigation included interior and exterior surveys, water tests, exploratory openings, and laboratory testing of concrete samples. SGH determined that the plaza damage was due primarily to setting bed deterioration related to a lack of a drainage layer at the waterproofing level. The waterproofing system was replaced as part of the comprehensive reconstruction that also included localized concrete repairs.

Working in collaboration with the landscape architect, SGH prepared waterproofing and structural repair design documents that incorporated their redesign of the outdoor terrace spaces. We evaluated the impact of these changes on the existing concrete structure.

SGH worked with the owner and construction manager to develop construction phasing that would limit the disruption to building occupants. We provided construction administration services and observed the as-built work throughout construction for comparison with the design intent.

Project Summary



Completion Date
Repair & Rehabilitation
Building Enclosures | Applied Science & Research | Structures
Specialized Capabilities
Repair & Strengthening | Condition Assessments | Roofing & Waterproofing | Materials Science | Microscopy

Key team members

Nick Floyd
Nick Floyd
Associate Principal
Niklas Vigener
Niklas Vigener
Chief Technical Officer