Why Correct Grades , Elevations and Drain Locations are so Important
Everything we build should be constructed in geometric straight planes . This enables concrete panels to move slightly without damage as they adjust to subgrade movement and or expansion . Concrete hardscape in theory should be constructed to float over structure and compacted subgrades and slip doweled at construction joints from panel to panel and building entries to prevent vertical displacement .
Considering A . D . A requirements , plazas should be engineered with slopes for surface drainage of not less than 0.75 % and not greater than 1.5 %. The perfect slope from a building finish floor to top of curb line is 1 %. If this set elevation is not obtainable , then surface or slot drains should be added . When area drains are added , they need to be dimensioned or designed within the exact layout of the decorative sawcut or design pattern and construction joint panels . This of course means that the importance of the drain installation per dimensional layout needs to be noted on the drawing . All too often drains are indicated on a plan but do not include horizontal control . The illustrations are examples showing the geometry requirements that include the maximum and minimum slopes and how the slopes should be verified .
Building Plazas
The locations and elevations of drain bodies are seldom installed in the exact location of where they need to be . Typically , if the drain body is on structure , then the location of the drain layout and drawing need to consider the substructure beams and supportive framing to ensure that penetration of the drain body and piping is possible . All too many times , our field crew reports that the drain locations are off due to improper layouts from the installer or the location was moved without thought towards the impact on design .
233