Knowledge Pool

Floor To Wall Transition Radius

Most people are aware after having swum in many-a-swimming pool that it’s common for the floor of the pool to gently curve into the wall rather than be configured as a boxed 90-degree corner. Did you know that this curvature in the floor to wall transition actually gives the pool strength? You may already know that concave shapes such as an arch can provide immense extra strength under compressive loads but in a pool it’s actually more than that. The pool is loaded from the exterior by the pressure of the soil. By curving the interior radius of the pool we are actually using the weight of the pool wall itself to push back against the soil. Engineers typically would call this a resisting force.

One of the confusions that often comes up with engineering plans in the field is how the specification of the pools’s wall to floor transition radius is to be applied. We have received literally hundreds of field RFI’s over the years from builders after they were written up by an inspector for the reinforcing steel not correctly approximating the radius as specified on the engineering plans.

However, the builders were saved from having to tear out the steel and re-do it when we explain that it is in fact not our intention that the reinforcing steel approximate the specified radius, it’s actually the finished surface of the shotcrete that is intended to be curved. As mentioned above, because the structural purpose of the radius is to cause the weight of the pool wall to resist inward pressure from the soil, it’s the finished surface of the wall that matters and not necessarily the reinforcing steel inside the wall.

TL;DR: It is our intent that the finished surface of the shotcrete approximates the radius specified on Pool Engineering, Inc. structural plans, not the shape of the excavated hole, or the radius bend in the steel reinforcement.