Check condition of the existing concrete
For the entire shell to last, the old concrete has to be in good shape. Inspect the shell, going under the plaster, pebble or other interior finish, to make sure it isn’t deteriorating.
If the concrete is falling apart, it will have to be knocked out until good, solid material is reached. Then, dowel into the stable existing material and shoot new gunite or shotcrete.
Also make sure that the existing concrete is thick enough, since the previous builder may have taken short cuts. Some professionals have reported finding walls as thin as 4-1/2 inches, which isn’t enough to provide the 3-1/2 inches of concrete coverage needed on either side of the rebar to help ensure stability and prevent rusting. Additional concrete may need to be added to the back of the wall.
Also check the bond beam. Some may have been built with too few bars inside, and if that’s the case, the entire thing may need to be reshot.
Toth often encounters this kind of shoddy workmanship. To help manage customer expectations, his bids generally include time for a new gunite rig even if it wouldn’t otherwise be required. This helps cover him if the extra concrete is needed, without customers becoming frustrated at added costs.
“Even where we’re not changing the shape of the pool, we always work in the cost of a rig coming in, in case we have to shoot a new spa or a new bond beam,” he says.
