This is in response to requests received by Pool Engineering, Inc. for information on the in place permeability of gunite or shotcrete utilized for Swimming Pool Construction

During the construction of swimming pools (and prior to plastering), it is not uncommon for water to seep through the gunite shell into the pool’s interior. Pool Engineering, Inc. has been asked if this seepage is an indication of unsatisfactory gunite and if seepage will detract from the structural integrity of the pool.

Gunite or shotcrete is the structural element in swimming pool construction and is not intended to be the waterproofing media. Waterproofing of the pool is accomplished by the application of a waterproof lining to the gunite surface usually immediately prior to filling the pool. This waterproof lining is typically a plaster made with Portland cement and special aggregates.

Seepage occurs because gunite is not a totally homogeneous material and variations in cement content and density are not uncommon throughout the pool structure. The American Concrete Institute, in their publication 506.4R-94 Guide for the Evaluation of Shotcrete states in Section 5.2.3.2 “There is little experience or published work on the permeability testing of shotcrete. Specifications for concrete permeability levels are not extensively used.” Further in Section 5.2.3.3 it is stated “At this time, it is not appropriate to recommend permeability limits for shotcrete.

Experience with hundreds of thousands of gunite swimming pool has demonstrated that water seepage through the gunite shell has not caused any deterioration of the structural integrity of the pool.


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