Membrane waterproofing, which provides a continuous self-healing barrier to the passage of water, is theoretically the perfect method because it will ordinarily bridge minor shrinkage cracks and is independent of the quality to the concrete on which it is placed, provided it is structurally adequate. The application of membrane waterproofing, however, presents some problems and its theoretical effectiveness is not always achieved. Hydrolithic waterproofing, also referred to as the iron method, does not have the disadvantages of the integral or membrane methods, but presents some problems of its own. The advantage of the hydrolithic method over the other two is that it is generally applied to surfaces accessible for repair throughout the life of the building. It has been used successfully to waterproof a wall against a hydrostatic head of 70 feet, which is generally more than subbasement walls are structurally designed to resist. Therefore, it is generally used in deep building basement waterproofing. The exceptions to this generalization develop when hydrolithic waterproofed surfaces must be covered with some finishing material and on floors which may be subject to hydrostatic pressure. It is desirable to place the hydrolithic waterproofing as long as possible after the concrete has been placed in order that greater part of the cracking resulting from shrinkage may take place before the waterproofing is done. This will permit cutting out of shrinkage cracks and honeycomb when the waterproofing is applied. Even then, continued shrinkage of concrete over a period of a year or two will result in further cracking, which must be repaired and which can de done simply and inexpensively if the waterproofed surface has received no finishing material.