I recall a previous restoration project home where there was a stone foundation with moisture issues.
The professional foundation contractor had rectified the situation that seemingly been almost impossible to resolve. I had the opportunity to talk to him about this.
The first issue was the soil in this case is a gumbo clay that retains moisture like crazy. This gumbo clay when it becomes saturated and with the force the soil exerts on the foundation creates what is known as hydrostatic pressure.
The second issue is poor drainage which compounds the situation by allowing the soil around the foundation to become saturated and with the pressure of the soil forces to water to go somewhere … path of least resistance… the foundation. After many years of the stone foundation being subjected to this the mortar breaks down and will create a path for water to infiltrate.
The method he used was to carefully excavate the entire perimeter of the foundation to the footings. He repaired the joints of the stones then used a spray on specific industrial water proof membrane ( not damp proof coating ). A dimpled sheet product called Platon Foundation Protector, which is an excellent product, then covered this. Here is a link to their site : http://www.systemplaton.com/.
This did have it’s challenges because of the unevenness of the stone foundation compared to the relative flat surface of a concrete block or poured foundation.
They laid an exterior perimeter weeping system encased with fabric. In this case because of local building code restrictions these weepers were tied into an interior sump pit with a large capacity sump pump to evacuate the water accumulated. The trench was lined with a commercial grade ground cloth then stone was used to fill the trench to approximately two feet below finished grade with the ground cloth laid over top. Then topsoil was used to bring it up to grade for allowing bedding plants to be used. The purpose of the ground cloth is to prevent soil from migrating in plugging the voids of the stone and preventing water to percolate through to the weepers.
I asked why he didn’t approach doing it from the inside like other contractors proposed.
He explained the idea is address the source of the moisture and to prevent it from coming from the outside to the inside. He went on to explain that he would never do an interior method of drainage , unless something prevented addressing the issue from the outside. His logic is it doesn’t make sense to allow to moisture to penetrate from outside to the inside. For example allowing the water to flow from the outside under the footing to the inside and then drain it away could cause undermining of the footing … it doesn’t make sense.
Another perspective … food for thought.