Older foundations can definitely be made permanently waterproof, but there is one very important thing to keep in mind. A hundred years or more ago, foundations were largely made of field stone which, as the name implies, were collected from farmer’s fields. These foundations were made of every size and shape of stone which were held together with mortar between the stones. After being buried underground for a hundred years, the mortar between the stones has often deteriorated to the point where it is now the earth outside which is holding the stones together. If the earth is removed by excavating to waterproof from outside, a structural concern can develop.
External waterproofing can be a dangerous exercise by its nature but excavating a century home requires several extra layers of safety procedure. Unlike most foundations you must pay closer attention to the condition of the foundation. If the foundation is made of large square cut stone, then that is a very strong and solid structure. If the foundation is made of smaller misshapen stones, then structural integrity should be a concern.
To excavate and make waterproof such a foundation, it should be treated in alternating sections of excavated and unexcavated areas ten feet in length. When the exposed areas are waterproofed, those sections are back filled and compacted. This process is then repeated for the unexcavated sections.
If it is necessary to excavate and waterproof the entire wall or basement simultaneously, then the weight of the house should first be lifted off the foundation. This is done by installing temporary jack posts and beams in the basement and gently applying pressure to the jacks until the weight is removed from the foundation. Now the walls can be excavated with no danger to the house if the foundation decides to fall apart.
Of course the interior sub-floor drainage system is always an available option and does not cause any structural concerns.
Heritage buildings are some of The Crack Doctor’s favorite projects and we provide both internal and exterior waterproofing solutions for stone foundations. Many of our repairs are covered by our famous lifetime transferrable warranty.