Foundation Drainage and Lot Grading Problems
While not all buildings with poor drainage will have structural issues, it is rare that we see a house with structural issues that has good grading! The single most important thing a person can do to improve the health of their foundation is to keep water away from it. Whether you need an interior or exterior foundation drain, a surface French drain, cut-off drain, or just need your lot regraded so that precipitation can naturally flow away from your home, Van Matre Construction can help.
Foundation Drains: If you have issues with a wet basement or crawlspace, and your exterior grading is in good shape, a foundation drain may be the solution you need. A foundation drain may be placed inside or outside your foundation, allowing ground water to collect in the horizontal drain, flow to a sump pit, and be pumped safely away from the home.
Exterior Drains: The worst part about an exterior foundation drain is the disruption to landscaping. The installation requires excavation of the exterior of the foundation to the base of the footings (or wall if it is poured on drilled caissons). Once the wall is excavated, we clean the wall, inspecting for cracks that may need attention. Van Matre Construction uses only the highest quality materials: While other companies spray the wall with asphalt, we cover the wall with the Cetco brand AquaDrain product. The solid plastic backing ensures no water will make it to your foundation, the dimples give a clear path for water to fall to the horizontal drain at the base, and the geo-textile fabric adhered to the face ensure that the product will not clog with mud. This quickly takes water to the base of the drain system. At the base, Van Matre installs a perforated pipe, wrapped in geo-textile fabric, surrounded by a foot of gravel, and again wrapped in geo-textile fabric.
The base drain slopes gently downhill to a sump pit where a high-quality cast-iron pump removes the water-pumping it away from your home
An interior foundation drain is placed just inside the foundation wall and footing, beneath the basement floor slab. An interior drain spares your landscaping, but does not allow for waterproofing of the exterior of the foundation wall. The foot wide swath of floor slab is cut and removed around the perimeter of the basement, and the underlying soil removed to the base of the footing, usually about 8”-10” from the base of the floor slab.
Similar to the drain at the base of the exterior drain, a perforated pipe wrapped in geo-textile fabric is surrounded by gravel and wrapped in another layer of geo-textile fabric. The pipe slopes gently downhill to a sump pit where a high-quality cast-iron pump removes the water-pumping it away from your home. The floor slab is patched and the job is complete
French Drains/Cut-off Drains: The term “French Drain”, cut-off drain, or surface drain are variations of the same theme: the purpose of these drains is to capture and redirect water flowing on the surface of the landscape or just beneath the surface. Depending on the application, most of these drains incorporate the same perforated-pipe surrounded by gravel and wrapped in geo-textile fabric as the interior and exterior drains, with the drain assembly placed anywhere from a few inches below the surface to a few feet. Ideally the drain will run to where it can intersect with natural grade and drain away from structures. Some situations require pumps.
Cut Off or French Drain
Historic Structures/Rubble Foundation Case Study
Old houses are different than new houses, and when I say ‘old’, I don’t mean 50 years old, I mean old enough to have been built not using modern construction practices. This house was built sometime around the turn of the 20th century, its exterior walls are two wythes (layers) of brick, and the brick rests on a rubble foundation.
There are a couple considerations when you are dealing with these types of structures: 1) a rubble foundation is not like a poured foundation. Most foundations are made by pouring concrete into forms, ideally with reinforcing steel, and allowed to cure. The building is then built on the cured foundation. A rubble foundation is built by excavating a trench a couple feet wide and a couple feet deep. Typically stones of varying size are stacked in the trench and typically mortared together for the top foot or so of the foundation. Both sides of the rubble stack get backfilled and the brick that will be the supporting walls is then stacked on the ruble foundation. There is no rebar in the rubble foundation, and the foundation itself has very little strength other than compressive. 2) Old, soft (sometimes called ‘low-fire’), brick is not very strong and is not very resistant to chemical weathering. Water migrating through the brick will quickly degrade the brick as well as the mortar.