Proper Drainage

Before construction on any project starts, the topic of proper drainage should be addressed. Good drainage is essential for the success of any construction project, commercial or residential, and begins with careful site planning and landscaping in order to limit or control any sources of water. Most leaky basements are caused from faulty landscaping, improper routing of downspouts, and failure to slope backfill away from the foundation. This allows water to run back against the wall penetrating into the wall structure or through any cracks or voids in the structure. Keeping water and moisture away from foundations, interior walls, and structures is key to a long lasting, safe, and healthy home or work environment. It is also key to achieving optimum long-term performance of any waterproofing system, including the HouseGuard™ Waterproofing Membranes and the HouseGuard™ Complete Waterproofing System™.

Drain tile is usually placed at the exterior of the footing, four inches below the top of the floor slab. It may also be placed along the inside of the footer along the perimeter of the floor and connected to the external drain tile system. Aggregate is placed on and around the exterior drain tile to a height of about six inches above the top of the floor slab or higher. This may vary depending upon local code requirements. A filter mat should be placed on top of the drain tile and aggregate to keep dirt, silt, and clay from infiltrating into the drainage system. This can eventually plug off drains and keep water from moving away from the foundation. Depending on individual site, soil conditions, and drainage characteristics, optimum performance of the waterproofing membrane system can be achieved with incorporation of insulating drainage boards such as Dow Perimate® or protective drainage mats such as Delta Drain® against the membrane prior to backfilling. These systems protect the waterproofing membrane from the damage that can occur with backfilling while providing a channel to quickly drain water away from the surface of the wall to the footer drain. This prevents hydrostatic pressure build-up along the wall surface. The drain tile system then carries the water away from the foundation and slab. Whenever possible, slop the drain tile one-eighth inch per foot to maintain a positive drain. A screen should be placed on all ends of any open drain tiles so that rodents do not enter and interfere with the drainage of the system.

It is important to note that hydrostatic pressure relief systems or dewatering systems alone will not provide protection against moisture infiltration into foundation or interior walls or floor slabs. Concrete is porous and will allow moisture to permeate through into interior walls. Concrete will also crack and allow a direct unobstructed path for water and moisture intrusion. This can only be prevented by the use of a high quality elastomeric waterproofing membrane system which bonds to the wall surface and provides crack bridging ability in combination with the proper drainage system. Damproofing will not bridge cracks and offers little protection.