Tanking is a moisture control technique that is often used on older foundations made from stone, brick or masonry block. Sometimes referred to as "cementitious tanking" or "cement-based tanking", this process calls for the application of a thin layer of mortar to foundation walls. The result is a smooth mortar surface that improves the appearance of a basement or cellar while also providing better moisture control.
Advocates of tanking as a means of keeping basements and cellars dry argue that a seamless application of mortar can effectively seal leaks in basement walls, preventing moisture intrusion. This is only partially true. It's important to remember that like most masonry materials, the mortar used for tanking will absorb and release moisture. Even if water isn't leaking through cracks in a basement wall, the thin mortar coat can and will absorb moisture from the soil and release this moisture into the basement or cellar area.
Tanking is supposed to work by holding back water that is saturating the soil surrounding a foundation. When the soil is full of water as a result of wet weather, basement walls and floors are subject to extreme hydrostatic (water) pressure. Basically, your foundation is like the hull of a boat, with one critical exception: Mortar can't flex or stretch like a boat hull. So when there's a great deal of pressure applied to a thin coat of mortar, cracks are certain to develop. High water pressure will then force water through these cracks, bringing water into the basement or cellar area.
At Basement Systems GB, we advise homeowners to keep basements and cellars dry with our patented WaterGuard® system. The WaterGuard® system is a concealed drainage channel installed inside your foundation walls. Instead of allowing hydrostatic pressure to build up by attempting to hold water back, our system allows water to drain to a sump pump, where it can be discharged to the exterior. WaterGuard® drainage channel is made from strong, durable plastic that won't corrode, clog or break. It's a fail-safe way to capture any water that leaks through the walls or along the critical junction between walls and the floor slab.