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 is simply applying a thin layer of mortar to the foundation walls.
There are debates out there saying that tanking is an effective method of preventing water and moisture from entering your basement. This is only partially true. It's important to remember that like most masonry materials, the mortar used for tanking is porous and it will absorb and release moisture. Even if noticeable water isn't leaking through cracks in your basement wall, the thin mortar coat will absorb moisture from the soil outside the foundation. That moisture will then "weep" into your basement..
Tanking is supposed to work by holding back water that is saturating the soil and collecting around your basement foundation. When the soil is full of water as a result of wet weather, basement walls and floors are subject to high levels of hydrostatic (water) pressure. Think of your foundation as the hull of a boat. Except, unlike the hull of a boat, mortar does not flex under pressure. So cracks in a thin coat of protective, "tanking" mortar will undoubtedly appear. And that pressurized water coming in through those cracks in the mortar will lead to a flooded basement.
At Basement Systems UK, we advise homeowners to keep basements and cellars dry with our patented WaterGuard® system. The WaterGuard® system is a concealed drainage channel we install inside your foundation walls. Instead of allowing that hydrostatic pressure to build by attempting to hold water back, our WaterGuard® system allows water to drain to a sump pump, where it can be pumped away from the foundation. Our WaterGuard® drainage channel is made from strong, durable plastic that won't corrode, clog or break. It's a failsafe way to collect any water that leaks through the walls or between walls and the floor slab.