Thursday, August 2, 2012

Positive Drainage

Drainage away from your house and buildings is critical, and may require maintenance. Backfill against basements, grade beams and frost walls settle, removing drainage. Water will only run down a slope. Yup. A fellow engineer even forgot that. Oh well. The whole building drains to the elevator shaft, and the sump is just below basement floor level over one metre above the elevator shaft elevation.

The ABC building code requires a 150 millimetre vertical separation between any untreated wood and soil. This is essential to prevent rot, mould, from moisture wicking into the wood. In addition the first 1.5 metre away should drop another 150 millimetres. In new construction, we recommend 300 mms in 3 metres to allow for some settlement. Two percent is recommended beyond.

Now what do we do if there is not sufficient grade for drainage? Well, we weight for wet basements and insurance claims. Exterior sumps can be installed, usually to some depth below the weeping tile, and it may have weeping tile attached to pick up any surface ponding. These exterior sumps are high maintenance, as in this country, these pumps need to pulled out in the fall, and reinstalled in the spring, to control freezing conditions. The alternative is heat tape, insulation, and dealing with water in the winter, unless the sump goes dry. Now what about spring, when we have daily cycles of melting and thawing.

The simple solution is to allow enough grade for drainage.

Housing has become a commodity in some areas, rather than a life time investment. Many people have become detached from the care and maintenance of there houses.

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