Drainage for a Cement Deck

Slope the Concrete

• Concrete decks should slope away from the foundation of the home at a 1 percent slope. This amounts to about 1/8 inch per foot of deck or about 1/2 inch per 4 feet of deck. This provides enough slope for any rain that falls on the deck to run away from the foundation of the building.

Part of the Plan

• The water running off the cement deck must end up somewhere. Include landscaping that carries the water away from the home area and to the street curb and storm sewer system or other water accumulation area. Planters or furniture along the edge of the cement deck should allow the water to drain through and away from the deck.

Build the Forms

• Builders pour cement decks in place within wood forms. The slope of the forms translates to the final slope of the deck. Hold a 4-foot carpenter's level with one end resting on the form next to the building. Elevate the other end of the level until the bubble shows level. The lifted end of the level should be 1/2 inch above the form.

Maintaining the Slope

• If the ground next to the building settles after the cement deck is poured, the slope of the deck may change. Adding reinforcing rods to the cement forms before pouring the cement deck helps maintain the proper slope. Ideally, drill holes in the building foundation and insert the reinforcing rods into the hole. These rods extend into the deck slab and tie the deck to the foundation at the proper position.