Plan the perfect garden with our interactive tool →

How Much Should a Deck Slope?

Ryan McVay/Photodisc/Getty Images

Slope refers to the slant of construction projects like patios, concrete slabs and shower pans. This slant is important for one major reason: It ensures that the project keeps moisture or water from pooling and staying on flat surfaces, where it can leak down or cause dirt and mold problems. Sloping is a key part of deck construction, too; for most common decks, however, slope only pertains to part of the project.

Deck Slope

There is a difference between talking about the slope of the ground for a traditional deck, and the slope of the deck itself. The deck, the planks and boards that make its surface, should not be sloped. Not only is this difficult and unnecessary, but it can also be dangerous, making trips and falls easier. Moisture on a deck falls between planks on its own. It is the earth underneath that needs to be sloped.

Concrete Slope

A concrete deck or patio is the exception to the deck slope rule. In this case, there is nowhere for water to go, so the concrete should be slightly sloped to encourage runoff. This is especially important for poolside concrete decks that receive a lot of a water. Use your level and trowel to make these decks slope downward out to the grass or pool, about 1/4 of an inch for every foot of space.

  • There is a difference between talking about the slope of the ground for a traditional deck, and the slope of the deck itself.

Ground Slope

When building a traditional deck, you will need to slope the soil underneath the deck. It is this soil that collects the moisture, and you do not want the water pooling near your foundation. To this end, when preparing the surface for your deck, slope the ground away from the house about 1 inch for every 15 inches of space covered.

Ground Preparation and Measurement

When sloping the ground, remove all sod to keep it from holding in moisture. When you finish sloping the soil and compacting it, you can cover the ground with 6-millimeter polyethylene to provide even more moisture protection. This works well if your deck sides will obscure the earth beneath so the plastic cannot be seen.

Related Articles

How to Build a Sandbox With a Kid's Pool
How to Build a Sandbox With a Kid's Pool
Why Should You Put Gravel Under a Deck?
Why Should You Put Gravel Under a Deck?
How to Install Log Posts for a Log House Deck
How to Install Log Posts for a Log House Deck
How Thick Should an Asphalt Driveway Be?
How Thick Should an Asphalt Driveway Be?
Is it Bad to Rake a Yard If the Grass Is Wet?
Is it Bad to Rake a Yard If the Grass Is Wet?
How to Build a Patio Foundation
How to Build a Patio Foundation
How to Protect My Composite Deck Under a Fire Pit
How to Protect My Composite Deck Under a Fire Pit
Problems With Dirt Under the Deck
Problems With Dirt Under the Deck
How to Stop Moisture From Coming Up Through a Garage Floor
How to Stop Moisture From Coming Up Through a Garage...
How Much Deck Do You Need Around an Inground Pool?
How Much Deck Do You Need Around an Inground Pool?
The Advantages of Soil Compaction
The Advantages of Soil Compaction
DIY Drainage of Surface Water Around a Patio
DIY Drainage of Surface Water Around a Patio
How to Find the Depth of House Footers
How to Find the Depth of House Footers
How to Grow Grass on Hard Dirt & Rocks
How to Grow Grass on Hard Dirt & Rocks
How to Set Deck Posts in the Sand
How to Set Deck Posts in the Sand
How Does a Pool Sand Filter Work?
How Does a Pool Sand Filter Work?
How to Plant Grass After Removing a Spruce Tree
How to Plant Grass After Removing a Spruce Tree
Garden Guides
×