Minimum Slope for Lawn Areas Near Building

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omarfernandez

April 26, 2025 23:02

What is the minimum grade slope on lawn areas to consider? 

As per my understanding, it is 5 percent minimum grade for the first 10 feet away from the building perimeter (with a minimum 8 inches drop at the foundation) and then a minimum of 2 percent after the 10 feet away from the building. 

Planning book stated that 2 percent is correct but other resources state 5% away from the building structure is the correct one. Please clarify. 

 

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  omarfernandez April 29, 2025 01:49

  According to the Ballast chart, the minimum slope next to the building should be 2%. Should I stick with 2%, or would it be better to use 5% minimum for the first 10 feet away from building? Please clarify. 
  

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  orhale May 09, 2025 21:54

  Hi Omar, 
  
  You want to slope the ground away from the building so that rain falling from the building's roof and near the building doesn't pond near the building or flow toward the foundation.  I've seen both 2% and 5% (1 inch in 50 inches or 2 feet in 100 feet) and (1 inch in 20 inches or 5 feet in 100 feet) as recommended percentages, it really depends on the local soil and climate as to which is the minimum slope away from the structure - wetter climates with expansive clays will require more slope, drier climates with well-draining soils won't be as restrictive.  
  
  For the ARE, I wouldn't expect to have to know which percentage is best, but I would expect to need to know that the ground should slope away from the building, not toward the building and not level around the building.  
  
  Best,
  Ralph, the Amber Book Team

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