GRADING CRITERIA
Too steep or too flat is not good! A set of standards should be used to determine: • Minimum and maximum grades for given locations on a site • Maximum Vertical grade differences • Standard locations for low points and inlets • Strategies for grading parts of sites
CET-2030 Construction Graphics STANDARD SLOPES & GRADES Use this list as a guide to when grading a site •Min. 1% slope on site pavement (lots) to avoid puddling. •Max. 2% slope on pedestrian paths ~ ADA requirement •ADA Pedestrian Ramps – Max. 1”/ft = 8.33% Streets/Roads • Longitudinal: 4% Max., 0.40% Min. (curbed) 0.24% Min. (shoulders) • Cross-slope: Normal 3/16”/ft = 1.56% ≈ 0.016 (ODOT) • Mowed Slopes 3:1 Max.
CET-2030 Construction Graphics CONTROLLING ITEMS Building Pads •A building Finished Floor Elevation (FFE) represents a large level area around which the site needs to be graded
•FFE needs to be set to help balance the amount of cut & fill on site as well as to facilitate proper drainage
CET-2030 Construction Graphics BUILDING PADS - FFE Establishing FFE
FFE Fill
Set FFE at highest point resulting in a fill condition
Cut FFE
Set FFE at lowest point resulting in a cut condition
Cut FFE Fill
Set FFE at midpoint resulting in a combination of cut and fill
CET-2030 Construction Graphics BUILDING PADS Grading adjacent to building •¼” (0.02’) Max. drop/lip at doors – ADA •6” (0.5’) lower around building wall elsewhere
•Grade away from building to prevent water intrusion •Leave additional areas around building for: •Bench area on fill slopes •Swales in cut areas
Cut Slope Bench FFE Fill Slope Swale
CET-2030 Construction Graphics BUILDING PADS Positive drainage strategies
CET-2030 Construction Graphics BUILDING PADS What do you think?
CET-2030 Construction Graphics CONTROLLING ITEMS Parking Lots
•Minimum 1% from any point to inlet/catch basin (CB) •Prevents ponding (birdbaths) •Maximum 2%+ in stall areas •Helps car door control •Flexibility in design •Choose CB locations carefully
CET-2030 Construction Graphics CB LOCATIONS What do you think?
CET-2030 Construction Graphics CONTROLLING ITEMS Roads •Long constant grades (4% max., 0.40% min.) •Three main methods for cross-section design
3/16”/ft standard Normal Crown cross-slope
Allows for single CB in center of road Inverted Crown
• Used along buildings without low side curb • Used in boulevards Single Slope with medians
CET-2030 Construction Graphics SLOPE TO EXISTING • Slope required from proposed to existing ground • Slope could be down to existing (fill) or up to existing (cut)
Toe of slope Existing Grade
• Need to locate toe of slope at existing grade for grading limits • Found on plans using sections, contours, distance & slope calculation or CADD
CET-2030 Construction Graphics EXISTING TREES Leaving existing trees in place requires planning and accommodations • Roots grow out to and past drip line
• Roots need access to oxygen and water
• Covering or exposing roots can lead to tree damage
• Attempt to leave area beneath drip line at existing grade
• Max. 1’ up or down over roots
• Use wells or walls for protection
CET-2030 Construction Graphics EXISTING TREES What do you think?
CET-2030 Construction Graphics ATHLETIC FIELDS Fields Crown fields to drain to sidelines
Courts Slope courts to one side
Check with sport governing body for grading limitations
CET-2030 Construction Graphics ATHLETIC FIELDS What do you think?
CET-2030 Construction Graphics RETAINING WALLS Walls are used for connecting large differences in elevation where a steep slope is not desirable.
•Generally a max 2:1 slope is desirable •Toe of 2:1 slope would interfere with door •A wall becomes the best option
CET-2030 Construction Graphics RETAINING WALLS What do you think? Why did they do this??
CET-2030 Construction Graphics RETAINING WALLS
•Contour lines run along wall face
•End of wall treatment must be considered to avoid steep slope where wall ends
CET-2030 Construction Graphics RETAINING WALLS •What do you think?
CET-2030 Construction Graphics RETAINING WALLS •Top of wall should protrude 6” above upper elevation if wall is accessible from above •Walls accessible from above with greater than 30” elevation difference require a protective railing
CET-2030 Construction Graphics RETAINING WALLS What do you think? Does it need a railing? Is it safe?
CET-2030 Construction Graphics STAIRS Used to traverse elevation differences on a walkway.
Site Stair Convention •1 Tread + 2 Risers = 24” to 26” •6” Riser & 12” Tread or 5” Rider & 15” Tread •Top/bottom elevations can be ramped to get even tread riser combinations •Treads should have 1/8 “/ft slope for drainage •Railings as required by code
CET-2030 Construction Graphics ACCESSIBLE GRADING ADA requirements for accessible route to building must be followed.
•Must be at least one accessible route to entrance •Grading along route •Max. 5% longitudinal slope •Max. 2% cross-slope •Steeper than max is classified as a ramp!!!
CET-2030 Construction Graphics ACCESSIBLE GRADING Curb Ramps
•8.33% max slope on ramp (1”/ ft.) •5’ x 5’ Landing Area •10% max flares (if used) Curb also works in non-walk areas •Detectable warning surfaces to alert user to roadway edge
CET-2030 Construction Graphics ACCESSIBLE GRADING What do you think?
CET-2030 Construction Graphics ACCESSIBLE GRADING Ramps
•Any slopes on accessible path > 5% follow ramp rules •30” maximum rise per ramp segment •Slope vs. Distance travelled (run) by ADA •5’ x 5’ level landing areas required at top and bottom
CET-2030 Construction Graphics ACCESSIBLE ROUTES What do you think?
CET-2030 Construction Graphics