Landscape architecture · field & studio reference

Site Desk

Grading, earthwork, walls, stairs and ramps, planting, irrigation and stormwater, with the rules of thumb behind them. Always confirm against the governing code and the project's civil and geotech reports.

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Grading

Slope, spot elevations and contour spacing

Slope from rise and run

Enter the elevation change and horizontal distance.

Percent
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Ratio H:V
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Degrees
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Spot elevation along a slope

Find the elevation at a set distance from a known spot.

Change
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End elevation
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Contour spacing on plan

Horizontal distance between contours for a target slope.

On ground
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On sheet
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Earthwork & walls

Cut and fill balance, segmental retaining walls

Cut and fill

Split the site into areas of roughly uniform change. For each, enter its plan area and the average existing and proposed elevations (average the grid corners). Shrinkage adds the extra soil needed to reach compacted fill.

Cut
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Fill (compacted)
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Fill + shrinkage
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Net
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Segmental retaining wall

Dry-stacked block (SRW) quantities and a first pass at embedment, base and geogrid. Gravity height limits vary by block system; use the manufacturer's charts.

Buried depth
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Courses
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Total height
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Blocks (+5%)
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Caps
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Trench depth
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Base gravel
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Drain aggregate
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Geogrid
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Steps & ramps

Exterior stairs and accessible routes

Exterior stair

Checks the 2R + T = 26" comfort rule (±1"). Outdoor stairs feel best with risers around 5–6" and deep treads.

Risers
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Actual riser
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Tread
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Total run
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Accessible ramp

2010 ADA Standards: 1:12 max running slope, 30" max rise per run, 60" landings at top, bottom and between runs.

Runs
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Ramp length
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Mid landings
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Overall length
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Planting

Quantities and soil for trees

Plants per bed

Triangular spacing fits about 15% more plants than square at the same on-center distance.

Plants
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Area / plant
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Tree soil volume

Common target: about 2 cf of loose, uncompacted soil per sf of mature canopy projection.

Soil volume
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Plan area needed
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Square side
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Native palette

Plants native to the North Carolina Piedmont

–F full sun · P part · S shade  |  D dry · M medium · W wet

    Bloom times are typical for the Piedmont and shift a few weeks with the season. Confirm availability and site fit with the NCSU Extension Plant Toolbox or a local native nursery.

    Project plant list

    Plants you add are kept on this device. Copy the list into a schedule or email.

      Materials

      Takeoffs for mulch, soil, stone and pavers

      Bulk volume

      Mulch, topsoil, aggregate base. Waste factor covers settling and spillage.

      Volume
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      Order
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      Weight
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      Unit pavers

      Count by face size. Add 5% for straight layouts, 10–15% for diagonal or curved edges.

      Pavers per area
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      Order
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      Irrigation

      Precipitation rate, run times and drip layout

      Spray or rotor zone

      PR = 96.25 × total GPM ÷ zone area. Assumes head-to-head coverage. Keep zone flow under the supply's safe flow (about 75% of meter capacity).

      Zone flow
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      Precip. rate
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      Run time / day
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      –

      Inline drip grid

      PR = 231.1 × emitter GPH ÷ (emitter spacing × row spacing, in inches). Typical grid is 12–18" each way.

      Tubing
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      Emitters
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      Zone flow
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      Precip. rate
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      Run time / day
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      Stormwater

      Peak flow, bioretention and roof harvest

      Rational method, Q = CiA

      For small drainage areas, typically under about 200 acres. Use the local IDF curve for intensity.

      Area
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      Peak flow
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      Same flow
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      Weighted C

      Area-weighted coefficient for a mixed site. Feed the result into Q = CiA.

      Weighted C
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      Total area
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      Bioretention / rain garden

      Sizes the ponding area to hold the design storm's runoff. Many states, NC included, use a 1" water-quality storm; check the state manual for credit rules.

      Runoff volume
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      Surface area
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      % of drainage
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      Drawdown
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      Roof rainwater harvest

      1 inch of rain on 1 sf yields 0.623 gallons.

      Captured
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      Typical bioretention section, top to bottom
      LayerDepthNotes
      Ponding6–12"NC caps ponding at 12". Overflow structure or spillway set at ponding elevation.
      Shredded hardwood mulch2–3"Double-shredded; floats less than pine bark.
      Planting media24–36"Sandy, low-fines mix with a little organic matter. 3' where trees and shrubs are planted.
      Choking / transition layer2–4"Washed sand or #78 stone between media and storage stone, often instead of filter fabric.
      Storage stone with underdrain12"+#57 stone around a perforated pipe. Needed where soils infiltrate under about 0.5 in/hr.

      Standards

      Rules of thumb to start a design from. Tables are in U.S. units.

      Slope guidelines by surface and use
      Surface / useMinPreferredMaxNotes
      Accessible route, running slope—≤ 2–3%5% (1:20)Steeper than 5% is a ramp under ADA.
      Accessible route, cross slope1%1.5%2% (1:48)Allow construction tolerance below 2%.
      Accessible ramp—1:14–1:168.33% (1:12)30" max rise per run; handrails both sides if rise > 6".
      Accessible parking / passenger loading—1.5%2%Any direction.
      Plazas, terraces, paved patios1%1.5–2%3%Pitch away from buildings.
      Concrete gutters / valley swales0.5%1%—Flat gutters pond; check with a level string.
      Lawn, active play1–2%2–3%5%Sports fields often crowned at 1–1.5%.
      Lawn, general / mowable1–2%2–10%25% (4:1) – 33% (3:1)3:1 is the usual mower limit.
      Grass swales1–2%2–4%~6%Above that, armor or check dams to limit velocity.
      Planted slopes, groundcover—≤ 33% (3:1)50% (2:1)Erosion blanket on anything steeper than 3:1.
      Away from building foundation5% for 10 ft——IRC R401.3: 6" of fall in the first 10'; 2% min for impervious.
      Runoff coefficients (C), rational method
      SurfaceC range
      Roofs0.75–0.95
      Asphalt0.70–0.95
      Concrete0.80–0.95
      Brick / unit pavers (sand joints)0.70–0.85
      Gravel drives and walks0.15–0.35
      Permeable pavers, porous paving0.10–0.40
      Lawn, sandy soil, flat (< 2%)0.05–0.10
      Lawn, sandy soil, average (2–7%)0.10–0.15
      Lawn, sandy soil, steep (> 7%)0.15–0.20
      Lawn, heavy clay soil, flat (< 2%)0.13–0.17
      Lawn, heavy clay soil, average (2–7%)0.18–0.22
      Lawn, heavy clay soil, steep (> 7%)0.25–0.35
      Woods and established planting beds0.05–0.25
      Circulation widths and clearances
      ElementDimensionNotes
      Accessible route, clear width36" minPassing spaces 60" × 60" at most every 200'.
      Two people side by side / passing wheelchairs60"Comfortable minimum for a main walk.
      Primary public walk6–10'Wider at entries and plazas.
      Shared-use path, two-way10–12'Plus 2' graded shoulders (AASHTO).
      Vertical clearance, walks80" minWatch tree limbs and signs.
      Vertical clearance, bike paths8–10'10' preferred.
      Standard parking stall9' × 18'Local codes vary widely.
      Accessible stall + aisle8' + 5' aisleVan: 11' + 5' or 8' + 8'.
      Handrail height, ramps and stairs34–38"Extend 12" beyond top and bottom of ramps.
      Guard height (drop > 30")36–42"IBC 42" for commercial; check residential code.
      Root ball size and planting pit (after ANSI Z60.1, shade trees)
      CaliperMin. ball dia.Pit width (2–3×)
      1"16"32–48"
      1½"20"40–60"
      2"24"48–72"
      2½"28"56–84"
      3"32"64–96"
      4"42"84–126"

      Set the root flare at or just above finished grade. Pit depth equals ball height so the ball sits on undisturbed soil. Remove burlap and wire basket from the top third at minimum.

      Conversions and drawing scales
      QuantityEquals
      1 acre43,560 sf · 0.405 ha
      1 hectare2.471 ac · 107,639 sf
      1 cubic yard27 cf · 0.765 m³
      1 cubic foot of water7.48 gal · 62.4 lb
      1 cfs448.8 gpm · 28.3 L/s
      1" rain on 1,000 sf623 gal
      Engineer's scale 1" = 20'1:240
      Engineer's scale 1" = 40'1:480
      Architect's scale ⅛" = 1'-0"1:96
      Architect's scale ¼" = 1'-0"1:48
      Architect's scale ½" = 1'-0"1:24 (details)

      Plan key

      Plant schedule conventions and site plan labels

      Plant schedule
      TermMeaning
      QP / QUE PHEPlant key: first letters of genus and species (Quercus phellos).
      Cal.Caliper. Trunk diameter 6" above grade up to 4" caliper, 12" above grade for larger trees.
      Ht. / Spr.Height / spread. Used for shrubs, evergreens and multi-stem trees.
      #1, #3, #7, #15Trade container sizes. A #1 is a "1 gallon" pot that holds somewhat less than a gallon.
      B&BBalled and burlapped, field-dug.
      CG / BRContainer grown / bare root.
      MS / SSMulti-stem / single stem.
      O.C.On center spacing.
      Plug / flatSmall plants grown in cell trays, often 32, 50 or 72 per flat.
      'Cultivar'Cultivar names go in single quotes, not italic. spp. = several species, var. = variety, × = hybrid.
      SpecimenSelected for superior form; often tagged at the nursery by the designer.
      Site plan labels
      LabelMeaning
      EG / FGExisting grade / finished grade.
      FFEFinished floor elevation.
      TW / BWTop of wall / bottom of wall, at finished grade on the exposed face.
      TC / BCTop of curb / bottom of curb (gutter line).
      TS / BSTop of stair / bottom of stair.
      HP / LPHigh point / low point.
      INV / RIMPipe invert (inside bottom) / top of structure grate or lid.
      MEMatch existing.
      LODLimit of disturbance.
      DBHDiameter at breast height, 4.5' above grade, for existing trees.
      CRZCritical root zone. Commonly 1–1.5' radius per inch of DBH.

      Resources

      Primary sources worth bookmarking

      2010 ADA StandardsU.S. Access Board guide, with the outdoor developed areas chapter. USDA Plant Hardiness Zone MapZone lookup by ZIP code (2023 map). NRCS Web Soil SurveySoil series, drainage class and hydrologic soil group for a site. NOAA Atlas 14 rainfallPrecipitation frequency and intensity data for i in Q = CiA. NCSU Extension Plant ToolboxPlant profiles with native range, site needs and photos. NC Stormwater Design ManualNCDEQ minimum design criteria for bioretention and other SCMs. Native Plant DatabaseLady Bird Johnson Wildflower Center, searchable by state. SITES rating systemSustainable site design and performance benchmarks. Landscape Architecture FoundationLandscape Performance Series case studies. ASLAProfessional practice, licensure and continuing education. CLARBL.A.R.E. exam and state licensure requirements.