HI Landscape cheat sheet

Concept plan → schematic design → design development → construction documents: each phase narrows scale; CDs are typically drawn at 1/8 in = 1 ft for planting and 1 in = 20–50 ft for layout.

Scale formulas: scale factor = drawing length ÷ real length. A 1:100 plan means 1 cm on paper equals 100 cm (1 m) on site.

Circulation rule: main walks 5 ft (1.5 m) minimum for two people passing; secondary paths 3 ft (0.9 m); service access 8–10 ft for vehicles.

Outdoor room proportion: comfortable enclosure height-to-width ratio is roughly 1:2 to 1:3; ratios beyond 1:6 read as open field, below 1:1 as confining.

Planting design layers: canopy, understory, shrub mass, groundcover/herbaceous; design intent usually specifies 60–70% evergreen structure in cold climates for winter presence.

Bubble diagrams and overlays (slope, sun, wind, views, circulation) come before form; a site analysis overlay set is the standard defensible basis for layout decisions.

Sun angles: at solar noon, altitude = 90° − latitude + solar declination. Use summer vs winter noon angles to size overhangs and shade structures.

Accessibility: ADA-accessible routes need 36 in (915 mm) clear width minimum, 60 in (1525 mm) passing spaces every 200 ft, and slopes ≤1:20 without handrails.

Right plant, right place: match USDA hardiness zone, AHS heat zone, soil pH, drainage class, and light exposure before aesthetic criteria.

Soil texture triangle: sand >0.05 mm, silt 0.002–0.05 mm, clay <0.002 mm. Loam ≈ 40% sand, 40% silt, 20% clay is the horticultural target.

pH availability: iron and manganese lock out above pH 7.0–7.5 (chlorosis); phosphorus locks out below pH 5.5; most landscape plants prefer pH 6.0–7.0.

Nursery stock grades: B&B (balled and burlapped), container, bare root. Caliper measured 6 in above grade for trees; root ball diameter ≈ 10–12 in per inch of trunk caliper.

Planting hole: 2–3× root ball width, same depth as root flare; do not amend backfill heavily - differences in texture create a bathtub effect.

Watering establishment: roughly 1 in (25 mm) per week for the first 1–2 growing seasons; deep infrequent irrigation builds deeper roots than daily light cycles.

Invasive risk screening: check regional noxious weed lists and native plant society guidance; cultivars of invasive species can still be regulated.

Spacing: use mature spread, not nursery size. Groundcover plugs at 12–18 in on center typically close canopy in one to two seasons.

Base aggregate: compacted crushed stone in lifts ≤6 in (150 mm) to 95% Standard Proctor; paver base typically 4 in for pedestrian, 6–8 in for vehicular.

Bedding sand: 1 in (25 mm) for pavers, screeded, never used as structural base. Concrete bedding for unit pavers uses 1–1.5 in mortar over 4 in slab.

Concrete: 4 in slab with welded wire or fiber for walks; 5–6 in for driveways; air-entrained 4,000–4,500 psi in freeze-thaw climates; control joints at 1.5–2× slab thickness in feet.

Subgrade slope for drainage: 1–2% away from structures; hardscape surfaces 1–2% cross slope; ADA max running slope 1:20 (5%), cross slope 1:48 (2%).

Retaining walls: gravity walls rely on mass; cantilevered walls use reinforced stem plus footing. Rule of thumb: geogrid every 2 courses on segmental walls over 3–4 ft.

Mortar and grout types: Type S for moderate exposure, Type N for above-grade non-load-bearing; polymeric sand for unit pavers with 1/8–3/16 in joints.

Freeze-thaw: use air-entrained concrete (5–7% air), avoid deicing salts on new concrete for the first year, and specify frost-depth footings.

Timber and decking: pressure-treated ground contact rated for soil contact; joist spacing 16 in o.c. for 5/4 decking, 12 in for diagonal layouts.

Precipitation rate formula: PR (in/hr) = 96.25 × GPM ÷ area (ft²). Match PR across zones to avoid wet/dry striping.

Application rate must not exceed soil infiltration rate. Sandy soils accept 1–2 in/hr; clay accepts 0.1–0.3 in/hr; cycle-and-soak is required on clay.

Distribution uniformity (DU) governs scheduling: low-quarter DU below 0.6 means large dry spots; schedule to the driest quarter, not the average.

Hydrozones: separate valves by plant water use, sun exposure, soil, and emitter type; never mix turf and shrubs on one valve.

Drip: 0.5–2.0 GPH emitters typical; pressure-compensating emitters require 15–40 psi operating range; filtration 100–200 mesh for drip.

Backflow protection: required by code; PVB for non-toxic, RPZ for high-hazard or toxic connections; test annually.

Controller: smart controllers use ET or soil moisture. Seasonal adjust should follow local ET minus effective rainfall.

Surface drainage: sheet flow, swales, and catch basins. Minimum swale slope 1–2%; pipe slope 0.5% minimum, 1% preferred; 4 in pipe serves roughly 1,000–2,000 ft² of roof at 1 in/hr.

Contour interval: the vertical distance between contours. Closely spaced contours = steep slope; widely spaced = gentle slope.

Slope formula: S (%) = (rise ÷ run) × 100. A 1 ft rise over 20 ft run = 5%.

Spot elevations and contour labels are the primary grading communication; spot elevations at all grade breaks, structures, and inlets.

Cut and fill balance: sum cut and fill volumes across the site; balanced sites minimize haul cost. Use average end area or prismoidal method.

Soils: identify hydric soils, seasonal high water table, and permeability via percolation or infiltration tests before designing infiltration facilities.

Stormwater: 1 in of rain over 1 acre = 27,154 gallons (≈ 43,560 ft² × 1/12 ft). Rational method Q = CiA for peak flow.

Buffer and setback: preserve tree protection zones (TPZ) at roughly 1 ft radius per 1 in trunk diameter, minimum 6 ft.

Erosion control: silt fence, inlet protection, and stabilized construction entrance are minimum BMPs; sequencing is critical (install before disturbance).

Quantity takeoff: measure from scaled plans, apply waste factors (typically 5–10% for pavers, 10% for plant material, 5% for concrete).

Unit costs: material + labor + equipment + overhead + profit. Markup on cost vs margin on price are different - margin = markup ÷ (1 + markup).

Contingency: 5–10% for design-bid-build, 10–20% for early schematic estimates.

Critical path method (CPM): longest path through the network determines project duration; float = late start − early start.

Change orders: written authorization required before work; track time and material with daily field records.

Retainage: commonly 5–10% held until substantial completion; release tied to punch list closure.

Schedule logic: planting windows, concrete cure, and permit review drive sequencing. Weather days must be built into the baseline.

Bid documents: drawings, specifications, general conditions, addenda. Bid leveling compares scope, exclusions, and alternates.

OSHA construction: 6 ft fall protection trigger for general industry, 6 ft in construction for unprotected sides and edges; guardrails at 4 ft height.

Excavation: protective system required at 5 ft depth; spoil pile and equipment kept at least 2 ft from the edge; ladder every 25 ft of lateral travel.

Hazard communication: SDS on site for every chemical; PPE matched to SDS requirements; silica dust controls (water, ventilation, respirators) for concrete and stone cutting.

Underground utility locate: call 811 before digging; respect color codes (red electric, yellow gas, blue water, orange communications, green sewer).

Pesticide and fertilizer application: licensed applicator, label is the law; posting and re-entry intervals must be observed.

ADA and local codes: accessible routes, ramps with 1:12 max slope, handrails at 34–38 in, landings every 30 in of rise.

Stormwater permits: NPDES Construction General Permit for disturbances ≥1 acre; SWPPP required with inspections.

Tree protection: fencing at TPZ, no storage or grading within the zone; violations can trigger fines and tree replacement requirements.