AR Landscape common mistakes
AR Landscape · Understand the traps and how to avoid them.
Setting spot elevations by adding a uniform round-number increment across a paved area instead of multiplying each horizontal run by the design slope and applying the correct up/down direction from a fixed control point.
Candidates treat slope as a whole-number step rather than a ratio, and lose track of which direction is uphill, so the arithmetic looks tidy but the surface drains to the wrong place.
What to do instead
Before computing, write the slope as a decimal (2% = 0.02) and label one control elevation with a direction arrow. Compute each elevation as control ± (run × slope), then close the loop by checking that contour spacing matches the intended slope, since spacing = contour interval ÷ slope.
Choosing a storm pipe or swale size from a chart using drainage area alone, ignoring slope, roughness, and the time of concentration.
Area-only shortcuts feel fast under exam time pressure, and the candidate has not practiced linking the rational method to a capacity check for the proposed geometry.
What to do instead
Compute peak flow with Q = CiA, then verify capacity with Manning's equation using the actual proposed slope and roughness for the chosen section. If capacity is short at the available slope, adjust the section or grade rather than forcing a smaller pipe; state the assumption when data is missing.
Going straight to a bubble diagram and layout before mapping site constraints, so the design responds to program alone and later collides with easements, steep slopes, or existing drainage patterns.
Design feels like the productive part of the exam, and sketching early relieves anxiety, but unresolved inventory data resurfaces as unfixable conflicts in the final plan.
What to do instead
Build a constraint-and-opportunity overlay first: slopes over the developable threshold, drainage ways, setbacks, easements, tree protection zones, and solar orientation. Grade each as a hard limit or a negotiable factor, and test every program element against the overlay before drawing it.
Calculating slope from a contour map using a scaled distance measured across the wrong interval, or counting contour lines rather than intervals, producing a gradient off by a factor of two or more.
Candidates confuse lines with intervals and forget to convert the graphic scale to feet before dividing, and the error propagates silently into every later grading decision.
What to do instead
Use slope = contour interval ÷ horizontal distance, where distance is measured perpendicular to the contours between two adjacent lines counted as one interval. Convert the scaled distance first, and sanity-check the result against the contour spacing pattern, where tight lines mean steep ground.
Laying out walks, ramps, and landings without checking running slope, cross slope, landing length, or turning space against accessibility criteria.
The layout reads well graphically, and dimensional code checks get deferred to documentation, but by then the grading and wall heights are locked in and the fix is expensive.
What to do instead
Keep a dimensional checklist taped to the workspace: maximum running slope, maximum cross slope, required landing size and spacing, clear width, and handrail triggers. Run every pedestrian route through the checklist at schematic stage, before vertical elements are set, and annotate slopes directly on the plan.
Designing a planting plan that lists species by appearance only, without matching exposure, soil moisture, mature size, or maintenance regime to the actual site conditions.
Plant selection is often prepared last, from memory of attractive species, and the candidate does not cross-reference the inventory data on sun, drainage, and soil that was already gathered.
What to do instead
Tabulate microsite conditions from the inventory, then screen each species against hardiness, light, moisture tolerance, mature canopy and root spread, and salt or drought exposure. Place plants at mature size, not nursery size, and note spacing and quantities so the plan is buildable.
Issuing a design clarification or field instruction directly to the contractor without routing it through the owner's representative and the contractual change process.
The candidate answers the situational question as a helpful designer rather than as a party to a contract, forgetting that direct communication can waive review rights and create unfunded scope.
What to do instead
Recall the standard chain: contractor to architect or landscape architect to owner, with changes documented in writing as a proposal request, change order, or supplemental instruction. When a question describes a verbal direction at a site meeting, the correct response is to document and route it, not to act on it.
Approving a substitution, pay application, or shop drawing without checking it against the specification section, the schedule of values, and prior approvals.
Review tasks look administrative, so candidates skim for completeness instead of comparing the submittal against the stated criteria and the contract sum breakdown.
What to do instead
For each submittal, name the governing specification section and the specific attributes to verify, then check quantities and percentages against the schedule of values. A substitution is only approvable if it meets or exceeds the specified performance criteria, and the stamp used must reflect the actual scope of review.
Producing plan dimensions, spot elevations, and detail callouts that disagree with each other, so the contractor cannot determine which value governs.
Drawings are assembled element by element under time pressure, and the candidate never performs a consistency pass across plan, section, and details or between graphic and written notes.
What to do instead
Do a dedicated coordination pass: reconcile every dimension to the stated scale, verify that spot elevations match the contour logic, and confirm that detail callouts appear in the detail sheet set. Establish and state a governing hierarchy where conflicts are possible, and remove duplicate dimensions rather than repeating them.
Submitting a grading and utility plan without erosion and sediment control measures, construction sequencing, or stormwater notes, relying on the plans to imply the intent.
Candidates focus on the finished condition and forget that construction-phase requirements are part of the documentation deliverable, not an optional add-on.
What to do instead
Before closing the set, check for a site protection and sequencing plan, limits of disturbance, silt fence or inlet protection locations, temporary stabilization notes, and stormwater management notes keyed to the approved calculations. Written general notes carry requirements that drawings alone cannot enforce.