NM Landscape common mistakes
NM Landscape · Understand the traps and how to avoid them.
Sets finished-floor and spot elevations directly off the survey's benchmark and contour lines without first reading the survey legend, datum statement and benchmark description, and without confirming whether the datum is assumed or NAVD 88.
Base plans look authoritative and the datum/benchmark note is small-print boilerplate; candidates also assume the plotted PDF is still at true scale after being resized to fit a sheet.
What to do instead
Before any layout, write a one-line datum statement (benchmark ID, elevation, datum, source) at the top of your scratch sheet, and verify the drawing scale by measuring a dimensioned element or two known coordinates. Convert every given elevation into that single datum before calculating anything, and flag any contour interval or 'do not scale' note as a constraint.
Starts sketching a layout within the first minutes of a case-study item and answers programming questions from memory of similar projects rather than from the client's stated goals, user groups, budget, phasing and decision-makers.
The clock pressures candidates into producing a drawing, and the program is usually buried in prose rather than presented as a table, so it feels optional compared with the plan view.
What to do instead
Spend the first pass building two written lists: a program table (space, users, approximate area, adjacency, indoor/outdoor) and a goals/constraints list drawn word-for-word from the prompt. Then test each design move against the list and state in your answer which constraint drove which decision.
Carries a construction budget through the project without ever reconciling it: no unit-cost assumptions, no design contingency at schematic and design development, no escalation, and no stated scope that would be deferred or value-engineered if the estimate exceeds the budget.
Cost is treated as a number to be met rather than a design variable, and candidates rarely practise estimating landscape quantities such as paving square footage, tree counts, wall height per linear foot, and irrigation zones.
What to do instead
Build a simple quantity times unit-cost model and carry a design contingency (commonly around 10 percent at schematic, tapering to roughly 3-5 percent at construction documents) plus a separate construction contingency and escalation allowance. Reconcile at each phase and write the result as a short memo: budget, estimate, variance, and the specific scope adjusted.
Produces a concept plan that ignores the strongest inventory findings - the drainageway, the mature tree grove, the noise source, prevailing winter wind, afternoon sun - and leaves the bubble diagram unresolved so conflicting circulation lines are simply drawn over as final walks and drives.
Candidates treat analysis and design as separate exam items instead of a chain, and under time pressure they draw the first plausible parti rather than testing two or three against the site's constraints.
What to do instead
Overlay the constraint map on your own sketch: every high-value resource and every hazard should have a visible response (preserved, buffered, crossed at a specific point, or used as a focal element). Resolve circulation conflicts explicitly - separate pedestrian and vehicle routes, show the crossing, and annotate how a pedestrian gets from parking to entry without crossing a service drive.
Lays out walks, ramps, plazas and building entries without verifying accessible route geometry - running slope steeper than 1:12, cross slope over 1:48, a ramp run exceeding 30 inches of rise with no landing, landings shorter than 60 inches, or a route that dead-ends at a curb with no curb ramp.
Accessibility is checked as a documentation box at the end rather than as a design generator, and the arithmetic of slope and rise is easy to skip when concentrating on composition.
What to do instead
Check the accessible route as a continuous path, not as isolated features: measure maximum running slope and cross slope, count ramp runs against the 30-inch rise limit, size landings, and confirm each level change and curb line has a ramp or lift. Annotate slopes on the plan in percent or ratio so the reviewer can see the check was done.
Submits a plan, section and detail set that contradict each other - a retaining wall dimensioned at 30 inches on plan but drawn at 42 inches in section, a pipe invert that does not match the spot elevation at the structure, or a wall cap shown in the detail but omitted from the wall schedule.
Elements are drawn once and copied without a reconciliation pass, and candidates work sheet by sheet rather than by system (grading, walls, planting, utilities).
What to do instead
Do a system-by-system cross-check before finishing: pick one controlling dimension or elevation per system (wall height, pipe invert, finish floor, top of curb) and trace it through plan, section, detail and schedule. Where two drawings deliberately differ, note why on the drawing. Any copied detail must be edited to match the project's actual dimensions and materials.
Draws construction details that cannot be built: no footing depth or width, no edge restraint, no drainage layer or weep points behind a wall, and no material test standard - for example specifying 'compact to 95 percent' without naming the test method, or 'topsoil' with no depth or pH requirement.
Candidates reproduce a familiar detail shape from memory and focus on the visible upper portion (cap, paving, planting), leaving the below-grade and quality-assurance information that actually controls construction unspecified.
What to do instead
For every detail, ask what a contractor would have to guess and answer it: dimensions and tolerances, depths below grade and frost depth, connection and restraint, drainage path and outlet, and the referenced test or standard (for example Standard Proctor ASTM D698 versus Modified Proctor ASTM D1557, topsoil depth and pH range, mulch depth). Put the soil and compaction requirements in the specification as well as the detail.
Assembles a bid or construction administration package with missing procedural documents - no bid form or unit-price schedule, no stated addenda cut-off, no substitution or RFI procedure - and uses addendum, change order and bulletin interchangeably when advising the client on a mid-construction change.
Attention goes to the drawings and technical specifications, while the procedural front end of the manual (bidding requirements, general conditions, contract forms) reads as boilerplate that is never tested until it is tested on the exam.
What to do instead
Know the sequence and the instrument for each purpose: an addendum modifies the bid documents before bids are opened and is issued to all bidders; after award, a change order modifies the contract by agreement, a construction change directive orders work before price is settled, and an RFI clarifies without changing the contract. Check that the package includes invitation, instructions to bidders, bid form, bid security, sample contract, general and supplementary conditions, and technical specifications.
Confuses slope notation and placement of spot elevations - labels a 2:1 slope as 2 percent, converts a ratio to percent by shifting a decimal, and either interpolates a single spot midway down a uniform slope instead of locating spots at grade breaks, or computes run along an oblique plan line rather than the horizontal distance along the direction of flow.
Both notations appear on the exam and in real drawings, and the conversion is done mentally under time pressure; spot elevations are treated as decoration rather than as control points that a contractor sets grade from.
What to do instead
Write the conversion every time: percent equals rise divided by run times 100, so 1 foot in 50 feet is 2 percent while 2:1 is 50 percent. Place spot elevations at every grade break - flowline, top and bottom of wall, back of walk, edge of pavement, inlet rim and throat, building threshold - and use the horizontal distance measured along the drainage or travel path as the run, not the diagonal between two spots.
Sizes a stormwater management facility by multiplying peak flow by a storm duration and calling that the storage volume, then leaves the design with no emergency overflow, no freeboard above the design water surface, and no statement of where the overflow goes or how off-site flow entering the site is handled.
The rational method gives a peak discharge, not a volume, and candidates mistake one for the other; overflow and off-site drainage are the parts of a facility that are never drawn on a typical grading plan.
What to do instead
Separate the two computations: use the peak-flow method to size conveyance, and derive storage from the difference between inflow and allowable release over the storm duration (or a routing calculation) so the stored volume is explicit. Show the allowable release rate, the design storm, freeboard (commonly about 1 foot), an emergency overflow set below the lowest building opening, a defined discharge point that does not send water onto a neighbour, and the path for off-site flow crossing the property.