CSLB C-27 Landscaping Trade Exam Study Guide (2026)

Two contractors bid the same backyard. One prices the work, signs a one-page proposal, takes half down, and starts trenching Monday. The other prices the work, writes a contract with the required cancellation notice, collects a legal deposit, hires an electrician for the new 120-volt circuit, and calls the notification center days before the dig.

Both can build a beautiful yard; only the second is protecting her license.

This section is where paperwork meets arithmetic, and it is a little under a fifth of the exam. Its questions come in three kinds: can I legally do this job and contract for it, can I read what the designer drew and fill in what the plan leaves open, and what does it cost. The chapter follows the same order.

1.1 What the C-27 License Authorizes

The C-27 classification is defined at 16 CCR §832.27, and the whole definition is one sentence of substance. A landscape contractor constructs, maintains, repairs, installs, or subcontracts the development of landscape systems and facilities for public and private gardens and other areas designed to improve the grounds within or surrounding a structure or a tract or plot of land, whether aesthetically, architecturally, horticulturally, or functionally. In connection with that work, the landscape contractor prepares and grades plots and areas of land for the installation of any architectural, horticultural and decorative treatment or arrangement.

Three phrases do most of the work on the exam:

"Landscape systems and facilities." The regulation does not list them. The list below is the working understanding of the trade and of this exam's six sections: irrigation, drainage, planting and turf, landscape lighting, decorative water features, and the hardscape that makes a yard usable (flatwork, masonry, posts and fences, retaining walls).

"Prepares and grades plots and areas of land." Grading for landscape purposes is inside the classification. A question that pairs "grading and preparing a yard for decorative treatment" against three obviously foreign trades has a clean C-27 answer.

"Or subcontracts." The classification anticipates that you will run jobs containing work outside it and hire licensed subcontractors for that work. B&P §7059 supports this: a specialty contractor may take and execute a contract involving two or more crafts if the work in the other crafts is incidental and supplemental to the work in the craft the contractor is licensed for. Subcontracting is not weakness. It is the mechanism the licensing law gives you. Note the test, though. "Incidental and supplemental" is a limit on how much of the contract can be work outside your classification, not a license to do it yourself because it came up.

B&P §7058(a) describes a specialty contractor as one whose operations involve construction work requiring special skill and whose principal contracting business involves specialized building trades or crafts. That is why a license exam in a specialty trade spends so much time on where the specialty ends.

1.2 Where the C-27 Line Is: Boundaries That Get Contractors Cited

Scope questions appear in every chapter, and candidates miss them because the wrong answer feels reasonable on a job site. "The trench is already open." "It's only fifty feet of cable." "It's in the landscape area." None of those extends a classification.

The boundaries below are the ones the exam keeps returning to. They are the author's reading of the §832.27 wording ("landscape systems and facilities") and of how scope questions are built, not text quoted from a regulation. Where the line between two classifications is a close call on a real job, call CSLB and ask; the exam, though, will always give you the clean case.

Electrical. The dividing idea is line voltage versus low voltage. Setting a low-voltage landscape-lighting transformer that plugs into an existing, code-compliant exterior receptacle, and running low-voltage cable to the fixtures, is landscape work. Running 24-volt valve wire from a controller to a solenoid is landscape work. Installing a new 120-volt branch circuit, adding a receptacle, or setting a subpanel is electrical work, however short the run, whether or not you sleeve it in conduit, whether or not an inspector will look at it later. If the new controller or transformer location has no power, the answer is a licensed electrical contractor.

Plumbing and the point of connection. Your irrigation system begins at the point of connection on the water service. Everything downstream (mainline, backflow assembly, valves, laterals, heads, drip) is landscape work. The potable water service that feeds the building, and the plumbing inside it, is not. When a homeowner watches your crew trench for irrigation and asks you to replace the corroded service line from the meter to the house, decline or subcontract it. An open trench is a fact about the job.

Engineered structures. A low garden wall holding landscape soil is landscape work. A retaining wall tall enough, or loaded enough, to need an engineered design and a building permit under the California Building Code is a structural question. The height at which that happens, and the effect of a surcharge such as a driveway or slope behind the wall, are set by the building code your local jurisdiction has adopted. This book did not read the 2025 California Building Code and prints no threshold; your reference book and your local building department give it. The principle is stable even though the number is not: when a wall needs engineering, you obtain the engineered design and the permit and build to it, or you subcontract it. An owner's waiver does not remove a code obligation, and stacking short terraces to dodge the threshold fails when the upper wall loads the lower one.

Other classifications. The licensing scheme has separate classifications for trades that a landscape job often touches, and the definitions are short enough to read yourself (16 CCR §832, as printed in the CSLB law book). C-53 Swimming Pool Contractor constructs swimming pools, spas, or hot tubs. C-39 Roofing Contractor installs products and repairs surfaces that seal, waterproof, and weatherproof structures. C-49 Tree and Palm Contractor plants, maintains, and removes trees and palms, including pruning, stump grinding, and tree, palm, or limb guying; the regulation became operative January 1, 2024. And three hardscape trades have their own classifications: C-8 Concrete (forms, pours, places, and finishes mass, pavement, flat and other concrete work), C-13 Fencing (fences, railings, posts, flagpoles, and gates, excluding masonry walls), and C-29 Masonry (installs concrete units, clay products, block, natural and manufactured stone, with or without mortar, including masonry walls and fences, and paving). C-10 Electrical covers placing, installing, or connecting any electrical wires, fixtures, apparatus, raceways, or conduits that generate, transmit, transform, or use electrical energy.

Two consequences. First, the C-27 exam tests how to build flatwork, masonry, fences, and walls because they are part of the grounds a landscape contractor improves; but the existence of C-8, C-13, and C-29 is the reason B&P §7059 and the "incidental and supplemental" test matter. If a job is mostly a masonry wall with some planting, you are not a landscape contractor on that job. Second, tree removal and pruning are regulated activities in their own right: B&P §7026.1(a)(4) makes a person who performs tree removal, tree pruning, stump removal, or tree or limb cabling or guying a "contractor" unless an exception applies, and the exceptions are narrow: a nurseryperson doing incidental pruning or guying of planted trees in the normal course of routine work, and a gardener doing incidental pruning of trees measuring less than 15 feet in height after planting. Chapter 5 returns to this. Where your classification stops on a given job is a question for CSLB, not for a fact pattern on a job site.

The exam's favorite distractors are all versions of one wrong idea: that a fact about the job can extend a classification. Location, dollar value, an open trench, an existing tee, a matching pipe size, who pulls the permit, or a homeowner's consent: none changes what your license authorizes.

1.3 Project Planning: Site, Program, Plans, and Specifications

Planning is the part of the work where mistakes are cheapest to fix and most expensive to make. A competent planner does four things before a dollar is priced.

Read the site. Walk it before reading the drawings and write down what the drawings cannot tell you: where water goes in a storm, where the sun lands in July, what is under the surface, how a truck gets in, where soil and materials will be staged, what must be protected (a mature tree, a neighbor's fence, a septic field), and where the point of connection and the electrical source really are. Measure static water pressure and flow at the point of connection. MWELO requires static pressure, dynamic (operating) pressure, and flow to be measured at the point of connection at the design stage, and at installation if the design-stage readings are not available (23 CCR §493.2.2(e)(2)). A plan drawn from a guess at pressure is a plan that fails at the farthest head.

Pin down the program. The program is what the owner needs the landscape to do: entertain, screen a view, shed water, grow food, cost little to maintain. Programs conflict with budgets, and a good estimate puts the conflict on the table before the contract is signed.

Read the plan set. A full set separates what each sheet is responsible for. In the MWELO performance path the contents are spelled out, which makes them a handy checklist for what a competent drawing contains.

• Landscape design plan (§493.2). Each hydrozone labeled by number, letter, or other method, with its plant factor identified as very low, low, moderate, high, or mixed; special landscape areas; the type and depth of mulch; the type and quantity of soil amendments; the type and surface area of water features; hardscapes, pervious and non-pervious; any stormwater best management practices with their retention or infiltration capacity; and the designer of record's signed statement.
• Irrigation design plan (§493.2.2(c)). Location and size of meters and submeters; the location, type, and size of every component (controllers, mainlines and laterals, valves, emission devices, sensors, quick couplers, pressure regulating devices, backflow prevention); the static water pressure at the point of connection; and, for each station, the flow rate (gpm), application rate (inches per hour), and design operating pressure (psi).
• Grading plan (§493.2.1). Finished configurations and elevations: heights of graded slopes, drainage patterns, pad elevations, finish grade, and stormwater retention improvements where applicable.

Plans and specifications together. Plans show geometry and location. Specifications state the materials, products, and workmanship standards. A bid that prices only the plans misses the spec'd product, and a bid based on the owner's verbal description is a bid on a rumor. When plan and specification conflict, the contract documents should say which controls; if they do not, ask in writing before the bid closes.

Reading scale. Find how many feet one inch represents, then multiply. At 1 inch = 10 feet, a bed that measures 4 inches on the plan is 40 feet long. At 1/8 inch = 1 foot, each inch of plan is 8 feet, so a wall measuring 5 inches is 40 feet. The classic error is dividing where you should multiply, and the exam always offers that answer. Check the scale bar on a plan that has been photocopied or reduced; a printed scale ("1/8" = 1'-0"") is wrong on a plan printed at a different size.

The legend and plant schedule. A schedule line such as QUAG, 24" box, 7 reads as three fields: abbreviated botanical name, container size, and quantity. Read the "24" as a count and the whole takeoff is wrong.

1.4 Design Decisions the Contractor Must Understand: Hydrozones, the Water Budget, Drainage, and Hardscape Layout

The official outline groups "hardscape, drainage, and irrigation design" into this section. A C-27 is often a design-build contractor, and even when the owner's designer draws the plans the contractor must be able to tell when a drawing will not work. The design decisions the exam tests are the ones with a calculation or a rule behind them.

Hydrozones and the plant factor

A hydrozone is a portion of the landscape with plants of similar water need and generally similar rooting depth (turf is shallow to moderate, shrubs moderate, trees deep). MWELO's plant-factor ranges, used in the water budget, are: very low less than 0.1; low 0.1 to 0.3; moderate 0.4 to 0.6; high 0.7 to 1.0 (23 CCR §493.3(b)(1)). Each valve should irrigate a hydrozone, or part of one, with similar site, slope, sun exposure, soil conditions, and plants of similar water use (§493.2.2(c)(7)). A hydrozone may mix low and moderate, or moderate and high, plant factors, with the water-use calculation based on either the proportion of each or the highest plant factor. Mixing high and low plant factors in one hydrozone is not permitted (§493.2.2(d)(7)-(8)). Where feasible, trees go on separate stations from shrubs, groundcovers, and turf (§493.2.2(d)(4)).

The water budget: MAWA and ETWU

Under the performance path, the designer proves the landscape will not use more water than the ordinance allows. Two numbers are compared.

MAWA = ETo × 0.62 × [ (ETAF × RLA) + (1.0 × SLA) ] (annual gallons)

• ETo is annual reference evapotranspiration for the site, in inches per year, from the ordinance's Appendix C table (or a nearby city in the same ETo zone). It describes the water use of a standard reference surface, a large field of well-watered cool-season turfgrass four to seven inches tall (§490.2). It is a weather number, not a plant number.
• 0.62 is the conversion factor that turns inches of water over square feet into gallons.
• ETAF is the ET adjustment factor. Its maximum allowed value in the MAWA equation is 0.55 for residential regular landscape areas and 0.45 for non-residential regular landscape areas (§493.3(a)(1)). For existing, non-rehabilitated landscapes over one acre that were installed before December 1, 2015, the ETAF cap is 0.8 (§491.1).
• RLA is the regular landscape area; SLA is the special landscape area. Special landscape areas get an ETAF of 1.0. They are irrigated areas permanently and solely dedicated to edible plants, recreational areas, areas irrigated with recycled water, and water features using recycled water (§490.2).

The estimated side is built hydrozone by hydrozone:

ETAF (for a hydrozone) = PF ÷ IE EWU = ETAF × area × ETo × 0.62 ETWU = the sum of the EWU of every hydrozone (§493.3 and the ordinance's Appendix A worksheet)

PF is the plant factor. IE is the irrigation efficiency the ordinance assumes: 0.75 for overhead systems and 0.81 for drip (§493.2.2(b)(2)). Water features use the high plant-factor in the calculation (§493.3(b)(2)); temporarily irrigated areas use the low one (§493.3(b)(3)).

The design passes when ETWU is equal to or less than MAWA. A larger ETWU fails, and the designer must change the plant palette, the irrigation method, or the turf area.

Worked MAWA example. See "Worked Example B" at the end of this chapter.

Which compliance path?

MWELO applies to new construction with a landscape area of 500 square feet or more that needs a building or landscape permit, plan check, or design review; and to rehabilitated landscapes of 2,500 square feet or more under the same conditions (§491(a)). Existing non-rehabilitated landscapes are limited to §491.1, and cemeteries have their own limits.

• A project with a landscape area of 2,500 square feet or less may comply by either path: the performance requirements (§493) or the prescriptive measures (§492) (§491(b)).
• §491.2(b) lets an applicant use either option for a new construction project between 500 and 2,500 square feet.
• §491.2(c) says an applicant shall use the performance option for any project of 2,500 square feet or greater.

Exam trap: the 2,500-square-foot line is written differently in different subsections. "2,500 or less" may choose either path; "2,500 or greater" must use performance. The two phrasings overlap at exactly 2,500, and a question pegged to that number is testing whether you notice the overlap. Read §491(b) and §491.2(c) as an author wrote them, then notice that the safe reading for planning is: at or below 2,500 square feet, check the local agency; above it, performance path. Local agencies may be stricter than the model ordinance.

The prescriptive path (§492) is a checklist rather than a budget. Highlights: compost at least 4 cubic yards per 1,000 square feet to a depth of 6 inches unless a soil test contra-indicates it (soils with more than 6 percent organic matter in the top six inches are exempt); an automatic controller using weather data or soil-moisture data plus a rain sensor; pressure-regulating devices; manual shut-off valves near the point of connection; emission devices meeting ASABE/ICC 802-2020 with a low-quarter distribution uniformity of 0.65 or higher; areas less than 10 feet in width in any direction irrigated by subsurface irrigation or another means that produces no water waste, runoff or overspray; climate-adapted plants (average WUCOLS plant factor 0.3) for 75 percent of the landscape area in residential and 100 percent in non-residential, with turf not exceeding 25 percent of a residential landscape area and not allowed in non-residential landscapes; no turf on slopes steeper than one foot of rise in four of run; and a minimum 3-inch layer of mulch on exposed soil in planting areas.

Existing landscapes

Local agencies run programs (audits, surveys, water-use analyses) for existing non-rehabilitated landscapes over one acre that were installed before December 1, 2015 (§491.1). For metered sites, the target is a MAWA computed as ETo × 0.62 × (0.8 × RLA + 1.0 × SLA). Audits must be done by a certified landscape irrigation auditor.

Drainage and grading decisions at the design stage

Design intent is to keep water on site and away from structures and pavement. §493.2.1 recommends grading so that all irrigation and normal rainfall remains within property lines and does not drain onto non-pervious hardscapes, avoiding disruption of natural drainage patterns and undisturbed soil, and avoiding compaction in landscape areas. Turf is not allowed on slopes steeper than 25 percent where the toe of the slope is adjacent to a non-pervious hardscape (§493.2(b)(5)), where "25 percent" is defined in the regulation as one foot of vertical change for every four feet of horizontal length (rise ÷ run × 100). High water use plants (plant factor 0.7 to 1.0) are prohibited in street medians (§493.2(b)(4)). Water features use recirculating systems, and recycled water where available (§493.2(c)).