CSLB Landscaping (C-27) Trade — All Questions

A retaining wall is designed with a driveway directly behind it. What does that condition add to the design?

• a.A requirement for a taller leveling pad under the first course
• b.A requirement to omit drainage rock so the base stays firm
• c.A surcharge load that must be accounted for by the engineer✓
• d.A reduction in the geogrid length because the drive confines the soil

Vehicles and pavement behind a wall impose a surcharge that increases the force the wall must resist, and the engineer must design for it. Drainage rock is more important with a surcharge, not less. Pad height is not the response to added load, and geogrid usually needs to be longer rather than shorter to reach beyond the loaded zone.

Why is the first course of a segmental block wall normally set below finish grade in front of the wall?

• a.To reduce the number of blocks needed in the wall face
• b.To hide the leveling pad from view along the base
• c.To allow the drain pipe to be placed above the first course
• d.To resist sliding and prevent undermining at the toe✓

Burying the base course gives passive resistance at the toe and protects it from erosion, which is why the detail is standard rather than cosmetic. Appearance is a side benefit. The drain typically sits behind the base course, not above it, and burying a course adds blocks rather than saving them.

A block wall leans outward after the first wet winter and the drain outlet has never flowed. What most likely occurred?

• a.The leveling pad was placed too deep below finish grade
• b.The wall was built with too much batter toward the retained soil
• c.Hydrostatic pressure built behind the wall as drainage failed✓
• d.The blocks absorbed water and expanded against one another

Water trapped behind a wall pushes with far more force than the soil alone, so a blocked or missing drain is the classic cause of a wall that leans after a wet season. Concrete blocks do not expand meaningfully. A deeper pad increases stability. Batter leaning into the slope resists failure rather than causing it.

What is the correct backfill immediately behind a segmental retaining wall?

• a.Native clay compacted in six-inch lifts against the block
• b.Topsoil, so plantings on the terrace above can root freely
• c.Clean drainage rock with a perforated pipe and filter fabric✓
• d.Sand, so water passes quickly through to the subgrade

A drainage chimney of clean rock with a collector pipe and fabric moves water out before it can load the wall. Clay against the block traps water and swells. Topsoil holds moisture and fines. Sand passes water but carries fines and clogs, which is why washed rock and fabric are specified together.

Geogrid is specified in a taller segmental wall. What does it do?

• a.It reinforces the retained soil mass so it acts with the wall✓
• b.It carries water from the drainage rock to the wall outlets
• c.It reinforces the block face against impact from the front
• d.It separates the base course from the leveling pad below

Geogrid layers extend back into the fill and tie the soil into a reinforced mass that behaves as one body with the facing blocks. It is not a facing reinforcement, it is not a drainage layer, and separation between the pad and the base course is neither needed nor its function.

A garden wall on expansive clay cracks in the same places every year. What soil behavior explains it?

• a.The clay conducts heat and expands the wall units themselves
• b.The clay consolidates permanently under the weight of the wall
• c.The clay dissolves during winter rain and loses bearing capacity
• d.The clay swells when wet and shrinks when dry, moving footings✓

Expansive clay changes volume with moisture content, lifting and dropping footings seasonally, which is why the same cracks reopen each year. Consolidation is a one-way settlement rather than a seasonal cycle. Clay does not dissolve, and thermal movement of the block units is far too small to produce this pattern.

A dry-stacked mortarless block wall is proposed at 30 inches high with level ground behind it. What primarily holds it in place?

• a.The steel reinforcement grouted through the block cores
• b.The friction of the topsoil placed against the back face
• c.The mass of the units, their setback, and the compacted base✓
• d.The mortar bond between the block courses

A low gravity wall stands on its own weight, the batter that leans it into the slope, and a properly compacted leveling pad. There is no mortar or grouted steel in a dry-stack system, which is what makes those details critical, and loose topsoil behind the wall provides no meaningful restraint.

Steps are being laid out on a garden slope. Which riser and tread combination is most comfortable for outdoor use?

• a.A 9-inch riser with a 12-inch tread
• b.A 4-inch riser with a 10-inch tread
• c.An 8-inch riser with a 9-inch tread
• d.A 6-inch riser with a 14-inch tread✓

Outdoor steps use lower risers and deeper treads than interior stairs, and roughly six inches with a fourteen-inch tread fits the common relationship of two risers plus a tread near 26 inches. An eight by nine step is an interior proportion. A four-inch riser with a ten-inch tread is awkwardly shallow. A nine-inch riser is too tall for garden use.

An accessible route is being built through a commercial landscape. What is the maximum cross slope generally allowed on the walking surface?

• a.About one twelfth, or 8.33 percent
• b.About two percent✓
• c.About five percent
• d.About eight percent

Accessible routes limit cross slope to roughly two percent so a wheelchair does not pull to one side. Five percent is the ceiling for running slope on a walk before it is treated as a ramp. Eight percent and the one in twelve figure describe maximum ramp running slope, not cross slope.

A path exceeds five percent running slope on a commercial site. How is it then treated?

• a.As a walk, with a coarse broom finish for traction
• b.As a step, requiring risers to be added at regular intervals
• c.As a ramp, with slope, landing, and handrail requirements✓
• d.As a swale, since it will convey water along its length

Once running slope passes about five percent an accessible route is a ramp and picks up limits on slope and rise plus landings and handrails. Adding texture does not change the classification. A path is not a drainage feature by definition, and converting it to steps would remove accessibility rather than provide it.

A decomposed granite path is specified with a stabilizer. What does the stabilizer provide?

• a.A binder that holds fines together and resists erosion✓
• b.A waterproof surface that sheds all rainfall
• c.A herbicide layer that prevents weeds in the path
• d.A colorant that keeps the granite from fading in sun

Stabilizers bind the fines so the compacted surface holds together underfoot and does not wash out in a storm. The path is still permeable rather than waterproof. Color is a property of the granite itself. Weed suppression comes from compaction and edging, not from the binder.

A steep cut slope must be planted and protected through the first winter. Which combination is most effective?

• a.Erosion control blanket with plantings and fiber rolls✓
• b.Sprinkler irrigation applied at a high rate to settle the soil
• c.Broadcast seed and a light straw scatter over the surface
• d.Plastic sheeting anchored at the crest and the toe

A blanket holds the surface while roots develop and fiber rolls break the slope into short runs that keep water from concentrating. Loose straw blows and floats off. Plastic sheeting sheds water to the toe in a concentrated flow and kills the plants beneath. High-rate irrigation on a bare slope causes the erosion it is meant to prevent.

Why are fiber rolls placed along the contour rather than up and down a slope?

• a.To create planting shelves that hold irrigation water
• b.To intercept sheet flow and shorten the distance water travels✓
• c.To mark the elevations the grading crew must hold
• d.To provide anchor points for the erosion blanket above them

Rolls set on contour catch water moving down the face and break a long slope into short segments so flow never gains erosive velocity. Blanket anchoring is done with staples. The rolls are not planting shelves, and grading elevations are marked with stakes and hubs rather than with erosion control products.

A crew is placing fill on a hillside terrace. What practice produces stable fill?

• a.Placing and compacting the fill in lifts on a benched surface✓
• b.Saturating the fill and allowing it to consolidate under its own weight
• c.Placing the fill against the existing slope face without preparation
• d.End dumping the material and letting it settle over the wet season

Fill placed in thin compacted lifts onto a benched, keyed surface bonds to the existing ground and reaches design density. End dumping leaves loose material that settles for years. Fill placed against an unprepared slope face can slide along that plane. Saturation produces settlement and instability rather than compaction.

A catch basin is being set in a lawn area. At what elevation should its grate be placed?

• a.Slightly below the surrounding grade so water flows into it✓
• b.At the same elevation as the outlet pipe invert
• c.An inch above the surrounding turf so mowers clear it
• d.Level with the highest point of the lawn nearby

A basin only collects water that can reach it, so the grate is set slightly low and the surrounding grade is shaped to fall toward it. Setting it high makes it an obstacle that water bypasses. Matching the high point of the lawn does the same. The outlet invert sits well below the grate by design.

A yard drain system backs up during heavy rain although the pipe is clear. What should be checked next?

• a.Whether the outlet is submerged or blocked at its discharge✓
• b.Whether the basins have solid lids rather than open grated lids
• c.Whether the trench was backfilled with native soil
• d.Whether the pipe was laid with too much fall

A gravity system can only discharge if the outlet is open and above the water it drains into, so a buried, silted, or submerged outlet backs the whole system up. Solid lids would show as no collection rather than as backup. Excess fall increases capacity. Backfill material does not restrict flow inside a clear pipe.

A dry well is proposed to handle roof runoff on a lot with heavy clay subsoil. What is the main concern?

• a.Roof water carries too much sediment for a dry well to accept
• b.Dry wells may only be used with landscape runoff, not roof runoff
• c.Clay will not hold the walls of the excavation during construction
• d.Clay infiltrates too slowly for the well to empty between storms✓

A dry well works by infiltration, and clay subsoil may take days to empty a well that must be ready for the next storm, so a percolation test governs the decision. Excavation stability is a construction issue rather than a performance one. Roof water is relatively clean, and roof runoff is a common and accepted source for infiltration devices.

Where should the finish grade of a lawn be set relative to an adjoining concrete walk?

• a.Level with the walk so the mower can ride on the concrete
• b.About two inches above the walk so the turf edge looks full
• c.About four inches below the walk to allow for thatch buildup
• d.About one inch below the walk so water sheds onto the lawn✓

Setting soil about an inch below the concrete lets water run off the walk into the lawn and keeps soil and mulch from washing across the surface. Grade above the walk sends soil onto the concrete and buries the edge. A flush grade scalps under the mower. Four inches low leaves a trip edge and a trench along the walk.

A laser level is set up to grade a large lawn panel. What does the rod reading at each stake give the operator?

• a.The compaction achieved at that point in the subgrade
• b.The elevation of that point relative to the level instrument plane✓
• c.The horizontal distance from the instrument to that stake
• d.The percent slope between that stake and the instrument

The instrument establishes a level plane and the rod reading tells how far the ground lies below it, which converts directly to elevation. Distance is measured with a tape or by stadia. Slope is computed from two elevations and the distance between them. Compaction is measured with a density test, not with a level.

A plan shows a spot elevation of 101.50 at a patio corner and 100.75 at a drain 25 feet away. What is the slope between them?

• a.About 0.75 percent
• b.About 3.0 percent✓
• c.About 1.5 percent
• d.About 2.0 percent

The fall is 0.75 feet over 25 feet, which is 0.03, or 3 percent. The 0.75 figure mistakes the fall in feet for a percentage. The 1.5 figure would come from half the fall or twice the distance. Two percent would require a fall of half a foot over the same run.

A patio is to be built over the root zone of a mature preserved tree. Which approach is most protective?

• a.A paver field with the base compacted to 95 percent
• b.A slab poured directly on the existing soil with no base
• c.A pier-supported deck or a permeable surface set on grade✓
• d.A conventional slab poured on four inches of compacted base rock

Roots are damaged by excavation and by loss of air exchange, so raising the surface on piers or using a permeable system placed with minimal disturbance is the protective choice. A conventional base requires excavation and heavy compaction over the roots. Higher compaction makes it worse. A slab poured on grade still seals the surface completely.

Bender board is installed to separate a lawn from a planting bed. What is its function?

• a.To carry the load of a mower wheel riding along the edge
• b.To hold the edge line and keep bed material and turf separated✓
• c.To stop irrigation water from crossing between the two areas
• d.To provide a level datum for the finish grade of the lawn

Edging holds a clean line and keeps mulch and turf from migrating into one another. It is not a water barrier, since water moves through and under it. It is not designed to carry wheel loads, and grading elevations are set from stakes and instruments rather than from a flexible edging strip.

A mow strip is specified between a lawn and a block wall. What is its practical purpose?

• a.To act as an expansion joint between the lawn and the wall
• b.To provide a drainage channel along the wall footing
• c.To reinforce the base of the wall against soil pressure
• d.To let a mower wheel run beside the wall without hand trimming✓

A mow strip gives the mower a hard surface to run on right up to the wall, which removes the hand trimming that would otherwise be needed on every visit. It is not a structural element. It is not a drainage channel. Expansion joints occur between rigid elements, and a lawn is not rigid.

Site work is sequenced on a full landscape installation. Which order is correct?

• a.Rough grading, then irrigation lines, then hardscape, then planting✓
• b.Irrigation, then rough grading, then planting, then hardscape
• c.Hardscape, then rough grading, then irrigation, then planting
• d.Planting, then irrigation, then hardscape, then rough grading

Grading establishes the shape of the site, buried utilities and irrigation go in before anything is paved over, hardscape follows, and planting comes last so it is not damaged by equipment. Every other sequence either buries work that must be dug up again or installs plants before the heavy work is finished.

A landscape project will disturb more than one acre of soil. What additional stormwater obligation typically applies?

• a.A dedicated landscape water meter for the disturbed area
• b.A geotechnical report certifying the compaction of all fill
• c.Coverage under the state construction stormwater permit✓
• d.A separate encroachment permit from the county road department

Disturbing an acre or more generally brings a project under the statewide construction stormwater permit, which requires a stormwater pollution prevention plan and site controls. Encroachment permits apply to work in the public right of way. A landscape meter is a water efficiency requirement. Compaction reports address structural fill, not stormwater.

Which practice keeps sediment from leaving a landscape construction site during rain?

• a.Watering exposed soil daily so it does not blow off site
• b.Protecting inlets and installing perimeter controls first✓
• c.Stockpiling excavated soil at the low corner of the property
• d.Sweeping the street at the end of each work week

Sediment control works only if inlet protection and perimeter barriers are in place before the storm, not after. Weekly sweeping lets a week of tracked material wash into the drain. Watering controls dust but does nothing about runoff. Stockpiling at the low corner puts loose soil exactly where water will collect and carry it away.

A boulder is being placed as a landscape feature on a slope. What placement practice is correct?

• a.Set it on the surface so its full shape remains visible
• b.Bury roughly a third of it and seat it on firm compacted ground✓
• c.Set it against a block wall so the wall carries part of its weight
• d.Set it on a bed of sand so it can be adjusted later

Burying part of the boulder on firm ground makes it look natural and keeps it from rolling or settling. A boulder resting fully on the surface reads as placed and is unstable on a slope. Sand bedding lets a heavy stone shift. Leaning a boulder against a wall loads the wall in a way it was not designed for.

Sleeves and conduits are installed under a new driveway before paving. Beyond irrigation, what else should be considered at that stage?

• a.Additional base rock so the sleeves are not crushed
• b.A second layer of sleeves at ninety degrees for future flexibility
• c.Concrete encasement of every sleeve for structural support
• d.Spare conduit for lighting and control wiring added later✓

The cheapest time to add capacity is before pavement goes down, so spare conduit for future lighting and control wiring belongs in that trench. Sleeves at proper depth under a compacted base do not need extra rock or concrete encasement, and a redundant perpendicular layer adds cost without serving a known need.

A retaining wall over four feet tall is part of a landscape contract. What is the appropriate step for a C-27 licensee who does not do engineered walls?

• a.Have the owner sign a waiver accepting responsibility for the wall
• b.Build it as drawn and have the inspector approve it after completion
• c.Obtain the engineered design and permit and use a qualified installer✓
• d.Reduce the wall to a series of three-foot walls stacked one above the other

An engineered design and permit are required, and the work must be performed by someone qualified to build to that design. Stacking terraces does not avoid engineering if the upper wall surcharges the lower one. Inspection does not retroactively substitute for design. An owner waiver does not remove code obligations or liability.

During final grading the crew finds the finish grade at the side yard is two inches above the weep screed at the base of the stucco wall. What must be done?

• a.Lower the grade to restore clearance below the screed✓
• b.Install a curb along the wall to hold the soil back
• c.Seal the base of the stucco with an elastomeric coating
• d.Add a gravel band at the wall so water drains through the soil

The weep screed drains the wall assembly and must stay above grade, so soil covering it has to be removed. A coating traps moisture inside the wall. Gravel placed at the same elevation still blocks the screed. A curb holds soil at the same height and leaves the screed buried.