CSLB Landscaping (C-27) Trade — All Questions

Finished grade around a building should slope away from the foundation at approximately what minimum for the first several feet?

• a.Sloping the grade back toward the building
• b.About 5 percent, or 6 inches over 10 feet✓
• c.Flat, with no slope in any direction
• d.A 45-degree drop at the foundation

A common standard is to slope soil away from a foundation about 6 inches over the first 10 feet, roughly a 5 percent grade, to carry surface water away from the structure. Sloping toward the building or leaving it flat allows water to pond against the foundation. Positive drainage protects the structure from moisture damage.

A French drain is BEST described as what?

• a.A raised planter box built along the wall
• b.A surface concrete drainage channel or swale
• c.A type of segmental retaining wall
• d.A gravel-filled trench with perforated pipe✓

A French drain is a trench filled with gravel around a perforated pipe that intercepts subsurface and surface water and carries it to a discharge point. Water enters the pipe through the perforations and flows by gravity away from the problem area. It is used to relieve soggy soils and protect foundations.

Before placing concrete pavers on a driveway, a compacted aggregate base is installed mainly to do what?

• a.A stable, load-bearing, well-draining foundation✓
• b.The final wearing surface of the driveway
• c.A replacement for perimeter edge restraints
• d.Added color and texture at the paved surface

A compacted crushed-aggregate base spreads loads, resists settling, and drains water away from the pavers, forming the structural foundation of the pavement. Without proper base compaction, pavers rut and settle unevenly. A sand setting bed and edge restraints are added on top of this base.

Aggregate base under hardscape is best compacted in what manner?

• a.Only after the pavers have been placed
• b.In thin lifts, each compacted before the next✓
• c.By soaking it thoroughly with water only
• d.In one thick lift with no compaction at all

Base material should be placed and compacted in thin lifts, commonly around 3 to 4 inches, so the compactor can achieve full density throughout. Compacting one thick lift leaves the lower portion loose, causing later settlement. Layered compaction produces a stable, uniform base.

A segmental retaining wall over a certain height typically requires what to prevent failure?

• a.Engineered design, drainage, and geogrid✓
• b.No drainage of any kind behind the wall
• c.Only a decorative facing on the wall front
• d.A smooth clay backfill packed tight

Taller retaining walls carry large lateral soil loads and usually require engineered design, gravel backfill with a drain to relieve water pressure, and geogrid soil reinforcement. Without drainage, water pressure builds behind the wall and pushes it over. Many jurisdictions require permits and engineering above a set height, commonly 3 to 4 feet.

Weep holes or a drainage system behind a retaining wall serve what purpose?

• a.To relieve hydrostatic pressure behind the wall✓
• b.To hold more water in the backfill zone
• c.To increase the soil pressure on the wall
• d.To add decorative accents to the wall face

Weep holes and gravel drains allow water that collects behind a wall to drain out, relieving hydrostatic pressure that would otherwise push the wall over. Saturated soil greatly increases the load on a wall. Proper drainage is one of the most important factors in wall longevity.

A slope is described as 4:1. What does this mean?

• a.A 40 percent grade down the bank
• b.A vertical cliff with no run at all
• c.4 feet of run for every 1 foot of rise✓
• d.4 feet of rise for each 1 foot of run

A 4:1 slope means 4 units of horizontal distance for every 1 unit of vertical change, a gentle 25 percent grade. The first number is run and the second is rise in this common landscaping convention. Flatter ratios like 4:1 are more stable and easier to mow than steep ones like 2:1.

Managing stormwater runoff on a site with a bioswale accomplishes what?

• a.Slows runoff, filters pollutants, and promotes infiltration✓
• b.Prevents any water from infiltrating
• c.Raises the water table intentionally
• d.Concentrates runoff into a single fast channel

A bioswale is a shallow, vegetated channel that slows stormwater, filters out sediment and pollutants, and encourages water to soak into the ground. This reduces peak runoff and improves water quality leaving the site. Such low-impact designs are increasingly required for stormwater management.

A concrete slab for a patio typically includes control joints. What is their function?

• a.Planned weak points so cracks follow the joint✓
• b.Eliminating the need for a compacted stone base
• c.Increasing the water content of the slab
• d.Adding decorative color to the surface

Control joints are grooved or cut lines that create a deliberate weak plane, so as concrete shrinks and cracks, the cracks form neatly along the joint rather than randomly across the slab. They are usually spaced in feet roughly equal to two to three times the slab thickness in inches. They control, not eliminate, cracking.

Edge restraints installed around a paver patio serve what main purpose?

• a.To replace the compacted gravel base layer
• b.To keep pavers from spreading outward over time✓
• c.To change the color of the paver surface
• d.To provide seating around the patio edge

Edge restraints lock the perimeter pavers in place so the field of pavers cannot creep or spread apart under traffic. Without them, edges migrate and joints open up, leading to failure. They are a small but essential part of a durable paver installation.

A paved surface should be sloped for drainage at about what minimum cross slope?

• a.0 percent (dead level)
• b.10 to 15 percent
• c.Sloped toward the house
• d.About 1 to 2 percent✓

Paved surfaces such as patios and walkways are typically sloped about 1 to 2 percent, roughly 1/8 to 1/4 inch per foot, to shed water without being noticeably tilted. A dead-level surface ponds water, while too steep a slope is uncomfortable and unsafe. Water should always be directed away from structures.

A catch basin connected to underground drain pipe is used to do what?

• a.Collect surface water and pipe it away✓
• b.Store irrigation water for later reuse
• c.Support the base of a retaining wall
• d.Filter drinking water before use

A catch basin is a boxed inlet set at a low point that collects surface runoff and channels it into buried drain pipe leading to a safe discharge. A grate on top keeps out leaves and debris. It is a key part of a yard drainage system that prevents ponding.

When laying out a site from a plan, a builder's level or laser level is used primarily to establish what?

• a.Plant spacing across the planting beds
• b.Consistent elevations and grades✓
• c.Soil pH in the planting areas
• d.Water pressure at the meter

A builder's level, transit, or rotary laser establishes accurate reference elevations so grades, slopes, and drainage can be set consistently across a site. This ensures the finished landscape drains correctly and matches the plan. Accurate layout prevents costly grading errors.

Compaction of subgrade soil before hardscape is measured against what standard reference?

• a.A percentage of maximum dry density✓
• b.The number of compactor passes only
• c.The measured pH of the subgrade soil
• d.The color of the compacted soil

Compaction is specified as a percentage of a soil's maximum dry density determined by a laboratory Proctor test, commonly 90 to 95 percent for hardscape subgrade. Field testing verifies the soil reaches the required density. Adequate compaction prevents future settlement under pavement.

On expansive clay soils, hardscape and foundations are at risk because the soil does what?

• a.Stays perfectly stable in all conditions
• b.Turns to sand over time
• c.Swells when wet and shrinks when dry, causing movement✓
• d.Never holds water

Expansive clays contain minerals that absorb water and swell, then shrink as they dry, producing repeated ground movement that cracks slabs and walls. Managing moisture and using proper base and drainage details reduces this movement. Severe cases may need engineered foundations.

A dry-stack (mortarless) segmental block wall relies on what for stability?

• a.Steel beams set behind the block face
• b.A mortared concrete cap along the top
• c.Mortar placed between every block course
• d.Interlock, batter, and gravel backfill✓

Mortarless segmental walls gain stability from the interlocking block design, a slight backward lean (batter or setback), free-draining gravel backfill, and geogrid reinforcement layers in taller walls. There is no mortar, so drainage and reinforcement carry the loads. Proper base preparation is also critical.

Directing a downspout's discharge onto a splash block or into a pipe that carries it away from the house prevents what?

• a.Better interlock between the patio pavers
• b.A higher soil pH near the foundation
• c.Faster plant growth beside the house
• d.Erosion and ponding at the foundation✓

Concentrated roof runoff from a downspout can erode soil and saturate the ground against a foundation, leading to settlement and moisture intrusion. A splash block or piped extension moves that water away from the structure. This is a basic but important part of site drainage design.

Permeable pavers differ from standard pavers because they do what?

• a.They require no base course at all
• b.They are decorative only, not structural
• c.They block all water from passing through them
• d.They let stormwater soak through the joints✓

Permeable pavers are set with open, aggregate-filled joints over an open-graded stone base so rainwater infiltrates rather than running off. This reduces runoff volume and helps recharge groundwater, supporting stormwater regulations. They require a specially designed base to store and drain the water.

On a steep planted slope, which practice BEST controls erosion during establishment?

• a.Leaving the slope soil bare and exposed
• b.Frequent heavy flood irrigation
• c.Smooth compaction with no plants
• d.Blankets, mulch, and quick groundcover✓

Covering a slope with erosion-control blankets or netting, mulch, and fast-establishing groundcover protects the soil surface from rain impact and runoff until roots hold it. Bare or heavily flooded slopes erode and rill quickly. Vegetation and surface protection together stabilize the slope.

A retaining wall's footing or leveling pad should be placed on what?

• a.A layer of dry leaves and loose topsoil
• b.Compacted, level base at the proper depth✓
• c.Loose topsoil raked out smooth
• d.A single row of bricks laid flat

The base or leveling pad of a retaining wall must rest on compacted, level base material set at the correct depth so the wall does not settle or lean. A poor base is a leading cause of wall failure. Getting the first course level and solid is essential for the whole wall.

A C-27 licensee is asked to build a wood-framed pool house with a bathroom as part of a backyard landscape package. How should the licensee proceed?

• a.Subcontract it to contractors holding the appropriate classifications✓
• b.Build the structure and subcontract only the finish carpentry
• c.Build it if the total value stays under the landscape contract amount
• d.Build it, since it sits within the landscape area being developed

The landscaping classification covers landscape systems and features and the grading that supports them, not habitable structures with plumbing and electrical work, so those trades must be subcontracted to properly licensed contractors. Being inside the landscape area, keeping the framing in house, or comparing dollar values does not extend the classification.16 CCR §832.27

Which of the following is most clearly within the C-27 landscaping classification?

• a.Reroofing a detached garage that faces the new patio
• b.Installing a new subpanel to power landscape lighting
• c.Installing a residential swimming pool and its equipment
• d.Grading and preparing a yard for decorative treatment✓

Preparing and grading plots for horticultural and decorative treatment is expressly part of the landscaping classification. A new subpanel is electrical work, roofing is a separate specialty, and swimming pool construction has its own classification, so each of those must be held or subcontracted separately.16 CCR §832.27

A landscape contract includes low-voltage path lighting fed from an existing exterior receptacle. What is the correct division of work?

• a.An electrical contractor must install every part of a lighting system
• b.The landscape crew adds a new receptacle first, then the transformer
• c.The landscape crew may run 120-volt cable if it stays under 50 feet
• d.The landscape crew sets the transformer and low-voltage runs at that receptacle✓

Plugging a transformer into an existing code-compliant exterior receptacle and running the low-voltage cable is landscape work. Adding a new receptacle or running any new 120-volt cable is electrical work regardless of length. It is also not the case that an electrical contractor must perform the low-voltage portion once the supply already exists.

Finish grade at a house is being set. What is the standard target for surface drainage away from the foundation?

• a.A slight fall toward the wall, drained by a perimeter french drain
• b.A crown at the wall with equal falls in both directions
• c.A fall away from the wall over the first several feet of ground✓
• d.A level pad with a swale at the property line to collect water

Positive fall away from the wall in the first several feet is what keeps water out of the foundation, and every other detail is downstream of it. A level pad ponds against the wall. Sloping toward the wall and relying on a drain fails the moment that drain clogs. Crowning at the wall would require the wall to be the high point of the pad, which it is not.

A patio must drain across its surface to a lawn edge. What cross slope is normally specified?

• a.Zero, with drainage handled by joints between the pavers
• b.About five percent, to move water quickly off the surface
• c.About one quarter percent, so furniture sits level
• d.About one to two percent, roughly an eighth inch per foot✓

Roughly an eighth of an inch per foot moves water reliably without being noticeable underfoot or under furniture. A dead level surface ponds even on permeable paving. A quarter percent is inside construction tolerance and will pond in low spots. Five percent is steep enough to feel and would be uncomfortable for seating.

A grading plan describes a slope as 3:1. Which statement is correct?

• a.The slope rises three feet for each foot of horizontal run
• b.The slope is expressed as a three percent grade
• c.The slope runs three feet horizontally for each foot of fall✓
• d.The slope drops three inches per foot of run

Slope ratios are written horizontal to vertical, so 3:1 means three feet of run for every foot of rise or fall, which is about a 33 percent grade. Reversing the ratio would describe a very steep bank. It is not a three percent grade, and three inches per foot would be a 25 percent grade written differently.

Contour lines on a grading plan are drawn close together across one part of the site. What does that spacing indicate?

• a.The area is proposed for fill rather than cut
• b.The area drains toward the nearest catch basin
• c.The ground is nearly level in that area
• d.The ground is steep in that area✓

Contours mark equal elevations, so a short horizontal distance between them means elevation changes quickly and the ground is steep. Widely spaced contours indicate flat ground. Cut and fill are shown by comparing existing and proposed contours rather than by spacing alone, and drainage direction is read from the shape of the contours, not their closeness.

A designer wants to move surface runoff across a yard without a piped system. Which feature does that?

• a.A shallow vegetated swale graded toward the outlet✓
• b.A dry well set at the low corner of the yard
• c.A french drain laid level along the fence line
• d.A catch basin with a solid lid at the midpoint

A swale is a graded surface channel that carries and slows runoff on its way to an outlet, which is exactly the described need. A dry well stores and infiltrates at one point rather than conveying. A catch basin collects into a pipe. A level french drain has no fall and only intercepts subsurface water where it sits.

A new grading plan would send additional runoff onto the neighboring downhill lot. What is the contractor's obligation?

• a.Install a berm on the neighbor's side to contain the added flow
• b.Design the drainage to an approved outlet off the property✓
• c.Proceed if the neighbor gives verbal permission on site
• d.Proceed, since water naturally flows downhill between properties

Concentrating or increasing runoff onto adjacent property creates liability and usually violates local grading rules, so the work must be designed to an approved point of discharge. Natural flow does not license added flow. Verbal permission is not a substitute for a compliant design, and building anything on the neighbor's land is not the contractor's to do.

Perforated pipe is being installed in a gravel-filled trench to intercept subsurface water. How should it be laid?

• a.Holes down, in washed rock wrapped in filter fabric✓
• b.Holes up, bedded directly on native soil without gravel
• c.Holes to the sides, with the trench wrapped in plastic sheeting
• d.Holes up, so water enters only after the trench fills

Perforations face down so water entering the trench at any depth can get into the pipe immediately, and washed rock with filter fabric keeps fines from silting the system. Holes up delays entry until the trench floods. Plastic sheeting stops the very water the drain is meant to collect. Bedding on native soil without rock plugs the perforations.

What minimum fall is normally used on a landscape drain line so it does not silt up?

• a.About one quarter percent, roughly a thirty-second inch per foot
• b.About five percent, roughly five eighths inch per foot
• c.About one percent, roughly an eighth inch per foot✓
• d.No fall is needed because the pipe flows full under head

Roughly one percent keeps velocity high enough to carry silt through the line without being so steep that water outruns the solids. A quarter percent is too flat to self-clean at landscape flows. Five percent is far more fall than most yards can give and is unnecessary. A gravity drain that is laid flat will silt in.

Downspouts on a house currently discharge onto a planting bed near the foundation. What is the appropriate landscape correction?

• a.Install a dry well directly against the foundation wall
• b.Connect the downspouts to a pipe discharging away from the house✓
• c.Regrade the bed level so water spreads out instead of channeling
• d.Add six inches of mulch under each downspout to absorb the flow

Roof water is concentrated flow and belongs in a pipe that carries it well away from the foundation. Mulch cannot absorb a roof's worth of water. A level bed holds the water against the wall rather than moving it. A dry well set against the foundation deliberately puts infiltration exactly where it does the most harm.

A bioswale is specified on a commercial landscape. What is its main stormwater function?

• a.To slow runoff and filter it through soil and vegetation✓
• b.To provide a lined channel that speeds runoff off the site
• c.To separate irrigation runoff from roof runoff for metering
• d.To store runoff until it can be pumped to the storm drain

A bioswale slows water, lets it soak in, and filters pollutants through the planted soil profile before any overflow leaves the site. It is not a pumped storage basin, and a lined fast channel is the opposite of what it does. Metering separation is a plumbing arrangement, not a swale function.

Aggregate base is being placed for a paver patio. How should it be compacted?

• a.In lifts of about four to six inches at optimum moisture✓
• b.In one lift, wetted thoroughly and compacted from the center outward
• c.In lifts of about twelve inches at optimum moisture
• d.In one lift, compacted dry so the fines do not migrate

Compaction energy only reaches a limited depth, so base goes in lifts of roughly four to six inches at optimum moisture and each lift is compacted before the next. A single thick lift leaves the bottom loose regardless of direction of travel. Dry material will not densify. Twelve-inch lifts exceed what a plate compactor can reach.

Two crews compact the same base material at very different moisture levels and get different densities. What explains this?

• a.Drier material compacts to a higher density in every case
• b.Wetter material compacts to a higher density in every case
• c.Moisture affects only the finish, not the resulting density
• d.Every soil has an optimum moisture content for maximum density✓

Water lubricates particles up to a point and then occupies space that soil would otherwise fill, so each material has an optimum moisture at which density peaks. Wetter is not uniformly better, since saturated material pumps under the compactor. Drier is not uniformly better either, because friction blocks rearrangement. Density is directly affected.

A specification requires 90 percent relative compaction of the subgrade. What is that percentage measured against?

• a.The maximum dry density from a laboratory compaction test✓
• b.The in-place density of undisturbed soil elsewhere on the lot
• c.The percentage of the trench volume filled with backfill
• d.The density of the aggregate base placed over the subgrade

Relative compaction compares field density to the maximum dry density established for that soil in a laboratory test, which is why a sample goes to the lab before the specification means anything. Base density is a separate material. Undisturbed soil nearby is not a standard. The share of trench volume filled is not a density measure at all.

A crew must compact a narrow trench backfill in cohesive clay. Which equipment is best suited?

• a.A water jet, which settles the fill by saturation
• b.A rammer or jumping jack, which delivers impact into cohesive clay soil✓
• c.A vibratory plate compactor, which works granular material well
• d.A smooth drum roller, which covers the length quickly

Cohesive clay responds to impact rather than vibration, so a rammer is the right tool in a narrow trench. Plate compactors are designed for granular material. A drum roller cannot fit or reach the bottom of a trench. Jetting saturates the fill and produces settlement later rather than compaction now.

A paver walkway settles in ruts within one season while the adjacent driveway holds. What is the most likely cause?

• a.The joint sand was not swept in deeply enough
• b.The bedding sand layer was screeded too thin
• c.The base was too shallow or inadequately compacted✓
• d.The pavers were laid in a running bond instead of herringbone

Pavers ride on the base, so ruts and dips almost always trace back to base depth or compaction rather than to the surface course. Joint sand locks pavers together but carries no load. Pattern affects interlock under vehicles more than settlement. Bedding sand should be thin, and a thin screed is correct rather than a defect.

How does base thickness for a paver driveway compare with base thickness for a paver walkway?

• a.The walkway needs the thicker base because it lacks edge restraint
• b.The driveway needs a thicker base because it carries vehicle loads✓
• c.The driveway needs a thinner base because vehicles compact it further
• d.The two are the same because the pavers are the same thickness

Base thickness follows the load, so a drive carrying vehicles needs substantially more base than a pedestrian walk. Paver thickness alone does not set base depth. Walkways carry less load, and every paver field needs edge restraint regardless. Traffic does not usefully compact a base that was undersized to begin with.

Why is a herringbone pattern preferred for pavers in a driveway?

• a.It allows a thinner bedding sand layer to be used
• b.It resists creeping and shifting under turning vehicle loads✓
• c.It reduces the amount of joint sand the field requires
• d.It requires fewer cuts along the perimeter of the field

Herringbone interlocks in two directions, so braking and turning forces cannot push a line of pavers along a continuous joint. It generally requires more perimeter cuts, not fewer. Bedding sand depth is fixed by the screed regardless of pattern, and joint sand quantity varies little between patterns.

What is the correct thickness of the bedding sand layer under interlocking concrete pavers?

• a.About three inches, screeded and compacted before laying
• b.About two inches, screeded loose and left uncompacted
• c.About one inch, screeded loose and left uncompacted✓
• d.No bedding layer, with pavers set directly on the base

Roughly one inch of loose screeded sand is enough to seat the pavers and no more, because a thick sand layer behaves like an uncompacted base and lets the surface rut. Two or three inches is far too much. Compacting the sand before laying defeats its purpose. Setting pavers directly on base leaves no way to level the surface.

Edge restraint is being installed around a paver patio. What does it accomplish?

• a.It seals the field so water cannot enter the joints
• b.It carries the load at the perimeter where the base is thinnest
• c.It keeps perimeter pavers from spreading and losing interlock✓
• d.It provides a level reference for screeding the bedding sand

Without restraint the outer courses migrate outward, joints open, and the interlock that makes the whole field work is lost. Screed rails, not edge restraint, guide the sand. Restraint does not carry vertical load. It also does not seal the field, since paver systems are designed to shed water at the surface rather than to be watertight.

How does the base under permeable pavers differ from the base under standard pavers?

• a.It uses open-graded clean stone that stores and passes water✓
• b.It uses a fines-rich base compacted to a higher density
• c.It uses a thinner base because water does not sit on the surface
• d.It uses the same base with a perforated pipe added at the bottom

Permeable systems are built on open-graded washed stone with large voids so water can pass through and be stored before infiltrating. Adding a pipe to a dense base does not create that void space. The base is usually thicker rather than thinner because it doubles as a reservoir. Fines are exactly what must be kept out.

A permeable paver parking area stops draining after four years. What is the usual cause?

• a.Sediment has clogged the surface joints and must be removed✓
• b.The subgrade has consolidated under repeated vehicle loading
• c.The pavers have absorbed water and swelled against each other
• d.The joint stone has settled and reduced the void space

Permeable systems fail at the surface, where windblown fines and landscape debris seal the joints, and periodic vacuuming restores them. Joint stone settlement is minor by comparison. Subgrade consolidation would show as rutting rather than as ponding. Concrete pavers do not swell enough to close joints.

Control joints are tooled into a new concrete patio. What determines their spacing?

• a.They are placed wherever the pour is interrupted for the day
• b.They are spaced at a fixed twenty feet regardless of slab thickness
• c.They are placed at every change in the color of the finish
• d.Spaced in feet at two to three times the slab thickness in inches✓

A common rule spaces joints in feet at about two to three times the slab thickness in inches, so a four-inch slab gets joints around eight to twelve feet apart. A pause in the pour creates a cold joint, which is a different detail. Finish color is unrelated. A single fixed spacing ignores thickness entirely.

How deep should a control joint be cut or tooled in a concrete slab?

• a.About one half the slab thickness
• b.About one eighth inch regardless of thickness
• c.Through the full thickness of the slab
• d.About one quarter of the slab thickness✓

A joint about a quarter of the slab depth creates a weakened plane deep enough to direct the crack without cutting the slab apart. A full-depth cut makes separate slabs and severs any reinforcement. Half depth is deeper than needed and weakens the section. A shallow scratch will not control where the crack goes.

A new concrete walk will abut an existing building slab. Which joint belongs at that line?

• a.A doweled construction joint tying the two slabs together
• b.An isolation joint with compressible material full depth✓
• c.A tooled control joint matching the pattern of the walk
• d.A saw cut made the following day at the building face

The building and the walk move independently, so a full-depth isolation joint with compressible filler lets that happen without cracking either one. A control joint only guides shrinkage cracking within one slab. Doweling would tie the walk to the structure, which is the opposite of the intent. A late saw cut does not create separation.

A driver arrives with concrete that has been in the truck longer than expected and asks whether to add water. What is the correct answer?

• a.Add water only to the last third of the load being placed
• b.Do not add water beyond the design mix, since strength falls✓
• c.Add water and compensate by finishing the surface more heavily
• d.Add water freely, since workability governs the finish quality

Strength drops as the water to cement ratio rises, so adding water on site to restore workability trades durability for convenience. Limiting the addition to part of the load creates inconsistent concrete. Heavy finishing of a wet mix brings fines and water to the surface and produces a weak, dusting slab.

Why is a new concrete flatwork slab kept moist or covered for several days after placement?

• a.To allow cement hydration to continue and develop strength✓
• b.To prevent the aggregate from settling to the bottom
• c.To keep the surface soft enough for later saw cutting
• d.To keep the surface color uniform as the slab dries

Cement gains strength through hydration, which requires water, so curing keeps moisture in the slab while that reaction proceeds. Color uniformity is a finishing matter. Aggregate segregation happens during placement, not during curing. Saw cutting is timed to the concrete's set and is not the reason for curing.

A segmental retaining wall is planned at five feet exposed height on a residential lot. What should the contractor expect?

• a.A permit and an engineered design from the local jurisdiction✓
• b.No permit, since the wall retains only landscape soil
• c.No permit, since segmental walls are not structures
• d.A permit only if the wall is closer than five feet to the property line

Most California jurisdictions require a permit and engineered design once a retaining wall passes roughly four feet or carries a surcharge, and a five-foot wall is squarely in that range. Segmental construction does not exempt a wall, retaining landscape soil is still retaining, and proximity to a property line is a separate setback question.

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.