The numbers,
in public.
Most of what makes a build last twenty years is buried before you ever see it — base depth, compaction, fall, drainage behind a wall. You cannot inspect any of it once the surface goes down. So here it is in writing, before you sign anything, with the standard each number comes from.
Why we publish this.
Three contractors quote "a paver patio," the prices differ by a wide margin, and nothing in any of the three documents tells you that one of them is pricing four inches of compacted class II base and another is pricing two inches of whatever came off the last job. Both patios look identical on the day they are finished. They stop looking identical in the second winter.
The only fix is for the numbers to be written down somewhere you can check them against. This page is that document. It is the specification we build to unless a drawing, a soils report or a licensed engineer says otherwise — and where one of those exists, it governs and this page yields to it.
How to read this page.
These are the figures we build to as a matter of course — a standard of practice rather than a warranty, which is a separate document and lives on its own page. Every property is different, and on plenty of them the right answer is to exceed these numbers rather than meet them; where a geotechnical report, a structural engineer's detail, a manufacturer's instruction or the local building department calls for something else, that document leads and we build to it. Ask us for the specific figures for your site and we will put them in writing.
Site preparation & compaction.
Compaction is the mechanical removal of air voids so that particles lock together and stop rearranging under load.
It is measured as relative compaction — the density achieved as a percentage of a laboratory maximum for that same material. It is the single most consequential number on this page and the one most often skipped, because skipping it stays invisible until the settling starts.
| Element | Standard | Notes |
|---|---|---|
| General fill | 90% relative compaction ASTM D1557 | Non-structural areas — planting beds, backfill away from paving or footings. |
| Structural fill | 95% relative compaction | Anything that will carry a slab, a pavement section or a footing. |
| Driveway subgrade | 95% relative compaction | Vehicle loads concentrate at the edges; the subgrade is compacted past the paving line. |
| Lift thickness | 3–4 in per lift, plate compactor | Deeper for a heavy roller. Each lift compacted before the next is placed. |
| Moisture | At or near optimum moisture content | Too dry and particles will not seat; too wet and the material pumps instead of compacting. |
| Soft or organic material | Removed, not bridged | Over-excavated and replaced with compacted aggregate rather than covered over. |
Compaction energy falls away with depth. A plate compactor is only genuinely effective through a few inches, so material dumped to full depth and hit once is dense on top and loose underneath — which is precisely how a patio settles two winters later.
On the word "gravel"
What a customer calls gravel and what belongs under paving are not the same material. Under a pavement section the right material is a crushed aggregate with angular faces and a graded range of sizes down to fines — class II aggregate base — which interlocks under compaction and stays locked. Rounded pea gravel or river rock cannot do that: the stones roll past each other under load and no amount of compaction makes them interlock. Clean drain rock is a third material again, with the fines deliberately washed out so water passes through, which is exactly why it belongs in a French drain and not under a patio.
Drainage & grading.
Water is solved before anything decorative is placed, because every decorative decision downstream depends on it.
Slope gets described three ways and they are the same number. One per cent is an eighth of an inch per foot. Two per cent is a quarter inch per foot. Five per cent is about five-eighths of an inch per foot.
| Condition | Standard | Notes |
|---|---|---|
| Paving, standard fall | 2% — ¼ in per ft | Sheds water reliably; gentle enough that furniture sits level and nobody perceives it. |
| Paving, absolute minimum | 1% — ⅛ in per ft | Smooth, hard-trowelled surfaces only, and genuinely marginal: a ¼ in construction tolerance swallows most of it and produces birdbaths. |
| Textured surfaces | 2% minimum | Broom-finished concrete and pavers hold surface water; they get the full two per cent. |
| Soil away from foundation | 5% over first 10 ft — 6 in of fall CRC R401.3 | Steeper than paving because loose soil settles and planting slows runoff. |
| Accessible route | Max 5% running, max 2% cross slope | Two per cent is simultaneously the drainage minimum and the accessibility maximum — the tightest constraint in flatwork layout. |
| Subsurface line | Minimum 1% continuous fall to outlet | Perforations down, sock or filter fabric where the surrounding soil is fine enough to migrate. |
| Outlet | Daylight where grade permits | Where there is no fall to daylight, the design changes — see the note below. |
Every drain gets a real outlet.
A perforated pipe in a gravel trench that terminates nowhere is a holding tank, so every run we lay gets somewhere to let go. On flat lots without fall to daylight there are three good answers: a pumped system with a basin and a check valve, an infiltration system sized to the soil's measured intake rate, or regrading the surface so water never collects in the first place. We will tell you which of the three your site needs, and what it involves, before it is priced.
Concrete flatwork.
Slab thickness is chosen from the heaviest thing that will ever sit on it or drive across it, not from what the area is called.
An extra inch of concrete over a poorly prepared subgrade buys far less than the same money spent on removing soft material and compacting properly — concrete is strong in compression and weak in tension, and a slab bridging a soft spot is in tension across the bottom, which is exactly where it cracks.
| Element | Standard | Notes |
|---|---|---|
| Pedestrian slab | Nominal 4 in | Patios, walkways, garden furniture. Thicker does not improve it. |
| Vehicle slab | 5–6 in | Heavier end for RV pads, trailers, or anywhere a delivery truck may cut a corner. |
| Slab edges, vehicle | Thickened edge or edge reinforcement | The middle of a driveway is supported on both sides and the edge is not, which is why the edge gets the extra thickness. |
| Mix | Minimum 3,000 psi; 4,000 psi typical for vehicle slabs | Specified on the ticket. Water added on site to improve workability reduces strength and is not permitted. |
| Control joint depth | At least ¼ of slab depth | Cut to full depth, the joint is the weakest line in the slab — which is precisely what makes it work. |
| Control joint spacing | Feet ≈ 2–3 × thickness in inches | A 4 in slab wants joints every 8–12 ft. Panels as close to square as possible. |
| Isolation joints | Full depth, compressible filler | Wherever a slab meets the house, a foundation, a column, a pool shell or existing concrete. |
| Curing | Moisture retained, minimum 7 days | Curing compound or wet cure. Concrete gains strength by hydration, not by drying. |
A control joint decides where the slab relieves its shrinkage, which is exactly the job it is there to do.
Crack-free concrete is not something anyone in the trade can promise. Control over where it goes is — and that is what a properly jointed slab buys you.
Saw cutting is timed — early enough that shrinkage has not already cracked the slab, late enough that the saw does not ravel the edge. A cold joint, by contrast, is not a design element at all: it is the seam where fresh concrete met concrete that had already begun to set, and it is a weakness. We place continuously and size pours to what can be finished in one go.
Segmental paving.
A paver pavement is an engineered sandwich and each layer has exactly one job.
Almost everything that makes hardscape last is in the base rather than in the surface.
| Layer | Standard | Notes |
|---|---|---|
| Subgrade | Shaped to finished slope, compacted | Everything above follows this surface. A subgrade that holds water holds water under the finished patio. |
| Base — pedestrian | 4 in class II, compacted to 95% ICPI | 6 in on soft or reactive clay. |
| Base — vehicular | 6–8 in class II, compacted | Driveways and anything carrying vehicles. |
| Base extent | Extends past the paving edge | The edge restraint must be spiked into base, not into soil. |
| Bedding | 1 in coarse washed concrete sand, screeded, not pre-compacted | One inch is deliberate — a thick bedding layer is a soft layer. Pavers set on two or three inches of sand rut and rock. |
| Bedding material | Washed concrete sand only | Stone dust and screenings hold water and turn to mud. This layer is for setting the units; the levelling is already done underneath it. |
| Pattern | Herringbone under vehicle load | Interlock resists rotation, which is what holds a driveway tight under turning loads. |
| Edge restraint | Rigid perimeter, spiked into base | Without it the field creeps outward, joints open, and the pavement loosens from the edges in. |
| Joint sand | Swept in, field compacted, topped and re-swept | Polymeric where joints are wide or the slope is steep enough to wash sand out. |
Retaining walls.
A retaining wall holds back soil, and soil behaves like a fluid that gets heavier when wet.
Lateral earth pressure increases with the square of the height, so a wall twice as tall needs considerably more than twice the engineering. It also means drainage behind the wall does as much work as the wall itself — not the block, not the mortar, the water.
| Element | Standard | Notes |
|---|---|---|
| Engineering trigger | Over 4 ft retained height, or any surcharge CBC | Measured from bottom of footing to top of wall. A slope, driveway, pool or structure above the wall is a surcharge and triggers engineering at any height. Verify the current threshold with the local building department. |
| Drainage aggregate | 12 in minimum clean drain rock behind wall NCMA | Open-graded, fines washed out — the opposite material to base rock. |
| Drain line | Perforated collector at base, fall to daylight | Non-negotiable on every retaining wall we build, at any height. |
| Separation | Filter fabric between drain rock and soil | Stops fines migrating into the drainage zone and clogging it. |
| Base course | Buried, on compacted aggregate leveling pad | Typically one course or 10% of wall height below finished grade, whichever is greater. |
| Geogrid | Per engineered design where required | Length and vertical spacing come from the design, not from habit. |
| Backfill compaction | In lifts, light equipment near the wall | Heavy compaction directly behind a segmental wall pushes it out of alignment. |
Structures & footings.
Pergolas, pavilions, outdoor kitchens and shade structures are buildings.
They get permitted, they get footings sized for the load and the soil, and the posts do not touch dirt.
| Element | Standard | Notes |
|---|---|---|
| Permit | Pulled for structures, gas, electrical CRC / CBC | Thresholds vary by jurisdiction; we confirm with the authority having jurisdiction before pricing. |
| Footing depth | Below the zone of seasonal soil movement | On the expansive clay common here this is a real constraint, not a formality. Depth follows the approved detail. |
| Post-to-concrete | Standoff base, 1 in above finished surface | A standoff base keeps the end grain clear of the concrete and dry, which is what gets you decades out of a post. |
| Fasteners & hardware | Hot-dip galvanised or stainless, exterior rated | Matched to the preservative in treated lumber, so the fastener lasts as long as the timber it holds. |
| Gas | Permitted, pressure tested | For fire features and outdoor kitchens. |
| Electrical | GFCI protection, exterior-rated enclosures NEC | Receptacles in wet locations get in-use covers. |
Irrigation & lighting.
An irrigation system earns its keep two ways: even delivery, and the right water in the right place at the right time.
Both are design decisions, and both are far cheaper to settle on paper than in the ground.
| Element | Standard | Notes |
|---|---|---|
| Backflow prevention | Required, per water purveyor | Device type and test requirements are set by the local agency. This protects the potable supply and is not optional. |
| Head spacing | Head-to-head coverage | Spray patterns overlap to the adjacent head. Anything less produces dry arcs no controller setting can fix. |
| Zoning | By hydrozone and by precipitation rate | Never mix spray and rotor on one valve — their application rates differ by a factor of several. |
| Hydraulics | Zones sized to available flow and pressure | Over-loaded zones starve the far heads. Pressure-regulating heads where static pressure is high. |
| Drip | Filter and pressure regulation at the zone | Emitters clog without filtration; unregulated drip blows fittings apart. |
| Controller | Weather-based, with a rain shutoff | Programmed to cycle-and-soak on clay so water infiltrates instead of running off. |
| Water efficiency rules | Per state and local ordinance MWELO | California's Model Water Efficient Landscape Ordinance applies above certain project sizes, and local agencies may be stricter. We confirm applicability during design. |
| Sleeving | Under all hardscape, oversized, capped | Put in during construction. Retrofitting a line under a finished driveway costs many times what the sleeve did. |
Low-voltage lighting
| Element | Standard | Notes |
|---|---|---|
| System | 12 V low voltage, transformer on GFCI | Transformer sized with headroom for later additions. |
| Voltage drop | Held within ~10% at the last fixture | Wire gauge follows run length and load. This is why a long run gets heavier cable, not more transformers. |
| Burial depth | 6 in minimum for low-voltage cable NEC 300.5 | Deeper under planting beds that will be dug. |
| Connections | Waterproof, gel-filled or heat-shrink | Twist-on connectors in a landscape are a future service call. |
| Color temperature | Consistent across the installation | Mixed color temperature is the most visible error in a finished lighting scheme. |
Soil & planting.
Plants are the only part of a build that is supposed to change after we leave.
The work is in the soil and in the first two summers.
| Element | Standard | Notes |
|---|---|---|
| Selection | Suited to USDA 9b and to the actual exposure | Sun, reflected heat off west-facing walls and hardscape, and mature size at ten years — not at purchase. |
| Soil preparation | Amended and decompacted across the bed | Not just in the planting hole. A hole of good soil in a pan of clay is a bucket. |
| Planting depth | Root flare at or slightly above finished grade | Setting the root flare at grade is the single biggest thing you can do for a young tree. |
| Staking | Only where needed, removed within a year | Taking the stake off on time is what lets the trunk build its own taper and stand on its own. |
| Mulch | 2–3 in, held clear of trunks and stems | Held clear of the bark, mulch keeps moisture exactly where the roots want it. |
| Establishment | Separate irrigation program for the first two seasons | Establishment watering is deeper and less frequent than the long-term schedule. We hand it over written down. |
The calls we make the same way every time.
A specification means most when it says which way a decision goes on a wet Tuesday with the excavator already on site. Each of these comes up on real jobs, and each one has a settled answer.
- Soft material comes out before anything goes on top
- Digging it out costs a morning. Bridging it with extra base or extra concrete settles later, and settles unevenly, which is the kind you notice.
- The base gets levelled, not the bedding sand
- The bedding layer sets the units; the levelling is already done underneath it. Keeping those two jobs separate is what keeps pavers tight underfoot for twenty years.
- Every retaining wall gets drainage
- At any height. Give the water a way out from behind the wall and hydrostatic pressure never gets a chance to build — it is one of the cheapest things in the trade to get right.
- Structural, gas and electrical work gets permitted
- Pulled, inspected and on the public record. That record is what makes the sale simple the day you list, and it costs a fraction of what it is worth to you then.
- Every drain line ends somewhere real
- A pipe is only as good as the place it lets go. Where there is no outlet to hand, the design changes until there is one — a pump and basin, an infiltration system, or a regrade.
- The mix arrives as specified and stays that way
- Water added to the truck on site improves workability and spends the strength you paid for. What the ticket says is what goes in the ground, and you are welcome to read it.
- Every excavation starts with a locate
- A ticket first, every time, on every job. This one is also the law — see Safety & Compliance.
- Anything we find goes in the proposal with a number on it
- If the site walk turns up a drainage fault, an undersized main or a wall near the end of its life, you get it as a priced line item — whether or not you asked about it, and whether or not you have us do it.
How to hold us to this.
This page only means something if you can check it, so here is how — on our jobs and on anyone else's.
Ask for the section in writing
Any proposal we issue names the base depth, the compaction target and the fall. If a competing bid does not, that is the question to ask before comparing prices.
Look at the excavation before base goes in
It is the only moment the subgrade is visible. We will tell you when that is and you are welcome on site.
Look at the base before bedding sand
Same reasoning. Depth is measurable with a tape at this point and at no point afterwards.
Ask to see the concrete ticket
It states the mix. Keep it.
Ask for the permit numbers
Where work is permitted, the numbers are yours and the inspection record is public.
Spotted something we should update?
Standards move and local amendments differ, so if you see something worth updating we would genuinely like to hear it. If you are a contractor, an engineer or an inspector and something here does not match current practice, tell us and we will fix it: daniel@dztlandscaping.com.
Bring us a bid to read.
Have three quotes and no idea why they differ? Bring them to the site walk. We will tell you what each one is actually pricing, including ours.
Book a site walk, or call (916) 222-2811.