Paver and hardscape installation field guide for patios, walkways, and driveways

The base makes the job, not the pavers

A paver installation is the whole layered section under a segmental concrete paver surface, and the part the customer never sees is the part that decides whether the job lasts. The pavers are the easy day. Anyone can set units into sand and make a flat field look good for the photo. The failures that bring you back in two years, the dips in the wheel path, the edge that fanned out, the puddle by the door, the heave after the first hard winter, almost never start in the pavers. They start in the base, the compaction, and the drainage under it.

So put the effort where the failure lives. The subgrade has to be proven and non-yielding, the aggregate base has to be the right depth and compacted in lifts, the surface has to slope so water sheds instead of ponding, and the edge has to be restrained so the field cannot spread. Get those right and the pavers go down fast and stay put. Get them wrong and a beautiful surface is just a problem with a nice finish on top.

This guide is the install: the dig, the subgrade, the base, the bedding, the compaction, and the joints. The pattern, the border, the cut layout, and the material takeoff are their own work, covered in the paver layout and field border guide. The drainage and the grade the patio ties into are covered in the drainage, grading, and slope guide. Read those two alongside this one, because a paver field is only as good as the layout that sets it and the grading that drains it.

How deep do you dig for a paver patio?

You dig to the sum of the layers, not to a single number off the top of your head. The excavation depth is the paver thickness plus the 1 in bedding sand plus the compacted base thickness, with a little extra for geotextile and tolerance. A 60 mm patio paver, about 2 3/8 in, on a 4 in base works out to roughly 7 1/2 in of dig. An 80 mm driveway paver, about 3 1/8 in, on an 8 in base is closer to a foot. Run the math for your actual section before the machine starts, because a hole dug too shallow means either a thin base or a high finish grade, and both are problems you cannot fix from the top.

Over-dig past the edge of the paved area. The base has to extend beyond the pavers so the edge restraint has compacted aggregate to spike into and so the perimeter units are not sitting on the unsupported lip of the excavation. ICPI guidance ties the spike distance back to the base thickness, so plan the base to run past the finished edge by at least the base depth, commonly 6 in to a foot of extra width all the way around. Cut the perimeter short and the edge restraint anchors into nothing and the field spreads from day one.

Strip to firm native soil, not just to depth. If the number says 8 in but at 8 in you are still in topsoil, fill, or organic muck, you are not done. Topsoil and uncompacted fill compress and rot, and a base built on them settles no matter how well you compacted the stone. Dig until you reach undisturbed, competent subgrade, then build the section up from there. The depth is a starting estimate. The soil you find is what actually sets the bottom of the hole.

How do you prepare and prove the subgrade?

The subgrade is the native soil the whole section sits on, and it has to be compacted, uniform, and non-yielding before any stone goes in. This is the foundation under the foundation. A base over a soft subgrade settles into the soft spot and takes the pavers with it, and you cannot compact your way out of it from above. You prove the subgrade is solid first, then you build.

Compact the subgrade to a real target, not until it looks done. Common practice is at least 95 percent of standard Proctor density, ASTM D698, for pedestrian work and 95 percent of modified Proctor, ASTM D1557, under vehicular traffic, with the project spec and the geotech report setting the actual requirement. On a small patio you confirm it by feel and by proof: walk it, run a loaded plate or a small roller across it, and watch for movement. The tell is the soft spot. Where the soil pumps, ruts, or springs back under the load, you have found the weak zone, and that is the spot that will fail later if you ignore it now. On commercial and vehicular jobs the proof is a proof-roll with a loaded truck plus spot density tests with a nuclear gauge or sand cone, because feel does not hold up on a submittal.

Where the subgrade is weak, wet, or pumping and you cannot dry it out or dig it out, separate it from the base with a geotextile. A non-woven separation fabric laid over the subgrade keeps the soil fines from migrating up into the aggregate and keeps the stone from punching down into the soil, which is the slow failure that shows up as ruts a year or two out. Lap the fabric a foot in decent soil and 2 ft over weak, poor-draining ground, turn it up at the edges so the base sits in a contained bathtub of stone, and run it down-slope. Over very weak soil a heavier geotextile or a geogrid earns its cost several times over by holding the base together under load. The fabric does not replace compaction. It protects the base you compacted from a subgrade that was never going to behave.

The blunt version: if the ground moves under your boot or the plate, it will move under the pavers. Fix it now, with depth, fabric, or a stabilized layer, while the hole is open. Nobody fixes a bad subgrade after the field is laid. They tear the field out and start over.

How thick should a paver base be?

Base thickness comes off the traffic and the soil, and the dense-graded aggregate base is the layer that carries the load and holds the grade. Over well-drained soil, ICPI guidance, now published under the Concrete Masonry and Hardscapes Association after ICPI merged into CMHA, commonly puts a pedestrian patio or walkway on a minimum 4 in (100 mm) of compacted aggregate, and a residential driveway on at least 6 in (150 mm). Vehicular and commercial work goes deeper, often 8 to 12 in or more. These minimums are over good soil, so they are the floor, not the answer for every site.

Weak or wet soil and cold climates drive the base thicker. ICPI guidance commonly adds 2 to 4 in to the base over continually wet or weak subgrade and in hard-freeze regions, and on a vehicular or commercial job the real number comes from the geotechnical report and the project structural section, which read the actual soil strength and the actual wheel loads. That is not a rule of thumb you carry in your head. It is a designed thickness, and it wins over any general minimum.

Use the right stone. The conventional base is a dense-graded crushed aggregate, a blend of sizes down to fines that locks together tight when compacted, often sold as crusher run, road base, or a state DOT dense-graded spec. It is not clean stone, not pea gravel, and not bank-run gravel full of clay. The fines are what let it compact to a hard, non-yielding plane. The open-graded base, the clean no-fines stone used for permeable and some modern conventional builds, is a different system covered further down. Pick the base type before you order, because the bedding and the compaction change with it.

Compacting the base in lifts

Aggregate compacts in lifts, never in one deep dump. Stone placed in a single thick layer compacts on top and stays loose underneath no matter how long you run the plate, and that loose bottom is where the field settles later. So you place the base in lifts of a few inches and compact each one fully before the next goes down. A small forward plate compactor handles about a 2 in lift to full depth. A large reversible plate moves 4 to 6 in. Match the lift to the machine, not to your patience.

Compact to a density, not to a number of passes. The target is commonly 95 percent of modified Proctor under vehicular traffic and 95 percent of standard Proctor for pedestrian work, set by the spec. On a commercial job you confirm the first lift with a nuclear density gauge and carry it through the rest. On a patio you read the stone: a fully compacted dense-graded base stops taking compaction, the plate quits sinking and starts to ring rather than thud, and the surface tightens to a hard plane you can barely scuff with a boot heel. If the plate is still walking the stone around after several passes, the lift is too thick or the moisture is wrong.

Moisture matters more than crews expect. Dense-graded aggregate compacts best at a damp, near-optimum moisture, not bone dry and not soupy. Bone-dry stone will not lock, and you chase density forever. Sopping stone pumps and never sets. A light water down before compaction, so the fines bind without the base turning to mud, is the difference between a base that hits density in three passes and one that fights you all day.

Build the slope into the base and hold it lift to lift. The finished surface pitch has to be set in the subgrade and the base, because you cannot create fall in the 1 in bedding without breaking the uniform-thickness rule. Grade each lift to the design slope, check it with a laser or string pulled to the fall, and keep the top of the base a true, flat plane held at the slope. The pavers will mirror whatever the base does. A wavy base makes a wavy field.

How much should a paver surface slope?

A paver surface needs a minimum slope of about 1 percent and ICPI commonly recommends up to 2 percent, which is 1/8 to 1/4 in of fall per foot. Below 1 percent, water sheets and ponds instead of running off, and a paver surface is not waterproof. Standing water works down through the joints into the bedding and the base, and on a freeze it lifts the field. The slope is what keeps the water moving across and off the surface before it gets the chance.

The fall runs away from the structure, always. Pitch a patio toward the house and you have built a chute that delivers surface water and roof runoff to the foundation, which is a callback with your name on it and a wet basement on the other end. The water goes out, toward a lawn, a swale, a drain, or wherever the site grading takes it. How that water gets off the lot to a legal outlet, and the foundation grade it ties into, is the whole subject of the drainage, grading, and slope guide. The paver field is one surface in that larger system, and it has to shed into the system, not fight it.

Carry the slope through every layer and check it, because 1/4 in per foot is invisible to the eye. You will not see the fall on a 20 ft patio. The water will find it the first hard rain, and so will you if it runs the wrong way. Set the slope in the subgrade, hold it through the base lifts, screed the bedding parallel to it, and confirm the finished pavers hold the same pitch with a level or a laser before you call it done. The number that bites is the dead-flat or back-pitched corner nobody checked.

The bedding sand and the 1 inch rule

The bedding is a screeded course of sand the pavers seat into, and it is a uniform 1 in (25 mm), full stop. ICPI and CMHA guidance, in Tech Spec 2, calls for about 1 in of bedding after screeding, and that thickness is not a suggestion you adjust to taste. The bedding is a setting bed, not a leveling course. It gives every unit the same uniform seat so the field sits flush, and it does that only when it is the same thickness everywhere.

Use washed concrete sand that meets ASTM C33, the coarse, angular sand graded for concrete. Do not use stone dust, limestone screenings, or mason's sand. This is the single mistake that defines amateur paver work. Screenings and stone dust hold water, carry too many fines, and break down under wetting and traffic, so the pavers rock, pump, and sink within a season or two. The trade switched off stone dust for bedding years ago for exactly this reason, and a field set on screenings tells on whoever set it the first wet spring.

Screed it, do not float it. Set two screed rails, lengths of pipe or square tube, on the compacted base at the bedding thickness, pull a straightedge across them to strike off a flat 1 in of loose sand, then pull the rails and fill the grooves carefully by hand. Screed only the area you will lay before the next compaction, because you do not walk on, kneel on, or disturb the screeded bed once it is struck. A footprint in the bedding is a low spot in the field.

The rule crews break under schedule pressure is using the bedding to fix a bad base grade. The day you start screeding 1/4 in over a hump and 2 in into a hollow, you have built differential settlement into the field, because thick sand consolidates more than thin sand and the surface ends up wavy. When the base is high or low, you fix the base. The sand follows the base. It never replaces grading it.

Open-graded vs sand-set construction

There are two ways to build the layers under pavers, and they are not interchangeable. The traditional sand-set system is a dense-graded aggregate base with fines, a 1 in washed concrete sand bedding, and sand-filled joints. The open-graded system uses clean, no-fines crushed stone for both the base and the bedding, with a small open-graded stone in the joints. The open-graded build drains through itself and is the basis of permeable pavement, and it is showing up on conventional jobs too because it sheds water down through the section instead of trapping it under a dense base.

The bedding stone is where people mix the two up and ruin a job. A sand-set field uses ASTM C33 concrete sand at 1 in. An open-graded field uses a clean, single-sized chip, commonly a No. 8 or similar small open-graded stone, over an open-graded base, not concrete sand. Put concrete sand on an open-graded base and the sand migrates down into the open voids and the bedding disappears. Put a permeable open-graded recipe under a job that was designed dense-graded and you have changed the structural and drainage behavior the design assumed.

Pick the system on purpose and build it all the way through. The base type, the bedding material, the joint fill, and the compaction approach all change with the choice, and a half-and-half hybrid born of whatever was on the truck is how fields fail in ways nobody can diagnose later. If the job is permeable, follow the permeable guidance and the engineered design. If it is conventional, build dense-graded with concrete sand and seal the surface to drainage. Do not improvise across the two.

Laying the pavers into the bedding

You lay pavers into the screeded bedding by placing each unit straight down, not by sliding it across the sand. Set it down against its neighbors and let it drop into place. Slide a paver and you plow a wedge of sand ahead of it, which lifts the unit and throws the joint off, so the move is place and release, not push and shove. The light click of one unit settling against the laid field is the sound you are listening for.

Work off the laid field, not off the bedding. Once the first courses are down, you kneel and stand on the laid pavers and reach out to set the next ones, so you never disturb the screeded sand ahead of you. That is why the bedding is screeded only a manageable area ahead of the laying, and why a tidy crew keeps the screed line close to the laid edge. Stage the pavers on the laid field or on plywood, never on the open bedding.

Keep the joints tight and consistent and hold the lines. Most segmental pavers have small spacer nubs that set a joint a few millimeters wide, and you snug the units against each other so the joint stays uniform. Pull a string or set a straightedge across the field every few rows and check that the joint lines have not wandered, correcting a 1/8 in drift before it grows into a 2 in problem and a wedge of bad cuts at the border. The pattern itself, the running bond or herringbone the traffic demands, the soldier-course border you lay first, and the cut layout that balances the edges are all set in the paver layout and field border guide. Lay to those lines. This part of the job is execution against a layout that was already squared and snapped before the first unit went down.

Cutting the field to the border

The field gets cut to meet the border and the edges, and the cuts are where a finished job looks finished or looks rough. The border goes in first, the field is laid into it, and the field pavers along the perimeter are cut to close the gap. Mark each cut from the actual opening, not from a tape measurement carried across the field, because small drift in the joints means the gap is rarely the size the plan said it would be.

Cut clean and cut with the right tool. A masonry splitter is fast for straight rough cuts. A wet saw with a diamond blade gives the exact, square cut a visible border edge needs and keeps the silica dust down, which matters for the lungs as much as the look. Wear the respirator on dry cutting. Cured concrete dust is respirable silica and it is a real hazard, not a nuisance.

No tiny slivers at the edge. A cut narrower than about a third to a half of a paver breaks under traffic, pops out of the field, and looks like a mistake because it is one. The fix is in the layout, where centering the field balances the cuts so both borders end in large, durable pieces instead of a row of slivers on one side. Balancing the cut and choosing the pattern that drives the waste factor are covered in the layout and border guide. On the install, the rule is simple: a sliver is a future loose paver, so adjust the cut or the course before you set a piece too small to hold.

Do you need edge restraint for pavers?

Yes, and it is the make-or-break detail of the whole install. Edge restraint is what holds the perimeter pavers from moving outward, and without it the field spreads, the joints open, the sand washes out, and the whole thing unravels from the edge in. This is not optional and it is not where you save a hundred dollars. A paver field with no edge restraint has a built-in failure date, and pairing a thin base with a missing restraint is the most common way a field comes apart early.

The mechanism is simple. Every load on the field, a footstep, a tire, a freeze-thaw cycle, pushes the pavers outward a hair. With a restraint, the perimeter pushes back and the interlock holds. Without one, the edge units creep out, the joint behind them opens, the joint sand leaves, and the next unit follows. Two seasons later the edge is a fan of loose pavers and a lawn full of sand. The interlock that carries the whole field by friction only works while the perimeter is held.

Use a real restraint and anchor it into the base, not the soil. ICPI Tech Spec 3 is clear that flat landscape edging does not hold pavers, because it lacks the vertical face to restrain them. A proper spiked paver edge restraint sits against the paver with at least about 1 in of vertical contact and spikes down into the compacted aggregate base, with the spike set back from the outside edge of the base by at least the base thickness so it has stone to grip. Spike it into soil and it pulls right out the first season. That set-back is exactly why the base has to over-run the paved edge, from the excavation step.

For vehicular and commercial work, spikes alone are not enough. The heavier answer is a poured concrete haunch or curb, a concrete edge cast against the perimeter course, because repeated tire loads walk a spiked plastic restraint out of even a good base. The restraint goes on the base, against the laid pavers, before the joint sand and the final compaction, so the field is locked at the perimeter when you fill the joints. Set it last, after the field is laid and seated, and set it tight to the pavers with no gap.

Seating the laid pavers with the plate

After the field and border are laid and the edge restraint is set, you run a plate compactor across the whole surface to seat the pavers into the bedding sand. This pass is not the joint sand pass. It presses each unit down into the 1 in sand bed so the field consolidates to a uniform plane, locks the units against each other, and works a little sand up into the bottoms of the joints, which starts the vertical interlock. Make two or three passes over the whole area, working from the edges inward so you do not chase the field outward against the restraint.

Run a protective mat or pad, always. A bare steel plate on bare pavers chips the edges and etches the faces, and the marks do not come out, so a rubber or neoprene pad on the plate, or a roller-style paver compactor, protects the surface. On a textured, tumbled, or premium paver this is not negotiable. ICPI calls for the pad and for a real machine: for vehicular work the plate should deliver around 5000 lbf of force at 75 to 90 cycles per second, because a light homeowner plate will not seat an 80 mm field.

Do not compact a wet field or a field with sand on the faces, and do not seat over a soft spot. If the bedding is saturated, the plate pumps and you lose the plane. If there is grit on the paver faces, the plate grinds it into the surface. And if a section dips under the plate, you have a base problem the seating pass just exposed, so stop and find it now, before the joints are filled and the only fix is pulling the field back up.

How do you install polymeric joint sand?

Joint sand is what makes the interlock work, so the joints have to be filled completely and then locked. The field is not a glued slab. It carries load by friction between units, and that friction only exists when the joints are full from the bottom up. After the seating pass, you sweep joint sand across the surface, run the plate again so the vibration carries the sand down into the joints, then sweep and compact again until the joints are full and stay full. That is usually several rounds. Top off and recompact until the sand quits dropping.

Polymeric sand is the common finish for residential work now, and it has one trap that bites crews constantly: haze. Polymeric sand is fine sand blended with a binder that hardens when you wet it, and it resists washout, weeds, and ants better than plain sand. The milky film it leaves on the paver faces, the haze, comes from activating the binder on the surface instead of down in the joint, and the fix is entirely in the prep, not the cleanup.

Install polymeric sand dry and clean, then activate it last. The whole surface and the joints have to be bone dry, with no rain in the forecast for the cure window the bag specifies. Sweep the sand in diagonally across the joints so you do not pull it back out, fill each joint to about 1/8 in below the paver bevel, compact it down, and top off. Then, before a drop of water touches it, sweep and blow every grain of poly off the paver faces. Only then do you mist it to activate, lightly, the way the bag says, enough to set the joint and no more. Overwater and the binder floats to the surface and hazes. Leave sand on the faces and it cements there. Get haze and you are into acid or specialty cleaners with no guarantee on a surface you just finished. Do it dry and do it clean the first time.

Follow the manufacturer over any general rule. Polymeric products differ in minimum and maximum joint width, in the number of mist cycles, in cure time, and in temperature limits, and the bag is the spec for that product. A joint too narrow for the sand will not take it. A joint too wide for that product will not lock. Read the bag, build to the joint width it wants, and water it on its schedule, not yours.

Driveways, vehicular load, and commercial plazas

Vehicular work is the same sequence with more under it and more on top. The base goes deeper, commonly 8 to 12 in or more set by the geotech and the structural section, the paver is thicker, the 80 mm (about 3 1/8 in) unit instead of the 60 mm patio paver, and the pattern is herringbone at 45 or 90 degrees because it resists the horizontal creep from turning, braking, and accelerating tires far better than running bond. The compaction targets climb to 95 percent of modified Proctor, and the edge restraint steps up from spikes to a concrete haunch or curb. None of that is optional on a surface cars drive on.

The interlock has to be complete or the field rolls. Under wheel loads the three-part interlock, vertical from the seated bedding, rotational from the joint sand, and horizontal from the herringbone pattern and the restrained edge, is what spreads a tire load across many units instead of letting one unit punch down. Skip the full joints, the herringbone, or the rigid edge and the field ruts in the wheel path within a year. The pattern choice and the structural reasons behind herringbone are detailed in the layout and field border guide.

Commercial plazas, parking lots, and the hardscape around data centers and institutional buildings are designed pavements, not patio recipes scaled up. The section comes from an engineer reading the actual loads, the soil, and the freeze depth, often with an open-graded or stabilized base, a thicker structural paver, and a full concrete edge, and the install has to match the drawings exactly because the loads and the liability are real. On that work, ICPI structural guidance and the project structural section govern, and the field job is to build the layers the design calls for and prove each one before it is buried.

Permeable pavers as a variant

Permeable interlocking concrete pavement, PICP, is built to let water pass through the surface instead of shedding it, and it changes the layers, not just the look. Instead of dense-graded base and concrete-sand bedding, PICP uses open-graded crushed stone throughout: a clean, single-sized bedding stone, an open base, and often a deeper open subbase that doubles as a stormwater reservoir, with the joints filled by small open-graded stone rather than sand because the water has to get through them. The minimum surface slope is commonly 2 percent.

The whole section is engineered to store and infiltrate a design storm, so the depths, the storage, the overflow, and the subgrade treatment come from a designer and the geotech, not from the standard patio recipe. Critically, the subgrade is often left uncompacted or lightly compacted to preserve infiltration, which is the opposite of a conventional build, and a geotextile manages migration without choking the system. Build a permeable section with conventional fines in the base and you clog the one thing it exists to do.

PICP follows its own ICPI and CMHA guidance, commonly the permeable construction tech spec, and often a different paver, ASTM C1782 for permeable units rather than ASTM C936 for conventional ones. It earns its place where stormwater rules cap runoff and a conventional surface would need a detention basin instead. Do not build it off a conventional detail. The deeper treatment of permeable systems and the layout side sit in the paver layout and field border guide and the drainage, grading, and slope guide. The point here is to know when the job is permeable, because the install rules flip.

Steps, raised patios, and the wall behind them

A raised paver patio or a set of paver steps is two trades in one, and the failure usually comes from the wall, not the pavers on top. A raised patio sits behind a retaining wall, and that wall holds back the structural fill the pavers are built on. If the wall settles, leans, or drains badly, the patio behind it tips, cracks the joints, and pulls away from the building. So the wall and its drainage are the real job, and the paver surface is the finish over a structure that has to be right first.

Build the fill behind the wall in compacted lifts and drain it. The space behind a raised patio wall gets free-draining gravel against the wall and compacted structural fill in lifts under the patio section, not loose dumped soil that will consolidate for years. A drain at the base of the wall carries water out to an outlet, because water trapped behind the wall builds the hydrostatic pressure that bows and blows out walls. The retaining wall, its drainage, and the height where it crosses into engineered design are covered in the drainage, grading, and slope guide. Above the heights a manufacturer's general detail covers, the wall is engineered, and the patio rides on whatever the engineer designed.

Steps carry their own rules. Each tread needs solid, compacted support so it cannot settle independently and create a trip lip, and the riser height and tread depth have to be consistent because people fall on the one step that is different. A step built on uncompacted fill is the unit that drops a half inch and catches a toe. Compact under every tread the same way you compact the field, and confirm the rise and run are even before the units are set.

Sealing, snow, and the maintenance the owner inherits

Sealing a paver surface is optional, and it is a finish choice, not a structural one. A penetrating or film-forming sealer can deepen the color, resist staining, and help stabilize the joint sand, and joint-stabilizing sealers add some lock to plain sand joints. It does not fix a bad base, it does not replace edge restraint, and it does not waterproof the field. Seal a field that was built wrong and you have sealed in the problem. If you do seal, the surface and joints have to be fully cured and dry, and you follow the sealer maker's window after install, because sealing too soon traps moisture and clouds the finish.

Tell the owner what they inherit, because a paver field is a maintained surface, not a slab you walk away from. The joints lose a little sand over time to wind, rain, and pressure washing, so they get re-sanded periodically, and a sealed field gets resealed on the maker's cycle. Pressure washing is the quiet killer here: a tight nozzle held close blasts the joint sand out and pits the paver face, so it gets done on a wide fan at distance, with a re-sand after. The owner who power-washes the joints empty every spring is slowly disassembling the interlock.

A settled or heaved area is a repairable thing, and that is the quiet advantage of a paver field over poured concrete. You lift the affected pavers, fix what went wrong underneath, the low base, the soft spot, the washed-out bedding, relevel to the slope, reset the same units, and re-sand the joints. The field hides the repair because the units are reused. But the reset only holds if you fix the cause, not just the symptom. Relevel a dip without rebuilding the soft base under it and you are back next year. Tell the owner that a small settled spot caught early is a morning's work, and a whole field left to spread is a teardown.

Snow removal is its own season of wear, and a new field is the most vulnerable to it. Plowing catches the edge of a raised or unrestrained unit and drags it out, so a plow blade gets shoes or skids set to ride just above the surface and the operator works with the joint lines, not across a high edge. And keep deicer off a new field. Fresh pavers and fresh polymeric joints have not fully cured, and deicing salts can scale the surface, attack the joint binder, and speed up freeze-thaw spalling on young concrete, so the bag and the paver maker both call for a wait, commonly through the first winter. Sand for traction in the meantime, and when you do use a deicer later, use the gentlest one that works and use less of it. The long defense against freeze-thaw is the one already built in: the slope that sheds the water, the full joints that keep it out of the bedding, and the base that drains instead of holding a frozen lens. A field that drains survives winters. A field that ponds gets taken apart by them.

What to document

The record is what answers the question a year out when a field settles, spreads, or ponds, and on a paver job every answer lives in a layer nobody can see anymore. Write it down while the layers are open, because once the field is laid the proof is buried with it.

Capture the paved area and its square footage, the excavation depth, the subgrade condition and how it was proven, whether a geotextile or geogrid went in, the compacted base type and depth, the slope and its direction, the bedding sand type and the 1 in depth, the edge restraint type and how it was anchored, the joint sand type, and the compaction equipment and passes. If you added base for soft soil, laid fabric, or changed the section, note why. A tool like FieldOS is built for exactly this, capturing the buried layers and the as-built section as one field record with photos, instead of a depth scribbled on a delivery ticket nobody can find when the question comes up. The next person standing on a dip needs to know what is under their feet and who decided it.

Common mistakes

• Building the base too thin for the traffic, or dumping it in one lift so it never compacts to the bottom.
• Laying the section over a soft, unproven subgrade with no proof-roll and no geotextile.
• Pitching the surface flat or back toward the structure instead of 1 to 2 percent away from it.
• Screeding the 1 in bedding thick in the hollows to fix a bad base grade instead of regrading.
• Setting the bedding on stone dust or screenings instead of washed ASTM C33 concrete sand.
• Skipping the edge restraint, or spiking it into soil instead of the compacted base, so the field spreads.
• Calling the field done with empty or half-filled joints, so the interlock never engages.
• Sweeping polymeric sand over damp pavers or leaving it on the faces, then washing in haze.
• Compacting the laid pavers with a bare steel plate and no protective mat, chipping the faces.
• Mixing an open-graded base with concrete-sand bedding so the bedding migrates into the base.

Field checklist

Standards and references

The governing guidance for segmental concrete paver installation comes from ICPI, the Interlocking Concrete Pavement Institute, which merged into the Concrete Masonry and Hardscapes Association, CMHA. Its tech spec series covers this work directly: the base and bedding construction in Tech Spec 2, the edge restraints in Tech Spec 3, the structural design for roads and parking lots, and the permeable construction in Tech Spec 18. The base thicknesses, the 1 in concrete-sand bedding, the slope range, the seating compaction, and the edge restraint anchoring in this guide trace to those documents, and they are revised, so confirm the current edition.

The materials carry their own specs. ASTM C936 is the standard specification for solid concrete interlocking paving units, ASTM C1782 covers permeable units, and ASTM C33 is the concrete-aggregate gradation the bedding sand meets. Compaction density references the Proctor standards, ASTM D698 for standard and ASTM D1557 for modified, and the polymeric joint sand follows the manufacturer's printed instructions for joint width, activation, and cure, which govern that product over any general rule.

The structural section, the base depth, and the subgrade treatment on a vehicular or commercial job are not set by a general minimum. The geotechnical report and the project specification govern them, because they read the actual soil and the actual loads, and they win over any rule of thumb whenever they are stricter. Accessible routes follow the ADA Standards for Accessible Design and any state amendment for slope, surface, and joint openings, and stormwater on permeable and commercial work follows the local code and the civil design. Cite the document that controls the point, confirm the adopted edition, and let the project spec and the geotech override the recommendation.

Units, terms, and conversions

A paver job mixes units across the supplier sheet, the spec, and the drawing, so the same layer reads differently depending on where you look. Knowing the conversions on sight keeps the section honest when the numbers come from three sources.

Paver thickness is given in millimeters and inches, with 60 mm (about 2 3/8 in) the common pedestrian unit and 80 mm (about 3 1/8 in) the vehicular one. Base and bedding depths are in inches, the bedding at 1 in (25 mm) and the base from 4 in (100 mm) for patios up. Slope reads as a percent or as fall per foot, where 1 percent is about 1/8 in per foot and 2 percent is about 1/4 in. Area is square feet for the field, aggregate is ordered in cubic yards or tons by density, and compaction density is a percent of a Proctor maximum from a lab test on the actual material.

Subgrade

The compacted native soil the whole section sits on; a soft subgrade is where settlement starts

Dense-graded aggregate base

Crushed stone blended down to fines that locks tight when compacted; the layer that carries the load

Open-graded base

Clean, no-fines crushed stone that drains through itself; the basis of permeable construction

Bedding sand

The screeded 1 in (25 mm) setting course of washed ASTM C33 concrete sand the pavers seat into

Proctor density

The lab maximum dry density a soil or aggregate compacts to; base targets are a percent of it, commonly 95

Geotextile

A separation fabric over weak subgrade that keeps soil fines and base stone from migrating into each other

Edge restraint

The spiked edge or concrete haunch anchored in the base that holds the perimeter from spreading

Polymeric sand

Joint sand with a binder that hardens when wetted; resists washout but hazes if installed wet or dirty

PICP

Permeable interlocking concrete pavement; open-graded layers that infiltrate water instead of shedding it

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