How to lay pavers

Laying the stones is the part that photographs well and the part that takes the least skill. Everything that decides whether the patio is still flat in five years happens below it, and most of it happens before a single paver is unwrapped.

The decision that dominates all the others is how deep to dig. It sets your excavation, your gravel tonnage, your disposal, and — because it is the largest material order on the job — most of your cost. It is also the number that looks most like a fact and behaves least like one.

Base depth: 4 in and 14 in are both correct, for different gardens

Here is the same question — how thick a compacted aggregate base does a residential patio need — answered by three published sources, read in July 2026.

Source	Patio / walkway	Residential driveway
ICPI Tech Spec 2	minimum 4 in “over well-drained soils”	at least 6 in over well-drained soils
Techo-Bloc, sandy or gravelly soil	4–6 in minimum	6–10 in minimum
Techo-Bloc, clayey or silty soil	6–8 in minimum	8–14 in minimum
Techo-Bloc, Quebec, clayey or silty	10–14 in typical	12–20 in typical
Unilock	6–8 in	10–14 in

Read across the patio column and the range is 4 in to 14 in — more than three times as much gravel for an identical surface. That looks like the sources contradicting each other, and it is worth being precise about why they don’t.

Every low number carries a soil condition, and it is easy to read past it. ICPI’s 4 in is not “4 in for patios”, it is 4 in over well-drained soils, and the same document adds that “in colder climates, continually wet or weak soils will require that bases be at least 2 to 4 in. (50 to 100 mm) thicker.” Techo-Bloc splits its whole table by soil type rather than publishing one figure, and its footnote for Quebec is what a hard frost does to the same table. Line the conditions up and the numbers land close together: ICPI’s driveway minimum plus its own cold-and-wet allowance is 8–10 in, and Techo-Bloc’s clay column for driveways is 8–14 in.

So the honest version of the rule is: you cannot look up your base depth without first knowing what your soil is and whether the ground freezes. Dig a test hole at the edge of the area before you price anything. If water stands in it, or if the spoil rolls into a sausage in your hand rather than crumbling, you are in the upper half of every table on this page.

Once you have a depth, the paver calculator turns it into cubic yards and tons of base — including the allowance for the fact that loose-delivered aggregate compacts substantially — and the paver sand calculator handles the bedding and joint sand separately, because they are different products bought in different units.

1. Lay out the fall before you dig

Both ICPI and Techo-Bloc put the same floor under drainage: slopes should be a minimum of 1.5%, which Techo-Bloc states in the units you will actually use — 3/16 in per foot. For roads ICPI raises it to a 1% minimum longitudinal slope with a 2% cross slope.

Set the stakes slightly outside the area so the excavator does not take them out, pull string lines, and mark the finished grade on them. Techo-Bloc’s instruction is that the excavation should mirror the final grade of the pavement, which is the practical way to build the fall in: you do not create the slope at the top with the sand, you carry it all the way down. Excavate wider than the paving too — the base has to extend past the edge of the paving by an amount equal to its own thickness.

Call the utility locate service before any of this. Both manufacturer guides open with it.

2. Compact the subgrade, then decide about geotextile

Compaction of the soil subgrade is recommended to at least 98% standard Proctor density per ASTM D698 for pedestrian areas and residential driveways, rising to 98% modified Proctor (ASTM D1557) under heavy vehicular traffic.

Geotextile is optional in ICPI’s sequence, and the conditions that call for it are named: soil that stays saturated part of the year, ground subject to freeze and thaw, and clay or moist silty subgrades. Its job is separation — keeping soil from migrating up into the aggregate under load. Techo-Bloc goes further on clay, recommending the soil be changed out for a lime and crushed stone blend before compaction, then covered with fabric.

Never build over a frozen subgrade, and do not place frozen base material.

3. Build the base in lifts the compactor can actually reach

This is the step most often shortened, and the published lift thicknesses are tied to the machine:

• ICPI: spread and compact in 4–6 in lifts using 7,000 lbf reversible plate compactors; “thinner lifts will be required for compactors in the 5,000 lbf (22 kN) range.”
• Techo-Bloc: 4 in lifts with a minimum 5,000 lbf vibrating plate, wetting the material first and passing in all directions.
• Unilock: layers of 2–3 in with a gas-powered plate compactor.

The rental plate a homeowner brings home is usually at the bottom of that force range, which is exactly the case where the thin lift is required. A 10 in base built in one pass is not a 10 in base; it is a compacted top and a loose bottom, and the loose part is what settles in the second winter.

Finish the base flat to ±3/8 in under a 10 ft straightedge. Both CMHA and Techo-Bloc give that same tolerance, and CMHA states plainly why it matters at this stage: the paver installer cannot correct deficiencies in the base surface later.

4. Edge restraints go on the base, before the sand

Install edge restraints against the finished base — CMHA’s specification is explicit that they are mounted directly to it and not on the bedding sand — and note the spike rule, which is a dimension people rarely check: the minimum distance from the outside edge of the base to the spikes must equal the thickness of the base, up to a maximum of 10 in. A 8 in base needs 8 in of compacted gravel outboard of the spike line, which is part of why the excavation is wider than the patio.

5. Screed the bedding, and leave it alone

The bedding course is struck off at a nominal thickness of 1 in (25 mm), taking its level from rails or from the restraints themselves. Unilock and Techo-Bloc both use pipe of 1 in outside diameter as the rails, laid on the compacted base.

Two rules govern what happens next, and both are counter-intuitive:

Do not compact the bedding sand. Techo-Bloc states it directly: the sand should not be compacted until all the paving stones have been laid, because “passing the vibrating plate over the paving stones causes them to settle approximately 3/8” (10 mm) into the bedding sand.“ That settlement is the compaction, and it is what seats each stone individually.

Do not screed more than one day’s laying. CMHA’s wording is that the screeded area shall not substantially exceed what will be covered by pavers that day, and that screeded sand must not be disturbed — rain, wind and footprints all undo it.

6. Lay square, and mix the pallets

Establish a right angle with a 3-4-5 triangle before the first course; Techo-Bloc describes measuring a 3 ft line and a 4 ft line and squaring the diagonal. String lines keep the bond lines honest as you advance. Walk on the laid pavers, never on the screeded bed.

Colour is produced in batches, so draw from several cubes at once — Techo-Bloc recommends working from more than two at a time, and taking stones from the top of the cube downwards — rather than emptying one pallet before opening the next.

Where cuts meet traffic, CMHA sets a minimum size: cut pavers exposed to vehicular tires should be no smaller than one-third of a whole paver. Plan the border so the offcuts land above that.

7. Compaction and joint sand are one operation, not two

The finish sequence is where a patio is either locked together or merely arranged, and CMHA specifies it tightly.

Use a low-amplitude plate compactor of at least 5,000 lbf (22 kN) at 75–100 Hz to vibrate the pavers into the sand, with a protective mat between plate and stone — Techo-Bloc recommends urethane mats and disclaims responsibility for scuffs and burns without them. Then spread, sweep and compact dry joint sand simultaneously and continuously until the joints are full, which CMHA notes “requires at least 4 passes with a plate compactor.” Sweeping the sand in once and calling it done leaves joints that are full at the surface and hollow below.

Two limits apply while you do it. Do not compact within 6 ft of an unrestrained edge — without a restraint in place the field simply walks outward. And at the end of each day, everything more than 6 ft back from the laying face should be left fully compacted with its joints filled, so an overnight downpour cannot empty them.

Match the sand to the joint. CMHA’s rule is that the largest sieve size must easily enter the smallest joint, with the worked example that 2 mm joints need sand of 2 mm and smaller.

Finally, expect the finished surface to sit slightly proud. CMHA notes that on an aggregate base the pavers may finish 1/8 to 1/4 in above final elevations after compaction, deliberately, to absorb the minor settling that is normal in any pavement. The finished tolerance is the same ±3/8 in under a 10 ft straightedge you held the base to.

One last condition that cancels the day regardless of how ready everything else is: do not place sand or pavers during heavy rain or snowfall, and never over frozen base material.