Pedestal Paver Calculator

Pavers and pedestals for common rooftop deck sizes (24 x 24 in pavers, straight grid)

Grid counts start full pavers at one corner, and cut edge pieces count as full pavers. Pedestals = (cols + 1) x (rows + 1) per the standard grid layout in the Tile Tech 07 76 00 spec. The Order column applies the 5 percent spare allowance the Bison spec recommends and rounds up.

Pedestal count from the paver grid: (C + 1) x (R + 1)

Every interior pedestal carries four paver corners, so the ratio falls toward 1.0 per paver as the deck grows (that’s the large-deck limit behind the Bison rule of about one pedestal per tile). Small or narrow decks run 1.4-1.8 pedestals per paver, so per-paver rules of thumb vary widely.

Paver format comparison (2 cm porcelain at 9 lb per sq ft)

Weight per the Archatrak 2 cm data (9 lb per sq ft, 36 lb per 24 x 24 paver), with other formats derived at the same 9 psf. Pavers per 100 sq ft is area-based and rounded up. Pedestal counts use the straight-grid formula on a 12 x 12 ft deck. Halving the paver in one direction nearly doubles the pedestal count, and that’s a big part of why 24 x 24 is the default rooftop format.

What this calculator covers, and what it does not

This calculator counts pavers and pedestals for an elevated deck (a rooftop, terrace, or balcony). The pavers rest on adjustable pedestals above a waterproof membrane. There’s no gravel base, no bedding sand, and no joint sand. Each paver sits on four pedestal heads, the open joints drain straight through, and the membrane below is never penetrated.

Building a patio on grade, with a compacted gravel base and sand bed? Use the paver patio calculator instead. That page covers excavation, base depth, and edge restraint for ground installations.

The dominant rooftop format is the 24 x 24 in porcelain paver at 2 cm (3/4 in) thick. Suppliers also typically stock 12 x 24 in planks, 18 x 18 in, and large 24 x 36 in units, plus hydraulically pressed concrete roof pavers around 2 in thick.

The calculator lays pavers in a straight grid from one corner and counts every grid position, so a cut edge piece still consumes a full paver. On pedestal decks most installers size the layout to avoid cuts entirely. A deck dimension that’s a multiple of 2 ft needs no cutting at all with 24 x 24 pavers.

The pedestal count math

Why more pedestals than pavers? Because pavers on pedestals share supports. An interior pedestal carries the corners of four adjacent pavers, a perimeter pedestal carries two, and a corner pedestal carries one. So a straight grid of C columns and R rows of pavers needs (C + 1) x (R + 1) pedestals, one at every line intersection, perimeter included. The Tile Tech installation spec (Section 07760) describes exactly this layout. Snap a grid of chalk lines in both directions, then place a pedestal at every intersection and wherever a grid line meets the perimeter.

Take a 12 x 10 ft deck with 24 x 24 in pavers. It runs 6 columns by 5 rows, so 30 pavers and 7 x 6 = 42 pedestals, or 1.4 pedestals per paver.

The ratio falls as the deck grows because interior sharing takes over. A 20 x 30 ft deck needs 176 pedestals for 150 pavers (1.17 per paver), and very large fields approach 1 per paver. That’s where the Bison FAQ rule of thumb comes from (about one pedestal per tile, or one support per 3-4 sq ft), and the area x 0.35 ballpark quoted by rooftop supplier SkyDeck USA.

Perimeter pedestals and edge restraint

Don’t treat perimeter pedestals as an add-on percentage. They fall out of the grid formula, and on small decks they usually dominate the count. On a 10 x 10 ft deck, 20 of the 36 pedestals sit on the perimeter. The Tile Tech spec has installers remove two spacer tabs on each perimeter pedestal and all four at corners so the pedestal tucks tight to the edge.

Irregular or L-shaped decks push the per-area ratio up. SkyDeck USA quotes roughly 0.40-0.55 pedestals per sq ft for those, against 0.30-0.33 for larger simple rectangles. Split an L-shape into rectangles, run each through the calculator, and share the pedestal row along the seam.

Every major manufacturer requires the finished deck to be restrained on all sides. The Bison spec calls for perimeter blocking or walls on every side with no more than a 3/16 in gap at any edge. The Tile Tech spec voids its warranty if cumulative lateral movement exceeds 1/8 in.

A pedestal deck is a loose-laid system, so there’s no adhesive holding it down. Containment keeps it in place.

Pedestal height: adjustable, fixed, or shims

Adjustable pedestals cover most of the range you’ll meet on a roof. The Bison Versadjust series runs 2-1/4 to 9 in across its four base models, and quick-clip couplers extend it in 4 in steps to a maximum of 36 in. Tile Tech Uni-Just pedestals adjust from 2-1/2 to 22 in on field-cut PVC pipe, and the Eterno NM sold by Archatrak reaches 39 in with extension parts.

Screw adjustment works under load. Built-in levelers compensate for the roof slope (0 to 4 percent on Versadjust, 0 to 6 percent on Uni-Just), so the deck stays flat while the membrane below drains.

Below about 1 1/4 in, adjustable pedestals no longer fit and fixed supports take over. Bison fixed pedestals come in a 1/8 in fixed unit plus 1/4, 1/2 and 3/4 in stackable heights (maximum four high). A low-height adjustable model covers 1-1/4 to 2 in, and 1/16 and 1/8 in shims fine-tune individual corners (maximum two shims per pedestal). The practical floor for a pedestal deck is 1/8 in.

Height is also a structural line. Bison requires its brace system on any pedestal over 24 in and caps the braced system at 36 in. Beyond that, the spec directs you to the manufacturer and the project engineer. Tile Tech is more conservative and requires bracing above 16 in.

Each pedestal is rated for 1250 lb with a factor of safety of 3. Any planter, hot tub, or other concentrated load needs one extra pedestal per 500 lb, placed directly beneath it.

Weight: what a paver deck adds to the roof

Porcelain is the light option here. A 2 cm porcelain paver deck adds 9 lb per sq ft of dead load, which works out to 36 lb per 24 x 24 paver, per the Archatrak product data. Concrete roof pavers are far heavier. The Hanover roof deck data sheet lists its 23-1/2 x 23-1/2 x 2 in Prest Paver at 25 lb per sq ft. The Tile Tech line spans 11-22 lb per sq ft depending on size and thickness.

On a 12 x 10 ft deck that’s the difference between roughly 1080 lb of porcelain and 3000 lb of 2 in concrete, before furniture and people.

The calculator reports added dead load. It doesn’t check your roof. Both the Bison and Tile Tech specifications put the responsibility on the installer and the engineer of record. They have to confirm the structure can carry the dead and live loads, and that any insulation under the pedestals resists crushing. Bison, for one, requires a bearing surface of at least 40 psi under each pedestal. Pedestal decks are rated for pedestrian traffic only. Have a structural engineer confirm capacity before ordering, especially on older buildings and anywhere concrete pavers are being considered.

Wind uplift: one honest caution

Loose-laid pavers can lift in high wind, and height makes it worse. In wall-of-wind testing at Florida International University reported by Archatrak, pavers on 8 in pedestals blew off at wind speeds 30-40 mph lower than the same pavers on 1/2 in pads. The windward edges failed first.

Tall parapet-free roofs, coastal wind zones, and light 2 cm porcelain are the risk combination, and any two of them together deserve a closer look.

Manufacturers sell engineered hold-down systems (Archatrak tray and kerf systems tested to average failure at 183 and 280 psf, Tile Tech Hex-Tray, Bison fastening splines). The Bison spec requires wind uplift ratings as demanded by the local jurisdiction, with design pressures set under ASCE 7. Check your local code or supplier on that before you order. On an exposed or high roof, price the restraint system with the deck, not after it.

Ordering notes

Order spares with the pavers. The Bison spec recommends an additional 2-5 percent in every order for damage replacement, and that’s what the spare slider adds.

Porcelain this hard needs a rail saw or bridge saw with a porcelain-rated diamond blade for any cuts, so a layout in full 2 ft modules usually saves real labor. Buy pavers and pedestals as separate line items, since the calculator rounds each up separately.

Pedestals usually ship as counts of bases, tops, and couplers. Order to the exact grid number plus the couplers your height demands, and add a bag of shims for final leveling.

Common questions

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