Do I need a permit for a floating deck?

Often no — many jurisdictions exempt floating decks under 200 sqft AND under 30″ off grade AND not attached to the house. BUT: always verify with your local building department before building. Some AHJs treat ALL decks the same regardless of attachment, requiring permit + frost-line footings. Better to ask than rebuild after a stop-work order.

What's a floating deck?

A free-standing deck that's not attached to your house. Sits on pier-block footings (or sonotubes) instead of a ledger-bolted to the house wall. Typically used for low-rise (<24″) outdoor patios, fire-pit pads, garden decks, or detached corners of a yard. Easier and cheaper to build than attached decks because there's no ledger flashing or lateral-load anchoring required.

Concrete deck blocks vs sonotube?

Concrete deck blocks (Dek-Block style): $11 each, no excavation, set on level gravel or compacted soil. Easiest DIY. Best for warm climates / temporary decks / decks under 24″. Sonotube buried: $95-175 per pier including concrete + form + post anchor. Required in cold climates (below frost line) by most AHJs. Permanent solution. Pre-cast pier cap is a compromise — $55 each, steel post anchor cast in, sits on shallow base.

How many piers do I need?

4 ft on-center grid — floating decks use closer pier spacing than standard decks because joists span directly pier-to-pier without beams. Example: 12×10 deck = (12/4 + 1) × (10/4 + 1) = 4 × 4 = 16 piers. Larger decks have more piers but each pier is cheaper than a standard deck's footing.

How much does a floating deck cost?

$15-35 per square foot installed depending on surface. A 10×12 (120 sqft) PT pine floating deck: $1,800-3,200 in materials + $1,200-2,000 labor = $3,000-5,200 total. Same dimensions in composite: $4,500-7,500. DIY install saves 50-60% of total. Multiply by 0.92× South or 1.28× West Coast labor.

Do I need a railing on a floating deck?

IRC R312 only requires a 36″ guardrail when deck is > 30″ above grade. Most floating decks are 4-18″ off grade and don't need a railing. If you're going above 24″, switch to the standard Deck Material Calculator — that handles railing requirements automatically.

Can a floating deck be on grass?

Yes, but better to set piers on a compacted gravel base or removed sod. Concrete deck blocks set directly on grass will sink unevenly within 1-2 seasons. Best practice: dig 4-6″ down at each pier location, fill with compacted #57 gravel, set the pier on gravel. Soil drainage prevents seasonal heave.

Will a floating deck heave in winter?

Concrete deck blocks on grade WILL heave in cold climates with freeze-thaw cycles — this is why most cold-climate AHJs require sonotube footings even on 'floating' decks. Pier blocks can shift 1-3″ per winter on poorly-drained soils. If you're in MN/ME/WI/NY/MA/MI/etc., spend the extra money on sonotube + frost-depth footings.

What's the best surface for a floating deck?

Composite (Trex Enhance, $3.80/lf, ~$25/sqft installed) is the best value for floating decks — no annual maintenance, 25-yr warranty, hides minor framing irregularities. PT pine is cheapest if you'll maintain it. Cedar is premium look but requires stainless screws + biennial oil. Ipe is overkill for a low-rise deck unless you want a 50-yr build.

Can I add a railing to a floating deck later?

Yes — railing posts can be retrofit anytime by drilling through deck boards into rim joists + adding through-bolts. But: if you're planning a railing eventually, build with 4×4 or 6×6 corner posts FROM THE START (cheaper than retrofitting). And if your deck will exceed 30″ off grade, IRC R312 mandates a railing — this is no longer a 'floating deck' in the simplified sense.

Free-standing · ground-level · DIY

Floating Deck Calculator

Q: Concrete deck blocks vs sonotube?

Concrete deck blocks (Dek-Block style): $11 each, no excavation, set on level gravel or compacted soil. Easiest DIY. Best for warm climates / temporary decks / decks under 24″. Sonotube buried: $95-175 per pier including concrete + form + post anchor. Required in cold climates (below frost line) by most AHJs. Permanent solution. Pre-cast pier cap is a compromise — $55 each, steel post anchor cast in, sits on shallow base.

Q: How many piers do I need?

4 ft on-center grid — floating decks use closer pier spacing than standard decks because joists span directly pier-to-pier without beams. Example: 12×10 deck = (12/4 + 1) × (10/4 + 1) = 4 × 4 = 16 piers. Larger decks have more piers but each pier is cheaper than a standard deck's footing.

Q: How much does a floating deck cost?

$15-35 per square foot installed depending on surface. A 10×12 (120 sqft) PT pine floating deck: $1,800-3,200 in materials + $1,200-2,000 labor = $3,000-5,200 total. Same dimensions in composite: $4,500-7,500. DIY install saves 50-60% of total. Multiply by 0.92× South or 1.28× West Coast labor.

Q: Do I need a railing on a floating deck?

IRC R312 only requires a 36″ guardrail when deck is > 30″ above grade. Most floating decks are 4-18″ off grade and don't need a railing. If you're going above 24″, switch to the standard Deck Material Calculator — that handles railing requirements automatically.

The simpler deck calc — for free-standing low-rise decks (under 24″ off grade, no ledger to house). 3 pier options (concrete deck blocks / sonotube / pre-cast pier cap), 4 surface materials. Many jurisdictions exempt floating decks from permits — DIY-friendly.

3 pier options4 surface materialsUnder 24″ off gradeNo ledgerNo railing requiredDIY-friendly

3·Pier styles

4 ft·Pier o.c.

16″·Joist o.c.

DIY·Friendly

Inputs

Deck dimensions

Lengthft

Widthft

Height off gradeunder 24″ for 'floating' classification

Pier / footing stylecold climates require sonotube

Surface material

State2-letter

Entry steps0-4 entry steps

Scope

Floating Deck · Pressure-treated pine 5/4×6·Northeast

$4,813 – $6,584$40–$55 /sq ft installed

16 piers · Concrete10 joists @ 16″ o.c.

Pier count

4 ft o.c. grid

Joist count

16″ o.c.

Materials

Low $1,111

Labor

1.22× region

Compliance · IRC + best practices

Floating deck classification — 8″ off grade

IRC R312

IRC R312 doesn't require a guardrail under 30″ off grade. Most jurisdictions exempt floating decks <200 sqft + <30″ from permit requirements (verify locally).

On-grade pier blocks — no frost-depth excavation

Manufacturer install spec

Concrete deck blocks set on level grade or compacted gravel. Suitable for warm climates + temporary decks. In cold climates with freeze-thaw cycles, blocks WILL heave 1-3″ per winter — switch to sonotube if needed.

Pier grid — 16 piers at 4 ft o.c.

AWC DCA-6 simplified framing

Floating deck framing uses 4 ft pier spacing (closer than standard 8 ft) so 2×8 PT joists span pier-to-pier directly — no beams needed. 10 joists at 16″ o.c.

Bill of materials

Item

Qty

Total

Decking — Pressure-treated pine 5/4×6

18 boards · 282 lf · 22 rows

Home Depot Lowe’s

18 board

$551

Decking — Pressure-treated pine 5/4×6

18 boards · 282 lf · 22 rows

Home Depot Lowe’s

18 board

—

$551

Floor joists — 2×8 PT (4 ft span)

10 × 10' at 16″ o.c. (no beams needed — joists span pier-to-pier directly)

10 joist

$230

Floor joists — 2×8 PT (4 ft span)

10 × 10' at 16″ o.c. (no beams needed — joists span pier-to-pier directly)

10 joist

—

$230

Joist hangers + post anchors

10 LUS28 hangers + 16 simple post anchors

26 pc

$212

Joist hangers + post anchors

10 LUS28 hangers + 16 simple post anchors

26 pc

—

$212

Piers — Concrete deck blocks (Dek-Block)

16 piers (4 × 4 grid at 4 ft o.c.)

Home Depot Lowe’s

16 pier

$176

Piers — Concrete deck blocks (Dek-Block)

16 piers (4 × 4 grid at 4 ft o.c.)

Home Depot Lowe’s

16 pier

—

$176

Galvanized deck screws

120 sqft × $0.22/sqft

1,440 screw

$26

Galvanized deck screws

120 sqft × $0.22/sqft

1,440 screw

—

$26

Materials subtotal

$1,195

Floating deck pricing 2026-Q1. No excavation — piers set on grade or compacted gravel.

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Floating decks under 24″ off grade are exempt from IRC R312 guardrail requirements. Many AHJs exempt floating decks under 200 sqft + under 30″ from permit requirements — verify with your local building department before building.

How to use

Three steps. Permit-ready output.

Set dimensions + height

Length × width in feet (typical 8×8 to 16×16 for floating decks). Height 4-18″ off grade is the sweet spot. Above 24″ triggers a redirect to the standard deck calc (railing required, ledger considerations, etc).

Pick pier style

Concrete deck blocks (Dek-Block, $11 each — easiest DIY, set on level grade or compacted gravel, no excavation, often permit-exempt). Sonotube buried ($145 each — required by code in most cold-climate jurisdictions even for floating decks; below frost line). Pre-cast pier cap ($55 each — premium with steel post anchor cast in).

Pick surface material

PT pine 5/4×6 ($1.95/lf — cheapest, annual stain), cedar A&Better ($3.40/lf — premium look, stainless screws req), composite Trex Enhance ($3.80/lf — best value for low decks, no maintenance), Ipe ($7.80/lf — premium hardwood, predrilling required).

Read your floating deck cost

Pier count, joist count, decking BoM, simplified labor (no ledger / railing / stair complexity). Save link, export PDF.

How we calculate

The math, fully transparent.

The Floating Deck Calculator solves a different problem than every other deck calc on DeckMath: a free-standing low-rise deck (under 24″ off grade) that doesn't attach to the house. Floating decks are the simplest residential deck build — no ledger flashing, no railing required (under 24″), often no permit (verify locally), and typically pier-block footings instead of frost-line sonotubes. Pick dimensions, pier style (concrete deck block / sonotube / pre-cast pier cap), and surface material (PT / cedar / composite / Ipe). DeckMath returns pier count, joist count, decking BoM, and project total. If your deck is over 24″ off grade, the calc redirects you to the standard Deck Material Calculator (full code-compliant build).

IRC references

IRC 2021 R507 — Decks (most prescriptive sections apply even to floating)
IRC 2021 R312 — Guards (NOT required when deck < 30″ off grade)
IRC 2021 R403.1.4 — Footings + frost depth (some AHJs require frost-line depth even on floating decks)
Local AHJ — many jurisdictions have specific floating-deck exemptions for small/low decks

Floating deck pricing 2026-Q1. Concrete deck blocks (Dek-Block style) at Home Depot $11/each. Sonotube + concrete poured costs vary by frost depth. Joist + decking pricing matches standard deck calculator.

Pier count

(ceil(length / 4) + 1) × (ceil(width / 4) + 1)

Floating decks use 4 ft pier spacing (closer than standard 8 ft) so joists span pier-to-pier directly without beams. A 12×10 deck = 4 × 4 = 16 piers.

Joist count

floor(length × 12 / 16) + 1

Standard 16″ on-center joist spacing. Floating decks typically use 2×8 PT (sufficient for 4 ft span without a beam).

Surface board count

ceil(width × 12 / 5.625) × length × 1.07

Same as standard deck — rows × length × 7% waste. Round up to nearest 16-ft stock.

Labor multiplier vs standard deck

0.85× to 1.30× depending on surface

PT 0.85× (face-screw + simple framing), cedar 0.95×, composite 1.10× (hidden-fastener premium), Ipe 1.30× (predrill premium). Floating decks save ~15% vs standard because no ledger flashing + no railing + simpler footings.

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Deck Cost Calculator

Estimate full deck project cost: materials, labor, permits, and per-square-foot pricing for any size and material.

Deck Material Calculator

Calculate exact decking boards, joists, beams, posts, footings, and fasteners for your deck — IRC 2021 compliant.

Deck Footing Calculator

Footing diameter, depth, concrete volume, and bag count — IRC R507.3 sized + frost depth lookup for all 50 states.

Floating Deck Calculator

Inputs

Compliance · IRC + best practices

Floating deck classification — 8″ off grade

On-grade pier blocks — no frost-depth excavation

Pier grid — 16 piers at 4 ft o.c.

Bill of materials

Need a full-size deck instead?

Three steps. Permit-ready output.

Set dimensions + height

Pick pier style

Pick surface material

Read your floating deck cost

The math, fully transparent.

IRC references

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