Floating / Ground-Level Deck
A floating or ground-level deck is the build path for any residential deck where the surface is less than 30 inches above grade at every point — the threshold below which Seattle DCI does not require a building permit, Washington State Residential Code does not require guardrails, and the deck can install on adjustable polymer pedestals (Bison Pedestal, Eterno IVICA, Wallbarn) or precast concrete piers (DekBlock-style) without poured concrete footings. The build skips the engineering review and the permit queue, which compresses the total project timeline from a 2-month elevated-deck pipeline to a 1 to 2-week installation. The trade-off is that the build only fits a flat or near-flat back yard where the surface can stay under the 30-inch threshold, and the absence of poured footings means the deck is genuinely floating — it can shift slightly with ground movement, which is acceptable structurally for a ground-level deck but is the reason these are not the right path for an elevated build. From $8,000 for a 12-by-12-foot 144 square-foot pressure-treated floating deck to $18,000 for a 16-by-20-foot 320 square-foot capped composite or cellular PVC floating deck with picture-frame border, integrated low-voltage lighting, and a built-in bench. Drainage detailing is the critical line item in PNW exposure — the gravel base, the slight slope toward natural drainage, and the air gap under the deck — because ponding water under a floating ground-level deck is the most common cause of premature joist rot and mildew. Any line-voltage lighting circuit routes to a licensed Washington L&I electrician.
Service
What Floating / Ground-Level Deck Construction Covers
A floating or ground-level deck is the fastest, lowest-cost, and least-regulated deck build path because the surface stays under 30 inches above grade at every point — the threshold below which Seattle DCI does not require a building permit, Washington State Residential Code does not require guardrails, and the deck can install on adjustable polymer pedestals or precast concrete piers without poured concrete footings or a structural engineer's stamp. The build window compresses from a 6 to 8-week elevated-deck pipeline (with engineering and permit review) to a 1 to 2-week on-site installation. Handis owns the carpentry; no permit is required so there is no permit pass-through line item; no structural engineering is required so there is no engineering line item; any line-voltage lighting circuit routes to a licensed Washington L&I electrician.
Site Assessment, Grading, and Drainage Analysis
The first visit confirms the back yard can stay under the 30-inch threshold across the entire intended footprint (sloped lots may need to be re-graded slightly to keep the deck below the threshold, or the deck footprint may need to be reduced or shifted to where the grade stays low). The drainage analysis is the most important part of a floating-deck visit in the PNW — we identify where stormwater currently flows, how the lawn slopes, and whether the deck location ponds water in the wet season. A floating deck installed over a ponding zone will rot the joists from below within 5 to 8 years regardless of decking material quality; the only mitigation is to fix the drainage before the deck goes in (or to relocate the deck).
Ground Preparation: Gravel Base + Weed Barrier
The deck footprint excavates 2 to 4 inches below grade, a permeable landscape weed barrier (Mirafi 140N or equivalent) lays across the excavation, and 2 to 4 inches of 3/4-inch minus crushed gravel goes down on top of the barrier sloped at 1/4 inch per foot toward whichever direction the yard naturally drains. The gravel base accomplishes three things — it suppresses weed growth under the deck (which would otherwise grow up through the gaps within a season), it gives the polymer pedestals or precast piers a stable bearing surface, and it provides drainage so any water that gets under the deck (rain wind-driven through the gaps, snowmelt, ice dam runoff) percolates through the gravel rather than ponding against the joist underside.
Adjustable Polymer Pedestals or Precast Concrete Piers
Adjustable polymer pedestals (Bison Versadjust, Eterno IVICA, Wallbarn) are height-adjustable plastic columns that sit on the gravel base, thread up or down to a precise height (typically with a built-in slope corrector that levels the joist top even when the pedestal sits on a graded slope), and carry the joist directly on a pedestal cap. They are the right answer when a perfectly level deck surface is needed over a slightly graded base, when the pedestal heights vary across the deck footprint to keep the deck top flat, or when speed of installation matters (a polymer pedestal field installs in a fraction of the time of precast piers). Precast concrete piers (DekBlock-style, with a notched top to receive joist or beam lumber) are the right answer for a perfectly flat base where simple stacking is sufficient, and they are slightly less expensive per support point. We name the support system on the quote based on the site conditions.
Pressure-Treated 2x Joist Frame on the Pedestal Grid
Joists are pressure-treated 2x in the size and spacing the deck width and the decking material span requires — typically 2x8 at 16-inch on center for a face-fastened PT or cedar deck up to 12 feet wide, 2x8 at 12-inch on center for hidden-fastener composite or PVC. Beams (where the deck width requires them) are doubled or tripled PT 2x sized to the span between pedestals. The frame can be free-standing (no ledger to the house) or attached with a flashed ledger — most floating decks are built free-standing both because the build is structurally simpler without a ledger and because it avoids the building-envelope code question that would re-trigger a permit on an attached deck. Picture-frame border boards mitered at corners go on with the field decking install.
Decking, Optional Single Step to Grade, Optional Low-Voltage Lighting
Decking installs in the homeowner-selected material — pressure-treated and cedar are the most affordable options for a floating ground-level deck (the floating path tends to attract more cost-conscious builds because it is exempt from the permit and engineering overhead); capped composite and cellular PVC are the longest-lived options. The deck typically has a single step down to the surrounding lawn or patio (a single step under 30 inches above grade does not require a handrail under code). If you want a small set of steps with more than 3 risers, code requires a graspable handrail — but on a ground-level deck this is uncommon. Low-voltage post-cap or perimeter lighting runs from a 12V transformer at a switched outdoor outlet; the licensed Washington L&I electrician handles any new line-voltage circuit.
How the Floating Deck Build Works
Five sequential phases from site assessment and drainage analysis to final walk-through — the actual working sequence we run on every floating ground-level deck under 30 inches above grade, no permit and no engineering needed.
Site Assessment, 30-Inch Threshold Confirmation, Drainage Analysis
Estimate visit confirms the back yard stays under 30 inches above grade across the entire intended footprint (so no Seattle DCI permit is required and no railing is required by code), identifies the existing storm drainage flow direction, and checks whether the deck location ponds water in the wet season. Ponding zones are the most common reason a floating deck fails prematurely in PNW; we either route around them or fix the drainage before the deck goes in.
Excavation, Weed Barrier, Gravel Base Sloped to Drain
Deck footprint excavates 2 to 4 inches below grade. Permeable landscape weed barrier (Mirafi 140N or equivalent) lays across the excavation. 2 to 4 inches of 3/4-inch minus crushed gravel goes on top of the barrier, sloped at 1/4 inch per foot toward whichever direction the yard naturally drains. The base suppresses weed growth, gives the pedestals a stable bearing surface, and lets water that gets under the deck percolate through rather than pond against the joist underside.
Polymer Pedestals or Precast Concrete Piers Laid Out on the Grid
Adjustable polymer pedestals (Bison Versadjust, Eterno IVICA, Wallbarn) thread up or down to precise heights with built-in slope correctors, or precast concrete piers (DekBlock-style) stack on the gravel where the base is flat enough. Pedestal grid spacing typically 4 to 6 feet on center based on joist sizing. Each support point gets leveled across the field with a laser level so the joist top is flat regardless of grade variation in the gravel base.
PT 2x Frame Up — Free-Standing or Attached with Flashed Ledger
Joists in PT 2x8 at 16-inch OC for face-fastened lumber, 12-inch OC for hidden-fastener composite or PVC. Beams sized to span between pedestals where required. Most floating decks are built free-standing (no ledger to the house) because it is structurally simpler and avoids re-triggering a permit through the building-envelope code question on an attached deck. If attached, the ledger gets the same full continuous flashing detail we use on elevated builds.
Decking + Optional Single Step + Optional Lighting + Final Walk
Decking installs in the homeowner-selected material (PT or cedar for budget builds; capped composite or cellular PVC for low-maintenance). Picture-frame border boards mitered at corners. Single step down to surrounding lawn or patio (no handrail required under 30 inches above grade). Low-voltage post-cap or perimeter lighting if specified — Handis runs the low-voltage wire; licensed Washington L&I electrician handles any new line-voltage circuit. Final walk with you, no inspection required since no permit was pulled.
Floating / Ground-Level Deck Pricing
Final pricing depends on square footage, decking material selection (PT is the most affordable; cellular PVC is the premium), support system (adjustable polymer pedestals vs precast concrete piers), drainage remediation if the back yard needs it before the deck goes in, and integrated lighting scope. No Seattle DCI building permit is required and no structural engineering is required because the deck surface stays under 30 inches above grade — so those pass-through line items do not appear on the quote. The licensed Washington L&I electrician's portion (for any new line-voltage circuit) is named line by line if integrated lighting is in scope. Request a free in-home estimate for an accurate quote.
Send us back-yard photos with rough elevation context (we need to confirm the deck stays under 30 inches above grade across the footprint), the deck size, and the decking material — we will quote the floating build.
Why Handis for Floating Ground-Level Decks
The floating ground-level decks we are called to repair almost always failed for one of two reasons — water ponded under the deck because the drainage was wrong from day one, or the polymer pedestals settled into a gravel base that was not properly compacted before pedestal placement. Both failures trace to the prep work, not to the decking material or the framing. Handis spends the same time on the drainage analysis and the gravel base preparation on a floating deck that we spend on the footing layout for an elevated deck — because the gravel and the slope are the foundation on a floating build. We will not quote a floating deck over a ponding zone without also quoting the drainage remediation; if the drainage cannot be fixed, the right answer is sometimes a different deck location or a deck on actual concrete piers rather than pedestals.
Drainage analysis on every floating-deck estimate visit
Water ponding under a floating ground-level deck is the single most common reason these decks fail prematurely in PNW exposure. A ponding zone keeps the joist underside damp year-round; the PT lumber begins to rot at the joist bottom within 5 to 8 years; mildew and mold thrive in the dark damp space under the deck. We identify the existing storm drainage flow direction at the estimate visit, walk the back yard during or just after a wet day if possible, and confirm the deck location does not sit over a ponding zone before quoting. If a ponding zone is in the footprint, we either route the deck around it or quote the drainage remediation (a French drain, a perimeter swale, regrading) as a named add-on line item. We will not quote a deck over a ponding zone without the drainage fix.
Gravel base compacted and sloped to drain, weed barrier underneath
The gravel base is the foundation on a floating deck. We excavate 2 to 4 inches below grade, lay a permeable landscape weed barrier (Mirafi 140N or equivalent — not the cheap landscape fabric that decomposes in 2 to 3 years and lets weeds grow up through the gaps within a season), and place 2 to 4 inches of 3/4-inch minus crushed gravel on top of the barrier. The gravel slopes at 1/4 inch per foot toward whichever direction the yard naturally drains so water that gets under the deck percolates through and runs out rather than ponding. The gravel gets compacted with a plate compactor before pedestal placement so the pedestals do not settle differently across the field as the gravel consolidates under load.
Polymer pedestals over precast piers for slope correction and longer warranty
On most Seattle back yards we recommend adjustable polymer pedestals (Bison Versadjust, Eterno IVICA, Wallbarn) over precast concrete piers (DekBlock-style) because the polymer pedestals have built-in slope correctors that level the joist top across a slightly graded base, the pedestal height is finely adjustable so the deck surface is perfectly level even when the gravel base has minor variation, and the manufacturer warranties on quality polymer pedestals run 25 to 50 years against UV degradation and load failure. Precast concrete piers are slightly less expensive per support point and are the right answer on a perfectly flat base where simple stacking is sufficient. We pick the right system per site at the estimate visit.
Free-standing default to keep the permit-exempt path clean
Most Handis floating decks build free-standing (no ledger attached to the house) rather than attached because the free-standing build is structurally simpler, faster to install, and avoids re-triggering the Seattle DCI permit through the building-envelope code question that comes up on an attached deck. If you specifically want the deck attached to the house, we add the flashed ledger as a named line item ($950 add-on) and the full continuous metal flashing assembly we use on elevated builds is applied so the rim joist behind the ledger does not rot. The decision is yours; we will quote both options if you want to see the comparison.
Insured, background-checked, 30-day workmanship + 2-year frame warranty
Every Handis carpenter carries liability insurance and has cleared a background screening before the first job. The 30-day workmanship guarantee covers any fastener that loosens, any picture-frame miter that opens, any board that lifts, and any cosmetic finish. The structural frame (pedestals or piers, joists, beams) carries our 2-year workmanship warranty on installation. The decking material (PT, cedar, capped composite, cellular PVC) carries its own manufacturer or species warranty — we register the lot numbers with the manufacturer at install. The licensed Washington L&I electrician warrants their portion under their own license terms if integrated lighting is in scope. All warranties in writing at project close.
Estimate
Tell us the back-yard layout (flat or gently sloped, where the deck location is relative to the house, whether the back yard ponds water in the wet season), the rough size you have in mind (12x12, 12x20, 16x20 are the most common), the decking material (PT, cedar, capped composite, cellular PVC), free-standing or attached, and any add-ons you want priced (integrated lighting, built-in bench, drainage remediation). We send back a clear estimate.
Customer Reviews
Floating ground-level deck construction reviews from real Seattle-area Handis customers.
1968 Wedgwood rambler, flat back yard, wanted a 14-by-18-foot floating deck off the back door for the BBQ and a dining table. Handis confirmed on the estimate visit that the entire footprint stayed under 30 inches above grade (so no permit and no railing was required), walked the yard during a wet afternoon, and identified one corner that ponded after rain. They re-graded the corner with a French drain to a side-yard swale (named on the quote at $1,800), then built the deck on adjustable polymer pedestals over a compacted gravel base. One-and-a-half working weeks. Three years in and the underside is bone dry every time I look.
We had a quote from another contractor that was $4,000 less but did not include any drainage analysis or any mention of the gravel base prep — just talked about laying joists directly on patio blocks. Handis was upfront on the estimate that the gravel base and the slope-to-drain were the line items that make a floating deck last, and named both on the quote. We paid the premium and got a 12-by-16-foot PT floating deck that has stood through five wet winters with zero joist rot at the underside. Glad we listened.
Cellular PVC floating deck on a 16-by-20 footprint for a Magnolia rambler back yard. Handis installed the AZEK boards over Bison Versadjust pedestals on a compacted gravel base. The leveling was perfect across the entire 320 square feet despite the back yard having a slight grade — the pedestal slope correctors handled it. The integrated low-voltage perimeter lighting (named on the quote with the licensed electrician's circuit add at $480) makes the deck usable into evening every summer. Two working weeks total, no permit needed.
1958 Wallingford bungalow, modest back yard, wanted a small 12-by-12 PT deck off the kitchen door for a few chairs and a grill. Handis kept it simple — precast concrete piers on a compacted gravel base, PT 2x8 joists at 16-inch OC, 5/4 PT decking, single step down to the lawn, picture-frame border. Came in at $8,200. One working week. The boards weathered to grey within 12 months and look like they have always been there.
We wanted the deck attached to the house instead of free-standing for aesthetic continuity with the house siding. Handis added the flashed ledger as a named line item ($950 add-on), did the full continuous metal flashing assembly that they use on elevated decks, and photographed it before the deck boards closed it in. 14-by-16-foot capped composite with hidden fasteners and a built-in bench at one end. One-and-a-half working weeks. The bench doubles as the back edge of the deck and gives us extra seating for evening gatherings.
Frequently Asked Questions
Common questions about floating and ground-level deck construction — pricing, permits, drainage, polymer pedestals vs piers, and what to expect on a Handis build.