Authorized ThruFlow dealer
Every panel ships factory-fresh with the full lifetime limited manufacturer warranty intact. We're not a reseller of overstock or seconds.
ThruFlow Legacy XP Decking Panel
Price range: $37.00 through $69.00
100+ panels ship free
Mix any sizes & either color. Continental US. Hudson, NH ships in 1–2 days.
Free shipping over 100 panels
Order 100 panels.
Ships free in the lower 48.
Mix any sizes, any colors. Cross 100 Legacy XP panels and the whole shipment moves free anywhere in the continental US — no freight quotes, no surprises at checkout.
43%
Light passes through to the water below
2,400+ lbs
Load capacity per panel — exceeds commercial spec
1.6 lbs/ft²
55% lighter than wood or composite
100+
Panels — free shipping anywhere in the continental US
The Panel
Why we stock Legacy XP.
ThruFlow makes five product lines. We stock one—Legacy XP—because it gets the trade-offs right where dock owners care about them most.
Open-grid drainage
Water, sand, and debris fall through instead of pooling on top. The walking surface clears quickly after rain or wave splash.
43% light penetration
Sunlight reaches the water and shoreline vegetation under the dock. The Army Corps of Engineers recommends open-grid decking for sensitive waterways.
2,400+ lb load capacity
Every Legacy XP size (1×3, 1×4, 1×5, 1×6) exceeds commercial construction load requirements. This isn't a residential-only panel.
1.6 lbs per square foot
55% lighter than wood or composite. One person can carry a panel where two are usually needed for a comparable wood plank.
Stays cooler in direct sun
The UV-resistant polypropylene base doesn't store heat the way wood, aluminum, or some composites do. Bare-foot friendly on hot afternoons.
360° non-slip surface
Engineered grip in every direction—wet or dry—that exceeds ADA accessibility specifications. The same surface used on government and municipal installs.
Backed by ThruFlow's lifetime limited manufacturer warranty against material defects, rot, decay, and termite damage.
The Dealer
Why buy Legacy XP from FWM.
Anyone can sell ThruFlow. Few stock it the way we do, and fewer still have spent decades on docks before selling them.
In stock in Hudson, NH
Every size and color we sell is in inventory at our Hudson, NH warehouse. Orders ship in 1–2 business days—not a drop-ship freight lane from a manufacturer.
We build docks ourselves
FWM has been installing dock systems for residential, marina, camp, and government clients for years. The product information on this page comes from real install experience, not a catalog.
100+ panels ship free
Mix any sizes. Mix any colors. Once you cross 100 panels in a single order, the whole shipment moves free to the continental US.
Online ordering
Every step—sizing, color, quantity, free-shipping eligibility—is handled on this page. No quote-and-wait. No back-and-forth on freight.
Trusted on government installs
The same Legacy XP panel we ship to homeowners has been used on US Fish & Wildlife Service waterfronts, municipal public-access projects, and Army Corps of Engineers sites.
Sizing
Four sizes. Pick the one that fits your framing.
Every Legacy XP panel is 12 inches wide and 1.2 inches thick. The four lengths give you flexibility based on how your dock framing is built. The on-center spacing column is the maximum joist spacing the manufacturer specifies for that size.
| Panel size | Best for | Joist on-center | Tab options |
|---|---|---|---|
| 36″ (1′×3′) | Tight layouts, repairs, ramps, stair treads, finished edges. | 18″ | Tab and no-tab |
| 48″ (1′×4′) | Most common residential dock-decking replacement. | 16″ or 24″ | Tab and no-tab |
| 60″ (1′×5′) | Wider framing layouts and large dock sections. | 15″ | Tab |
| 72″ (1′×6′) | Long-run replacement decks and commercial walkways. | 18″ or 24″ | Tab |
Common dock layouts
Quick reference for the most common dock dimensions we ship. Always confirm your dock's actual joist spacing and length before ordering.
| Dock size | Recommended panel | Layout | Approx. panels |
|---|---|---|---|
| 4′ × 20′ walkway | 48″ (1×4) | 4 rows, 5 panels each | 20 panels |
| 5′ × 20′ dock | 60″ (1×5) | 5 rows, 4 panels each | 20 panels |
| 6′ × 20′ dock | 72″ (1×6) | 6 rows, 4 panels each (using two 60″+12″ or three 36″ alternatives) | ~20 panels |
| 8′ × 20′ dock | Two 48″ rows across | 8 rows, 5 panels each | 40 panels |
| 10′ × 20′ dock | Two 60″ rows across | 10 rows, 4 panels each | 40 panels |
| 12′ × 20′ dock | Two 72″ rows across | 12 rows, ~3 panels each | ~36–40 panels |
Calculator
How many Legacy XP panels do you need?
Enter your dock dimensions. We'll size the order, show your panel mix, and tell you whether you qualify for free shipping.
Color
Gray or Maple. Pick the look that fits your dock.
Both colors come from the same UV-resistant Legacy XP base. They wear the same, install the same, and carry the same lifetime limited manufacturer warranty. The choice is aesthetic.
Gray
Reads modern and cool. Hides marine wear, sand dust, and sun-bleached edges better than warm tones. Pairs naturally with composite docks, aluminum framing, and contemporary waterfront builds. Our most-ordered color across both residential and commercial projects.
Maple
Warmer beige tone. Blends into wood docks, cedar trim, and natural shorelines. The right pick when you want the open-grid performance of Legacy XP without losing the visual warmth of a traditional dock.
Why only two colors? ThruFlow makes the panel in additional colors (Seafoam, Slate, Walnut, IPE). We stock Gray and Maple because they're what customers actually order, and they're the two colors we can ship within 1–2 business days from our Hudson, NH inventory.
Engineering
What open-grid decking actually does for your dock.
Drains quickly
Water passes through the panel surface instead of pooling on top. The open-grid design helps reduce standing water and the slip risk that wood and composite decking deal with after rain or wave splash.
Lets light through
Legacy XP panels allow 43% of sunlight to pass through to the water and any vegetation below the dock. This matters for shoreline ecology and, in some jurisdictions, permitting.
Reduces wind and wave uplift
Solid decks behave like a sail in a storm. Open-grid panels let wind pass through, which can reduce uplift on the dock structure during storm surge and high winds.
Stays cooler underfoot
The UV-resistant polypropylene base doesn't store heat the way wood, aluminum, or some composites do. Walking the dock barefoot on a hot afternoon is comfortable in a way other materials aren't.
Slip-resistant wet or dry
A 360° engineered surface designed to maintain grip in wet and dry conditions, including with sunscreen, surface algae, ice, or rain present. Exceeds ADA accessibility specifications.
Sheds debris
Sand, leaves, pine needles, and snow tend to fall through the grid rather than building up on the surface. Most owners pressure-wash their Legacy XP dock once a year and skip the sanding, staining, and sealing entirely.
Compare
Legacy XP vs. wood, composite, and aluminum.
Every decking material has trade-offs. Here's the honest comparison.
| Legacy XP | Pressure-treated wood | Composite | Aluminum | |
|---|---|---|---|---|
| Upfront cost | Higher | Lowest | Mid–high | High |
| Maintenance | None (pressure-wash yearly) | Annual sealing, board swaps | Periodic cleaning | Cleaning, possible powder-coat repair |
| Slip resistance (wet) | 360° non-slip; exceeds ADA | Slick when wet | Variable; can become slick | Slick when wet |
| Bare-foot heat | Stays cooler in direct sun | Hot in direct sun | Can get hot | Very hot |
| Drainage | Open-grid, drains quickly | Surface puddles | Surface puddles | Surface puddles |
| Light passes through | 43% | None | None | None |
| Weight per sq ft | 1.6 lbs | ~3.5 lbs | ~3–4 lbs | ~2–3 lbs |
| Rot / mold / termite | Immune | Vulnerable | Resistant; surface mold possible | Immune; corrosion in salt |
| Lifespan | Lifetime limited warranty | 10–20 yrs with maintenance | 20–30 yrs | 20+ yrs |
Wood is cheapest upfront. Aluminum is the most rigid. Composite looks most like real wood. Legacy XP wins on the dimensions dock owners live with day to day—drainage, slip resistance, bare-foot heat, weight, and total maintenance over the life of the deck.
Install
Installation in plain English.
Most homeowners install Legacy XP themselves over a weekend. No special tools, no pre-drilling on wood, and nothing to seal or stain afterward. The official details live in the ThruFlow installation guide (PDF); here's what matters most.
- Works on wood, aluminum, or composite framing. Same panel, same install pattern across substructures.
- Use stainless steel screws. #10 or #12 pan-head, 2.5″ minimum length. Galvanized screws will corrode in marine environments—don't use them.
- Don't pre-drill on wood. Countersink holes are already molded into the panel. On metal substructures, use a self-tapping or self-drilling stainless screw.
- Don't overtighten. Leave a small gap at the screw head so the panel can expand and contract with temperature.
- Confirm joist spacing before ordering. 18″ on-center for 36″ panels, 16″ or 24″ for 48″, 15″ for 60″, 18″ or 24″ for 72″.
- Cut with a hand saw or circular saw. Standard carbide blade. Tabs can be removed for a flush edge against railings, posts, or stair stringers.
Stainless screws aren't always stocked at local hardware stores. We carry 316 stainless #10×2.5″ pan-head screws sized for Legacy XP—add them to your order at the same time.
Pre-flight
Before you order.
Six checks that take ten minutes and prevent the most common ordering mistakes.
-
1
Measure the area you're covering
Width and length, in feet. Round up to the nearest foot. If you have an irregular shape, break it into rectangles and measure each.
-
2
Confirm your joist or cross-member spacing
Crawl under the dock if you can. Joists at 16″ on-center? That's a 48″ panel. 18″? 36″ or 72″. 15″? 60″.
-
3
Choose Gray or Maple
Both wear identically. Gray is modern and hides marine wear. Maple blends into wood and natural settings. Pick whichever fits the dock.
-
4
Decide your priority: fewest cuts or fewest panels
Longer panels mean fewer joints and fewer panels overall, but they need wider on-center spacing in your framing. Shorter panels are easier to handle and waste less material on cuts.
-
5
Run the calculator
Enter your dimensions and confirm quantity. Add a 5% buffer for cuts, edges, and handling waste.
-
6
Add stainless screws to the order
316 stainless #10×2.5″ pan-head. Roughly 6–12 screws per panel depending on size. Galvanized screws will corrode in salt or freshwater marine environments—use stainless.
FAQ
Frequently asked questions.
Sixteen questions in the order a buyer's brain asks them.
What is ThruFlow Legacy XP?
Legacy XP is a fiberglass-reinforced polypropylene dock-decking panel made by ThruFlow Inc. Panels are 12 inches wide, 1.2 inches thick, and come in 36″, 48″, 60″, and 72″ lengths. The open-grid surface drains water, allows sunlight through, stays cooler in direct sun than wood or aluminum, and is engineered for non-slip grip wet or dry.
What sizes do you stock?
FWM stocks all four standard Legacy XP sizes in our Hudson, NH warehouse: 36″ (1′×3′), 48″ (1′×4′), 60″ (1′×5′), and 72″ (1′×6′). All ship in 1–2 business days.
What colors do you stock?
Gray and Maple. ThruFlow makes the panel in additional colors (Seafoam, Slate, Walnut, IPE) but we stock the two colors customers actually order at scale, in the volumes that ship within 1–2 business days.
How many panels do I need?
Depends on your dock dimensions and the panel size you choose. The calculator above handles this in seconds, and the common dock layouts table covers the most ordered sizes. As a rule of thumb: each panel is 12 inches wide, so panels-per-row equals your dock's width in feet.
What joist spacing do I need?
18″ on-center for 36″ panels, 16″ or 24″ for 48″, 15″ for 60″, 18″ or 24″ for 72″. Confirm your existing dock's framing before ordering—if the joists don't match the panel size you want, you'll need to re-frame or pick a different panel length.
Can I install it on aluminum framing?
Yes. Legacy XP installs over wood, aluminum, or composite substructures. On metal framing, use self-tapping or self-drilling stainless steel pan-head screws (#10 or #12, 2.5″ minimum).
What fasteners do I use?
316 stainless steel pan-head screws, #10 or #12, 2.5″ minimum length. Roughly six per 36″ panel, eight per 48″, ten per 60″, twelve per 72″. Galvanized screws corrode in marine environments—use stainless.
Can I cut the panels?
Yes. Cut with a hand saw or a circular saw fitted with a standard carbide blade. Most installs require trimming a few panels to fit around posts, dock hardware, or odd geometry. Cuts at edges are usually hidden by the dock frame or trim.
Is it slippery when wet?
The panel surface is engineered with a 360° non-slip texture designed to maintain grip wet or dry, and exceeds ADA accessibility specifications. Drainage through the open grid also helps reduce standing water on the surface.
Does it get hot in the sun?
The UV-resistant polypropylene base doesn't store heat the way wood, aluminum, or some composites do. Most owners report comfortably walking the dock barefoot on hot afternoons.
Does it let sunlight through?
43% of incoming sunlight passes through the open-grid surface to the water and any vegetation below the dock. The Army Corps of Engineers recommends open-grid decking for sensitive shoreline projects.
Is it good for marinas and commercial docks?
Yes. Every Legacy XP size exceeds 2,400 lbs of load capacity, surpassing commercial construction requirements. The panels are used on marina walkways, yacht clubs, HOA waterfronts, and government installations including the US Fish & Wildlife Service.
How does the 100-panel free shipping work?
Any combination of 36″, 48″, 60″, and 72″ panels in any combination of Gray and Maple counts toward 100. Once your single order crosses the threshold, the whole order ships free to the continental US. No code needed—the discount applies automatically at checkout.
How fast does FWM ship?
Orders placed on a business day ship the same day or the next business day from our Hudson, NH warehouse. We don't quote freight and we don't wait on the manufacturer—we stock the panels you order.
Do you ship to all 50 states?
We ship to the continental US (lower 48). Free shipping applies to orders of 100+ panels in the continental US. Alaska, Hawaii, and international orders are not currently supported online.
What is the warranty?
Every Legacy XP panel is backed by ThruFlow's lifetime limited manufacturer warranty covering material defects, rot, decay, and termite damage. Save your order receipt and a photo of the date wheel on the back of a representative panel for warranty claims.
Bulk & commercial
Planning a marina, camp, HOA, or municipal project?
Buy 100 or more Legacy XP panels in any mix of sizes and colors and shipping is free anywhere in the continental US.
- Mix 36″, 48″, 60″, and 72″ panels in one order
- Mix Gray and Maple toward the 100-panel threshold
- Approved on government, municipal, and Army Corps installs
- 1–2 business day ship-out from Hudson, NH
Used on
Residential, commercial, and public waterfront projects.
Legacy XP is the same panel we ship to homeowners, marina operators, summer camps, public-access waterfronts, and government installations.
- Residential docks
- Camps and youth organizations
- Public-access waterfronts
- Marinas and yacht clubs
- Commercial walkways and gangways
- Rowing and recreational facilities
- HOA and association docks
- Municipal and government installs
Authorized Dealer
FWM Docks is an authorized ThruFlow dealer. Every Legacy XP panel ships with the full manufacturer-backed lifetime limited warranty intact.
Legacy XP is protected under US Patent No. 7,500,336 and backed by ThruFlow Inc.'s lifetime limited manufacturer warranty.
Ready when you are.
Pick your sizes, mix your colors, hit 100 panels for free shipping. Orders ship in 1–2 business days from Hudson, NH.
Configure your Legacy XP order
Still researching?
- ThruFlow Dock Decking Buyer's Guide — sizes, joist spacing, colors, and how to order.
- Replacing Wood Dock Decking? Why Open-Grid Panels Are Worth Considering
- Best Dock Decking for Marinas, Camps, HOAs, and Commercial Waterfronts