Fiberglass Deck New Construction — Engineered Right From Day One
Important scope note: Our New Construction service applies to newly built homes where the deck is already framed (with the correct drainage slope built into the joists by the builder) and the first plywood layer is in place. From that point on, Seashore takes full ownership of the waterproofing system. Framing and the first subfloor are typically the builder's responsibility — Seashore IS capable of full framing on rebuild projects, but for standard new construction, we begin at the 1/2″ ACX overlay.
Our New Construction fiberglass service is designed for newly built homes where the deck has already been framed with the correct drainage slope built into each joist, and the first layer of plywood is in place. From that point, we take full ownership of the waterproofing system — installing the second plywood layer, setting PVC drip edges, integrating wall and post flashings, applying the fiberglass membrane, and finishing with marine-grade gelcoat. Getting these details right from day one prevents the failures we are called in to fix years later.
New construction is where we install every layer of the system the way the technical manual specifies — dual-layer plywood, chamfered transitions, PVC perimeter, flashings before siding, and a continuous membrane with marine-grade gelcoat. You get a deck that is engineered for the Shore from the joists up.
Our new construction system — from framing to gelcoat
- 1
Framing (by the builder, before Seashore arrives)
Framing is completed by the general contractor using pressure-treated lumber (typically 2x10 or 2x12 joists) with attachment points for railing and posts. Seashore does not perform framing on standard new construction projects.
- 2
Drainage slope (by the builder, verified by Seashore)
The 1/4″ per foot drainage slope is established by the general contractor at the joist level during framing. Seashore verifies the slope is correct before proceeding.
- 3
Packer boards
5/4 pressure-treated boards (~1-3/4" wide) on joists at the perimeter to build out the edge for metal flashing and drip edge.
- 4
Perimeter metal flashing
Installed after packer boards and before plywood, to shed water at the deck perimeter.
- 5
First plywood layer (by the builder)
The 3/4″ CDX subfloor is installed by the general contractor, glued to framing and fastened per specification. Seashore does not install the first plywood layer on standard new construction projects.
- 6
Second plywood layer (Seashore scope begins here)
We install the 1/2″ ACX overlay, glued and screwed to the existing 3/4″ subfloor for a stable monolithic substrate. From this point forward, every layer is installed by Seashore.
- 7
Chamfer strips
45-degree transitions at all wall-to-deck corners so fiberglass can turn without sharp folds that fail.
- 8
PVC drip edge
1x4 (~3.5" wide) rot-proof perimeter edge, wider than the packer board, so water sheds clear of the fascia.
- 9
Surface grinding
Mechanical prep of the plywood for fiberglass adhesion.
- 10
Screw and seam filling
Bondo or equivalent over screw heads and seams for a smooth plane before lamination.
- 11
Fiberglass membrane
2-oz mat fully saturated with resin, continuous across the field and up transitions.
- 12
Wall flashings
Minimum 12" up vertical surfaces, integrated before siding where applicable.
- 13
Post flashings
Minimum 6" vertical wrap at every post penetration.
- 14
Door transition system
Custom-fabricated pan and flashing integration with the building envelope.
- 15
Post-cure grinding and acetone clean
Surface prepared for the final cosmetic and UV layer.
- 16
Marine-grade textured gelcoat
UV-resistant, non-slip finish suitable for coastal exposure.
Ready for a free inspection?
We will diagnose your deck honestly and give you a clear scope — no pressure.