Plywood Replacement During Re-Roofing | Bigfoot Windows & Roofing

Why This Matters

The Plywood Problem No Contractor Can Predict Until Tear-Off

Hidden rot is the number-one source of mid-project surprises on South Florida re-roofs.

Here is what happens on almost every re-roofing job in Miami-Dade: the crew pulls off the old shingles or lifts the tile, and instead of a solid plywood deck underneath, they find dark, spongy sections that crumble when pressed. Sometimes it is a few sheets in the corner near the A/C curb. Sometimes it runs along an entire valley or eave line. The homeowner had no idea.

This is not negligence — it is physics. South Florida’s combination of intense UV, high humidity, frequent afternoon thunderstorms, and hurricane-season driving rain creates conditions where water infiltration works silently for years behind intact-looking roofing materials. By the time the exterior surface signals a problem, the structural damage underneath can be substantial.

The question is not whether you will have some decking replacement — it is how much, why, and how your contractor’s bid handles it. Understanding the answer before work starts keeps your project on budget and avoids the shock of a mid-job change order conversation.

South Florida & HVHZ Context

Why Miami-Dade and Broward Are Different From the Rest of Florida

The High-Velocity Hurricane Zone sets stricter rules — and your roof deck is where those rules start.

Miami-Dade and Broward counties sit within Florida’s High-Velocity Hurricane Zone (HVHZ), the most stringent building-code jurisdiction in the United States for residential construction. Under the Florida Building Code (FBC) as adopted locally, roof sheathing is not just a substrate — it is a structural component that must meet specific thickness minimums, fastener schedules, and span requirements before a new roof system can be installed and inspected.

When the Miami-Dade Building Department issues a roofing permit, the inspector does not just look at the finished roof. They verify that the deck itself meets current HVHZ standards. If your original plywood was installed under an older code cycle — or if it has been compromised by moisture — it may need to be brought up to current standards before the new roofing system goes on. That process can trigger additional deck replacement beyond whatever rot removal was already planned.

Palm Beach County follows the standard Florida Building Code rather than HVHZ, which means slightly different nailing schedules and inspection thresholds — but the moisture damage dynamics are identical given the shared climate. Regardless of which county your home is in, the South Florida climate means you should plan for some level of decking work on any re-roof.

What Drives the Numbers

How Much Additional Plywood Replacement Is Actually Needed?

The honest answer depends on your roof’s age, material, slope, and penetration count — here is how to think through it.

There is no universal percentage that applies to every re-roof. What experienced South Florida roofing contractors use instead is a damage-probability framework based on the characteristics of your specific roof. Here are the primary drivers:

Roof Age and Material Type

A concrete tile roof installed in the 1990s has had 25+ years of water cycling through thousands of small crack points, fastener holes, and mortar joints. The deck underneath has almost certainly absorbed moisture in multiple locations. Shingle roofs shed water faster but can still develop concentrated rot at valleys, eaves, and anywhere a flashing has failed. As a general planning reference:

These are directional planning ranges based on field experience in Miami-Dade, Broward, and Palm Beach — not guaranteed project quantities. Actual replacement is confirmed at tear-off.

Penetrations: A/C Curbs, Vents, and Solar Mounts

Every penetration through a roof deck is a potential water entry point, and in South Florida, flat and low-slope roofs commonly have five to ten or more penetrations for A/C curbs, exhaust vents, plumbing stacks, and — increasingly — solar racking anchors. Each penetration creates a moisture-concentration zone. The plywood immediately surrounding an A/C curb that has had any flashing gap is almost always compromised. Budget for at least one to two sheets of replacement per major penetration as a conservative planning assumption.

What the Code Requires for HVHZ Decking

Under HVHZ requirements incorporated into the Florida Building Code, roof sheathing must meet specific minimums. As a general reference:

• Minimum thickness: 19/32" (5/8") plywood or equivalent structural panel is commonly required for most residential rafter spans in HVHZ applications — verify the applicable span table for your specific framing.
• Fastener type: Ring-shank nails are required (smooth-shank nails do not meet HVHZ uplift requirements).
• Nailing schedule: The Miami-Dade Building Department inspector verifies fastener spacing at the field and panel edges — typically 6" on center at edges and 12" in the field, though the applicable NOA or approval document for the specific roof system governs.

If your existing deck was nailed with smooth-shank nails — common on pre-2000 construction — the inspector may require re-nailing even on structurally sound panels. Re-nailing adds labor cost but is far less expensive than full replacement.

How to Read Your Contractor’s Bid

Most South Florida re-roofing bids handle decking in one of three ways:

1. Included allowance: The bid includes a fixed number of sheets (often 5–10) as part of the base price. Anything beyond that triggers a per-sheet change order.
2. Excluded entirely: Decking replacement is listed as "not included — charged at cost per sheet at time of installation." This is technically transparent but gives you zero budget certainty.
3. Line-item estimate: The contractor estimates a probable quantity based on roof age and visible damage signs, lists a per-sheet unit price, and explains the change-order trigger. This is the most homeowner-friendly approach.

When comparing roofing estimates for South Florida projects, ask every contractor explicitly: "How many sheets of decking are included in this price, and what is your per-sheet rate if more are needed?" A contractor who cannot answer that question clearly has not thought through your project scope.

Cost Breakdown

Plywood Replacement Cost Factors: What Moves the Number

Per-sheet pricing varies — here is what to expect in Miami-Dade and Broward versus Palm Beach.

All figures are directional market-range estimates for planning purposes only. Actual pricing varies by material availability, project complexity, slope, and access. Bigfoot provides firm per-sheet pricing in writing before any decking work begins.

Palm Beach County projects typically run toward the lower end of the HVHZ range on labor because the HVHZ fastener schedule does not apply — but material costs are similar given the same South Florida lumber market. The biggest single variable is roof slope: a low-slope or flat roof costs less per sheet to deck than a steep residential roof where crews must use safety lines and scaffolding.

Material Guidance

What Goes Back On: Roofing Systems Over a Repaired Deck

The decking is the foundation — the roofing system on top has to be matched to it correctly.

Once damaged decking is replaced and the HVHZ nailing schedule is satisfied, the new roofing system gets installed over a full-deck underlayment. For shingle roofing in South Florida, Bigfoot installs GAF architectural shingles with a full-deck peel-and-stick underlayment. Under the 2024 Florida Building Code update, a full-deck peel-and-stick system is now permitted as a direct-to-deck application and can qualify as a Secondary Water Resistance (SWR) feature on the Florida wind mitigation inspection form (OIR-B1-1802) — which may qualify for an insurance discount, depending on your carrier and wind mitigation inspection results.

For standing seam metal roofing, Bigfoot installs Englert panels roll-formed on-site from 24-gauge C4 steel, using Englert-stamped clips at the specified schedule. Metal roofing over a properly decked and re-nailed HVHZ deck gives the full structural assembly the best chance of performing as designed through hurricane season.

For tile roofing, the deck repair is especially important because tile is heavy — an undersized or moisture-compromised deck can deflect under tile weight, cracking the substrate and restarting the moisture cycle within a few years. Bigfoot uses Westlake concrete and barrel tile products, verified for the applicable wind-speed ratings for your county.

If you are considering financing your roof replacement, PACE programs allow you to spread both the base installation cost and the decking replacement allowance over time — and the decking line item is eligible as part of the same qualifying improvement.

What to Expect

The Decking Replacement Process: Step by Step

Knowing the sequence reduces mid-project anxiety.

1. Pre-job estimate: At the estimate stage, we assess visible signs of moisture damage — staining on soffits, sagging field areas, cracked or lifted tile — and note penetration count. We provide a probable decking allowance in writing as part of the bid.
2. Tear-off and inspection: Once old roofing is removed, we walk the entire deck and mark every compromised panel with chalk. We document each area with photos before any replacement begins.
3. Replacement and re-nailing: Damaged panels are removed and replaced with code-compliant structural plywood at the correct thickness, fastened with ring-shank nails at the HVHZ-required schedule. Sound panels that were previously under-fastened are re-nailed in place.
4. Inspector verification: The Miami-Dade Building Department inspector (or the applicable county inspector) verifies the deck before underlayment goes down. This is a mandatory hold point — the roof cannot proceed until the deck passes.
5. Change-order documentation: Any decking replacement beyond the bid allowance is documented by sheet count and location before billing. You see the evidence before you see the invoice.
6. Underlayment and finish roofing: Once the deck passes inspection, the full underlayment system and chosen roofing material are installed in sequence per the applicable Miami-Dade NOA or Florida Product Approval.

Who We’re Not the Right Fit For

We believe in being direct about where we are and are not the best match. Here are situations where another contractor may serve you better:

1. You need the absolute lowest bid and want to sort out scope differences later. We include a written decking allowance, a per-sheet change-order rate, and photo documentation in our proposals. That process adds a few days to scoping. If speed-to-lowest-number is the priority, a contractor who excludes decking entirely will look cheaper on paper — and may be more expensive once the job is open.
2. Your project is in a county or municipality we do not currently serve. We operate in Miami-Dade, Broward, and Palm Beach counties. If your property is outside that area, we are not set up to pull permits or manage inspections for your project effectively.
3. You need roofing only — no decking assessment, no code compliance review. If your roof deck was recently replaced and independently inspected, and you simply need a new surface system installed, a roofing-only contractor may be a faster fit. Our approach is thorough; that thoroughness has value when the stakes are high, but it is more process than some straightforward re-roofs require.
4. Your project requires licensing classes we do not hold. We do not hold electrical, plumbing, mechanical, pool, or HVAC licenses. If your re-roofing project requires those trades under a single GC umbrella, you will need a contractor with that full licensing portfolio or separate licensed subcontractors coordinated by your GC.