What a re-roof actually requires

Tear-off and disposal Required on every re-roof

Almost every re-roofing job in LA should involve a full tear-off, removing the existing roofing down to the bare deck. California allows up to two layers of shingles in some cases, but most experienced contractors recommend against overlay (installing new material over old) because:

• You can't inspect the deck for damage without removing the old material
• Two-layer roofs are heavier (relevant in a seismic zone)
• The next re-roof costs more because you're now removing two layers
• Underlayment quality is compromised by the uneven base

Disposal of old roofing material is included in most LA contractor bids, confirm this explicitly. Asphalt shingles are recyclable in some cases; most end up in a roll-off dumpster and hauled to a landfill. Expect a dumpster in the driveway for the duration of the job.

Roof decking Only if needed

The decking (also called sheathing) is the structural substrate everything else fastens to, typically 1/2" or 5/8" plywood or OSB panels nailed to your rafters. You don't see it once the roof is finished, but it's the foundation of the entire assembly.

A full tear-off exposes the entire deck for inspection. A good contractor will walk it, literally walk across it, and note soft spots, delamination, rot, or areas where fasteners have pulled through. In LA, common deck problems include:

• Termite damage: Active or historical subterranean termite channels are common in LA homes, particularly in older wood-framed construction. A compromised deck section needs replacement before anything goes on top of it.
• Heat-related delamination: In areas with extreme attic heat (like the San Fernando Valley), OSB sheathing can delaminate over time. Visible bubbling or separation is a replacement indicator.
• Moisture damage from previous leaks: Dark staining, soft spots, or actively rotted sections around old flashing failures and penetrations.

Decking replacement is typically billed per sheet (4x8 panel). Ask your contractor for their per-sheet rate upfront so you're not surprised when the invoice comes.

Underlayment Required on every re-roof

Underlayment is the membrane laid over the bare deck before the finish material goes on. It's your second line of defense, if water finds a path through a failed shingle, cracked tile, or lifted metal panel, the underlayment is what keeps it off the deck.

Felt underlayment (15 lb and 30 lb)

The traditional option. Asphalt-saturated felt is inexpensive and adequate for lower-slope roofs with well-overlapped courses. It's susceptible to moisture absorption and can tear under foot traffic during installation. Still widely used, but synthetic underlayment is taking over for good reason.

Synthetic underlayment

Woven polypropylene or polyester sheet, significantly stronger, more tear-resistant, and more water-resistant than felt. Better UV stability during the window between tear-off and new material installation (in LA's sun, a roof can sit exposed for a day or more between stages). Most quality contractors default to synthetic today. Ask which product your contractor uses and whether it's approved for use with your finish material.

High-temp underlayment for metal

Standard felt or synthetic underlayment can degrade under a metal roof's elevated deck temperatures in LA summers. Standing seam and other metal roofing systems require high-temperature-rated underlayment, typically a modified bitumen product or specifically rated synthetic. This is a detail that separates experienced metal roofers from general contractors who occasionally do metal.

California Title 24 cool-roof requirements

For re-roofing projects meeting certain thresholds in LA, Title 24 energy code applies. Cool-roof compliant underlayments and materials are available and commonly specified. Your contractor should be familiar with this, it affects product selection on most LA re-roofs.

Water and ice barrier Standard at vulnerable spots

Despite the common name, this product is just as important in LA as in cold climates, the "ice" in the original name refers to ice dam protection, but the product's real value is sealing around fasteners and providing a waterproof membrane at vulnerable locations.

Self-adhering modified bitumen membrane is applied at:

• Eaves and rakes: The first 3 feet (minimum) from the edge of the roof, where wind-driven rain can penetrate upward under the finish material during Santa Ana events or heavy winter storms
• Valleys: Where two roof planes meet, water concentrates significantly, the valley is the highest-flow point on any complex roofline
• Around all penetrations: Chimneys, skylights, pipes

On a full re-roof, this should be included as standard at these spots. If a bid skips it or specifies only felt at eaves, ask why.

Fascia and soffit Only if needed

The fascia is the vertical board at the edge of the roof, what your gutters attach to. The soffit is the horizontal surface on the underside of the roof overhang. Both are part of the roof system even though they're not on top of it.

A re-roof is the best time to assess fascia and soffit condition because the fascia board needs to be sound to support new drip edge and gutters. Common LA-specific problems:

• Dry rot and termite damage: Fascia boards are a prime target. Exposed wood in LA's warm, humid coastal microclimates (and occasionally in inland areas where moisture enters from a failed roof) rots faster than many homeowners expect.
• Failed paint: Peeling and bare wood on fascia accelerates deterioration. If you're spending tens of thousands on a roof, addressing deteriorating fascia at the same time makes sense.

Fascia and soffit replacement is typically a separate line item but can be bundled with the roofing contract. Many roofing contractors can handle it; some subcontract it to a carpenter. Clarify this before work begins.

Flashing Required on every re-roof

Flashing is the sheet metal (typically galvanized steel, aluminum, or copper) installed at all roof-to-wall junctions, around chimneys, skylights, dormers, and where different roof planes meet. It directs water away from these vulnerable intersections and toward the field of the roof where it can drain properly.

New flashing should be installed on every re-roof. No exceptions. This is the single most important quality indicator in a roofing bid. Reusing old flashing is a common shortcut, it's faster and cheaper for the contractor. It's also the number-one reason roofs leak shortly after replacement. Old flashing is already embedded with sealant, nail holes, and fatigue from years of thermal cycling. It won't perform like new flashing, and any leak will be in the exact spots that new flashing would have protected.

Step flashing at walls

Where a roof meets a vertical wall (common at additions, dormers, and chimney sides), step flashing, individual L-shaped pieces woven with each course of shingles, is the correct method. Continuous caulked counterflashing isn't a permanent solution; it fails within years in LA's UV and heat.

Chimney flashing

The most complex flashing detail on most homes. Done right, it involves base flashing, step flashing up the sides, and counterflashing embedded in the mortar or sealed against the chimney face. LA's chimney inventory includes a lot of older mortar work that needs attention at re-roof time, a contractor who looks at the chimney carefully and mentions it is one to trust.

Coastal considerations

Within a mile or two of the coast, galvanized steel flashing can show corrosion within 5–10 years. Copper or stainless steel are better specifications for coastal LA homes. Ask what flashing material your contractor uses, it's worth specifying in writing.

Pipe boots and penetration seals Required on every re-roof

Every plumbing vent, HVAC penetration, and conduit that exits through the roof needs a seal, typically a rubber "boot" over a metal flange that nails to the deck. These are one of the most common leak points on any aging roof, and they're inexpensive to replace at re-roof time.

Standard pipe boots have a rubber collar that works fine for 10–15 years. After that, LA's UV and heat cause the rubber to crack, stiffen, and eventually fail. Neoprene boots are more UV-resistant than standard EPDM and worth specifying for an LA installation.

More recent are lead-free all-metal pipe boots, more durable than rubber long-term, no UV degradation risk. Ask whether your contractor uses rubber or metal boots; either is acceptable, but knowing which is in the scope helps with maintenance expectations later.

Count your roof penetrations and confirm they're all addressed in the bid scope. It sounds obvious, but overlooked pipes are a real thing on complex rooflines.

Permits and inspections Required on every re-roof

In LA County and LA City, roof replacements require permits in most cases, and the permit triggers at least one (usually two) inspections: a mid-job inspection of the exposed deck and underlayment, and a final inspection after the finish material is installed.

Permits in LA typically run $400–$800 depending on jurisdiction and project scope. Never let a contractor skip the permit process to save you money. The reasons are significant:

• An unpermitted roof can create complications when you sell the home (disclosure requirements, buyer inspection flags)
• Insurance claims after fire or storm damage may be complicated if the roof was unpermitted
• The permit inspection is an independent check on the work, particularly on the deck and underlayment that get covered up and become impossible to inspect later

A contractor who resists pulling permits is a contractor who doesn't want independent verification of their work. That's the actual reason permits get skipped, most of the time.