Tear-off is the most consequential day of a roof replacement. Most homeowners think of it as the noisy part, the day the dumpster shows up, the day the crew rips off the old roof, the day to keep the kids and the dog inside. From the roofer’s perspective, it is the day when most of what determines the long-term performance of the new roof actually gets decided. What we find under the old roofing, how we handle it, and how cleanly the deck gets prepared for the new system is the part of the job that nobody can see once the new shingles or tiles go on, but it’s the part that controls everything that happens for the next 25 or 30 years.
Homeowners in San Jose, Sunnyvale, Cupertino, Los Gatos, and across the South Bay sometimes ask for a walkthrough of what to expect on tear-off day. Here is what actually happens, hour by hour, and what we’re doing and looking for at each stage.
Before the Crew Arrives: Site Prep
The night before tear-off, the project site needs to be ready. Your Roofing Consultant will have already walked you through what to expect: where the trucks park, which side yards or driveways the crew will use, where the staging happens. If you have outdoor furniture, planters, BBQs, or anything else within ten feet of the house perimeter, those items get moved. If you have solar panels, the solar installer needs to have them removed in advance and schedule them for re-install after the new roof is on.
The crew lead also confirms that interior items in the attic and garage, anything on rafter shelves, anything stored on the attic floor, have been moved or covered. Tear-off creates significant vibration and shedding of debris through the underside of the roof deck. Insulation gets disturbed. Whatever is up there gets dusty. The garage can take the worst of it if no ceiling exists…cars need to be removed, laundry machines and valuable items need to be covered.
Hour 1–2: Tear-Off Begins
The Los Gatos Roofing tear-off crew arrives at the start of the workday, typically around 7 a.m. The first vehicle on site is the dump truck, one of our five, backed into position close to the perimeter of the house. Tarps are often used around the foundation, on top of landscape beds, over walkways, and across any windows or features that need protection from falling debris, as needed.
The crew starts at the highest peak and works down. The old shingles or tiles come off in sections, fed across the roof to a fall zone, and shoveled or dropped into the dump truck. On a typical tract home in Sunnyvale or Cupertino, 20 to 25 squares, the tear-off itself is about a four- to six-hour job. On a steeper Saratoga or Los Gatos hillside home, it can run a full day.
During tear-off, the crew is also pulling old underlayment, removing flashings around chimneys and vent stacks, and stripping back the metal at valleys, drip edges, and eaves. The goal is a clean roof deck, usually plywood, sometimes original 1×8 sheathing on older Bay Area homes, exposed and ready for inspection.
Hour 3–4: What We Find Under the Old Roof
This is the moment in the project where the homeowner and contractor discover the actual condition of the underlying decking. Until the old roofing comes off, even the most thorough estimate is partly an educated guess. What we find under the shingles can include any of the following.
- Dry rot: Areas where moisture has worked under the existing roofing, often around chimneys, vent penetrations, valleys, or eaves, and rotted the sheathing underneath. Dry rot needs to be cut out and replaced. The extent only becomes clear when the roof is open.
- Termite damage: Less common than dry rot in the Bay Area but not rare, particularly in older homes that have not been treated. Termite-damaged sheathing or rafter tails need to be removed and replaced.
- Skip sheathing: Many Bay Area homes built before about 1970 were originally roofed over with spaced 1x board, “skip sheathing”, rather than a solid plywood deck. Modern asphalt shingle roofs need a solid deck underneath. If we find skip sheathing on a home in Willow Glen, Almaden, or older neighborhoods of San Jose, we install a new layer of plywood over it before the new roof goes on. This can be determined during the initial roof inspection with an attic inspection.
- Old underlayment that is bonded to the deck: On some older roofs, the original felt paper has effectively glued itself to the plywood. Removing it requires extra labor and sometimes plywood replacement.
- Inadequate ventilation: Inspecting the deck from outside often reveals that the original construction did not have enough ridge venting, soffit venting, or both. A new roof is the right time to fix that. Title 24 cool roof and ventilation standards in California require minimum airflow that many older homes do not meet.
When we find any of these conditions, the next step is to document them. The crew takes photos. The Roofing Consultant or foreman walks the homeowner through what we found and explains what it’s going to cost to address. These items need verbal approval before any additional work is performed. Time is of the essence to get repairs completed and close up the exposed decking for weather protection.
Hour 4–6: Deck Repair and Preparation
Once the deck is exposed and the homeowner has been apprised of any necessary repairs, the crew gets the deck ready for the new roofing system. Dry rot is cut out and patched with new plywood, typically 1/2-inch CDX, fastened to the rafters with code-required nail spacing. Damaged rafter tails or fascia are replaced. Skip sheathing is overlaid with new plywood. The deck gets walked, swept, and inspected.
This is also when the new flashings get prepped: chimney pans, vent stack flashings, valley metal, drip edges, and step flashings at any wall intersections. For a Los Gatos Roofing project, all of those sheet metal pieces are fabricated in our sheet metal shop, often custom-cut to the specific dimensions of your roof rather than pulled from generic stock.
Hour 6–8: Underlayment Goes On
Once the deck is clean and prepped, the crew installs new underlayment. Underlayment is the secondary water barrier under the visible roofing material. It is the layer that takes over when the shingles or tiles fail, which is why a quality underlayment installed correctly is one of the single biggest factors in the long-term performance of a roof.
Tear-off day ends with the deck completely covered and weather-tight, if possible. Even though the visible roofing material isn’t installed yet, your home is protected from rain overnight. A residential reroof should never end day one with bare plywood exposed in times of inclement weather; if you ever drive past a project that does, you’re looking at a crew that lost control of the schedule.
Why Tear-Off Day Determines the Roof
The roofing material on top (the shingles, the tiles, the metal) is the part homeowners think about. It’s what you see from the street. But the part that determines whether the roof lasts 25 years or 12 years is what happens under it. A premium shingle installed over rotten plywood and improperly prepped flashing will fail in five years. A modest shingle installed over a clean deck, with proper underlayment and code-compliant ventilation, will last for decades.
That’s why tear-off matters more than the brand name on the shingle package. It’s also why the question of who does your tear-off your contractor’s employees or a subcontracted crew that the contractor hired off a phone call- is one of the most important questions you can ask before signing a contract. Los Gatos Roofing runs five in-house tear-off crews and five dump trucks. The same company that bids the job, manages it, and warrants it is the company that owns the tear-off.
If you’re comparing roofing bids in San Jose or the South Bay, the tear-off day is what to ask about. The shingle warranty is fine. The price is what it is. But ask what the crew does when they find dry rot. Ask what the crew does when they find skip sheathing. Ask what the crew does at 4 p.m. on tear-off day when an unexpected rain is rolling in over Santa Clara. The answers to those questions tell you everything you need to know about the roof you are about to buy, and the contractor who stands behind it.