Free roof inspection with deck photos before we talk money - GAF and Owens Corning certified installation
Before
After
Before
After
Before
AfterFast, Reliable Roof Installation Across Union City
Roof installation in Union City typically costs $11,500 – $22,000 for a full tear-off and architectural shingle replacement on a standard 1,800-square-foot ranch, with the job completed in 3 – 7 days once materials arrive. We know these numbers cold because we’ve torn off hundreds of roofs across the Decoto, Alvarado, and Mission Boulevard corridors. If you’re watching water stains creep across your ceiling or your 1970s three-tab has started curling at the edges, call (743) 200-8347 and we’ll give you a written price before a single nail goes in.
Key Takeaways
- Full tear-off roof installation on a Union City ranch home runs $11,500 – $22,000; low-pitch Decoto shed sections add $1,800 – $4,200 when modified bitumen is required.
- We never overlay new shingles onto marine-layer-damaged three-tab. Union City’s salt air and wind demand a tear-off to decking.
- Every Mercer technician is background-checked, identity-verified, and arrives in a marked uniform with a photo ID badge. We send their name and photo before they knock.
- Your written price includes a 365-Day Done Right Promise. If the work isn’t right within a year, we make it right.
Why Mercer Roofing Is Union City’s Preferred Roof Installation Company
Union City homeowners call us because we treat their roof the way they’d treat it themselves: carefully, honestly, and with the real trade words for what’s actually wrong up there. We’ve worked the tract ranches off Alvarado-Niles Road, the splits near James Logan High, and the older bungalows around the Decoto district. The homes here share a DNA: single-story or split-level frames from the 1960s through 1980s, three-tab shingles on their second cycle, and low-slope garage transitions that collect moisture and corrode flashing.
Grant Whitlock leads our Union City crew. He’s the person who walks the ridge, inspects the decking, and writes your quote. Not a sales rep with a tablet full of upgrade packages. And when the crew arrives, you’ll already know their names and faces because we send them ahead of every visit. Uniformed, photo-badged, background-checked. That’s the Threshold Standard, and every independently owned Mercer location is held to it.
We answer the phone with a live person, 24/7. Not a call tree, not a “leave a message and we’ll get back to you within two business days.” When your roof is leaking on a Friday night in Union City, you talk to a person who can dispatch a crew.
Roof Ventilation in Union City
Roof ventilation in Union City is the difference between a 15-year roof and a 30-year roof. It’s the system of intake vents at the soffits and exhaust vents at the ridge that moves air through the attic, carrying out the heat and moisture that would otherwise cook your shingles from below and rot your decking from above. On a Union City ranch home with a low-pitch hip or gable roof, the original builders often cut corners here: a handful of static box vents on a 1,800-square-foot roof where modern code and shingle warranties want a continuous ridge vent paired with proper soffit intake.
What We Inspect Before Any Shingle Goes Down
Every full-install quote includes an attic inspection. Grant checks whether your existing vents actually move air or just decorate the roof. He measures intake area against exhaust area. On 1970s tract homes off Decoto Road, we commonly find soffit vents painted over, blocked by insulation, or never cut in the first place. Marine-layer moisture gets trapped, and the underside of the decking starts to gray and soften.
When ventilation is undersized, we correct it during the tear-off, not as a surprise add-on. Your written quote reflects real vent counts and air-movement math before work starts.
What a Ventilation Upgrade Costs Here
On a typical Union City ranch, adding a continuous ridge vent with proper soffit intake runs $1,400 – $2,800 depending on linear footage and how much soffit work is needed. If we’re already tearing off the old shingles, the labor overlaps and the cost comes in lower than a standalone retrofit. A failing box vent replaced with a turbine or power vent runs $350 – $850.
Roof Flashing Installation in Union City
Roof flashing installation in Union City is where most roof failures actually begin. Flashing is the metal, usually galvanized or painted steel or aluminum, that seals the joints where the roof plane meets a chimney, a wall, a skylight, or a valley. When flashing is old, corroded, or improperly lapped, water finds a way in. Union City’s salt-laden air accelerates the corrosion. We’ve pulled chimney flashing off 50-year-old Alvarado bungalows that crumbled in our hands like wet cardboard.
Where We See It Fail on Union City Homes
The western flatland sections of Union City sit on bay mud and alluvial fill. The soil consolidates unevenly, and the roof frame racks over time. Ridgelines walk out of line. When the ridge moves, the flashing at chimneys and valleys takes the stress and the seal cracks. A patch of caulk won’t hold that joint. The fix is re-flashing with proper step flashing, counterflashing, and fresh sealant, and sometimes sistering the racked framing first.
The attached-garage transition on single-story ranches is another chronic trouble spot. The plane changes pitch there, and if the original installer used one continuous piece of trim metal instead of properly lapped step flashing, water backs up under the shingles and rots the fascia.
Replacement Cost on a Union City Roof
Re-flashing a chimney runs $600 – $1,400 depending on chimney size and whether we need to cut a reglet into the brick. Valley flashing replacement runs $400 – $900 per valley. Wall flashing along a garage or addition tie-in runs $300 – $850 per wall. These are line items on your written estimate, not a vague “flashing included” line that disappears into the shingle price.
Trusted Brands We Service in Union City
We install and stand behind shingle brands that hold up to Union City’s specific conditions: GAF architectural shingles for the wind uplift you get on the open plain, CertainTeed for its algae-resistant granules on north-facing slopes, and Tamko for budget-conscious reroofs that still meet code. We stock fast-turnaround materials for Union City jobs at our Bay Area supply partners, so you’re not waiting three weeks for a special-order color to arrive. If a storm takes a section of your roof, we can match most common shingle lines within days.
Common Roof Installation Problems We See in Union City Homes
- Racked ridges on the western flatlands. Bay mud settles unevenly, and roofs on the flatland tracts between Decoto and Alvarado show ridgelines that have walked an inch or more out of line. That movement cracks chimney and valley flashing and turns minor gaps into leaks that keep coming back. We sister the framing before we lay the new decking.
- Marine-layer damage on north and west slopes. The persistent moisture off the bay breeds algae and moss, and the salt accelerates underlayment breakdown. Homeowners see dark streaking and assume it’s cosmetic. By the time we tear off, the decking underneath is often spongy at the eaves. A full tear-off to decking is standard on these homes, not an upgrade.
- Failed flashing at garage transitions. The single-story ranches off Mission Boulevard all have that low-slope change where the house roof meets the attached garage. When the original flashing was single-piece trim metal, it leaks within 15 – 20 years. We open it up during the tear-off and replace it with properly lapped step flashing.
- Low-pitch Decoto sheds with the wrong material. Pre-war homes in the Decoto district often have shed or near-flat sections pitched too low for composition shingles. Shingle manufacturers void warranties below 2:12 pitch. These sections need modified bitumen or rolled roofing, and we write that into the quote before the tear-off, not after we discovery it.
Pricing for Roof Installation in Union City, CA
A full tear-off and architectural shingle installation on a standard 1,500 – 2,200-square-foot Union City ranch runs $11,500 – $22,000. Smaller homes in the Alvarado bungalow stock can come in around $9,000 – $14,000, especially if the roof plane is simple. Larger or steeper roofs push toward $28,000. A partial reroof on one plane runs $3,500 – $7,000. Low-pitch Decoto sections requiring modified bitumen add $1,800 – $4,200 depending on square footage. The variables that move the number: decking replacement, ventilation correction, flashing scope, permit fees, and whether the roof is walkable or needs staging. Your written price from Mercer includes every one of these line items before work begins. Call (743) 200-8347 for a free estimate.
We Also Serve Cities Near Union City
Our crews serve the whole southern East Bay from our Bay Area dispatch office. If you’re in Fremont, Newark, San Lorenzo, or Castro Valley, we bring the same written-price and badge-at-the-door standard to your Roof Installation project. A lot of our Union City customers ask us to handle a parent’s roof in Fremont or a rental in Newark, and we’re set up for it.
Serving Union City, CA - Our Local Coverage Area
We’re based in the Union City area and know this community well. Use the map below to see our service coverage - if you’re nearby, we can almost certainly help.
FAQs About Roof Installation in Union City
You need a full tear-off. Union City’s marine-layer moisture and salt air get under the old three-tab course, and overlaying new architectural shingles on top traps that moisture against the decking and voids the manufacturer’s warranty immediately. On 1960s – 1980s tract homes off Decoto Road and Mission Boulevard, we remove everything down to the decking, inspect what’s underneath, and only then lay the new underlayment and shingle course. Call (743) 200-8347 and we’ll write the scope honestly.
The flatland sections west of the hills sit on bay mud and alluvial fill that settles unevenly, and the roof frame racks with it. Your ridge has literally moved out of line. That movement is what cracked the flashing seals at your chimney and valleys, which is why you’re getting leaks that keep coming back even after a patch job. We correct the framing before we install the new roof, so the new shingles land on a straight, stable plane.
No. Shingle manufacturers require a minimum 2:12 pitch, and many Decoto sheds and near-flat sections fall below that. When shingles are laid too flat, wind-driven rain pushes up under the tabs and soaks the underlayment. These sections need modified bitumen or rolled roofing instead, which we’ll write into your quote as a separate line item. Call (743) 200-8347 to have someone actually walk the pitch before you get a number.
On a 1972 split-level ranch off Decoto Road, we tore off the second-cycle three-tab and found the ridge had walked about an inch out of line. It had popped the chimney and valley flashing seals and let marine-layer moisture rust the old vent collars. That kind of find is common in Union City, not rare. We sistered the racked framing, laid ice and water shield at the valleys, set new underlayment and GAF architectural shingles with a starter strip and a continuous ridge vent, and finished the drip edge and fascia so the soffit line closed clean against the new decking. All of that was priced and approved in writing before we touched the framing. No surprises on the invoice.
Yes, typically ventilation and underlayment. Union City’s building department enforces current California building codes on reroofs, which means your new roof must meet modern attic ventilation standards and class A fire-rated underlayment. If your 1970s home was built with the minimum vents the code allowed then, the new code requires more. We build those upgrades into your written quote before we pull the permit, so the inspection passes and your shingle warranty stays intact. Call (743) 200-8347 for an exact quote on your home.
Where We Work in Union City
We install roofs across every Union City neighborhood. The tract ranches off Alvarado-Niles Road, the split-levels near James Logan High School, the 1950s stock around Old Alvarado, the Decoto district bungalows and lower-pitch sheds, the newer builds along Mission Boulevard, and the western flatland sections between the two old neighborhoods. If you’re in the 94587 or 94536 ZIP and your roof is on its second cycle, we’ve probably reroofed a house on your block already.
Written by Grant Whitlock, Owner at Mercer Roofing, serving Union City since 2000.
Call (743) 200-8347 to schedule your free roof installation estimate in Union City. A live person answers, every call, any hour.