Metal roofing
Architectural shingles
Tile roofing
Owens CorningFree roof inspection with deck photos before we talk money - GAF and Owens Corning certified installation
Fast, Reliable Roofing Company Across El Cajon
Roof repair and replacement in El Cajon runs $650 – $2,800 for most repairs and $11,000 – $28,000 for a full replacement, depending on roof size, pitch, and decking condition. We’re Mercer Roofing Co San Diego, founded in 2000 and part of the Threshold Group family. Our crews serve El Cajon neighborhoods from Fletcher Hills to Rancho San Diego, and we know what your roof is up against here. Intense summer heat, occasional heavy winter downpours, and 1950s – 70s ranch construction with limited attic ventilation create failure patterns you won’t see in coastal cities. That’s why our quoting process includes a written price before any work starts, and every repair carries a written 365-day guarantee. Call (619) 810-5520 for a free estimate.
Why Mercer Roofing Co San Diego Is El Cajon’s Preferred Roofing Company
We build trust through specifics. When we send a technician to a home near Grossmont College or along Chase Avenue, you get their name and photo before they arrive. They wear a marked uniform and present a photo ID badge at the door. No surprises at the threshold. That’s the Threshold Verified standard, and every Mercer technician is background-checked, identity-verified, and held to it. Our Roofing Company team has handled hundreds of El Cajon roofs over the years, and the failure patterns here are consistent. We know what to look for on a 1960s ranch off Avocado Avenue that a technician from a coastal city might miss.
Grant Whitlock leads our operation, and he’s built the crew around one principle: homeowners should know exactly who’s walking onto their property and exactly what the job will cost before it starts. That’s the written quote. That’s the badge at the door. That’s the 365-Day Done Right Promise: if the work isn’t right within a year, we make it right. We answer the phone 24/7 with a live person. Not a voicemail tree. Not a callback form. A real human.
Styles & brands we work with
Commercial Roofing in El Cajon
Commercial Roofing in El Cajon means two things: low-slope membrane systems on the retail and office buildings along Main Street and Broadway, and multifamily housing scattered through the city’s older neighborhoods. These roofs take intense UV exposure. Built-up roofs and modified bitumen systems expand and contract hard in El Cajon’s heat, and the failures cluster at parapet walls and drainage valleys where water concentrates. A commercial flat roof here needs reinforcement at transitions and a drainage plan that survives brief but heavy winter rain. Most commercial repairs in El Cajon run $1,200 – $6,500 depending on membrane type and damage extent. Full commercial replacement typically lands between $8,000 and $45,000.
Low-Slope Membrane Repair and Coating
Older commercial buildings in El Cajon often have original built-up roofing that’s outlived its service life. We inspect for membrane splits at parapet intersections, ponding around scuppers, and deteriorated flashing at HVAC curbs. Coating systems can extend a roof’s life by several years, but only if the underlying membrane is sound. We’ll tell you honestly whether a coating is worth it or whether you’re better served replacing the system.
Parapet Wall and Flashing Replacement
Parapet walls on El Cajon commercial buildings take direct sun on two sides, which means the flashing fails faster than anywhere else on the roof. We replace rusted or cracked metal coping, install new membrane up the wall face, and tie everything into a continuous drainage path. This is the single most common commercial repair we perform in El Cajon.
Metal Roof Installation in El Cajon
Metal Roof Installation in El Cajon is a strong match for the climate: standing seam and metal shingle systems reflect heat far better than composition shingles, which matters when summer temperatures push past 100°F. Metal also handles thermal expansion better than built-up roofing. For a typical single-story El Cajon ranch, a metal roof installation runs $16,000 – $38,000 depending on gauge, profile, and whether the existing roof must be torn off first. It’s a premium product with a service life that routinely exceeds 40 years.
Standing Seam for Low-Slope Ranch Homes
Many of El Cajon’s 1950s – 70s ranch-style homes have low-slope roofs that barely meet minimum pitch for shingles. Standing seam metal with a mechanical lock system performs well on these slopes and eliminates the membrane split failures common to built-up roofing in this heat. If your roof has repeated leak issues at the same spots, metal is worth considering.
Metal Re-Roof Over Existing Shingles
In some cases, metal can be installed over a single layer of existing shingles, which saves tear-off cost and landfill waste. We check decking condition and roof slope first. El Cajon’s older homes often need selective decking replacement before a re-roof, and we flag that in the written quote, never as a surprise later.
Trusted Brands We Service in El Cajon
We install and repair using manufacturer-recognized shingle brands, including GAF, CertainTeed, Owens Corning, IKO, Atlas, Tamko, and Boral. For El Cajon’s climate, we often recommend GAF architectural shingles for their wind uplift ratings and heat tolerance, plus Atlas StormMaster or Tamko for homeowners seeking higher impact ratings. Parts for these systems are stocked locally, which means faster turnaround when you need a repair before the next winter rain. If you already have a roof from one of these manufacturers, we can match the product line and preserve whatever warranty remains.
See the difference
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After
Before
After
Before
AfterCommon Roofing Company Problems We See in El Cajon Homes
- Membrane splits at parapet walls and valleys: Thermal expansion from El Cajon’s heat cycles stresses built-up roofing at exactly the points where drainage concentrates. These splits leak during the heavy winter downpours and are easy to miss if the inspection only looks at the field of the roof, not the transitions.
- Brittle, baked-out underlayment on 1950s – 70s ranch homes: Limited attic ventilation traps heat under the decking, and after 30 – 40 years the original felt underlayment turns to the consistency of dried leaves. Shingles can look fine from the ground while the water barrier beneath them has failed.
- Cracked and curled composition shingles from UV exposure: El Cajon gets over 260 sunny days a year. That constant exposure breaks down shingle binder faster than in coastal cities, and the first signs are granule loss in gutters and curling at the eaves.
- Uninsurable original shake roofs in Fletcher Hills: Many 1950s – 60s homes in Fletcher Hills still carry original wood shake. Insurance carriers now routinely deny coverage or cancel policies on shake roofs. Replacement with a fire-rated system is often the only path to insurability.
Pricing for Roofing Company in El Cajon, CA
Here’s what you can expect for roofing work in El Cajon as of 2026. Minor repairs like a broken shingle, small flashing leak, or isolated membrane patch run $350 – $900. Moderate repairs including valley re-flashing, penetration boots, or small sections of decking replacement run $900 – $2,800. Full roof replacement on a typical single-story El Cajon ranch with composition shingles runs $11,000 – $19,000. If your home needs extensive decking replacement, a higher wind rating, or has a steep Spanish tile profile, expect $19,000 – $28,000. Metal roofing starts at $16,000 and can reach $38,000 for standing seam on a low-slope roof with significant prep work. Every quote is written, line-item, and fixed before any work starts. Call (619) 810-5520 for your free estimate.
What changes the number most in El Cajon is decking condition. Original 1950s – 70s homes often have deteriorated plywood or skip sheathing that must be replaced to meet current code and pass inspection. We include that in the written quote. Some cheaper bids leave it out, then add a change order once the old shingles come off. We don’t work that way.
We Also Serve Cities Near El Cajon
Our crews cover El Cajon and the surrounding East County communities. We regularly serve El Cajon proper along with Santee, Bonita, Alpine, and National City. If you’re in one of these cities and need a roof inspected, repaired, or replaced, the same team, the same written prices, and the same 365-day guarantee apply. Call (619) 810-5520 and we’ll route you to the nearest crew.
Serving El Cajon, CA - Our Local Coverage Area
We’re based in the El Cajon 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 Roofing Company in El Cajon
El Cajon sits in a wind design zone that requires shingle systems rated for 90 – 110 mph uplift, and some hillside exposures in Fletcher Hills and Granite Hills require higher ratings. Our written quote specifies the exact wind rating of the system we’re installing, the manufacturer’s technical data sheet that documents it, and the nailing pattern and fastener count that achieves it. If the quote doesn’t name a wind rating, it hasn’t committed to one. Call (619) 810-5520 and we’ll specify exactly what your roof needs.
El Cajon’s housing stock was largely built between the 1950s and 1970s, and many homes still have the original plywood or skip sheathing. Decades of heat from under-ventilated attics dries out and warps that decking. Current code requires solid, sound decking before any new underlayment or shingles go on. We include decking replacement in the written quote when we can see signs of deterioration during the pre-bid inspection, and we document exactly what we found with photos. A cheap quote that omits decking isn’t cheaper; it’s a deferred change order. We’ll give you the real number up front.
Sometimes. Insurance carriers in California increasingly request roof condition reports before renewing policies, especially on original shake roofs or composition roofs older than 20 years. A new roof with a documented wind rating, fire rating, and permitted inspection record gives your carrier evidence the roof meets current code. We provide documentation after every install: permit confirmation, inspection sign-off, manufacturer warranty registration, and our written 365-day guarantee. That paperwork doesn’t guarantee a premium reduction, but it removes the biggest reason carriers cancel or deny El Cajon policies. Call (619) 810-5520 for a documented, code-compliant installation.
On low-slope built-up roofs, we reinforce membrane transitions at parapet walls and valleys, because those are the points where El Cajon’s thermal expansion cycles cause splits and leaks. We install ice and water shield at all penetrations and valley lines, not just at eaves. We inspect the drainage path and correct ponding issues by adding tapered insulation or re-sloping crickets where needed. Many competitive bids omit one or all three of these steps. Our written quote lists each one as a line item so you can compare honestly. The 365-Day Done Right Promise covers whatever we install.
Yes. Many of El Cajon’s Spanish-style homes originally used clay tile, and some were transitioned to flat built-up roofs with parapet facades. If you want to keep the Spanish look, we can install barrel-profile concrete tile that meets California’s Class A fire requirements, or a flat tile profile in a lighter color that reflects heat better than the original dark clay. The fire rating is built into the tile system, and we document the class rating in the quote and on the permit documents. Your insurance company gets the documentation; your neighbors just see a roof that belongs in the neighborhood.
Need a roof inspected, repaired, or replaced in El Cajon? Call Mercer Roofing Co San Diego at (619) 810-5520 for a free written estimate. A live person answers, day or night. You’ll know who’s coming to your door before they arrive, and you’ll know the exact price before any work starts.
Written by Grant Whitlock, Owner at Mercer Roofing Co San Diego, serving El Cajon and East County since 2000.