Asphalt shingles are the most common roofing material in the Inland Empire, and for good reason. They're affordable, they come in a wide range of styles, and when properly installed, they hold up reasonably well. But "reasonably well" in Riverside, California is different from "reasonably well" in Portland, Oregon. Our heat, UV exposure, and Santa Ana winds put specific stresses on asphalt shingles that homeowners need to understand.
I've been replacing and repairing asphalt shingle roofs across Riverside, Corona, Moreno Valley, and the surrounding area for 35 years. Here's what I see go wrong, what it means, and what you should do about it.
Granule Loss - The First Warning Sign
Every asphalt shingle has a coating of ceramic granules on its surface. Those granules aren't decorative - they're the shingle's primary defense against ultraviolet radiation. When granules start coming off, the underlying asphalt is exposed to direct sun, and in the Inland Empire, that means degradation accelerates fast.
Some granule loss is normal, especially on a new roof. Manufacturers apply excess granules during production, and loose ones wash off in the first few rains. That's nothing to worry about. What you're watching for is ongoing, progressive granule loss on a roof that's been installed for more than a year or two.
Check your gutters after a rainstorm. If you're finding a heavy accumulation of gritty, sand-like material in the bottom of your gutters or at the base of your downspouts, your shingles are shedding granules at a rate that matters. You might also notice areas on the roof where shingles look darker or shinier than the surrounding ones - that's bare asphalt showing through where granules have worn away.
In the Inland Empire, granule loss is accelerated by our intense UV. We get roughly 280 sunny days per year in Riverside, and summer roof surface temperatures can hit 150 to 170 degrees Fahrenheit. That sustained heat and UV exposure breaks down the bond between granules and the asphalt substrate faster than it would in a cooler, cloudier climate. A shingle rated for 30 years by the manufacturer may start showing meaningful granule loss at 15 to 20 years here.
If you notice sudden, heavy granule loss after a hail event - even small hail - the impact may have knocked granules loose across a wide area. This kind of damage is often covered by homeowners insurance and should be documented with photos and a professional roof inspection promptly.
Curling Shingles
Shingle curling takes two forms, and both are common in our climate.
Cupping is when the edges of a shingle turn upward while the center remains flat or dips down. This creates a concave shape that catches wind and holds water. Cupping is typically caused by moisture issues - either the shingle is absorbing moisture from below (poor attic ventilation) or the asphalt is drying out from above due to UV exposure.
Clawing is when the center of the shingle humps upward while the edges stay flat or curve down. This is almost always heat-related. The asphalt expands and contracts with our extreme temperature swings - a roof in Riverside can go from 50 degrees on a winter morning to 130 degrees on a summer afternoon. Over years of that cycling, the shingle material fatigues and the center lifts.
Either form of curling is a problem because it breaks the seal between overlapping shingles. That seal is what keeps wind-driven rain from getting underneath. Once the seal is broken, the shingle is also more vulnerable to being caught and lifted by wind. During Santa Ana events, curled shingles are the first to go.
If curling is limited to a small area - maybe around a vent or in one section - targeted roof repair is usually feasible. If curling is widespread across the roof, you're looking at a replacement conversation. Spot-repairing dozens of curled shingles across an entire roof isn't cost-effective.
Cracked and Broken Shingles
Cracking in asphalt shingles is a sign of advanced aging. It happens when the volatile oils in the asphalt evaporate over time, leaving the material brittle and inflexible. In the Inland Empire, this process is faster than in moderate climates because our heat drives those oils out more quickly.
You'll see cracking most often on south-facing and west-facing roof slopes - the ones that take the most direct sun throughout the day. The cracks typically run vertically through the shingle and may appear in patterns across multiple shingles in the same area.
Cracked shingles can't be repaired. Each cracked shingle needs to be replaced individually if the damage is limited, or the roof needs replacement if cracking is widespread. Individual shingle replacements in the Inland Empire typically cost $150 to $400 per shingle including labor, depending on accessibility and roof pitch. If you're replacing more than 15 to 20 shingles, a full roof replacement usually makes more financial sense.
Thermal Splitting
A specific type of cracking we see frequently here is thermal splitting - long, clean cracks that run horizontally through the shingle, often right along the nailing line. This is caused by repeated thermal expansion and contraction. The shingle is literally being pulled apart by the daily temperature cycle. Thermal splitting is more common on roofs with inadequate attic ventilation, because poor ventilation makes the temperature swings even more extreme on the roof surface.
Missing Shingles
This is the most obvious sign of trouble. If shingles are missing from your roof, the underlayment (and potentially the decking) is exposed. Missing shingles are usually the result of wind damage - particularly from our Santa Ana events - but they can also indicate that the shingle adhesive strips have failed due to age and heat exposure.
After any major wind event, walk the perimeter of your property and look for shingles on the ground. Also look at your roof from the street or driveway - you're looking for any patches of different color or exposed underlayment. If you find missing shingles, get them replaced promptly. The underlayment provides temporary water protection, but it's not designed for long-term UV exposure, especially at our intensity levels. Exposed underlayment in Inland Empire summer sun can deteriorate in weeks.
Dark Streaks and Algae Growth
Dark streaks running down your roof are typically caused by a type of blue-green algae called Gloeocapsa magma. This is less common in the Inland Empire than in humid Southern states because our air is generally dry. However, homes near irrigation runoff, in neighborhoods with lots of tree cover, or in areas that get morning fog (parts of Corona and the Santa Ana River corridor) can develop algae growth.
The algae itself doesn't directly damage shingles, but it feeds on the limestone filler in the shingle material. Over time, this can accelerate granule loss. More importantly, dark streaks absorb more heat than the surrounding lighter-colored shingle surface, creating hot spots that increase thermal stress in those areas.
Algae can be cleaned with appropriate solutions - typically a mix of water and sodium hypochlorite applied at low pressure. Never pressure wash asphalt shingles. The high pressure strips granules far faster than the algae does. If algae is a recurring problem, algae-resistant shingles (which contain copper granules) are worth considering when it's time for replacement.
Moss is different from algae and is more damaging. Moss has roots that work under shingle edges and lift them, allowing water intrusion. In the Inland Empire, moss is rare except on heavily shaded north-facing slopes that stay damp. If you see actual moss (thick, green, raised growth), it needs to be addressed - the shingles underneath may already be damaged.
Age-Related Decline: What to Expect in the Inland Empire
Manufacturer warranties on architectural asphalt shingles range from 25 to 50 years, but those warranty periods assume moderate climate conditions. Here in the Inland Empire, the actual service life of asphalt shingles is typically shorter than what the warranty suggests.
In my experience working on roofs across Riverside and surrounding cities, here's what I've observed for common shingle types in our climate:
- 3-tab shingles: Rated for 20-25 years. Actual Inland Empire lifespan: 12-18 years. These thin, single-layer shingles suffer the most from our heat and UV.
- Architectural (dimensional) shingles: Rated for 30-50 years. Actual Inland Empire lifespan: 20-30 years. The heavier construction holds up better, but the heat still takes its toll.
- Premium/luxury shingles: Rated for 40-50+ years. Actual Inland Empire lifespan: 25-35 years. These have more material and better granule adhesion, which helps in our conditions.
These ranges assume proper installation, adequate attic ventilation, and a roof with reasonable slope. Poor ventilation can knock 5 or more years off the lifespan because it increases the temperature differential the shingles experience daily.
Heat Damage Specific to the Inland Empire
I want to spend some time on this because it's the single biggest factor affecting asphalt shingle roofs in our area and it's underappreciated.
When ambient air temperature hits 110 degrees - which happens multiple times each summer in Riverside, San Bernardino, and Moreno Valley - roof surface temperatures can reach 160 to 170 degrees. At those temperatures, the asphalt in shingles softens. You can actually press a thumbnail into the shingle surface on a hot afternoon and leave a mark. That softening does several things:
- Accelerates oil evaporation. The volatile compounds that keep asphalt flexible escape faster at high temperatures. This is why shingles become brittle sooner here than in cooler climates.
- Weakens adhesive strips. The factory-applied adhesive that bonds overlapping shingles together can soften to the point where shingles shift slightly. Over many hot days, this can permanently misalign shingles and break the seal.
- Causes thermal shock. When a sudden summer thunderstorm drops cold rain onto a 170-degree roof surface, the rapid temperature change stresses the material. This is one cause of the thermal splitting I mentioned earlier.
- Blisters form in the shingle. Trapped moisture inside the shingle material turns to vapor in extreme heat, creating visible bumps or blisters on the shingle surface. Blisters are weak points that eventually crack and allow water intrusion.
Proper attic insulation and ventilation are the most effective ways to reduce heat damage to asphalt shingles. A well-ventilated attic reduces roof surface temperature by allowing hot air to escape, which reduces the temperature differential between the roof surface and the cooler air below the decking. This is one area where a relatively modest investment in better ventilation can meaningfully extend the life of your shingles.
When to Repair vs. When to Replace
Here's my general framework after 35 years of making this call:
Repair makes sense when: The damage is localized to a specific area, the rest of the roof is in serviceable condition, the roof is less than 15 years old in our climate, and the issue is limited to a few dozen shingles or less. A typical shingle repair in the Inland Empire runs $300 to $1,200 depending on the scope.
Replacement makes sense when: Multiple signs of aging are present across the roof (curling, granule loss, cracking all showing up), the roof is approaching or past 20 years old in our climate, repairs in the last few years have been frequent and you're spending money on an ongoing basis, or the damage is widespread enough that repair would cover more than 25 to 30 percent of the roof area. A full asphalt shingle roof replacement in the Inland Empire typically costs $8,000 to $18,000 for a standard residential home, depending on the size of the roof, the shingle quality selected, and the complexity of the roof design.
Get Your Shingle Roof Assessed
Thompson Roofing provides free roof inspections for homeowners across Riverside, Corona, Norco, Moreno Valley, Colton, Eastvale, and the broader Inland Empire. If your asphalt shingle roof is showing any of the signs I've described here - or if it's simply getting up in years and you want to know where things stand - give us a call. I'll come out personally, look at your roof, and give you a straight answer about what it needs. No pressure, no scare tactics - just an honest assessment from someone who's been looking at these roofs for a long time. Call us at (951) 688-9469.