What Can a Drone Roof Inspection Detect That I Can't See?
Updated: Oct 8
Standing in the driveway, most roofs look fine. The tiles line up, nothing is obviously missing, and the ceilings inside are dry. The trouble is that the parts of a roof most likely to let water in are often the parts you cannot see from the ground: the top of a chimney chase, the flashing around a plumbing vent halfway up a steep slope, or the transition where a tile roof meets a wall.
To see what's included and how to schedule, visit our drone roof inspection services in San Diego County.
This post is written for two readers in particular: the homeowner with an older roof who has started to wonder about its condition, and the home buyer purchasing a property with a roof of unknown history. Below are two real examples from recent inspections, an explanation of how I decide between walking a roof and flying it, and a plain list of what a drone inspection cannot tell you.
Why the View From the Ground Falls Short
Many homes in North San Diego County have concrete or clay tile roofs, often at a 4:12 slope or steeper. From the street, you see the lower courses of tile and the edges of the roof. From a ladder at the eaves, you see a few more feet. What you usually cannot see is the upper field of the roof, the back side of a chimney, the top of a chimney chase, or flashing at penetrations set well back from the edge. On a two story home, the viewing angle makes this even harder.
Walk, Ladder, or Drone Roof Inspection: How I Decide
I often walk single story roofs covered with asphalt (composition) shingles, which are not uncommon in North San Diego County. On that type of roof, walking can be done safely and gives a close look at the surface.
Two story structures are different, especially those covered with tile. Concrete and clay tiles can crack under foot traffic, and on these roofs the risk of breaking tiles or falling is too great. For difficult to inspect roofs like these, a drone inspection is the best option. As an FAA Part 107 certified drone pilot, I can position the camera directly over areas that would otherwise go unexamined, without putting any weight on the roof covering.
Two Real Examples From Recent Inspections
Example 1: A Deteriorated Chimney Chase Cover on a Clay S-Tile Roof
This home had a high profile clay S-tile roof that was not possible to walk safely. From the drone, the sheet metal chase cover and the chimney cap on top of the chimney chase appeared deteriorated, with corrosion visible across the cover surface.
This condition would have been missed from the ground or from a ladder. In fact, even if the roof could have been walked, the height of the chase would have kept its top out of view. A chase cover is there to shed water off the top of the chimney chase. When it deteriorates, water can find its way into the chase and the framing below, often without obvious signs inside the home at first.
Note: The solar panels visible in this photo are outside the scope of a home inspection and were not evaluated.
Example 2: Failed Plumbing Vent Flashing on a Steep Slate Roof
This property had a very steep slate roof that could not have been walked properly, and slate can break under foot traffic. Because the roof was inspected by drone, I was able to view a plumbing vent penetration that was either not properly flashed or had flashing that had failed.
A roof penetration without effective flashing allows moisture to reach the underlayment, and possibly the roof sheathing beneath it. On a roof this steep, the vent sat well above anything visible from the ground.
What Shows Up Most on North County Tile Roofs
Across the tile roofs I inspect in North San Diego County, flashing defects are among the most common findings, especially on high profile S-tile roofs. The flashing is either failing due to age or was not properly installed in the first place. On many of these homes, there is also evidence of moisture penetration in the attic.
Tile is durable, but the tile itself is not the primary waterproofing layer. The underlayment and flashing beneath and around the tile do most of that work, and flashing is where problems tend to start. For more on how these roofs are built and what an inspector looks for, see The SoCal Homeowner's Guide to S-Tile Roofs.
From above, a drone can document conditions such as:
Flashing at plumbing vents, chimneys, skylights, and roof to wall transitions
Chimney chase covers and caps
Cracked, slipped, or missing tiles, and damaged ridge or hip caps
Debris collecting in valleys and behind chimneys
The general condition of the roof covering in areas that cannot be reached safely
Why This Winter Matters
Here is something many homeowners don't realize: a lot of roofs in San Diego County have small leaks. In a typical year, it simply doesn't rain often enough or long enough for those leaks to become a noticeable problem. A sustained rainy season is a different matter.
With a super El Niño forecast and significant wet weather predicted, a homeowner with a leaky roof is likely to be reminded of it often. Now is the time to identify and address roof and flashing deficiencies, while repairs can still be scheduled ahead of the storms. Our earlier post on preparing your San Diego County home for El Niño covers the rest of the house.
If you are buying, the same reasoning applies. A roof of unknown condition is one of the larger unknowns in a purchase. Identifying a flashing defect during the inspection period gives you time to get a roofing contractor's opinion and plan accordingly, rather than discovering it during the first heavy rain.
What You Receive
Whether the drone inspection is a standalone roof inspection or part of a full home inspection, you receive a detailed written report describing the roofing systems, their condition, and any deficiencies observed. Findings are documented with a descriptive narrative, along with photos and video as needed, so you can see what was found and where.
As an optional add-on, I can produce an orthomosaic map of the roof, which is a single high resolution 2D image of the entire roof surface, along with a 3D model of the roof that can be used to take measurements of the roof system. Homeowners who want an ongoing record may also find our post on annual drone roof inspections helpful.
What a Drone Roof Inspection Cannot Detect
A drone roof inspection is a visual inspection only. Being clear about its limits is part of giving you an accurate picture:
The underlayment beneath tile, slate, or shingles cannot be inspected.
A standalone drone roof inspection does not include the underside of the roof as viewed from the attic, or the interior of the home for evidence of roof leaks.
A standalone drone roof inspection does not cover landscaping or water drainage around the structure and foundation, and gutter downspouts are not inspected.
A drone roof inspection is not a roof certification. In California, roof certifications are issued by licensed roofing contractors (C-39).
With a full home inspection, the attic, interior, exterior drainage, and the other major systems are covered, so the roof findings can be read alongside what is happening inside the house.
Frequently Asked Questions
Is a drone roof inspection as thorough as walking the roof?
On a roof that can be walked safely, walking allows a close look at the surface, and I often walk single story shingle roofs. On steep, tall, or tile roofs, a drone provides a view of areas that could not otherwise be examined at all, without the risk of breaking tiles. The two approaches complement each other.
Can a drone find an active roof leak?
Not directly. A drone can identify conditions that commonly lead to leaks, such as failed flashing or a deteriorated chimney chase cover. Looking for evidence of an active leak requires access to the attic and interior, which is part of a full home inspection.
Is a drone roof inspection the same as a roof certification?
No. A drone roof inspection documents the visible condition of the roof. A roof certification in California is issued by a licensed C-39 roofing contractor.
Get a Clear Look at Your Roof Before the Rain
If you have an older roof, or you are buying a home with a roof you know little about, now is a good time to see what is up there. Cedrus Property Inspections offers full home inspections, drone roof inspections, and pool and spa inspections throughout San Diego County. Schedule your inspection online or call (760) 879-2604.
A Methodical Approach. Clear, Objective Reporting. Less Anxiety.
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