Commercial Roof Inspection Schedule: The Best Time to Inspect in the Northwest
Quick answer: A commercial roof inspection schedule in the Northwest should include two routine inspections: one in spring, after winter, and one in late summer or early fall, before the rains begin. Add an inspection after major storms, before buying a building, before installing rooftop equipment such as solar, and before the roof warranty expires.
Most building owners inspect a roof when it leaks. By then, water has usually been working through the insulation and deck for weeks or months, and the repair is no longer a small one.
A schedule changes the question. Instead of asking where the leak is, you ask what's developing and what it will cost to fix now versus later. In the Northwest, where winters are hard on flat and low-slope roofs, the timing of that schedule matters.
How Often Should a Commercial Roof Be Inspected?
The industry-recommended schedule is two inspections a year, in spring and fall, plus an inspection after severe weather. That's the guidance from Ted Michelsen, director of the Roofing Industry Educational Institute, in The Importance of Inspections (Professional Roofing, 2001). Spring and fall let you find and repair damage before and after the harsh seasons.
Frequency should rise with risk. Michelsen notes that a new roof may be inspected once a year until problems appear, while older roofs with problem histories warrant twice a year. Owners who can't inspect twice a year should inspect before winter, because roofs in good condition are more likely to survive harsh weather. Roof age, membrane type, warranty terms, rooftop traffic, and repair history all shift the right number.
Why the Northwest Is Different
Weather splits the region in two:
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Western Washington and western Oregon see long stretches of rain and constant moisture.
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Eastern Washington (including Spokane), North Idaho, eastern Oregon, and higher elevations see snow, ice, freezing temperatures, and repeated freeze-thaw cycles.
Both punish a roof. Rain finds every weak seam and clogged drain. Freeze-thaw pries at membranes, flashing, and sealants. That's why the two seasons on either side of winter carry most of the schedule.
Late Summer to Early Fall: Inspect Before the Rainy Season
If you can only inspect once a year, make it August through early October. The roof has just finished a season of UV exposure and heat, drains have collected a year of debris, and the wet weather hasn't arrived. Problems found now get repaired while conditions still favor roof work. Give flashings and penetrations the closest look, since a large share of leaks start there.
A fall inspection can find:
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Damaged or deteriorating membrane
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Open seams and deteriorated sealants
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Loose or damaged flashing
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Clogged drains and blocked scuppers
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Ponding water areas
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Damaged penetrations and problems around HVAC equipment
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Debris buildup and previous repairs that need attention
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Conditions that warrant a moisture investigation
Each of these costs far less to address in September than after a month of rain.
Spring: Inspect After Winter
An April or May inspection shows what winter did. In the east, that means freeze-thaw damage, ice, and snow load. In the west, it means months of standing moisture.
Look for storm damage, drainage problems, membrane deterioration, flashing failures, sealant cracks, debris around drains, and damage near rooftop equipment. Older roofs and buildings with a history of leaks gain the most from a spring inspection, because it gives you the whole summer to plan and complete repairs.
After Storms
Inspect after high winds, heavy snow, hail, and falling debris. Wind damages membrane edges, flashing, and rooftop equipment. Branches and debris puncture surfaces. Heavy snow loads stress equipment and drainage.
A post-storm inspection can be more focused than a routine one. Concentrate on perimeter attachments, flashings, rooftop equipment that may have lost parts, and the roof field for blown debris or hail damage.
Storm damage doesn't always cause an immediate leak. Water can enter the roof assembly and travel before it shows up inside, so the stain may sit far from the entry point. That's why waiting for an interior symptom is unreliable. We explain how this works in why flat roofs leak in the first place.
Before Buying a Building
A roof can look fine from the parking lot, and even on a quick walk, while hiding problems that cost six figures. Inspect it during due diligence. Ask:
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How old is the roof, and what system is installed?
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Has it been repaired repeatedly?
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Where does water pond, and are the drains working?
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What shape are the flashing and penetrations?
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Do any findings warrant a moisture investigation?
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Is major maintenance or replacement likely soon?
The answers feed your capital budget and your negotiation.
Before Installing Solar or Other Rooftop Equipment
A solar array can stay on a roof for decades. Installing one over a roof that needs major repair means removing and reinstalling the system, or living with a problem you can't reach.
Inspect before installation to document the roof's condition and flag repairs that should come first. Inspect again afterward. HVAC, communications, and solar crews bring foot traffic, tools, materials, and new penetrations. A before-and-after record shows what changed and who was on the roof.
Before the Warranty Expires
Know your warranty expiration date, and schedule the inspection before it, not after. Read the terms too. Some warranties require periodic inspections or maintenance to stay valid.
Keep a roof file that includes:
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Installation details and the manufacturer
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Warranty documents
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Previous inspection reports
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Repair records and contractor invoices
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Photographs, drone imagery, and thermal imagery
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Moisture investigation results
Over time, that file shows how the roof has changed and makes problems easier to spot.
Where Drone and Thermal Inspection Fit
Large commercial roofs cover tens or hundreds of thousands of square feet. A drone documents the whole surface with high-resolution imagery, keeps people away from edges, skylights, and wet or fragile areas, and creates a consistent record you can compare year over year. Property managers with several buildings get the same benefit across a portfolio. See why a drone inspection is safer than walking the roof.
Thermal imaging adds a second layer on suitable roofs. An infrared roof moisture survey finds temperature patterns that suggest wet insulation beneath the membrane.
Late spring through early fall is the best season for thermal surveys in the Northwest. Longer days and generally drier weather create more suitable conditions. Results still depend on solar heating, cloud cover, wind, recent rain, roof construction, and insulation type, so we fly the thermal pass about an hour after sunset, after a day of solar heating on a dry roof, and we plan each survey around the forecast.
A thermal anomaly is not proof of water. It marks where a roofer should verify with a moisture meter, test cut, or core sample.
A Practical Inspection Calendar for the Northwest
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Spring (April to May): Inspect after winter. Check for storm damage, drainage problems, membrane condition, flashing, and maintenance needs.
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Late spring through early fall: Complete the repairs the spring inspection found. This is the best season for an infrared moisture survey, when the roof and conditions suit.
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Late summer to early fall (August to early October): Prepare for the rainy season. Inspect drains, scuppers, membrane, flashing, penetrations, rooftop equipment, and earlier repairs.
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After major storms: Check for wind, snow, hail, and debris damage.
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After rooftop work: Inspect when other trades have worked on the roof.
Frequently Asked Questions
How often should a commercial roof be inspected? The industry-recommended schedule is twice a year, in spring and fall, plus after severe weather. A new roof with no problems may start at once a year, but older roofs and roofs with known problems should get both inspections.
Is spring or fall the better time for a commercial roof inspection? Both matter. If you can only schedule one, choose late summer to early fall so repairs happen before the rainy season.
What is the best time of year for a thermal roof inspection? Late spring through early fall. Longer days and drier weather create more suitable conditions for a thermal survey, which Western UAS flies about an hour after sunset.
Should a roof be inspected after a storm even without a leak? Yes. Damage doesn't always cause an immediate leak, and water can travel inside the roof before it appears in the building.
Should I inspect a roof before buying a commercial building? Yes. A roof inspection during due diligence shows the roof's age, condition, drainage, and likely near-term cost, which helps you budget and negotiate.
When should I inspect a roof before installing solar panels? Before installation. Document the roof's condition and complete needed repairs first, so you aren't removing a solar array to fix the roof beneath it.
Don't Wait for a Ceiling Stain
The costliest way to manage a commercial roof is to wait for water to enter the building. By the time a stain appears, moisture may have reached insulation, decking, equipment, or inventory, and the source is harder to find. The repair bill is only part of the cost. Unseen building damage, lost business revenue, and slip injuries on wet floors add to it.
A schedule turns inspection from leak hunting into planning.
Western UAS provides drone roof inspections and thermal roof surveys for commercial and industrial buildings, schools, churches, and property managers across Washington, Oregon, Idaho, Montana, Nevada, and Northern California. Tom Ethen is an ITC Level 1 Certified Thermographer and FAA Certified Drone Pilot with more than eight years of drone-based thermal inspection experience.
Western UAS is inspection-only. No repairs, no replacements, no pressure to buy anything you don't need.
Call Tom at (509) 638-7198 to put your roof on a schedule before the next Northwest storm arrives.
What an Infrared Camera Sees
An infrared camera detects thermal anomalies by imaging infrared energy emitted, reflected, or transmitted from surfaces. While it does not measure moisture content directly, it highlights areas of concern where further verification through moisture probes or intrusive test cuts may be necessary. This method ensures a thorough and accurate analysis of the building envelope.
The Value of a Skilled Thermographer
A skilled thermographer knows where to look and how to interpret infrared readings accurately. Proper verification techniques, such as moisture probes and other test methods, help minimize errors and ensure reliable results.
Old Moisture Intrusion Detection Methods
Traditional moisture meters required contact with surfaces every few inches, making the process time-consuming and expensive. Testing large buildings, like a 100,000-square-foot roof, could take days and cost tens of thousands of dollars.
The Benefits of Infrared Cameras
With infrared technology, you can identify the location of problem areas with high accuracy, taking the guesswork out of trying to find issues hidden within walls, ceilings, or roofs.
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Faster Inspections: Infrared can scan large areas in hours rather than days.
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Accurate Results: Pinpoint problem areas with high precision.
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Non-Destructive Testing: No need to drill or damage surfaces to find moisture.
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Cost-Effective: Reduces labor and time costs significantly.