How to Inspect a Roof for Leaking?

Written By Adam Paul - Waterproofing Expert

Roof inspection is the process of checking all the roof parts and their functionalities by the homeowner or roofing expert. Roof inspection helps to identify the existing roof damage and upcoming roof damage before they are growing. Identifying these problem help to address them on time and save a lot of money, labor, time, and effort. So How to inspect a roof for leaking in a proper way?

Follow these 8 steps when you inspect a roof for leaks.

Check for water stains on ceilings and walls
Inspect the attic for moisture or mold
Examine flashing around chimneys, vents, and skylights
Check for clogged or damaged gutters and downspouts
Look for pooling water on flat roofs
Inspect roof valleys for debris and damage
Check for soft or sagging spots on the roof surface
Examine roof sealant and caulking for cracks or gaps

These are the 9 reasons for roof leaking, such as damaged or missing shingles, cracked flashing, clogged gutters, poor roof slope, broken or unsealed skylights, failures in roof valleys, cracked chimneys, aging underlayment, and improper roof installations.

Aqviz always recommends you to use a roofing expert or waterproofing expert for the roof inspections because they can identify the upcoming roof leak rather than the home owner.

1. Check for Water Stains on Ceilings and Walls

First things first, you should check water stains on the ceiling and walls because the walls and ceiling are the most affected areas by the roof leaking. Water stains are discolorations or blotches on interior surfaces caused by moisture intrusion from a leaking roof.

They usually appear as yellow, brown, or rusty rings with irregular edges, often expanding over time. If you observe the darker or more saturated stain marks, it means the roof has been leaking for a long time into that area. As well as if the stains are larger than 12 inches in diameter, suggest a more severe or long-term roof leak.

We typically find water stains below vulnerable roof zones like valleys, flashing points, skylights, or eaves. These areas collect and redirect water, and any failure there leads to leaks inside. From experience, if you notice new stains after storms or snow melts, that’s a sign your roof has lost its water-tight integrity.

2. Inspect the Attic for Moisture or Mold

Mold is a type of fungus that grows in damp, poorly ventilated spaces like an attic affected by roof leaks. It often appears in black, dark green, or white patches with a fuzzy or slimy texture. You’ll usually smell it before you see it.

Mold carries a distinct musty, earthy odor that indicates stagnant moisture. You should inspect wooden rafters, insulation batts, and plywood decking for mold growth in the attic area. We recommend inspecting the attic during rainy or humid days, and especially after storms. When you observe mold signs early in the attic, it can prevent costly replacements and protect your roof’s overall insulation system.

3. Examine Flashing Around Chimneys, Vents, and Skylights

Flashing is a thin metal sheet, usually aluminum or galvanized steel. We install flashing around roof penetrations like chimneys, vents, and skylights. Its job is to create a watertight seal where different materials meet and shift. Over time, flashing can corrode, crack, lift, or separate due to thermal movement or poor installation. This causes the roof to leak over time.

To detect leaks under these components, we look for rust stains, water trails, and darkened areas on nearby roof decking or attic surfaces. These elements tend to leak because they interrupt the roof’s slope and often face direct weather exposure. In our experience, most leaks we find near these spots stem from aged or improperly sealed flashing rather than the elements themselves.

More than that you should check these 37 roof parts to identify any damage due to the excessive water or moisture.

4. Check for Clogged or Damaged Gutters and Downspouts

Clogged or damaged gutters are one of the most overlooked causes of roof leaks. When leaves, debris, or shingle granules block the gutters or downspouts, water overflows and backs up onto the roof edges. This often leads to rotted fascia boards, water intrusion under shingles, and damaged soffits. Damaged gutters can also sag, crack, or pull away from the house, breaking the flow path for proper drainage.

To observe this, we always recommend inspecting gutters after rainfall. Overflowing water, plant growth in gutters, or visible gaps and cracks are telltale signs. We’ve also found that downspouts clogged with debris or ice in colder climates can push water back toward the roof, turning a moistureproof roof into a leaky mess. To prevent this you should do regular maintenance on the gutters properly.

5. Look for Pooling Water on Flat Roofs

Pooling water, or “ponding,” on the roof happens when water remains stagnant on a flat or low-slope roof for more than 2-24 hours after rainfall. It usually results from poor drainage, sagging in the roof decking, or improper slope design. Even small pools over 1 inch (2.5 cm) in depth of water can stress roofing materials and shorten their lifespan. Prolonged water pooling can cause roof leaks due to structural and membrane damage.

You should check for pooling on the roof during or right after heavy rain, when standing water is visible across the membrane. If water remains on the roof for more than one day without evaporating, it indicates improper roof drainage and proper roof waterproofing.

6. Inspect Roof Valleys for Debris and Damage

Roof valleys are the V-shaped channels where two sloped sections of the roof meet, guiding rainwater down to the gutters. These areas handle high volumes of water and are vulnerable to debris accumulation. Leaves, twigs, moss, and even bird nests often clog valleys, especially under overhanging trees. These clogs can cause to water blocks and leaks during the rainy season. As well as Aqviz experts have observed the cracked shingles, worn underlayment, or rusted flashing are cause to roof leak.

If water backs up in a valley, it easily seeps through the roof layers. That’s why we inspect valleys closely after storms or during seasonal cleanups to ensure they’re free of obstructions and still providing proper runoff protection.

7. Check for Soft or Sagging Spots on the Roof Surface

Soft or sagging spots are areas on the roof surface where the structure feels spongy or dips under pressure. These spots often signal underlying water damage, typically caused by long-term leaks that have weakened the roof decking or compromised insulation layers. Moisture softens plywood or OSB sheathing, eventually causing sections to bow or collapse under weight.

We detect these by walking the roof gently and feeling for uneven or springy areas. From inside, dark patches or warped ceilings can also point to sagging issues. Spotting these early helps prevent larger structural failures and costly repairs on both sloped and flat roof types.

8. Examine Roof Sealant and Caulking for Cracks or Gaps

Roof sealant is a waterproof material. The most use roof sealants are silicone, polyurethane, or asphalt-based sealants. Sealants are used to seal joints, cracks, and seams on the roof. It’s often applied around flashing, vents, skylights, nail holes, and roof edges to maintain a watertight barrier. Over time, sealants can shrink, dry out, or crack due to sun exposure and temperature changes. This can cause to leak the roof during rainy snow season.

We always inspect these high-risk zones up close. Look for visible splits, peeling, or missing caulking. Any breach in the sealant layer can let water sneak into the system, especially during wind-driven rain. A cracked sealant is often the silent culprit behind what looks like a minor roof leak but can lead to major interior water stains.

What Are the Reasons for Roof Leaks?

There are 9 common reasons why a roof leaks, and we’ve seen all of them in our service life.

Damaged or missing shingles
Cracked flashing
Clogged gutters
Poor roof slope or ponding
Broken or unsealed skylights
Roof valley failure
Cracked chimney crowns or flashing
Aging underlayment
Improper roof installation

How to Stop Roof Leaking?

These 10 ways help to stop the roof from leaking.

Aqviz has prepared an in-depth guide on How to Stop Roof Leaking? This guide includes practical solutions that you can apply in your home.

What Roof Types Require Regular Inspections?

All roofs need inspection, but certain types demand more frequent checks due to design and material vulnerabilities.

Flat roofs: Flat roofs are the most important inspected roof type because flat roofs are highly prone to water pooling and membrane wearing. So we recommend that you inspect the flat roof several times a year.
Low-slope roofs: Low-slope roofs have a slower runoff speed. It causes to water lingers longer and is more prone to leak inside over time. So we recommend to check low slope roof at leat once a year.
Shingle roofs: Shingle roofs should be inspected regularly because asphalt shingles can degrade with UV and wind exposure over time.
Wood shake roofs: Wood shake roofs should be inspect regularly because wood shake roofs are susceptible to rot and moss buildup if not cleaned and inspected seasonally.
Green roofs: Green roofs should be inspected regularly because soil and vegetation in green roofs can mask drainage issues. So you should inspect it by using an expert to maintain waterproofing layers.
Roofs with multiple penetrations: Essential penetration in the roof like skylights, chimneys, solar panels increase failure points and increases the leaking possibilities. Hence these types of roofs should be inspect regularly to prevent the leaking damages.

What Is Ceiling Mold?

Ceiling mold is a fungal growth that forms on ceiling surfaces due to excess moisture and poor ventilation. Ceiling mold appears in black, green, gray, or even orange patches and ranges in size from small speckles to large, spreading blotches over 12 inches wide. It often results from roof leaks, plumbing issues, or high indoor humidity. We frequently spot it after prolonged roof water intrusion, especially when leaks go unnoticed behind insulation or ceiling drywall.

What Is Roof Blistering?

Roof blistering is the formation of raised, bubble-like swellings on roofing materials, especially asphalt shingles or flat roof membranes. It happens when moisture or air gets trapped between roofing layers, then expands due to heat. Roof blistering occurs due to poor roof ventilation, substandard materials, trapped moisture during installation, or excessive solar exposure. Over time, this distorts the surface, making the roof vulnerable to cracking and leaks.

What Is Roof Alligatoring?

Roof alligatoring is a type of cracking pattern on the roofing layer that looks like the rough, dry skin of an alligator. Roof alligatoring is mostly visible on flat roofs. Mostly alligatored roofs are asphalt-based roofs, built-up roofing (BUR), modified bitumen roofs, and older flat roofs with asphalt coatings.