Roofing Mistakes We Often See on Homes in the NW Suburbs

At Peterson Roofing, we work on roofs across the northwest suburbs every week. We see the same avoidable errors over and over. Installation shortcuts and small oversights that turn into big, expensive problems under Chicagoland weather. If you live in Mount Prospect or elsewhere in the northwest suburbs of the Chicagoland area, this article is for you. We’ll walk through the top mistakes we find, explain why they matter in our climate, and give clear steps you can take to avoid them.

Why these mistakes matter in the NW suburbs

Our area gets a lot of extremes: hot, humid summers, spring wind storms, and cold winters with ice and heavy snow. A small installation error that might be harmless in a mild climate can cause leaks, ice dams, and early roof failure here. The best roofs are built with details in mind flashing, ventilation, nailing, underlayment, and proper materials and those details are where we see most problems.

1) Improper flashing (the number-one leak cause)

Flashing is the metal (or sometimes composite) barrier that keeps water from getting into roof-to-wall intersections, chimneys, skylights, and valleys. When flashing is bent incorrectly, nailed through, or not seated down tight to the roof deck, water finds its way behind shingles and into the house. We see flashing left loose after repairs, cut short at transitions, or installed with gaps that allow ice and wind-driven rain to penetrate.

Why it matters here: wind-driven rain and freeze-thaw cycles force water into any tiny opening. If flashing is wrong, damage progresses quickly, rot, mold, and structural issues follow. Skilled flashing work often costs less than the damage it prevents.

What to look for and ask your roofer:

• Properly bent step flashing at walls and chimneys.
• Counter-flashing where masonry meets roof, cut into the brick.
• No caulk-only fixes in areas that face heavy weather.
• Flashing that’s fastened and sealed correctly.

2) Missing starter strip (small omission, big consequences)

Starter strips are the first row of shingles along your eaves and rakes. They offer the correct edge seal and bite for the first row of full shingles. Without them, shingles at the roof edge have nothing to lock into; they’ll lift in wind and allow water under the first course.

We commonly see jobs where the starter strip was skipped to save time or material. The result is curling edges and blown-off shingles in storms. The up-front cost of a starter row is tiny compared to having to replace edge shingles after a wind event.

What to check:

• Look for a continuous starter strip along the eaves.
• Check for shingle edges that are not fastened or are exposed.
• Confirm with your contractor that starter shingles were installed under the first row.

3) No ventilation balance (attic hot or cold, roof suffers)

Roof ventilation is more than a single vent product; it’s a system. A balanced ventilation system has intake vents at the eaves or soffits and exhaust vents at or near the ridge. Without balance, the attic temperature and moisture levels swing wildly. In summer that means shorter shingle life; in winter it causes ice dams and moisture damage.

Common mistakes we find:

• Only ridge vents installed without soffit intake.
• Randomly placed box vents that don’t create a continuous airflow.
• Blocked soffits due to insulation or debris.

Homes need continuous airflow from low to high. A ridge vent by itself won’t work unless fresh air can come in low. Proper intake and exhaust sizing matters; it’s not one-size-fits-all.

How we fix it:

• Inspect soffit openings, remove insulation blocks and install baffles where needed.
• Add continuous ridge vent or roof vents and high-quality perforated soffit where needed.
• Calculate net free ventilation area based on attic square footage.

4) Incorrect nailing patterns and fastener mistakes

Fasteners are a roof’s mechanical backbone. Incorrect nailing patterns (wrong number, wrong placement, or wrong nail type) are one of the simplest but most common DIY or low-quality contractor mistakes. Nails driven at an angle, placed above the tar line, or left under driven leave shingles vulnerable to wind uplift. An improperly fastened roof also voids the manufacturer warranty.

What we often see:

• Roofing nails placed too high in the shingle tab.
• Using staples instead of nails.
• Too few nails per shingle in high-wind areas.

Why it matters: under wind pressure or uplift can pry the shingle off. The right nailing pattern, using ring-shank or coated nails of correct length, holds shingles through storms. Manufacturers’ installation instructions exist for a reason, follow them.

5) Low-quality ridge vent installs

Ridge vents can be great when installed correctly, but poor ridge vent work is common. Low-quality installations include uneven cutting of the ridge, small vent opening left under the cap, or using cheap caps that don’t lock out water. Sometimes a ridge vent is installed but the airflow path is blocked by roof deck debris or insulation.

Ridge vents must be continuous, centered, and paired with proper soffit intake to be effective. Otherwise, you’ll see hot attics in summer and more ice damming in winter. We inspect ridge vents for proper spacing and secure cap attachment during every roof evaluation.

6) Poor underlayment choice or installation

Underlayment is the extra protective layer under shingles. Using a cheap underlayment, skipping ice-and-water shield where required, or improperly overlapping rolls invites trouble. We often find underlayment that was loosely installed, not fastened, or that didn’t run up the roof valleys and penetrations properly.

In the NW suburbs, the ice-and-water barrier along eaves and valleys is a small investment that prevents big leaks from ice dams and wind-driven rain. Don’t let installers assume underlayment is optional or minimal.

7) Wrong shingle overhang and missing drip edge

A correctly sized shingle overhang, plus a metal drip edge, ensures water sheds into gutters and not beneath the shingles. We see roofs where the shingles don’t extend properly over the drip edge, or where drip edge isn’t fastened, allowing water to run back into the fascia and roof deck.

Signs of trouble:

• Water staining under fascia boards.
• Rot at the eave edge.
• Shingles that lift at the very edge.

Fix it by adding a properly installed drip edge and making sure the shingles have the correct overhang and sealing.

8) Valley mistakes (wrong technique or wrong materials)

Valleys are where two roof planes meet and are naturally vulnerable. We see three common mistakes: using the wrong valley flashing technique (open vs. closed) for the roof type, cutting shingles improperly at the valley, and not using metal flashing where needed.

A poorly done valley will leak early. Use proper valley installation technique, align shingles for correct water shedding, and choose the valley method recommended for your roof system. If a valley has been patched repeatedly, it’s a sign that the underlying detail needs rework.

9) Gutter and drainage issues that sabotage a good roof

Gutters and downspouts are part of the roof system. Clogged, undersized, or misaligned gutters back water onto the eaves, causing rot and ice dams. We frequently find blocked gutter outlets or negative slopes that allow water to pool.

What to do:

• Clean gutters at least twice a year, more if you have trees.
• Check downspouts and ensure water is directed away from the foundation.
• Replace sagging gutter runs and fix improper slopes.

A great roof with terrible drainage won’t last. Keep gutters working.

10) DIY shortcuts and temporary fixes left permanent

We understand homeowners want to save money. But temporary fixes, tar patches, caulking over flashing, or partial shingle repairs often become chronic problems. A temporary patch may hold in mild weather but fail in a windstorm or heavy snow.

When we inspect roofs with repeated patches, we often recommend a targeted repair or full replacement because the underlying materials or deck may be compromised. Permanent solutions now prevent repeat calls later.

11) Neglecting roof inspections and maintenance

Routine inspections catch small problems before they become big ones. Homeowners who skip annual checks end up with problems that could have been fixed for a fraction of the cost. We recommend at least one professional inspection per year and after major storms.

What our inspections include:

• Flashing checks at chimneys, walls, and skylights.
• Soffit and ridge vent airflow analysis.
• Nail and shingle placement review.
• Underlayment and deck condition assessment.

How Peterson Roofing approaches these problems

We inspect the details other companies miss. For the northwest suburbs, that means:

• Prioritizing ice-and-water shield in vulnerable eaves and valleys.
• Confirming balanced ventilation, intake and exhaust, sized for your attic.
• Using proper starter strips, drip edge, and manufacturer-approved nailing patterns.
• Installing quality flashing and ensuring counters and step flashing are mechanically sound.

When we replace shingles or a roof system, we document what we did and why. We want you to have a roof that’s built to last in our specific climate, not a one-size-fits-all job.

Quick homeowner checklist before hiring any roofer

1. Ask to see photos of the exact details: flashing, starter strip, drip edge, and ridge vent work.
2. Confirm the type and brand of underlayment and whether ice-and-water shield will be used in critical zones.
3. Ask how they will ensure balanced ventilation where intake and exhaust be placed?
4. Verify the nailing pattern and fastener type they plan to use.
5. Request references from nearby projects in the northwest suburbs and ask to see completed jobs.

A good contract includes these details in writing the products, techniques, and estimated timeline. If your roofer hesitates to discuss specifics, that’s a red flag.

Small details, big difference

In our experience, the difference between a roof that performs and one that fails early comes down to the small details: how flashing is seated, whether a starter strip was used, how ventilation is balanced, and whether proper nailing patterns are followed. These are not optional extras; they’re the parts of a roofing system that keep water out and life inside your home comfortable.

If you live in the northwest suburbs and want an honest, local inspection focused on real roofing details (not sales pressure), we’re here to help. We’ll point out what needs immediate attention, what can wait, and exactly why. Contact our team for a roof check and we’ll walk your home with a checklist that focuses on the trouble spots listed above.