The Complete Technical Guide to Evaluating Roofers and Replacing a Residential Roof

Roof replacement is a construction event that exposes hidden structural damage, tests the competence of contractors, and affects the long-term integrity of the building envelope. This document creates a structured framework for identifying the correct contractor, selecting correct materials, enforcing installation discipline, and controlling contractual risk. Every section is written to supply operational clarity. No assumptions of contractor honesty or skill are made. You control the system by understanding every component and enforcing verifiable conditions.

1. Understanding Why Roof Replacement Fails for Most Homeowners

Most roof failures originate before the first shingle is nailed. Homeowners lose control of the project during contractor selection and scoping. They accept “free inspections” that are sales calls, sign contracts without line-item controls, and allow incomplete tear-offs that hide deck damage. They misunderstand ventilation and flashing mechanics. Materials are selected based on appearance instead of structural requirements. Workmanship shortcuts create moisture traps and premature failure. This document removes ambiguity so you prevent these errors.

2. The Structural Foundation: What the Roof System Actually Is

A roof is not shingles. It is an integrated system composed of the deck, underlayment, waterproof membranes, fasteners, flashing, ventilation, and the outer covering. Each component interacts. Ignoring any one of them invalidates the whole.

2.1 Roof Deck

The deck is the base plane to which the system attaches. Most homes use OSB or plywood sheathing. Problems arise from rot, delamination, warping, and insufficient fastening. These issues cannot be diagnosed from the ground. They require attic inspection and surface inspection after tear-off. Correct decking must lie flat with correct nail penetration depth and structural soundness under load.

2.2 Underlayment

Underlayment provides secondary moisture protection. Tar paper (felt) is obsolete. Synthetic underlayment resists tearing and moisture saturation. Ice and water shield is a self-adhering membrane required at valleys, eaves, and penetrations. If omitted, leaks occur under severe weather conditions.

2.3 Flashing

Flashing redirects water away from vulnerable intersections. This includes step flashing, counter-flashing, valley flashing, drip edge, and chimney flashing. Flashing must be replaced during every roof replacement. Reusing flashing is a failure mode. Fasteners must not penetrate areas where water flow is concentrated.

2.4 Shingles or Other Outer Layers

Shingles provide the public-facing surface but are only one layer of protection. Architectural shingles outperform three-tab shingles. Impact-rated shingles provide additional durability in hail regions. Installation patterns and nail placement determine lifespan more than marketing claims.

2.5 Ventilation

Ventilation prevents heat buildup and moisture accumulation. Intake (soffit vents) and exhaust (ridge vents or box vents) must be balanced. Poor ventilation destroys shingles and fosters mold. Many contractors ignore ventilation to reduce labor. That omission shortens roof life by years.

3. Identifying the True Condition of Your Current Roof

You cannot choose materials or contractors until you classify the existing roof condition.

3.1 Surface Indicators

Observe blistering, curling, cracking, granule loss, lifted edges, exposed nail heads, and algae streaking. Granule loss exposes the asphalt substrate. Blistering indicates trapped moisture or poor ventilation. Curled shingles indicate heat stress. Nail pops indicate deck movement.

3.2 Attic Indicators

Inspect the attic without contractor filtering. Look for moisture staining, mold growth, sagging sheathing, rusted nails (“nail rain”), daylight leaks, deteriorated insulation, and disconnected ductwork. These reveal ventilation and deck failure.

3.3 Structural Indicators

Observe dips or waves in the roofline. Check fascia boards for rot. Examine soffits for sagging or discoloration. Identify locations where past repairs created mismatched shingles or flashing inconsistencies.

3.4 Hidden Risk Zones

Valleys, chimneys, skylights, vents, and wall intersections accumulate failure events. Contractors often cut corners here. You must know where these weaknesses exist before assigning the scope.

4. Contractor Evaluation: Rigorous Methods for Eliminating Unqualified Roofers

Selecting the contractor determines project outcome more than materials. Use a screening method that eliminates risk instead of trusting resumes or sales language.

4.1 Licensing and Legal Verification

Confirm state licensing. Confirm city licensing if applicable. Demand liability insurance and workers’ compensation. Require certificates delivered directly from insurers to you. Decline contractors who provide photocopies. Without workers’ comp, you absorb injury liability.

4.2 Operational Stability

Reject companies that appeared after a storm. Demand identification of permanent business location, years in operation, and proof of in-house crews. Outsourced one-day labor crews create inconsistency and void workmanship warranties.

4.3 Work Volume Verification

Ask for at least three completed roofs within the last thirty days. Drive by the homes. Observe cleanup, shingle pattern, ridge vent alignment, and flashing. Look for debris left behind. A stable company maintains consistent work quality.

4.4 References With Traceable Work

Ask for references matched to job type: tear-off, re-decking, ventilation modification, chimney flashing, skylight integration. Call references. Ask about schedule control, cleanup, change orders, and post-installation issues.

4.5 Technical Competence Tests

Ask contractors to explain ventilation balancing, attic airflow, deck repair protocols, membrane placement, and fastener type. If they cannot articulate specifics, decline the bid.

4.6 Permit Behavior

Verify they pull required permits. Absence of permits signals shortcuts.

4.7 Crew Management

Confirm crew size, foreman identity, project duration, daily start and stop times, weather protocols, and workload. Confirm that the project is not split across multiple crews.

5. Defining the Project Scope With Precision

You create the scope; the contractor executes it. Never rely on a contractor’s default template.

5.1 Tear-Off Requirements

Require full tear-off of all existing layers. Multiple layers trap heat and moisture. Require magnetic sweep of nails and debris. Require documentation of deck exposure before installing underlayment.

5.2 Decking Replacement Rules

Specify price per sheet for deck replacement. Require photos before and after replacement. Require written approval for each sheet. This prevents false deck replacement charges or hidden rot.

5.3 Underlayment Protocol

Require synthetic underlayment across entire roof. Require ice and water shield in valleys, at eaves, around penetrations, and low-slope areas. Demand coverage measurements in linear feet.

5.4 Flashing Replacement Enforcement

Specify replacement of all flashing: step flashing, counter-flashing, valley metal, drip edge, chimney flashing, and pipe boot flashing. Require metal thickness specifications.

5.5 Ventilation Control

Calculate required intake and exhaust based on roof size. Enforce equal airflow. If intake is insufficient, specify installation of additional soffit vents. Require ridge vent installation unless roof design disallows it.

5.6 Fasteners and Nailing Rules

Specify ring-shank nails of correct length. Require four nails per shingle minimum, six in high-wind regions. Demand manufacturer-approved fastening pattern. Prohibit staples.

5.7 Weather Protocols

Require protection if forecast calls for rain. Require tarping when crews leave site. Require penalties if house interior is damaged due to incomplete covering.

6. Material Selection for Performance, Not Marketing

Materials must be matched to climate, roof pitch, building code, and insurance requirements.

6.1 Shingle Classification

Architectural shingles are the minimum acceptable standard for modern homes. Three-tab shingles offer inferior durability and wind resistance. Impact-rated shingles matter only in hail zones. Identify the region’s insurance premium reductions for impact-rated products.

6.2 Underlayment Materials

Select high-grade synthetic underlayment with high tear resistance. Select ice and water shield for all sensitive areas. Never combine incompatible membranes.

6.3 Flashing Materials

Select galvanized or aluminum flashing with correct gauge. Chimney flashing must include step flashing and counter-flashing layered correctly. Skylights require manufacturer-specific flashing kits.

6.4 Ventilation Hardware

Select ridge vents instead of box vents where possible. Choose continuous soffit vents over discrete units. Avoid cheap plastic vents that warp under UV exposure.

6.5 Nails and Fasteners

Select corrosion-resistant nails. Fasteners must penetrate decking to correct depth. Overdriven nails puncture shingles; underdriven nails cause lift.

7. Pre-Installation Checklist: Enforcing Control Before Work Begins

You must inspect and document the site before the contractor removes a single shingle.

7.1 Site Preparation

Photograph gutters, fascia, soffit, siding, landscaping, HVAC components, and windows. This prevents false damage disputes. Require contractors to protect landscaping, AC condensers, and driveways.

7.2 Material Delivery Verification

Confirm all materials were delivered: underlayment rolls, shingles, ridge caps, flashing, drip edge, pipe boots, nails, and ventilation hardware. Confirm quantities match contract.

7.3 Crew Briefing

Obtain schedule, foreman name, and daily timeline. Require confirmation that full crew, not partial, will be present.

7.4 Dumpster Placement

Confirm dumpster location does not block garage, damage driveway, or impede emergency access.

8. The Tear-Off Phase: Critical Observations

The tear-off phase reveals hidden defects. You must observe or require documentation.

8.1 Deck Exposure

Demand photos of entire deck. Identify rot, water damage, delamination, mold, and structural sag. Document before any repairs.

8.2 Ventilation and Attic Openings

Inspect soffit pathways. Identify blockages. Many older homes have painted-shut or insulated-over soffits.

8.3 Flashing Condition

Observe all old flashing. If contractor proposes reusing flashing, terminate the agreement immediately. Reuse indicates shortcut culture.

9. Deck Repair Phase: Ensuring Structural Integrity

Deck repair ensures correct substrate for new roof.

9.1 Evaluating Deck Condition

Rotting OSB must be replaced. Mold indicates ventilation or leak failure. Sagging indicates structural weakness.

9.2 Correct Replacement Practices

New decking must match existing material thickness. Edges must land on rafters or trusses. Gaps must follow manufacturer requirements. Fasteners must penetrate framing lumber, not just neighboring sheets.

10. Underlayment and Membrane Installation

This layer prevents catastrophic leaks.

10.1 Synthetic Underlayment

Must be installed flat, without wrinkles. Wrinkles telegraph through shingles and create water channels.

10.2 Ice and Water Shield Application

Required in valleys, low-pitch surfaces, eaves, and penetrations. Membrane must extend past interior heated wall line in cold regions.

10.3 Overlap Rules

Underlayment must overlap in manufacturer-specified direction and measurement. Poor overlap creates reverse-flow leaks.

11. Flashing Installation

Flashing failures cause most leaks. This section demands precision.

11.1 Drip Edge

Installed under underlayment at eaves and over underlayment at rakes. Many crews install incorrectly.

11.2 Valley Flashing

Open valleys require metal. Closed valleys require consistent shingle trimming pattern. Exposed nail heads are prohibited.

11.3 Step Flashing

Each shingle course requires its own step flashing piece. Continuous flashing is unacceptable. Flashing must integrate with siding or counter-flashing.

11.4 Chimney Flashing

Requires step flashing and counter-flashing. Mortar joints must be properly cut. Sealant alone is not flashing.

12. Shingle Installation

Shingles must be installed in manufacturer-specified patterns. Deviations void warranties.

12.1 Nail Placement

Nails must be placed in the nail line, not too high or too low. Overdriven nails tear shingles. Underdriven nails lift shingles.

12.2 Shingle Pattern

Stagger pattern prevents water channels. Mis-staggered shingles trap water.

12.3 Ridge Caps

Ridge caps must match shingle series. Some crews cut three-tab shingles as caps. This is unacceptable.

13. Ventilation Implementation

Improper ventilation destroys roof systems. You must confirm correct airflow.

13.1 Intake Vent Control

Intake vents must provide sufficient CFM. Blocked soffits are common. New vents may be required.

13.2 Exhaust Vent Control

Ridge vents must be cut to correct width. Mixed ventilation systems (ridge + box vents) create airflow conflict.

13.3 Airflow Balancing

Calculate ventilation using building code formulas. Ensure equal intake and exhaust.

14. Cleanup and Site Restoration

Cleanup reflects contractor discipline.

14.1 Nail Removal

Magnet sweep must be comprehensive. Nails in yard cause injuries.

14.2 Debris Removal

All debris must be removed daily. Dumpsters must be emptied promptly.

14.3 Gutter Cleaning

Gutters must be inspected and cleared.

15. Final Inspection and Verification

Do not release payment until verifying every component.

15.1 Visual Inspection

Check ridge alignment, shingle cuts, flashing integration, valley execution, and nail heads. Any exposed nails must be sealed.

15.2 Structural Inspection

Check attic for daylight leaks. Check ventilation airflow.

15.3 Warranty Registration

All manufacturer warranties must be registered in your name. Obtain serials and packaging.

15.4 Photo Documentation

Obtain full set of install photos for your records.

16. Contract Architecture That Prevents Abuse

Contracts must bind the contractor to measurable outcomes.

16.1 Payment Terms

Limit deposits to 10–20%. Pay remainder after inspection. Avoid financing through contractors.

16.2 Line-Item Scope

Specify each material, flashing type, fastener, membrane location, and deck repair procedure.

16.3 Penalties for Deviations

State financial penalties for failure to protect property, reuse flashing, improper underlayment, or leaving roof exposed.

16.4 Material Substitution Control

Contractor cannot substitute materials without written approval.

17. Common Contractor Manipulation Tactics and How to Counter Them 17.1 “We Can Reuse Flashing”

Reject immediately.

17.2 “We Don’t Need Ice and Water Shield”

Incorrect. This reduces labor cost at your expense.

17.3 “We Found More Damage Than Expected”

Require photos before approving deck replacement.

17.4 “We Use Only the Best Materials”

Reject vague claims; require SKUs and quantities.

17.5 “Verbal Promises”

Ignore. Only written terms matter.

18. How to Audit a Completed Roof Like a Professional Inspector 18.1 Shingle Integrity

Look for consistent patterning and proper nail placement.

18.2 Flashing Quality

Verify full integration at all roof-to-wall intersections.

18.3 Ventilation Adequacy

Check airflow through soffits and ridge vents.

18.4 Attic Performance

Look for moisture, mold, daylight leaks, and insulation displacement.

19. Planning for the Next Roof Cycle

Roof replacements occur every 20–40 years depending on climate and materials. Store all documents, photos, warranties, and material specifications. Maintain ventilation. Inspect annually after storms. Track minor repairs to prevent cumulative failure.

20. Conclusion

You prevent roof failure by controlling scope, enforcing technical standards, and refusing contractor shortcuts. You build the conditions for a stable installation by understanding the structural layers, validating the contractor’s capabilities, monitoring workmanship, and anchoring the contract to objective standards. Termination here.