Illinois Roofing License IDFPR #19HC00108700 · GAF Certified Contractor
If you’re getting roofing quotes, you might see two options: tear off the old shingles and install new ones, or “overlay” – install new shingles directly over the existing layer. Overlay is cheaper upfront. It also costs you more in the long run, voids most warranties, and hides decking damage that turns into bigger repairs later. This is why Trill Roofing always tears off – even when it’s not the cheapest line item on the quote.
What Illinois code allows
The Illinois adoption of the International Residential Code (IRC R908) allows up to two layers of asphalt shingles on a residential roof. So if your current roof has one layer of shingles, overlay is technically legal. If it already has two layers, code requires tear-off – you can’t add a third.
Some local jurisdictions (City of Edwardsville, parts of Madison County) have additional restrictions, and HOA covenants in some subdivisions prohibit overlay regardless of code. Always confirm local rules before quoting overlay.
Why overlay is the wrong call (almost always)
Here’s what overlay actually does to your roof system:
1. It hides decking damage. The single most important reason to tear off: you can’t inspect the roof decking without removing the shingles. Soft spots, rotted plywood, ice dam damage at the eaves, water damage around chimneys – none of these are visible from above the shingles. Overlay puts new shingles over decking that may need replacement. A few years later, when the soft spot fails and you get a leak, the fix is to tear off the new shingles, replace the deck, and re-shingle. You pay twice.
2. It compounds underlayment problems. The original underlayment under the existing shingles is now decades old. Overlay traps it between two shingle layers. If there are gaps, tears, or missing ice and water shield, none of that gets corrected. Modern synthetic underlayment, proper ice barrier extension, and a new starter strip – all the things that come standard on a tear-off – are skipped.
3. Weight matters. Two layers of architectural shingles weigh approximately 480-680 lbs per square (100 sq ft). On a 2,500 sq ft roof that’s 12,000-17,000 lbs of load. Most modern roof framing is engineered to handle two layers, but older Illinois homes (1950s and earlier) sometimes have rafters that are marginal at two layers. Overlay on a structurally questionable roof is a problem.
4. Flashing rarely gets replaced. Overlay typically reuses existing step flashing, chimney counter-flashing, drip edge, and pipe boots. These items have a defined service life and are usually past it by the time you’re considering a new roof. New shingles over old flashing means the flashing fails first, you get leaks within 5-10 years, and the new shingles you just paid for aren’t the limiting factor.
5. Warranty implications. Most major shingle manufacturers (GAF, CertainTeed, Owens Corning) require tear-off for their full warranty to apply. Overlay installations often get reduced warranty coverage (10-15 years instead of 30-50) or warranty disqualification entirely. As a GAF Certified Contractor we cannot register the extended GAF Silver Pledge or Golden Pledge warranties on overlay installations.
6. Aesthetic issues. Two layers of shingles produce a thicker, lumpier roof line. Edges at rakes and eaves look bulkier. Valleys can be hard to seal cleanly. The roof looks heavier and less crisp than a single-layer tear-off install.
The narrow case for overlay
There’s exactly one scenario where overlay can be defensible:
- The existing roof has a single layer (not two)
- The existing shingles are flat and in reasonable condition (no curling, no significant granule loss)
- You’re selling the home within 1-2 years and the inspection report flagged the roof
- You’ve confirmed code and HOA allow it
- You’ve confirmed the buyer’s home inspector won’t flag overlay as a defect (most do)
And even then – tear-off costs typically run $1.50-$2.50 more per square foot than overlay. On a 2,000 sq ft roof, that’s a $3,000-$5,000 difference. If you’re selling within two years and need a cosmetic refresh, talk to your realtor about whether the price-difference savings actually translate to a higher sale price. Often they don’t.
What tear-off actually involves
For the same 2,000 sq ft roof, a Trill Roofing tear-off and replacement includes:
- Tear-off: remove all existing shingles, underlayment, drip edge, and any failed flashing. Inspect every square foot of decking.
- Decking work: replace any soft, rotted, or damaged sheathing at our cost (no markup on materials).
- Ice and water shield: self-adhered ice barrier at all eaves (to 24″ inside the warm-wall line per IL code), in all valleys, and around all penetrations.
- Synthetic underlayment: across the rest of the deck.
- New drip edge: at all eaves and rakes, properly layered with underlayment.
- Starter strip: manufacturer-specific starter at eaves and rakes (required for the wind warranty to apply).
- New shingles: architectural or Class 4, manufacturer-spec install with the appropriate nailing pattern (6-nail in our wind zone).
- New flashing: step flashing at sidewalls, chimney flashing (including counter-flashing kerfed into mortar), new pipe boots, new ridge cap.
- Ventilation balancing: verify intake and exhaust meet code; correct if needed.
- Cleanup: magnetic sweep for nails, debris haul-off, jobsite restoration.
This is a different product than overlay. It’s also why a properly installed tear-off lasts 30-50 years while many overlays start leaking within 10.
What it costs
Tear-off pricing in the Riverbend for 2026 is typically $4.50-$7.50 per square foot installed for standard architectural shingles. The variables that move the number:
- Roof pitch (anything over 8/12 adds labor)
- Complexity (valleys, dormers, multiple chimneys)
- Number of existing layers to tear off (two-layer tear-off doubles dump weight)
- Decking condition
- Shingle line and grade
Compare to overlay quotes in the $3.00-$5.00 per square foot range – and ask the question: what’s the actual lifespan of each option, and what’s the total cost over 30 years?
How to evaluate quotes
If you’re collecting roofing quotes, ask each contractor in writing:
- Is this an overlay or a tear-off?
- If overlay: how many existing layers are on the roof now? (If two, overlay is not code-compliant.)
- Does the quote include decking replacement if soft spots are found? At what cost?
- What flashing items are being replaced?
- What warranty terms apply? (Check whether the manufacturer registers the extended warranty on this installation method.)
Get the answers in writing on the estimate, not just verbally.
Schedule a Trill Roofing free inspection at /free-inspection/. We’ll give you an itemized written estimate that you can take to other contractors to compare apples to apples.
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