Removing an old roof is a heavy, labor-intensive process that dictates up to 15% of your total invoice. If your roof currently has two layers of shingles, removing them requires double the labor time and incurs double the municipal landfill fees. Furthermore, building codes strictly forbid installing a third layer of shingles. Beware of contractors offering a cheap “Overlay” quote—nailing new shingles over old ones hides structural rot and immediately voids your manufacturer warranty.
Before a single new shingle can be installed, your contractor must strip your home down to its wooden decking. This demolition phase is calculated by professional estimators based on two variables: Material Type and Layer Count.
The Physics of Demolition: The Weight of Water
Why do roofers charge so much for demolition? Because they pay municipal landfill fees by the ton. A standard bundle of asphalt shingles weighs roughly 70 lbs brand new. However, an old roof that has been exposed to the elements for 20 years traps moisture and dirt, making it significantly heavier upon removal.
| Material / Condition | Weight Per Square (100 Sq Ft) | Total Debris Weight (30-Square Roof) |
|---|---|---|
| 1 Layer (Asphalt) | 250 lbs to 300 lbs | ~ 8,000 lbs (4 Tons) |
| 2 Layers (Asphalt) | 500 lbs to 600 lbs | ~ 16,000 lbs (8 Tons) |
| Wood Shake / Cedar | 200 lbs (Very bulky) | ~ 6,000 lbs (Requires massive dumpster volume) |
| Clay Tile | 900 lbs to 1,200 lbs | ~ 30,000 lbs (15 Tons – Requires heavy machinery) |
Tear-Off Tonnage & Dumpster Calculator
Calculate the exact physical tonnage your contractor must remove, and the estimated municipal dump fees added to your bill.
Some contractors will offer a significantly cheaper bid by proposing an “Overlay”—nailing new shingles directly over the old ones to avoid demolition costs. You must refuse this offer.
- Building Code Violations: The International Residential Code (IRC) Section R908.3.1.1 strictly prohibits the installation of a new roof covering over an existing roof if it already has two or more applications of any type of roof covering.
- Voided Warranties: Shingle manufacturers (like GAF and Owens Corning) will instantly void your 30-year warranty if their product is installed over old shingles. Old shingles trap attic heat, causing the new shingles to blister and bake from underneath.
- Hidden Rot: If you do not tear off the old roof, the contractor cannot inspect the structural plywood decking underneath for water rot or termite damage.
Insurance & Xactimate Demolition Codes
If you are reviewing an insurance claim or a professional estimate, ensure the contractor is using the correct removal codes. Removing wood shake or double-layer asphalt carries massive labor surcharges.
| Demolition Type | Labor Surcharge Impact | Xactimate Code |
|---|---|---|
| Remove 1 Layer (Asphalt) | Base removal rate (Standard) | RFG REM |
| Remove 2 Layers (Asphalt) | + 80% to + 100% removal labor | RFG REM2 |
| Remove Wood Shake | + 150% removal labor (Extremely messy) | RFG SHKR |
| Remove Asbestos Shingles | Requires Hazmat Abatement Subcontractor | HMR ASB |
If your home currently has an old cedar wood shake roof and you want to convert it to modern asphalt shingles, you face a massive hidden cost. Wood shakes were historically installed on “skip sheathing”—wooden slats with 3-inch gaps between them to let the wood breathe. Asphalt shingles require a solid deck. When the contractor tears off the wood shake, they must install entirely new OSB or plywood over the entire roof before laying the new shingles. This “re-decking” phase will add $3,000 to $6,000 to your bill.
Calculate Your Exact Demolition Costs
Do not get surprised by dump fees or re-decking costs. Our 40-Factor Calculator allows you to input your current roof layers and material type to instantly calculate your precise demolition surcharge.
Launch the 40-Factor Estimator →Frequently Asked Questions
Can I put a new roof over an old roof to save money?
No. While it may save you upfront demolition costs, installing an “overlay” voids your new manufacturer warranty, traps heat which drastically shortens the lifespan of the new shingles, and prevents inspectors from finding structural rot. Furthermore, building codes in most states prohibit it if there are already two layers present.
Why does removing two layers cost more than double?
Removing two layers of shingles requires significantly more labor because the nails from the top layer are driven through the bottom layer, locking them together. Crews must pry through two layers of hardened asphalt simultaneously, and the total debris weight doubles the municipal dump fees.
Academic & Legal References
- International Code Council (ICC): 2021 International Residential Code (IRC) Section R908.3.1.1 – Roof Recovering and Tear-off requirements.
- Xactware Solutions, Inc: Xactimate Pricing Data Guidelines – Parameters for RFG REM2 (Tear off multiple layers) and RFG SHKR (Tear off wood shake).