Re-Roofing Code Requirements: Layers, Permits, and Wind
Applies to one- and two-family dwellings. The model code is a baseline: each state or city adopts its own edition and amendments, and some of the most important rules (permits, layer limits) are set locally. Always confirm with your building department.
The two questions homeowners ask most about a new roof, "can I put shingles over the old ones?" and "do I need a permit?", have no single national answer. The International Residential Code has a clear rule for the first one, but it only binds where your state or city has adopted it. The second is mostly decided by your local building department, and at least one state exempts roof replacement from permits below a cost threshold.
What the model code does say is specific. A new roof covering may go over an existing one only if the old roof is sound, is not slate, clay, or cement tile, and has no more than one existing covering. Otherwise it is a tear-off down to the deck. The code also controls the ice barrier on cold-climate roofs, the shingle fastener count, the slope limits for asphalt shingles, and the drip edge.
A few states go well beyond that baseline. Florida requires a secondary water barrier on re-roofs of older wood-deck homes not permitted under its building code and applies a 25% repair rule. Texas coastal counties require windstorm inspection for insurance eligibility. California requires a fire-retardant covering on the whole roof in very high fire hazard severity zones once more than half of it is replaced in a year. This page covers the model rules in detail and the states we have been able to cite to a state source.
Once you know whether you are tearing off or recovering, size the job: shingle bundles, underlayment, drip edge, and nails for the roof area. Free, no signup.
Tear-Off or Recover: When You Can Roof Over the Old Layer (2024 IRC R908.3 and R908.4)
The code separates a roof replacement, which removes existing layers of roof coverings down to the deck (R908.3), from a roof recover, which installs a new covering over the existing one (R908.4). A recover is allowed in several situations, including where the new covering is installed per the manufacturer's approved instructions, and for complete and separate systems like standing-seam metal that carry their own loads. But a recover is never permitted in three conditions, which is where most "can I shingle over shingles?" answers come from.
| Condition | Recover over the old roof allowed? | Section |
|---|---|---|
| Existing roof or covering is water soaked or deteriorated so it is not an adequate base | No, tear off | R908.4 Exception 1 |
| Existing covering is slate, clay, cement, or asbestos-cement tile | No, tear off | R908.4 Exception 2 |
| Existing roof already has two or more applications of any type of roof covering | No, tear off | R908.4 Exception 3 |
| One existing layer in sound condition, new covering installed per the manufacturer | Yes, permitted | R908.4 item 1 |
| Metal panel, metal shingle, or concrete/clay tile over existing wood shakes | Yes, with the wood-shake provisions | R908.4 item 3, R908.4.1 |
Underlayment and Ice-Barrier Exceptions on a Replacement (R908.3)
Even on a tear-off, the 2024 code allows some existing underlayment to stay. An adhered ice-barrier membrane may stay in place and be covered with another layer of ice barrier where the sheathing is not water soaked or deteriorated and both roof-covering and new-underlayment manufacturers permit it. An existing self-adhered underlayment may likewise stay and be covered with new underlayment meeting the code tables. A second layer of self-adhered underlayment may go over one existing layer that cannot be removed without damaging the deck, but only if both manufacturers allow it, the sheathing is sound, and material buildup at walls, valleys, roof edges, and laps does not exceed two layers.
Ice Barrier: Where It Applies and How Far It Goes (R905.1.2)
An ice barrier is required where Table R301.2 designates a history of ice forming along the eaves and causing backup of water. It consists of at least two layers of underlayment cemented together, or a self-adhering polymer-modified bitumen sheet, and it must extend from the lowest edges of all roof surfaces to a point at least 24 inches inside the exterior wall line of the building. On roofs of 8:12 or steeper, the barrier must extend at least 36 inches measured along the roof slope from the eave edge. Detached accessory structures without conditioned floor area are exempt. Two common mistakes: the 24 inches is measured inside the wall line, not up the slope, and whether your location needs an ice barrier at all is a local designation, not a national one.
Asphalt Shingle Rules That Inspectors Check
Slope: asphalt shingles are permitted only on slopes of 2:12 or steeper, and slopes from 2:12 up to 4:12 need double underlayment. Fasteners: galvanized steel, stainless steel, aluminum, or copper roofing nails with at least a 12-gage shank and a 3/8-inch head, long enough to go at least 3/4 inch into the sheathing or through it where the sheathing is thinner. Count: the manufacturer's minimum, but never fewer than four fasteners per strip shingle or two per individual shingle, with the manufacturer's instructions governing above 21:12 slopes. Drip edge: required at eaves and rakes, lapped at least 2 inches, extending at least 1/4 inch below the sheathing and 2 inches back onto the deck, fastened at no more than 12 inches on center, with underlayment over the drip edge at eaves and under it at rakes.
| Item | Requirement | Section |
|---|---|---|
| Minimum slope | 2:12; double underlayment from 2:12 up to 4:12 | R905.2.2 |
| Nails | 12-gage shank, 3/8-in head, corrosion resistant, at least 3/4 in into sheathing | R905.2.5 |
| Fastener count | Manufacturer minimum, not fewer than 4 per strip or 2 per individual shingle | R905.2.6 |
| Drip edge | Eaves and rakes, 2 in lap, 1/4 in below sheathing, fastened at 12 in o.c. or less | R905.2.8.5 |
Wind Rating: Shingle Class by Design Wind Speed (R905.2.4.1)
Asphalt shingles are tested to ASTM D7158 (or ASTM D3161 where D7158 does not apply) and must meet the classification for the ultimate design wind speed of the site, shown in Table R905.2.4.1. The package must carry a label showing compliance. At 110 and 116 mph, classes D, G, or H (D7158) or A, D, or F (D3161) qualify; at 129 mph D drops out; from 142 mph only G or H (D7158) or F (D3161) qualify; from 168 mph only H or F. Your design wind speed comes from your jurisdiction's adopted maps, so ask the building department for the number before you buy shingles.
| Ultimate design wind speed (mph) | ASTM D7158 classes | ASTM D3161 classes |
|---|---|---|
| 110 and 116 | D, G, or H | A, D, or F |
| 129 | G or H | A, D, or F |
| 142 and 155 | G or H | F |
| 168, 181, and 194 | H | F |
Do You Need a Permit?
The model code exempts "ordinary repairs" from permit applications, and a full roof replacement is usually treated by building departments as a permitted alteration rather than an ordinary repair, but that is local practice, not a single national rule. North Carolina is a documented exception: its statute exempts construction, repair, replacement, or alteration costing $40,000 or less from the state building permit unless it involves listed items such as load-bearing structural work or the addition of roofing, excluding replacement. The State Fire Marshal reads that as covering replacement of roofing and up to 15% of the roof deck, though local jurisdictions and HOAs can still impose requirements. Florida, Texas coastal counties, and California wildfire zones add requirements on top of the permit, covered below. The practical answer is to call your building department and ask about both the permit and any required inspections before the tear-off.
States With Their Own Re-Roof Rules
These are the states where we have cited a state source for a rule that differs from, or adds to, the model code. Many other states follow the IRC as adopted locally, but we have not verified them, so they are not listed. Statutes and codes change, and Florida's code edition changes on December 31, 2026, so confirm the current text with your building department.
| State | What is different | Source |
|---|---|---|
| Florida | When the roof covering is removed and replaced on an existing structure with a sawn-lumber, plank, or wood-panel deck, deck attachment and a secondary water barrier are required, unless the structure was permitted under the Florida Building Code. The tear-off list also includes existing wood shake, which the model IRC does not. A 25% rule requires the whole roof or roof section to conform when more than 25% is repaired, replaced, or recovered in 12 months, with an exception for roofs built, repaired, or replaced under the 2007 FBC or later. | FBC-Existing Building 706.1.1, 706.3, 706.7 (8th Ed., eff. 12/31/2023) |
| Texas (14 coastal counties and 5 Harris County cities) | Most roof replacements and major repairs need a TDI windstorm inspection and certificate of compliance for insurance eligibility; repairs under 100 sq ft that do not involve decking are exempt. Cities east of SH 146 in Harris County (La Porte, Morgan's Point, Pasadena, Seabrook, Shoreacres) are included. Outside this area, the municipality sets the rules. | TDI windstorm program; Ins. Code ch. 2210; Local Gov't Code §214.212 |
| California | In a very high fire hazard severity zone, where more than 50% of the roof area is replaced within one year, the entire roof covering must be a fire-retardant covering, and local rules can be stricter. The state wildfire-construction rules (formerly CBC Chapter 7A and CRC R337) moved into a new Part 7 of Title 24 on January 1, 2026. | Health & Safety Code §13132.7; 2025 Title 24 |
| North Carolina | Statutory permit exemption for work costing $40,000 or less, which includes roofing replacement but not the addition of roofing; the 2018 NC Residential Code still applies, with the 2024 code delayed by session law | G.S. 160D-1110(c); OSFM guidance paper |
| Minnesota | Residential roofer license required for those meeting the statutory definition; residential code is the 2020 MN Residential Code on a 2018 IRC base | Minn. Stat. §326B.805; Minn. R. ch. 1309 |
| Indiana | 2020 Indiana Residential Code (2018 IRC base): ice barrier 24 in inside the exterior wall line, 36 in along slope on 8:12 and steeper, where Table R301.2(1) designates ice history | 675 IAC 14-4.4; IDHS notice 2020-02-25 |
Common Misconceptions
Several claims repeated on roofing sites are wrong or overstated. The two-layer limit is a model-code rule that applies where the IRC chapter is adopted; it is not a federal or universal law, and Texas adopts the IRC only as a municipal baseline that cities may amend. A permit is not required in every state for every re-roof: North Carolina exempts roofing replacement under its $40,000 statutory threshold. The 2024 IRC did not remove the 36-inch ice barrier rule for steep roofs. In Florida, the 25% rule is not "over 25% means a brand-new roof": the 8th Edition covers recover as well as replacement and exempts roofs built, repaired, or replaced under the 2007 FBC or later, and the secondary water barrier requirement does not apply to structures permitted under the FBC. In Texas, a windstorm inspection is tied to the coastal designated catastrophe area and insurance eligibility, not to every roof in the state. And manufacturer warranty requirements, such as extra nails or a branded underlayment system, are not code minimums.
Standards & Citations
| Standard | Code / Section | Requirement |
|---|---|---|
| Roof Replacement and Recover | 2024 IRC R908.3, R908.4 | Replacement removes existing coverings to the deck; recover is not permitted over deteriorated roofs, slate/clay/cement tile, or two or more existing coverings. |
| Ice Barrier | 2024 IRC R905.1.2 | Where ice history is designated, barrier from the eave to 24 in inside the wall line; 36 in along the slope on 8:12 and steeper. |
| Asphalt Shingles | 2024 IRC R905.2.2, R905.2.4.1, R905.2.5, R905.2.6 | Minimum 2:12 slope; wind class by design speed; 12-gage 3/8-in-head nails; at least 4 fasteners per strip shingle. |
| Florida Re-Roof Secondary Water Barrier | FBC-Existing Building 706.1.1, 706.7 | Deck attachment and secondary water barrier on re-roofs of older wood-deck structures; 25% repair rule. |
Apply These Requirements
Open a calculator to run this guide’s requirements against your own project.
Roofing & Shingle Calculator
Once you know whether you are tearing off or recovering, size the job: shingle bundles, underlayment, drip edge, and nails for the roof area.
Roof Area Calculator
Roof area drives every quantity on a re-roof, and a pitch correction matters for the steep-slope ice barrier distance.
Roof Pitch Calculator
Slope decides the 8:12 ice barrier rule and the 2:12 and 4:12 shingle underlayment thresholds, so measure pitch before ordering materials.
Get Accurate Pricing From Local Contractors
Compare real pricing from licensed professionals in your area based on your estimate.
- Free, no obligation quotes
- Local licensed contractors
- Faster than manual estimating
Frequently Asked Questions
Can I put new shingles over old shingles?
Under the model IRC, only if the existing roof is sound, is not slate, clay, or cement tile, and has no more than one existing covering. A recover is not permitted where the existing roof or covering is water soaked or deteriorated, or where it already has two or more applications of roof covering. Your state or city may adopt a different rule, and many insurers and manufacturers prefer a tear-off anyway.
How many layers of shingles are allowed?
The model IRC allows a recover only where there is not already two or more applications of roof covering, which is why people say "two layers maximum." That rule applies where your jurisdiction adopted that chapter of the IRC. Check with your building department, and note that some manufacturers and warranties require a full tear-off regardless.
Do I need a permit to replace my roof?
In most places a full replacement needs a permit, but it is decided locally. North Carolina is an example of the opposite: its statute exempts work costing $40,000 or less (including roofing replacement) from the state building permit, though local rules and HOAs may still apply. Call your building department before the work starts, and ask about inspections.
What is an ice barrier and do I need one?
An ice barrier is a self-adhering membrane or two cemented layers of underlayment along the eaves that stops ice dams from forcing water under shingles. The IRC requires it where your jurisdiction designates a history of ice along the eaves, extending from the eave to 24 inches inside the exterior wall line, and 36 inches along the slope on roofs of 8:12 or steeper.
How many nails per shingle does code require?
The 2024 IRC requires the manufacturer's minimum number of fasteners, but never fewer than four per strip shingle or two per individual shingle. Nails must be corrosion resistant with at least a 12-gage shank and a 3/8-inch head, long enough to penetrate at least 3/4 inch into the sheathing or through thinner sheathing. Always follow the shingle package instructions, which often require more in high wind.
Does Texas require a windstorm inspection for a new roof?
In the 14 designated coastal counties and five Harris County cities east of SH 146, most roof replacements and major repairs need a Texas Department of Insurance windstorm inspection and certificate of compliance to keep Texas Windstorm Insurance Association eligibility. Repairs under 100 square feet that do not involve decking are exempt. Elsewhere in Texas, the municipality sets the requirements.
What does Florida's 25% roof rule mean?
If more than 25% of a roof or roof section is repaired, replaced, or recovered in a 12-month period, the Florida Building Code-Existing Building requires the whole roof or roof section to be brought into compliance, with an exception for roofs built or repaired under the 2007 FBC or later. When the roof covering on an existing wood-deck structure is removed and replaced, deck attachment and a secondary water barrier are also required, unless the structure was permitted under the Florida Building Code.
Where do these requirements come from?
The 2024 IRC sections were read directly from the International Code Council's digital code site. State rows are limited to rules tied to a state statute, adopted code, or agency page, with the section named for each. States not listed have not been verified against state sources.
Related Code Guides
Texas Windstorm Roofing Requirements
Texas Department of Insurance Seacoast windstorm rules: shingle ratings, fastening, WPI-8 inspection, and Tier I/II requirements for the Texas coast.
Florida HVHZ Roofing Requirements
Florida HVHZ wind-zone roofing rules: shingle ratings, fastener schedules, NOA approval, and underlayment per FBC 8th Edition (2023) and Miami-Dade County.
Ground Snow Load by State: How to Find Your Design Number
The 70 psf prescriptive limit, the free ASCE lookup tool, and the 7 states that publish their own ground snow load numbers by county or town.
Residential Building Code Edition by State: IRC, NEC, and Energy Code
Which IRC, NEC and energy code edition each state has adopted for homes, with effective dates, pending updates, and states with no statewide code.