Measure the house footprint (length times width), add the overhang on every side, and multiply that plan area by the pitch multiplier for your roof’s slope: 1.054 at 4/12, 1.118 at 6/12, 1.202 at 8/12, 1.414 at 12/12. Divide by 100 to get squares. A 50 by 30 foot house with a 12 inch overhang and a 6/12 pitch has about 1,860 square feet of roof, or 18.6 squares, before waste. Add roughly 10 to 20 percent waste depending on how cut up the roof is.
Roofing Calculators
Roofing Calculators: Roof Size, Pitch, Materials, Ventilation and Gutter Sizing
Roofing is full of numbers that sound simple until you try to use them: squares, pitch, bundles, net free area, gutter capacity. This page puts seven working calculators in one place and shows the math behind each one, so you can check a contractor’s numbers, plan a budget, or understand what you are looking at on an estimate.
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Before you start
Calculators are good at arithmetic and bad at roofs. A formula cannot see the second layer of shingles under the first, the soft decking over the kitchen, or the valley that was flashed wrong years ago. Use these tools to get into the right range and to ask better questions, not to replace a measurement or an inspection.
Three habits keep the numbers honest. Measure from the ground and never climb a roof to get a number; a slightly worse estimate is always better than a fall. Keep units straight: pitch is inches of rise per 12 inches of run, overhangs are usually in inches, and areas are in square feet until you divide by 100 to get squares. And read the product label. Bundles per square, starter coverage, underlayment coverage and vent ratings vary by manufacturer and even by product line, which is why every coverage number in the materials tool is editable.
A note on code. South Carolina homes are built to the 2021 International Residential Code with South Carolina modifications, in force since January 1, 2023; the 2024 edition takes effect January 1, 2027. Code sections cited on this page are from the 2021 edition. One South Carolina change matters for roofs: the state replaced the model code’s drip edge rule with one that requires drip edge where the shingle manufacturer requires it. Your local building official has the final word on how the code applies to your house.
Calculator 1
Roof area and squares
Roof area and squares calculator
How it works
The footprint method is the fastest reasonable way to size a roof without climbing it. Measure the outside of the house, add the overhang on every side, and multiply by a pitch factor that converts flat plan area into the real, sloped surface area. For any roof where every plane has the same pitch, the sloped area equals the plan area times the pitch multiplier, no matter how many hips or gables there are. A hip roof and a gable roof over the same footprint at the same pitch have the same surface area; the hip roof just cuts it into more pieces, which is why it wastes more material.
The pitch multiplier is the length of a rafter over one foot of horizontal run, straight from the Pythagorean theorem. At 6/12 it is 1.118, so every 100 square feet of plan area becomes about 112 square feet of roof.
Roofers sell and order by the square, 100 square feet of roof surface. A 1,860 square foot roof is 18.6 squares. Material orders then add waste: shingles cut off at every rake, hip, valley and penetration, plus starter and cap pieces some crews cut from field shingles.
roof area = (length + 2 × overhang) × (width + 2 × overhang) × √(1 + (pitch ÷ 12)²)
Assumptions
- One pitch everywhere. If your house has a 6/12 main roof and a 3/12 porch, run each section separately and add them.
- A rectangular footprint. For an L- or T-shaped house, split it into rectangles, run each, and add. Do not double count where two wings meet.
- The same overhang on every side. If the gable ends have short rakes and the eaves are deep, average them or run the sections separately.
- Waste factors are common rules of thumb, not published standards: around 10 percent for a simple gable, 15 for a hip roof, and 20 or more for roofs cut up with valleys and dormers. Your roofer’s takeoff may differ.
Where it goes wrong
The footprint method ignores dormers (which add roof area of their own), attached garages at a different height, chimneys and skylights. It also cannot tell you how many layers are on the roof now, which affects tear-off cost but not new material. If you are comparing bids, ask each contractor how many squares they measured. A large difference between bids is worth a question.
Pitch multipliers, 1/12 to 12/12
| Pitch | Angle | Multiplier | Grade | 1,000 sq ft of plan becomes |
|---|---|---|---|---|
| 1/12 | 4.8° | 1.003 | 8% | 1,003 sq ft |
| 2/12 | 9.5° | 1.014 | 17% | 1,014 sq ft |
| 3/12 | 14.0° | 1.031 | 25% | 1,031 sq ft |
| 4/12 | 18.4° | 1.054 | 33% | 1,054 sq ft |
| 5/12 | 22.6° | 1.083 | 42% | 1,083 sq ft |
| 6/12 | 26.6° | 1.118 | 50% | 1,118 sq ft |
| 7/12 | 30.3° | 1.158 | 58% | 1,158 sq ft |
| 8/12 | 33.7° | 1.202 | 67% | 1,202 sq ft |
| 9/12 | 36.9° | 1.250 | 75% | 1,250 sq ft |
| 10/12 | 39.8° | 1.302 | 83% | 1,302 sq ft |
| 11/12 | 42.5° | 1.357 | 92% | 1,357 sq ft |
| 12/12 | 45.0° | 1.414 | 100% | 1,414 sq ft |
Calculator 2
Pitch finder
Roof pitch finder
How it works
Pitch is the rise of a roof in inches for every 12 inches of horizontal run, written as 6/12 or “6 in 12.” The same slope can be described as an angle in degrees, as a percent grade, or as a ratio. Rise over run gives the angle through the arctangent, angle back to pitch goes through the tangent, and percent grade is rise divided by run times 100.
The safest way to find your pitch is from inside the attic or at a gable end you can reach from the ground. Hold a level horizontally against the underside of a rafter or the rake board, mark 12 inches along the level, and measure straight up to the rafter. That measurement is your rise. If you can only measure 6 inches of run, the tool normalizes it: 3 inches of rise over 6 of run is 6/12. A phone inclinometer laid on a rafter gives you the angle directly; switch the tool to degrees.
Minimum slopes by roof covering
| Roof covering | Minimum slope (2021 IRC) | Section |
|---|---|---|
| Asphalt shingles | 2/12; two layers of underlayment from 2/12 up to 4/12 | R905.2.2 |
| Metal roof shingles | 3/12 | R905.4.2 |
| Lapped metal panels, no lap sealant | 3/12 (1/2 in 12 with applied lap sealant) | R905.10.2 |
| Standing seam metal | 1/4 in 12 | R905.10.2 |
| Modified bitumen, EPDM, TPO | 1/4 in 12 for drainage | R905.11.1, R905.12.1, R905.13.1 |
There is no pitch that is safe to walk without fall protection
OSHA defines a low-slope roof as 4/12 or less and requires fall protection for construction work at height on both low-slope and steep roofs. Professional crews treat roughly 8/12 and up as needing roof jacks and harnesses for every step, which is why steep roofs cost more to install. If you need a number, get it from the ground, the attic, or an aerial report.
Calculator 3
Shingle roof materials estimator
Shingle roof materials estimator
What each line means
- Shingle bundles
- Squares with waste times bundles per square, rounded up. Most architectural shingles come three bundles to the square, but some heavyweight designer shingles need four or five, so the number is editable. Never mix lots or product lines to make up a shortage; color varies between production runs.
- Starter strip
- Starter goes along every eave, and many manufacturers also call for it along the rakes, which is what the checkbox controls. It matters more than it looks in the Midlands: the enhanced wind ratings manufacturers advertise usually assume their starter at both eaves and rakes. Linear feet are divided by the coverage printed on the bundle, with 5 percent added for cuts.
- Hip and ridge cap
- Total hip and ridge length divided by the linear feet each bundle covers, plus 5 percent. Coverage depends on the cap’s size and exposure, which is why the default of 25 feet is only a starting point. A ridge vent does not remove the need for cap; the cap goes over the vent.
- Underlayment
- Roof area with waste divided by the roll’s coverage. Synthetic underlayments commonly cover about 1,000 square feet a roll, #15 felt roughly 400 and #30 roughly 200. On roofs between 2/12 and 4/12 the code requires two layers (2021 IRC R905.1.1), so roughly double the result for those sections.
- Drip edge
- The national code requires drip edge at eaves and rakes of shingle roofs, lapped at least 2 inches where pieces meet (R905.2.8.5). South Carolina amends that section to require it where the shingle manufacturer does, and the major manufacturers’ instructions call for it. The tool divides eave plus rake length by 9 feet 10 inches, the effective length of a 10-foot piece after the lap.
- Self-adhered membrane
- Often called ice and water shield. The code requires it along the eaves (as an “ice barrier”) only where the local jurisdiction marks a history of ice damming in its code table (R905.1.2); ask your building department whether yours does. The tool counts valleys by default, where most roofers use it anyway, and adds the eaves only if you tick the box. When you do, it follows the code’s geometry: from the edge to 24 inches inside the exterior wall line, converted to slope length and split into 36-inch courses with a 3-inch lap.
- Nails
- Squares with waste times shingles per square times nails per shingle, plus 10 percent for starter, caps and drops. The code floor is four nails per strip shingle unless the manufacturer requires more (2021 IRC R905.2.6), and many manufacturers require six for their high-wind installation or enhanced warranties. The manufacturer’s number is the one that counts.
What the tool does not count
- Flashing: step flashing at walls, counterflashing, chimney and skylight kits, and pipe boots are counted piece by piece, not by area.
- Ventilation products: sized separately in the ventilation tool below.
- Decking replacement: unknown until the old roof is off. Estimates usually carry a per-sheet price for replacing rotted plywood or OSB.
- Tear-off and disposal: driven by the number of existing layers and the weight of the old roof, not the new material list.
- Gutters: sized in calculator 5. If new gutters are going up with the roof, ask whether the drip edge or gutter apron is being coordinated with them.
Calculator 4
Attic ventilation (net free area)
Attic ventilation (NFA) calculator
How it works
Attic ventilation is sized by net free area (NFA), the open area air can actually move through once louvers, screens and baffles are accounted for. It is always smaller than the hole. The code states the requirement as a fraction of the vented space, meaning the attic floor area under the roof, not the roof area.
The 2021 residential code, Section R806.2, which South Carolina has not modified, sets the base requirement at 1/150 of the vented area. An exception allows 1/300 provided both of two conditions are met. The first applies only in Climate Zones 6, 7 and 8 (a vapor retarder on the warm side of the ceiling). The second: not less than 40 percent and not more than 50 percent of the required vent area is in upper vents no more than 3 feet below the ridge, with the balance in the bottom third of the attic.
Every county in the Midlands is in Climate Zone 3A, so the first condition does not apply here and the 1/300 path runs entirely through a balanced layout: ridge or high vents doing 40 to 50 percent of the work, soffit vents doing the rest. That is what the calculator asks you. In a Columbia summer, a well-vented attic matters for more than code compliance: heat that cannot escape bakes the underside of the shingles and loads the air conditioner.
Worked example
A 1,500 square foot attic at 1/150 needs 10 square feet of NFA, which is 1,440 square inches. Split 50/50, that is 720 square inches of intake and 720 of exhaust. A ridge vent rated at 18 square inches per linear foot needs 40 feet of ridge to deliver 720, and a continuous soffit vent rated at 9 square inches per foot needs 80 feet of soffit. At 1/300, every one of those numbers halves.
Rules that matter more than the number
- Keep exhaust at or below intake. When the ridge pulls harder than the soffits can feed it, the exhaust vent draws air from wherever it can, including other exhaust vents and the conditioned house below, which in a Columbia summer means paying to cool the attic.
- Do not mix exhaust types on one attic. A ridge vent plus box vents or a powered fan can short-circuit, with one exhaust pulling air in through the other.
- Make sure intake is real. Soffit vents painted over, blocked by insulation, or installed over solid wood do nothing. The code requires insulation to be kept clear of eave and cornice vents (2021 IRC R806.3), which usually means baffles.
- Check the warranty. Shingle warranties often have their own ventilation language, and a roof that does not meet it can lose coverage.
Calculator 5
Downspout and gutter sizer
Downspout and gutter sizer
How it works
Gutters fail at the outlets first. A gutter can have room to spare and still overflow if too few downspouts are carrying the water away, so the tool sizes downspouts first and then checks how much water each stretch of gutter has to carry.
Downspouts use the method in the SMACNA Architectural Sheet Metal Manual, the sheet metal industry’s design reference. Take the horizontal roof area that drains to the gutter, multiply it by a pitch factor for wind-driven rain on steeper roofs, and compare it with what one downspout can serve: 1,200 divided by the 5-minute rainfall intensity, times the downspout’s effective opening. SMACNA uses a 10-year or 100-year storm; the tool offers both, from NOAA’s Atlas 14 figures for Columbia Metropolitan Airport: 8.14 inches per hour for five minutes in a 10-year storm and 10.7 in a 100-year storm. It also caps each downspout at about 50 feet of gutter, SMACNA’s practical maximum.
For the gutter itself, the tool works out the flow each section carries, using the plumbing code’s formula (gallons per minute = 0.0104 × rainfall rate × roof area) and its design rate, the 100-year one-hour rainfall, which Atlas 14 puts at 3.78 inches at the Columbia airport. The plumbing code’s gutter table lists only semicircular (half-round) gutters, so the tool compares against those as a conservative yardstick. K-style gutters, the common residential shape, are not in the code table; for a borderline run, ask for the installer’s product data.
Columbia averages about 45 inches of rain a year (NOAA 1991–2020 normal), with June and July the wettest months, when afternoon thunderstorms dump a lot of water in a few minutes. Those short bursts are what gutters are sized for. See the gutter installation guide for sizes, materials and hanger spacing.
one downspout serves (1,200 ÷ rainfall rate) × downspout area; flow in gpm = 0.0104 × hourly rate × roof area
Roof area one downspout serves at Columbia rainfall rates
| Downspout | Effective area | 10-year storm (8.14 in/hr) | 100-year storm (10.7 in/hr) |
|---|---|---|---|
| 2 x 3 in rectangular | 4.8 sq in | 708 sq ft | 538 sq ft |
| 3 x 4 in rectangular | 10.31 sq in | 1,520 sq ft | 1,156 sq ft |
| Roof pitch | Pitch factor |
|---|---|
| Flat to 3/12 | 1.00 |
| 4/12 to 5/12 | 1.05 |
| 6/12 to 8/12 | 1.10 |
| 9/12 to 11/12 | 1.20 |
| 12/12 and steeper | 1.30 |
| Semicircular gutter (1/8 in per ft slope) | Capacity in the plumbing code table |
|---|---|
| 5-inch | 74 gpm |
| 6-inch | 110 gpm |
Calculator 6
Repair or replace decision helper
Repair or replace decision helper
How it works
The helper weighs six factors: age against expected life, how much of the roof is damaged, the number of layers, deck condition, leak history, and the cost math. Each answer adds a point toward repair or replacement, and the tool shows every reason rather than just a verdict. A soft or rotted deck tips the result to replacement on its own, because a surface repair needs something solid to fasten into.
The 25 percent rule is the part people most often misapply. The rule of thumb says that when a roof is inside roughly its last five years of expected life, replacement usually makes more sense once a repair would cost more than about 25 percent of a new roof. Versions of it float around from 25 to 50 percent. It only applies near the end of life: a sizable repair on a 10-year-old roof with 15 years ahead of it can be excellent value even when it is more than a quarter of the price of a new roof. The tool applies the rule only when your roof’s age puts it near the end of the range for its material, and says so when it is ignoring it.
“Near the end” is measured against the midpoint of the material’s range. For architectural asphalt at 20 to 30 years, the midpoint is 25, so the tool treats 20 years and older as near the end.
- Layers are a hard limit, not a preference. The code does not allow a new roof over two existing layers (2021 IRC R908.3.1.1), so a two-layer roof must be torn off when it is replaced. It can still be repaired.
- Insurance changes the math. If storm damage is covered, the comparison may look nothing like the one you would face out of pocket. See the roof insurance claims guide before deciding.
- The tool cannot see the roof. Hidden rot, how far a leak has traveled in the insulation, and whether damage is from a storm or from age all take a hands-on inspection, on the roof and in the attic.
Calculator 7
Remaining roof life estimator
Remaining roof life estimator
How it works
The estimator starts from the Midlands lifespan ranges in our article on how long roofs last in Columbia, then adjusts for installation quality, attic ventilation, maintenance and exposure. For architectural asphalt it swaps in specific ranges: about 25 to 30 years for a roof built as a full system, and 15 to 20 years for a bargain install with skipped ventilation and reused flashing. For other materials, known shortcuts take 30 percent off the range.
The other adjustments are multipliers, and they are our rules of thumb, not published data. Neglect takes 25 percent off, occasional maintenance 10 percent. Poor ventilation takes 20 percent off asphalt, where a baking attic does the most damage, and less off metal; flat membranes ignore it. Full southern or western sun or open lakefront wind takes about 7 percent, heavy shade about 5. However many penalties stack, the tool will not cut the range below 65 percent of its starting point, because claiming more precision than that would be pretending.
Remaining life is the adjusted range minus the roof’s age. If the roof is already older than the top of the range, the tool says so instead of showing a negative number. That is a signal to inspect yearly and budget, not a death sentence.
| Material | Base range used | Notes |
|---|---|---|
| 3-tab asphalt shingles | 15 to 20 years | Single-layer, flat look; the shortest-lived asphalt option in Midlands heat |
| Architectural asphalt shingles | 20 to 30 years | 25 to 30 when installed as a full system; 15 to 20 after a bargain install |
| Designer / luxury asphalt shingles | 30 to 50 years | Heavyweight multi-layer shingles, the highest asphalt ratings |
| Metal (standing seam or panels) | 40 to 70 years | Standing seam at the top of the range; exposed-fastener panels need screw and washer upkeep |
| TPO membrane (flat) | 20 to 30 years | The commercial low-slope standard; seams and flashings set the pace |
| EPDM membrane (flat) | 25 to 30 years | Black rubber membrane; seams, ponding and punctures set the pace |
| Built-up roof (tar and gravel) | 15 to 20 years | Older tar-and-gravel roofs; often near the end when a building changes hands |
Getting the numbers
Measuring a roof from the ground
- Footprint and a tape measure
- Walk the outside of the house with a 100-foot tape and a helper, measuring each wall at the foundation. Sketch the shape, split it into rectangles, and note which sections have their own roof. Measure the overhang from the ground with a tape held up to the fascia, or estimate it from the soffit width. Feed the rectangles into the area calculator one at a time.
- County property records
- Richland and Lexington counties, like most in South Carolina, publish parcel records online, often with a building sketch and exterior dimensions. They are drawn for tax purposes, so treat them as approximate and confirm which areas are included, but they are a good cross-check on your tape.
- Satellite imagery
- The free desktop version of Google Earth Pro has a polygon ruler that measures the area of a shape you trace over the roof. Trace the roof edge all the way around and the result is plan area including overhangs; multiply by the pitch multiplier for roof area. Midlands tree cover is the main trap: pines and oaks hide edges. Measure two or three times and average.
- Aerial measurement reports
- Several companies sell roof reports built from high-resolution imagery, listing every plane’s area and pitch plus eaves, rakes, ridges, hips and valleys. Most roofers use them, and many will share the report if you ask. Heavy tree cover, recent additions and very complex roofs are where they miss.
- Pitch from the ground
- Stand back from a gable end, square to it, and take a photo with the phone held level. Many free inclinometer apps can measure the angle of the rake line in the photo. Round to the nearest half-inch of rise and run the pitch finder.
Stay off the roof
Every number on this page can be gathered from the ground, the attic or a screen. If you use a ladder to reach a gable end, set it at roughly a 1-to-4 angle on firm, level ground, extending at least 3 feet above the landing point, with someone holding the base and well clear of power lines. In the attic, step only on joists or a floored walkway, watch for roofing nails through the deck, and in summer go early in the morning: Midlands attics can pass 130°F by afternoon.
Beyond houses
Flat and commercial roofs
Most of these tools work for commercial buildings with a few adjustments. On flat and low-slope roofs the pitch multiplier is essentially 1 (a quarter inch per foot adds far less than one percent), so roof area is plan area plus parapet wall flashing, which estimators add separately in linear feet times height. Membrane roofs are ordered by the manufacturer’s roll dimensions, so the shingle materials tool does not apply.
Drainage is the big one. Flat roofs drain through interior drains, scuppers and gutters, and they are sized to the same rainfall numbers as the gutter tool above, but under the plumbing and building codes, usually by a design professional. Ponding water on a flat roof is a drainage problem first and a membrane problem second.
The ventilation rules in R806 are residential-code provisions for vented attics. Commercial low-slope assemblies are usually unvented, insulated above the deck, and governed by the commercial building and energy codes instead. The remaining-life estimator’s TPO, EPDM and built-up ranges are reasonable planning numbers for a capital budget, but a core cut and moisture survey tell you much more about a specific roof than age does.
Calculator FAQ
Roofing math questions
How do I figure out how many squares my roof is?+
What is the pitch multiplier and how is it calculated?+
It is the sloped length of a rafter over one foot of horizontal run: the square root of 1 plus (rise divided by 12) squared. It converts flat plan area into real roof area. At 6/12 it is 1.118, meaning the roof surface is about 11.8 percent larger than the area it covers.
How many bundles of shingles are in a square?+
Most architectural shingles come three bundles to a square; GAF Timberline HDZ, Owens Corning Duration and CertainTeed Landmark all do. Some heavier products take four, such as Owens Corning Duration MAX. The bundle wrapper states the coverage; order from the manufacturer’s number plus waste.
What is the minimum roof pitch for asphalt shingles in South Carolina?+
2/12. The residential code South Carolina enforces (2021 IRC, Section R905.2.2) allows asphalt shingles only on slopes of 2 in 12 or greater and requires two layers of underlayment from 2/12 up to 4/12. Below 2/12 you need a low-slope system such as modified bitumen, EPDM, TPO or standing seam metal.
How much attic ventilation does South Carolina code require?+
Net free vent area equal to 1/150 of the vented attic floor area (IRC R806.2). The code allows 1/300 when both of two conditions are met, but the first applies only in Climate Zones 6 to 8; the Midlands are Zone 3A. In practice, 1/300 here means 40 to 50 percent of the vent area in high vents within 3 feet of the ridge and the rest at the soffits. Designing to 1/150 is the cautious choice. Try the ventilation calculator.
Is drip edge required in South Carolina?+
South Carolina amended the model code: drip edge is required at eaves and rakes of asphalt shingle roofs where the shingle manufacturer requires it. The major manufacturers’ installation instructions call for it, so on a typical shingle roof you should expect it, lapped at least 2 inches where pieces meet.
What size downspouts does a house in Columbia need?+
Using the SMACNA method and NOAA’s rainfall figures for Columbia, a 2 x 3 inch downspout serves roughly 700 square feet of roof in a 10-year storm and a 3 x 4 inch roughly 1,500 (about 540 and 1,160 in a 100-year storm), after adjusting for pitch. Keep each downspout to about 50 feet of gutter. The downspout and gutter sizer runs it for your roof.
Are satellite roof measurements accurate?+
Aerial measurement reports are generally reliable on clear, unobstructed roofs and are what many roofers use to build estimates. Accuracy suffers under heavy tree cover, which is common in the Midlands, on recent additions the imagery does not show yet, and on very complex roofs. Tracing your roof in Google Earth Pro gives you plan area only; multiply by the pitch multiplier for roof area.
Does the 25 percent rule mean I should replace my roof?+
Only if the roof is near the end of its life. The rule of thumb says that when a roof is inside roughly its last five years, replacement usually wins once a repair costs more than about 25 percent of a replacement. On a younger roof with many years left, a larger repair can be good value. The rule is a starting point, not a verdict.
Can I put a new layer of shingles over my old roof?+
Only over a single existing layer, and only if it is sound. The code (IRC R908.3.1.1) does not permit a recover where the roof already has two or more layers, where it is water-soaked or deteriorated, or where it is slate, clay, cement or asbestos-cement tile. Even where an overlay is legal, it hides the deck, and many manufacturers limit warranties on it.
How accurate are these roofing calculators?+
The arithmetic is exact; the inputs are where error comes in. On a simple roof measured carefully, the area and materials results should be in the right neighborhood for budgeting. Complex roofs, mixed pitches and unknown product coverage widen the gap. The repair-or-replace and remaining-life tools are deliberately given as leanings and ranges because the real answer depends on things only an inspection can see.
Still have questions?
Want the real numbers for your roof?
A calculator gets you into the right range. A measured roof, a look in the attic and a check of the decking get you the real answer. If you would like that for your home, Cola City Roofing will measure it and walk you through the numbers, whether or not you hire us.
Keep reading
Related roofing resources
Browse all guidesRoofing glossary
Plain definitions for every term on this page and more.
How to read a roofing estimate
Squares, line items, and what should be on every bid.
Roof ventilation guide
What an under-vented attic does to a roof in a Columbia summer.
Gutter installation guide
Sizes, materials, hangers and downspout placement.
Repair or replace?
The longer version of the decision helper’s reasoning.
Roof replacement cost guide
What drives the price of a new roof in the Midlands.
Sources
Checked September 24, 2026. Codes and programs change; confirm anything that affects a decision with the agency named.
- 2021 International Residential Code as adopted in South Carolina, Chapter 8 (R806.2 minimum vent area; R806.3 vent clearance) and Chapter 9 (R905.1.2 ice barriers; R905.2.2 shingle slope; R905.2.6 fasteners; R905.2.8.5 drip edge, as modified by SC; R905.4.2, R905.10.2, R905.11.1, R905.12.1, R905.13.1 minimum slopes; R908.3.1.1 recover limits): https://up.codes/viewer/south_carolina/irc-2021
- SC Building Codes Council, codes in effect and 2021 / 2024 modification indexes: https://llr.sc.gov/bcc/
- 2009 International Energy Conservation Code as adopted in SC, climate zones by county and Table 402.1.1: https://up.codes/viewer/south_carolina/iecc-2009
- 2021 International Plumbing Code as adopted in SC, Section 1106 (storm drainage sizing, Equation 11-1, Table 1106.6 gutters): https://up.codes/viewer/south_carolina/ipc-2021/chapter/11/storm-drainage
- NOAA Atlas 14, Volume 2, precipitation frequency estimates for Columbia Metropolitan Airport (5-minute and 60-minute depths): https://hdsc.nws.noaa.gov/pfds/
- NOAA NCEI 1991–2020 climate normals, Columbia Metropolitan Airport (USW00013883): https://www.ncei.noaa.gov/access/us-climate-normals/
- SMACNA Architectural Sheet Metal Manual, 7th ed., gutter and downspout sizing (Tables 1-1 to 1-3), via SMACNA’s calculator page: https://www.smacna.org/technical-standards/apps/view/downspout---gutter-sizing-calculator
- OSHA 29 CFR 1926.500 definitions (low-slope roof 4 in 12 or less): https://www.osha.gov/laws-regs/regulations/standardnumber/1926/1926.500
- Manufacturer data sheets for bundle counts: GAF Timberline HDZ, Owens Corning Duration and Duration MAX, CertainTeed Landmark (current product literature on each manufacturer’s site).
- Material lifespan ranges: Cola City Roofing, How long do roofs last in Columbia, SC?