平屋根の排水溝、池の水、および曲がり根太¶

緩やかな傾斜と ** 平らな屋根 (TPO、 EPDM、 PVC single-ply membranes, modified bitumen, and built-up tar-and-gravel roofs surrounded by perimeter parapet walls)** on residential rowhouses, modern flat-roofed homes, apartments, and commercial warehouses rely entirely on internal roof drain bowls (cast-iron strainer domes) and through-wall parapet scuppers to shed torrential rainwater and melting snow. When autumn leaves, pine needles, wind-blown plastic bags, roof gravel, or ice dams block the primary drain and no unobstructed secondary emergency overflow scupper is open, the roof parapet walls transform the top of the building into an elevated swimming pool. Because every 25 millimeters (1 inch) of standing water weighs 25.4 kilograms per square meter (5.2 pounds per square foot), a mere 15 centimeters (6 inches) of ponded water imposes 152 kilograms per square meter (31.2 pounds per square foot) of dead weight across the roof deck, exceeding the total 96-to-144-kilogram-per-square-meter (20-to-30-psf) live-load design limit of standard wood-joist or open-web steel bar-joist roofs. Worse still, a self-accelerating structural physics trap called Ponding Instability (Progressive Deflection Amplification) takes over: as the weight of the initial puddle bends the middle of the roof joists downward by 25 millimeters (1 inch), water from the entire roof rushes into that deepened depression, doubling the depth and weight at the exact mid-span until the wood joists, glue-laminated (Glulam) beams, or steel bar joists snap and drop thousands of liters of water and roof framing straight into the living space below. If you hear loud cracking or popping overhead, see interior doors jamming in their frames, or see ceiling drywall bowing downward under a flat roof, evacuate the building immediately and call your local emergency number (911 in the United States and Canada, 112 across the European Union, 999 in the United Kingdom, 000 in Australia, 111 in New Zealand) or consult our global directory of 緊急電話番号. For closely related structural and roof-water emergencies, read our guides on heavy snow, ice dams, and roof collapse、 ceiling collapse, waterlogged drywall, and plaster sagging hazard、 structural damage and collapse、そして roof leak and emergency tarping。

今すぐこれを実行してください¶

1. If you hear loud gunshot-like cracking overhead, see ceiling joists or drywall bowing downward by more than 25 millimeters (1 inch), or find interior bedroom/hallway doors suddenly binding shut in their frames, EVACUATE THE BUILDING IMMEDIATELY and NEVER climb onto the roof: A flat roof undergoing active progressive ponding deflection can transition from initial joist cracking to total catastrophic pancake collapse in under 60 seconds. Walking out onto a ponded flat roof adds your dynamic body weight directly to the overstressed joists and risks sucking you down into the collapse or down an unclogged vortex drain. Get everyone outside and call the fire department.
2. If the roof structure is NOT creaking or bowing internally and can be accessed safely from a stairwell bulkhead, upper window, or exterior ladder at the strong perimeter parapet wall, clear the clogged Scupper or Internal Drain Dome from the perimeter edge: Stay strictly within 60 centimeters (2 feet) of the load-bearing exterior parapet wall (never walk out into the deep middle of a ponded roof lake). Use a long-handled garden rake, stiff broom, or boat hook to pull leaves, plastic bags, or slush away from the cast-iron internal drain dome or parapet scupper box.
3. NEVER stick your bare hand or arm blindly underwater into a clogged internal roof drain after removing the strainer dome (The Suction-Entrapment & Downspout-Plug Trap): First, when 30 centimeters (12 inches) of ponded water suddenly drains into an un-domed 100-to-150-millimeter (4-to-6-inch) vertical leader pipe, it creates a powerful hydrostatic suction vortex that can pin a hand or forearm against the pipe opening. Second, if you pull the cast-iron strainer dome off completely while a plastic trash bag or tennis ball is floating nearby, the vortex sucks the bag straight down into the 90-degree elbow inside the ceiling wall, permanently plugging the internal pipe where you cannot reach it. Always rake debris away from the outside of the strainer cage, keeping the strainer dome in place.
4. If the internal drain pipe or scupper downspout is frozen solid with ice, NEVER chop at the rubber/TPO roof membrane with an axe, shovel, or ice pick, and NEVER use a propane blowtorch: Puncturing a submerged EPDM、 TPO、または PVC single-ply roof membrane under 15 centimeters (6 inches) of standing water dumps hundreds of liters of water straight into your ceiling insulation and drywall within minutes, while open-flame torches ignite dry wood cant strips inside parapet walls. Melt ice plugs using mesh stockings filled with calcium chloride (CaCl2) or magnesium chloride ice melt laid across the drain dome, or pour hot tap water down a PVC pipe held directly against the ice plug.
5. If the internal drain leader pipe is clogged deep inside the building wall and cannot be snaked immediately, start an Emergency Garden-Hose Siphon or Submersible Utility Pump over the parapet wall: Drop a submersible utility pump (plugged into a dry indoor GFCI outlet) onto a rubber welcome mat or folded towel in the ponded zone (so the pump base cannot chafe the roof membrane) and discharge the water over the parapet wall onto the street/yard; or submerge a 15-meter (50-foot) garden hose completely in the roof pond to purge all air, cap one end with your thumb, and drop that end 3 meters (10 feet) down over the parapet edge to start a free gravity siphon.
6. If a wet gypsum drywall ceiling inside the house bulges downward like a water-filled balloon after a flat-roof leak, shut off the room's ceiling light circuit breaker, move people out from under it, place a 120-liter (32-gallon) trash barrel underneath, and poke a single 6-millimeter (¼-inch) drainage hole at the lowest point of the bulge using a screwdriver taped to a broomstick: Draining the trapped water puddle out of the ceiling cavity relieves dead weight before the wet gypsum paper tears and drops a 45-kilogram (100-pound) slab of soggy drywall onto someone's head.

Decision tree: flat roof clogged drain, ponding water, and bowing joist triage¶

flowchart TD
    Start["Flat Roof Emergency: Ponding Water, Clogged Scupper, or Sagging Ceiling"] --> CollapseCheck{"1. Are there signs of structural roof collapse?"}

    CollapseCheck -->|"YES: Loud cracking, ceiling bowing >25 mm (1 in), or doors binding"| EvacNow["IMMEDIATE STRUCTURAL EVACUATION: 1. Evacuate all occupants immediately 2. NEVER climb onto the roof or stand under bowed spans 3. Shut off gas/electric from outside & call 911 / 112 / 999"]

    CollapseCheck -->|"NO: Framing quiet & straight; water ponding around drain"| AccessCheck["2. SAFE PERIMETER ACCESS: 1. Access via interior hatch or tied ladder at load-bearing parapet corner 2. Stay within 60 cm (2 ft) of exterior parapet wall (Do NOT wade into mid-span pond)"]

    AccessCheck --> DrainType{"3. Surface leaves, frozen ice, or deep pipe clog?"}

    DrainType -->|"表面葉/ストレーナードーム上のビニール袋"| RakeClean["SURFACE RAKE PROTOCOL (KEEP DOME ON): 1. Use long rake from parapet edge to pull leaves/plastic away from drain dome or scupper 2. DO NOT remove strainer dome while debris floats nearby (Vortex sucks debris deep into wall elbow)"]

    DrainType -->|"排水管または排水管上の凍結した氷のプラグ"| MeltIce["NON-DESTRUCTIVE ICE MELT PROTOCOL: 1. NEVER chop membrane with axe/shovel or use a blowtorch 2. Lay nylon stockings filled with Calcium Chloride (CaCl2) across ice dome 3. Pour hot water through a PVC pipe into drain throat"]

    DrainType -->|"Internal Pipe Clogged Deep Inside Building"| SiphonPump["EMERGENCY OVER-PARAPET SIPHON OR PUMP-OFF: 1. Set submersible utility pump on a thick rubber mat in ponded zone & pump water OVER parapet wall 2. Or submerge 15 m (50 ft) garden hose in pond to purge air, thumb-cap end, & drop 3 m down exterior wall to siphon"]

Deep dive 1: The structural engineering of flat roof water weight and warning signs of collapse¶

Understanding the exact weight of standing water on a flat roof and recognizing the five indoor early-warning signs of joist overload gives you the minutes needed to get your family or employees out before a roof fails.

1. The Exact Hydrostatic Weight of Ponded Water and Rain-on-Snow Loads¶

Building codes (International Building Code IBC Section 1611 / ASCE 7 / Eurocode 1 EN 1991-1-3) design standard flat residential and light commercial roofs for a Live / Snow Load of 96 to 192 kilograms per square meter (20 to 40 pounds per square foot [psf]). Compare that structural limit against the weight of trapped water on a 10-by-10-meter (33-by-33-foot, 100-square-meter / 1,076-square-foot) flat roof:

2. The Five Indoor Warning Signs That a Flat Roof Is About to Collapse¶

Because the top of a flat roof is hidden from view on the ground, 80 percent of flat-roof collapses take occupants inside the building by surprise. Watch and listen inside the top floor for these five progressive engineering red flags: 1. Interior Doors and Closet Doors Suddenly Binding, Sticking, or Refusing to Latch: - Before ceiling drywall visibly cracks, bowing roof joists transfer downward compressive loads onto interior partition walls. Even a 6-to-12-millimeter (¼-to-½-inch) downward bow in the top plate of an interior wall racks the rectangular door frame into a parallelogram so the top corner of the bedroom or office door binds tightly against the jamb. 2. Visible Downward Bowing (Deflection > L/240) or Cracking Along Ceiling Drywall Seams: - Sight horizontally across the ceiling from one wall to the other or hold a taut string/laser level across the room. Under building codes, maximum allowable roof joist deflection is Span / 240 (または Span / 360 for plaster ceilings): on a 4.8-meter (16-foot) room span, any downward sag greater than 20 millimeters (¾ inch) indicates severe structural overload. 3. Sharp Acoustic "Pops," "Creaks," or "Rifle-Shot Cracks" From the Ceiling Cavity: - Wood joists splitting horizontally along their neutral axis (horizontal shear failure), engineered wood I-joist OSB webs buckling, or steel bar-joist bottom-chord welds snapping emit sharp, percussive pops that sound like a 2x4 snapping or a pistol shot. Evacuate the building within 10 seconds of hearing structural cracking overhead. 4. "Nail Pops" and Diagonal Shear Cracks Radiating From Top Corners of Windows and Doors: - Rows of circular drywall screw/nail heads popping through the ceiling paint along joist lines mean the joists are flexing far below the rigid gypsum board. 5. Sudden Dirty-Brown Water Pouring Through Recessed Can Lights, Smoke Detectors, or HVAC Diffusers: - When ponded water rises above the 15-to-20-centimeter (6-to-8-inch) base-flashing termination height along parapet walls, HVAC curb frames, or plumbing vent boots, water bypasses the waterproof membrane completely and pours straight into the ceiling plenum and electrical conduit boxes.

====================================================================================
     FLAT ROOF DRAINAGE ARCHITECTURE: PRIMARY DRAIN vs. OVERFLOW SCUPPER
====================================================================================

   PARAPET WALL                                                     PARAPET WALL
   +--------+                                                       +--------+
   |        |  [ Secondary Emergency Overflow Scupper ]             |        |
   |        |  Cut 50 mm (2 in) ABOVE roof deck so water            |        |
   |        |  waterfalls down outside wall if main drain clogs     |   ||   |
   |        |                                                       |   \/   |
   |        |                     Ponded Water Level                +--------+
   |        |=======================================================|========|==>
   |        |     \                 (Mid-Span Bow)                / | Scupper|
   +--------+      \         +------------------------+          /  +--------+
   |  ROOF  |=======\========| [Clogged Strainer Dome]|=========/===|  WALL  |
   |  DECK  |        \       +-----------++-----------+        /    |        |
   +--------+         \__________________||___________________/     +--------+
                       Bowing Roof Joist || Internal Drain Leader Pipe
====================================================================================

Deep dive 2: How to clear clogged internal roof drains, parapet scuppers, and ice dams safely¶

If the building shows zero signs of structural bowing or creaking and you can safely reach the roof perimeter during or after a storm, how do you restore drainage without damaging the membrane or getting trapped by suction?

1. Primary vs. Secondary (Emergency Overflow) Flat Roof Drains¶

Every code-compliant low-slope roof enclosed by parapet walls (IPC Section 1106 & 1108 / IBC Section 1502) is supposed to have two completely independent drainage systems: 1. The Primary Drainage System (Internal Roof Drains または Low Scuppers): - Sits at the lowest sumped valleys of the roof. - An Internal Roof Drain consists of a recessed cast-iron bowl clamped to the waterproof membrane, topped by a removable cast-iron or aluminum slotted strainer dome (or gravel guard) that prevents leaves and roof stones from entering the vertical 75-to-150-millimeter (3-to-6-inch) internal leader pipe running down through the interior walls of the building to the storm sewer. - A Primary Through-Wall Scupper is a square or rectangular sheet-metal tunnel cut flush with the roof deck right through the exterior masonry parapet wall, discharging into an exterior conductor head (collector box) and downspout on the outside facade. 2. The Secondary (Emergency Overflow) System (Overflow Scuppers または Secondary Standpipe Drains): - Positioned 50 millimeters (2 inches) higher than the primary drain inlet. - Its sole purpose is life safety: if a plastic trash bag or autumn leaf mat seals the primary drain 100 percent shut, the ponding water rises 50 millimeters (2 inches) and then gushes out through the secondary overflow scupper down the outside face of the building, both preventing water weight from ever exceeding 50 kg/m2 (10.4 psf) AND visually alerting people on the sidewalk that the primary roof drain is blocked. - The Deadly Older-Building Trap: Millions of older rowhouses, commercial buildings, and DIY re-roofing jobs have NO secondary overflow scuppers (or roofers accidentally tarred over the scuppers or iced over the exterior collector box). When the single primary drain clogs on a single-drain flat roof, water depth has no limit until the parapet wall tops out at 30 to 60 centimeters (12 to 24 inches) and the roof collapses.

2. Step-by-Step Safe Clearing of a Submerged Primary Roof Drain or Scupper¶

1. Locate the Submerged Drain in Murky Water Using Parapet Reference Marks:
2. When 10 centimeters (4 inches) of muddy water covers a flat roof, you cannot see the black cast-iron drain dome. Look at the lowest point of the tapered insulation valleys and sweep sideways with a wooden broom handle or plastic garden rake (never a sharp metal pitchfork or shovel blade) until you feel the raised cast-iron dome.
3. Rake the Leaf/Debris Mat Outward While Leaving the Cast-Iron Strainer Dome IN PLACE:
4. As soon as leaves, pine needles, or a plastic bag are pulled off the outside slots of the strainer dome, water will roar down the pipe in a whirlpool vortex. Never unbolt or lift off the cast-iron strainer dome while murky water is deep, because the whirlpool immediately sucks floating sticks, gravel, and plastic bottles straight down into the open pipe throat where they jam inside the first 90-degree elbow buried above your ceiling.
5. What If the Strainer Dome Is Missing and the Drain Throat Is Plugged at the Top?
6. Never reach your bare hand down into the drain throat under standing water. Use a long-handled mechanical claw grabber, bent coat-hanger hook, or closet auger from a kneeling position beside the drain to pull the obstruction upward out of the bowl, and immediately place an inverted weighted milk crate or wire mesh basket over the open drain hole as a temporary strainer cage.

====================================================================================
     HOW TO SET UP AN OVER-PARAPET GRAVITY GARDEN-HOSE SIPHON FOR A PONDED ROOF
====================================================================================

                           Parapet Wall
                            +--------+
       Submerged Intake     |  ____  | <-- Hose Crests Parapet
       in Weighted Bucket   | /    \ |
            +------+        |/      \|
      ======| [==] |========/========\====  Ponded Roof Water Level
      ======+------+=======+          \
         ROOF MEMBRANE     |           |  Gravity Drop (2 to 4 m / 6 to 13 ft)
                           |           v  Pulls Continuous Vacuum Siphon
====================================================================================

3. Clearing a Frozen Parapet Scupper (Winter Ice-Dam Ponding）¶

In winter, snow melts on the sun-warmed roof membrane during the day, trickles out through the metal parapet scupper tunnel, and freezes solid overnight inside the shaded exterior sheet-metal collector box and downspout until a block of clear ice seals the scupper: - Never Chop Ice Off a Flat Roof Membrane: Cold TPO、 PVC、 EPDM, and modified-bitumen membranes become stiff at sub-zero temperatures; striking an ice dam with a metal crowbar, axe, or shovel slices straight through the flashing seam. - The Calcium Chloride (CaCl2) "Ice-Melt Sock" Channel Technique: Fill two old nylon stockings with 2 to 3 kilograms (5 to 7 pounds) of Calcium Chloride (CaCl2) or Magnesium Chloride (MgCl2) pellet ice melt (which generate exothermic heat and melt ice down to -25 to -32 degrees Celsius [-13 to -25 degrees Fahrenheit], unlike rock salt which stops working below -9 C and corrodes aluminum). Lay the calcium chloride sock lengthwise right through the frozen parapet scupper throat; within 30 to 45 minutes, it melts a 10-centimeter-wide (4-inch) drainage tunnel through the bottom of the ice dam.

Deep dive 3: Emergency siphoning, pumping, and draining bulging indoor drywall ceilings¶

What if the internal roof drain pipe is blocked deep inside the building core, rain is still falling, and water is rising on the roof?

1. Two Ways to Pump or Siphon Water Over the Parapet Wall Immediately¶

1. Method 1: Submersible Utility Pump on a Protective Rubber Pad (6,000 to 11,000 Liters / Hour):
2. Place a ¼-to-½-horsepower submersible utility transfer pump in the deepest accessible perimeter section of the ponded roof.
3. Mandatory Membrane Protection Rule: Never set a metal or hard-plastic pump directly onto a bare TPO、 PVC、または EPDM roof membrane. Motor vibration and suction can abrade or suck a hole through the 1.5-millimeter membrane. Always set the pump on top of a thick rubber welcome mat, folded heavy canvas tarp, or inside a smooth-bottomed plastic dishpan with holes drilled 2 centimeters up the sides.
4. Run a 19-millimeter (¾-inch) garden hose or 38-millimeter (1.5-inch) lay-flat discharge hose over the parapet wall down to the street gutter, and plug the pump into an indoor GFCI-protected receptacle.
5. Method 2: Zero-Electricity Multi-Hose Gravity Siphon (1,200 Liters / Hour per Hose):
6. If the power is out during a thunderstorm, gravity will drain a flat roof for free using ordinary garden hoses:
   • Coil a 15-meter (50-foot) garden hose flat underwater inside the roof pond for 2 minutes so 100 percent of the trapped air bubbles out and the hose is full of water.
   • Weight the intake end underwater inside a perforated bucket so it cannot suck air or leaves.
   • Press your thumb tightly over the outlet fitting to seal it, carry that sealed end over the parapet wall, and lower it 2 to 3 meters (6 to 10 feet) down the outside wall below the bottom of the roof pond. Release your thumb to start a continuous gravity siphon drawing 1,000 to 1,500 liters (260 to 400 gallons) per hour.

2. How to Safely Drain a Bulging "Water-Balloon" Drywall Ceiling Indoors¶

When a flat roof leaks into a room finished with gypsum drywall painted with latex paint, the flexible paint stretches downward into a blister holding 20 to 80 liters (5 to 20 gallons) of dirty water: 1. Shut Off the Room's Lighting and Receptacle Breakers First: Water pooling on ceiling drywall travels into 120V/240V ceiling junction boxes and light fixtures. Flip the circuit breakers for that room OFF at the main panel before entering. 2. Stand to the Side and Puncture the Center of the Bulge From a Distance: Center a 120-liter (32-gallon) trash barrel beneath the lowest point of the ceiling bulge. Never stand directly underneath a sagging wet drywall ceiling. Tape a Phillips screwdriver or awl to a 1.5-meter (5-foot) broomstick, stand to the side wearing safety glasses, and poke a single 6-millimeter (¼-inch) hole straight up through the bottom center of the paint blister so water streams into the barrel.

Regional emergency numbers and building code standards¶

よくある質問¶

How much does standing water on a flat roof actually weigh, and how deep can it get before the roof collapses?¶

Water weighs **1,000 kilograms per cubic meter (62.4 pounds per cubic foot)**. That means **every 25 millimeters (1 inch) of standing water adds 25.4 kilograms per square meter (5.2 pounds per square foot)** of dead weight across the roof. On a modest $10\times 10\text{ meter}$ ($1,076\text{ square foot}$) flat roof, just **15 centimeters (6 inches) of trapped water weighs 15.24 metric tons (33,600 pounds)**, which already **exceeds the entire 20-to-30-psf live-load structural limit** of most residential and light commercial flat roofs. If water reaches **20 to 30 centimeters (8 to 12 inches) deep** or combines with wet snow, catastrophic joist collapse can occur at any moment.

What is "Ponding Instability" and why does it make flat roofs collapse so suddenly?¶

**Ponding instability (progressive deflection amplification)** is a self-feeding structural trap on flat roofs: when a clogged drain traps a shallow 5-centimeter (2-inch) layer of water on a flat roof, the weight causes the flexible wood or steel joists in the center of the room span to **sag downward by 2 to 4 centimeters**, turning the center of the roof into a bowl. Because water is a liquid, water from the outer edges of the roof immediately flows inward to fill that deeper center bowl. That concentrated weight bends the center joists down *even further*, pulling in *even more* water until the center of the roof is holding a 30-centimeter-deep (12-inch) lake that snaps the joists in half.

What are the indoor warning signs that a flat roof is overloaded and about to collapse?¶

Watch and listen for five urgent warning signs inside the top floor of the building: (1) **Interior bedroom, office, or closet doors suddenly sticking, rubbing, or refusing to latch** (caused by bowing roof joists pushing down on interior partition walls and racking the door frames); (2) **visible downward bowing (`sagging > 20 mm / 3/4 inch`)** or cracking along ceiling drywall seams; (3) **sharp popping, creaking, or gunshot-like cracking noises** coming from the ceiling; (4) **rows of drywall nail/screw heads popping out**; and (5) **brown water pouring out of recessed ceiling lights**. If you see bowing joists, binding doors, or hear cracking, **evacuate the building immediately**.

Why should I NEVER unbolt or pull off the cast-iron strainer basket while deep water is standing over a clogged roof drain?¶

When a flat roof drain is submerged under 15 to 30 centimeters (6 to 12 inches) of murky water, leaves, sticks, plastic bags, and roof stones are floating right around the drain. If you reach into the water and pull the **cast-iron domed strainer cage** completely off the drain bowl, the sudden whirlpool vortex sucks all of that floating debris **straight down into the vertical drain pipe**, where it packs solid inside the first 90-degree elbow buried deep inside your building's walls or ceiling. Always leave the strainer dome bolted in place and use a **long-handled rake or broom** to pull leaves away from the outside of the dome.

How can I get standing water off a flat roof if the internal drain pipe is clogged deep inside the building?¶

If snaking the drain does not work immediately, remove the water weight **over the parapet wall** using one of two methods: (1) Place a **submersible utility pump** on top of a thick rubber welcome mat or folded towel (so the pump cannot rub a hole in the roof membrane) and pump the water through a garden hose over the parapet wall to the street; or (2) use a **Zero-Power Garden Hose Siphon** by submerging a 15-meter (50-foot) garden hose completely underwater in the roof pond until all air bubbles escape, sealing one end with your thumb, and dropping that end **2 to 4 meters (6 to 13 feet) down the outside of the parapet wall** below the roof level to start a continuous gravity siphon.

関連ガイド¶

• 大雪、アイスダム、屋根の崩壊
• Ceiling collapse, waterlogged drywall, and plaster sagging hazard
• Structural damage, bearing wall cracks, and building collapse
• Roof leak, attic water tracing, and emergency tarping
• Skylight hail shatter, chimney flashing blow-off, and emergency roof tarping

情報源と公式ガイダンス¶

• American Society of Civil Engineers (ASCE) & Structural Engineering Institute (SEI): ASCE/SEI 7-22 Minimum Design Loads and Associated Criteria for Buildings and Other Structures (Chapter 8: Rain Loads, Hydrostatic Head Calculations, and Section 8.4 Ponding Instability / Progressive Deflection Amplification).
• International Code Council (ICC): International Building Code (IBC Section 1502 Roof Drainage & Section 1611 Rain Loads) and International Plumbing Code (IPC Chapter 11: Mandatory Secondary Emergency Overflow Roof Drains and Scuppers Set 2 Inches Above Primary Drains).
• Federal Emergency Management Agency (FEMA, United States) & National Roofing Contractors Association (NRCA): Snow Load and Rain-on-Snow Safety Guidance for Low-Slope Roofs (FEMA P-957) and The NRCA Roofing Manual: Membrane Roof Systems (TPO/EPDM/PVC Drain Bowl Sump Details and Ice-Melt Compatibility).
• British Standards Institution (BSI): BS 6229:2018 (Flat roofs with continuously supported flexible waterproof coverings: Code of practice for minimum 1:80 finished falls and parapet overflow warning scuppers) and BS EN 12056-3.