2.3 General Regulations: Materials, Protection, Support, Trenching & Structural Safety
Key Takeaways
Piping other than cast iron or galvanized steel that passes through framing less than 1-1/4 inches from the nearest edge must be protected by a steel shield plate at least 0.0575 inch thick (No. 16 gage) (IPC 305.6).
A pipe passing through a foundation wall needs a relieving arch, or a sleeve two pipe sizes larger than the pipe (IPC 305.3).
Exterior water supply piping must be at least 6 inches below the frost line and at least 12 inches below grade (IPC 305.4).
Table 308.5 hanger spacing examples: PVC and ABS 4 feet horizontal; cast iron 5 feet (10 feet with 10-foot lengths); copper tubing 1-1/4 inch and smaller 6 feet; PEX 1 inch and smaller 32 inches.
Where rock is found in a trench, remove it to at least 3 inches below the pipe and backfill with tamped sand (IPC 306.2.2); backfill in 6-inch layers until there are 12 inches of tamped earth over the crown (306.3).
What "General Regulations" covers
Outline area L (5 items) draws on IPC Chapter 3 together with the administrative rules covered in Section 2.2. Chapter 3 rules apply to every system, whether drainage, water or storm, so questions can combine them with other chapters.
Prohibited wastes and materials (IPC 302 and 303)
- 302.1: ashes, cinders or rags; flammable, poisonous or explosive liquids or gases; and oil, grease or other insoluble material that could obstruct, damage or overload the drainage or sewer system or interfere with sewage treatment must not be deposited into these systems.
- 302.2: industrial wastes may not enter the public sewer until the code official or other authority determines they will not damage the system or the treatment plant.
- 303.1: every length of pipe and every fitting, trap, fixture and device must bear the manufacturer's identification and the markings required by its standard.
- 303.2: materials are installed according to their standards or, if there are none, the manufacturer's instructions. When those instructions fall below the code's minimum, the code governs.
- 303.3 and 303.4: plastic pipe, fittings and components must be third-party certified to NSF 14, and products required to meet a standard must be listed by a third-party certification agency.
- 303.5: cast-iron soil pipe, fittings and couplings must be third-party listed and labeled.
Rodentproofing (IPC 304)
- Strainer plates on drain inlets: openings not greater than 1/2 inch in least dimension (304.2).
- Meter boxes must keep rodents from entering by way of the water service pipe (304.3).
- The annular space around pipes passing through walls, floors or ceilings must be sealed with caulking or closed with a compatible gasketing system (304.4).
Protection of pipes (IPC 305)
| Section | Rule |
|---|---|
| 305.1 Contact | Metallic piping, except cast iron, ductile iron and galvanized steel, must not be in direct contact with steel framing, concrete, cinder or masonry walls and floors, or corrosive soil. Plastic sheathing used to separate them must be at least 0.008 inch (8 mil) thick and must let the pipe move where it passes through concrete or masonry. |
| 305.2 Stress and strain | Install piping to prevent stresses that exceed the pipe's strength, and provide for expansion, contraction and structural settlement. |
| 305.3 Foundation walls | A pipe through a foundation wall needs a relieving arch, or a sleeve two pipe sizes larger than the pipe built into the wall. |
| 305.4 Freezing | Water, soil and waste pipes must not be installed outside a building, in attics or crawl spaces, in outside walls, or anywhere subject to freezing unless protected by insulation, heat or both. Exterior water supply piping must be at least 6 inches below the frost line and at least 12 inches below grade. |
| 305.4.1 Sewer depth | The 2021 IPC leaves the building sewer depth as a blank for the adopting jurisdiction. Virginia's amendments do not fill it in, so the local building official sets the requirement. |
| 305.5 Waterproofing | Roof joints around vent pipes must be made watertight with lead, copper, galvanized steel, aluminum, plastic or other approved flashing, and exterior wall openings must be watertight. |
| 305.6 Physical damage | In concealed locations, piping other than cast iron or galvanized steel passing through holes or notches in studs, joists, rafters or similar members less than 1-1/4 inches from the nearest edge must be protected by steel shield plates at least 0.0575 inch (No. 16 gage) thick. The plates cover the area of the pipe where the member is notched or bored and extend at least 2 inches above sole plates and below top plates. |
| 305.7 Components | Components installed along alleyways, driveways, parking garages or other locations exposed to damage must be recessed into the wall or otherwise protected in an approved manner. |
Frost depth is a local design value. Use the frost line set by the local building department; Chapter 3 does not set a statewide number.
Joints between dissimilar metals are covered in Chapter 6, not Chapter 3. Under 605.23.1, copper tubing joins galvanized steel pipe through a copper-alloy fitting, dielectric fitting or ASSE 1079 dielectric union. Under 308.3, hangers must be made of material that will not promote galvanic action.
Trenching, excavation and backfill (IPC 306)
- 306.1: buried piping must be supported throughout its entire length.
- 306.2: where the trench bottom is the pipe bed, provide solid, continuous support between joints with bell holes, hub holes and coupling holes. Pipe must not be supported on blocks to grade. If the manufacturer's instructions are stricter, follow them.
- 306.2.1 Overexcavation: backfill to the pipe's installation level with sand or fine gravel in layers not greater than 6 inches, compacting each layer.
- 306.2.2 Rock removal: remove rock to not less than 3 inches below the bottom of the pipe and backfill with tamped sand. The pipe and joints must not rest on rock at any point.
- 306.2.3 Soft soil: overexcavate at least two pipe diameters and backfill with fine gravel, crushed stone or a concrete foundation bedded in tamped sand.
- 306.3 Backfilling: backfill must be free of debris. Place loose earth free of rocks, broken concrete and frozen chunks in 6-inch layers, tamped, until the pipe crown is covered by 12 inches of tamped earth. Bring the backfill up evenly on both sides.
- 307.5 Footings: trenches parallel to footings must not extend into the bearing plane, which is a line extending down at 45 degrees from the outside bottom edge of the footing or wall.
Structural safety (IPC 307) and framing limits
IPC 307.2 states that framing members shall not be cut, notched or bored beyond the limits in the International Building Code. 307.4 prohibits cutting or altering truss members without written approval from a registered design professional. The common conventional-framing limits from the IBC and IRC are:
| Member | Limit |
|---|---|
| Joist notch | No more than 1/6 of the depth, no longer than 1/3 of the depth, and not in the middle third of the span; end notches no more than 1/4 of the depth |
| Joist hole | No more than 1/3 of the depth, and not within 2 inches of the top or bottom edge or of another hole or notch |
| Bearing stud | Notch up to 25% of the width; hole up to 40% of the width, or 60% when the stud is doubled and no more than two successive doubled studs are bored; hole edge at least 5/8 inch from the stud edge |
| Non-bearing stud | Notch up to 40%; hole up to 60% |
| Top plate cut more than 50% of its width | Galvanized metal tie at least 0.054 inch thick and 1-1/2 inches wide, fastened with eight 10d nails on each side and extending at least 6 inches past the opening |
Pipe support (IPC 308)
Hangers and supports must carry the pipe and its contents, be attached to the structure in an approved way, and not promote galvanic action (308.3 and 308.4). Table 308.5 maximum spacing (horizontal / vertical, in feet):
| Material | Horizontal | Vertical |
|---|---|---|
| ABS and PVC pipe | 4 | 10 |
| Cast-iron pipe | 5 (10 where 10-foot lengths are installed) | 15 |
| Copper or copper-alloy pipe | 12 | 10 |
| Copper tubing 1-1/4 inch and smaller | 6 | 10 |
| Copper tubing 1-1/2 inch and larger | 10 | 10 |
| CPVC 1 inch and smaller / 1-1/4 inch and larger | 3 / 4 | 10 |
| PEX, PE-RT and PP 1 inch and smaller | 2.67 (32 inches) | 10 |
| PEX, PE-RT and PP 1-1/4 inch and larger | 4 | 10 |
| Steel pipe | 12 | 15 |
| Lead pipe | Continuous | 4 |
For the materials marked with footnote b in the table (the plastics and stainless steel drainage systems), sizes 2 inches and smaller need a guide midway between the required vertical supports. Under 308.6, horizontal drainage pipe 4 inches and larger that changes direction by more than 45 degrees needs rigid bracing against movement of the upstream pipe. Under 308.7.1, pipe larger than 4 inches needs restraint at every change of direction and at changes in diameter greater than two pipe sizes. Under 308.10, a thermal expansion tank must be supported according to the manufacturer's instructions and not by its connecting piping.
Other Chapter 3 items
- 309: in flood hazard areas, water service pipes, drainage piping, water heaters and vents follow IBC Section 1612.
- 310: washroom light and ventilation follow the IBC and IMC; fixture locations and compartments follow 405.3.
- Section 311 (toilet facilities for workers) is deleted in Virginia.
- 315.1: the annular space around a pipe in a sleeve, or a pipe through the building envelope, must be sealed with caulking, foam sealant or gaskets compatible with the materials. Fire-rated penetrations follow the IBC.
- 316: alternative engineered designs require submittal and approval.
Under IPC 305.6, which installation requires a steel shield plate?
A 3/4-inch PEX line bored through a wall stud 3/4 inch from its face, before drywall
A 2-inch PVC drain bored through the center of a 2x10 joist, 4 inches from each edge
A 4-inch cast-iron stack notched into a stud 1 inch from the face
A copper line running exposed in an unfinished basement
Under IPC Table 308.5, what is the maximum horizontal hanger spacing for 1-inch PEX tubing?
10 feet
6 feet
4 feet
32 inches
A building sewer trench hits ledge rock at the planned pipe invert. What does IPC 306.2.2 require?
Lay the pipe directly on the rock if every joint is a mechanical coupling
Remove rock to 3 inches below the pipe and backfill with tamped sand
Support the pipe on concrete blocks at each joint, then backfill around them
Overexcavate 12 inches and backfill with crushed stone up to the pipe invert
Sections you finish are checked off in the contents.