A trade is not an island, meaning that, in the piping trades, our own work can impact the installation work of other trades. At the construction phase, we as plumbers, pipefitters and gasfitters must consider the needs and installation nuances of electricians, sheet metal workers, roofers, carpenters, and any other trades in completing our work. This consideration applies to both residential wood frame and commercial concrete construction. This learning task will be split into those two arenas.

Residential Wood Frame Construction

In general, residential wood frame construction is sequenced in this order:

• Site excavation
• Footing/foundation concrete installation, possibly slab-on-grade or basement concrete floor at the time
• Framing to “lockup” stage (roofing on, doors and windows installed and lockable)
• Rough-in sheet metal work/venting for furnace or heat pump, if used
• Rough-in plumbing
• Electrical rough-in
• Insulation and vapor barrier (after all inspections of the above are completed)
• Drywall and taping/mudding
• Interior painting
• Cabinets and millwork installation
• Flooring and casing/trim installation

The house is now ready for the fixtures, both electrical and plumbing, to be installed and commissioned. Final inspections can be scheduled, and cleanup by all trades is an expectation of a finished product. Siding or exterior finish such as stucco, Hardie® plank, or other can occur at any time after the lockup stage, as well as can exterior concrete sidewalks/driveways, and any landscaping work.

Exterior Conflicts

Penetrations of the building envelope must conform to the Building Code, in that they must be sealed against heat loss/gain, vapor migration, and the elements (rain, snow, etc.). Structure penetrations are discussed in Level 1 Piping Trades Learning Guides.

The two areas of most concern for plumbers are pipes penetrating the roof and the exterior walls. To ensure a proper and warranted seal, any roof penetrations for plumbing vents, Radon gas vents, bathroom exhaust fans (if in the plumbing contract), or vents and combustion air pipes from furnaces must be located and cut out by the plumber before the roofing medium is installed. The appropriate flashings or termination fitting(s) are then handed over to the roofing contractor for them to install. If a plumber installs these pipes or vents by cutting the installed roofing material themselves, they are generally held responsible for any damages and remediation caused by leakage. If neoprene vent flashings are used and the roofing is to be placed prior to the rough-in piping installed, they should have a piece of the appropriate pipe pushed through them that will extend into the attic space where they can be connected to during the piping rough-in stage. Otherwise, any pipe projections through the roof should have a flashing over them that is acceptable to applicable codes (building and plumbing) as well as to the roofing contractor for the type of roofing material used.

Exterior hose bibbs, horizontal gas/combustion air pipes from furnaces, and gas piping to barbeques and meters are example of horizontal wall penetrations needing coordination between trades. There are boxes and termination fittings available for most of the above that suit various types of wall finishes. These should be considered as they are both functional and aesthetically acceptable. The most common problem/complaint, with possibly the most serious outcomes, is with frost-proof hose bibbs and horizontal wood or Hardie® plank siding. To be truly as frost-proof as possible, hose bibbs should be installed with a slight downward grade to the exterior so that the barrel drains after it is shut off. If there isn’t a box accompanying the hose bibb and the wall penetration conflicts with the lower edge of the siding plank, a not-so-professional siding installer will likely either push the hose bibb upward or downward to suit, which may negate the self-draining feature of the bibb or even damage it. If the siding can be installed before the interior walls of the building are covered by drywall, the vertical position of the bibb can be adjusted by the plumber. If not, the siding installer should be consulted and an acceptable solution for both parties can be arrived at. The same considerations apply to penetration of gas lines and piping from furnaces and air conditioning equipment. If available, manufactured termination fittings should always be used where possible.

Interior Conflicts

Time is money, it is often said, and many contractors translate that into getting into the house first so that there are fewer impediments, caused by other trades, to slow them down. This does not bode well for sheet metal contractors when plumbers and electricians “jump the gun” and create problems by roughing in without consulting them. Sheet metal components are large and inflexible and can be difficult to locate in relation to the building structure. Therefore, sheet metal ducting should be considered the “first in” of the subtrades. Improperly located plumbing pipes and electrical wires can easily confound a sheet metal job, and the inevitable solution is to rip out the pipes and wires, causing much angst between the subtrades. The best solution is to pre-establish all the duct placement and run piping and wiring accordingly.

The next subtrade work should be that of the plumbing contractor. Plumbing drainage and venting piping must be installed with proper slope and can be as large as 4-inch diameter in a house, so although not as difficult to conform to the building layout as the sheet metal, it is less forgiving than electrical wiring or water lines. Close coordination between the plumbing and sheet metal contractors ensures that ductwork and drainage/venting piping can coexist and be functional.

Potable water lines and electrical wiring are on par with each other as far as being able to be most easily adapted to structural issues, and these installations should be the last in line. Holes for PeX tubing and electrical cables can be drilled through wood frame members to conceal the pipes/wires while deterring any penetrations by drywall screws and the like (remember to consult the applicable literature for drilling or notching engineered floor trusses). Whenever there may be conflict between trades as to positioning of components, the best solution is collaboration.

Another area where a plumber’s work needs to be coordinated with others is in the placement of drainage pipes and vents in a bathroom. There should be unobstructed access to the space between floor joints directly below the bottom plate of the plumbing wall of a bathroom. This is especially critical where engineered floor trusses are used, as the top and bottom chords of the truss cannot be cut or notched at all. To do so requires much remedial work by a carpenter to make them structurally acceptable. During the framing stage, when floor joists are being placed, the plumber should consult with the carpenter to avoid conflict in this area as well as the areas where the toilet and bathtub or shower drains are projected to be. This may involve adding or moving joists at the framing stage but is usually easier and less expensive to accomplish than having to remedy the situation once the initial framing has been done.

Bathroom vanity cabinets can be a problem area for a plumber if an owner changes the cabinet drawer location between rough-in and finishing stages without notifying the plumber. Plumbing lines exiting the wall at revised drawer locations must be relocated and, if the cabinet is already in place, this will be quite a difficult job, usually resulting in extra charges to the owner. This type of faux pas normally falls on the shoulders of the owner, especially if the fixture has been roughed-in according to the drawings at the time. Early correspondence with the plumber can usually keep extra costs and angst to a minimum, and a good idea from the plumber’s standpoint is to have the general contractor or owner verify at the end of the rough-in stage that the plumber’s work has been done correctly and that any changes thereafter are chargeable.

Normally, the continuous vent from a bathroom group will be directly behind the lavatory location, which can conflict with both recessed medicine cabinets as well as electrical boxes for a light placed on the wall above the vanity. A good idea for plumbers is to double check the plans for any sign of a recessed medicine cabinet, and to check with the electrician regarding the position of any boxes in that area.

Still within the bathroom, the cold-water supply (“stubout”) to a toilet can be problematic for two reasons, the first being the height of the baseboard trim. Normal rough-in dimensions for water closet supplies are 6 inches to the left of the toilet’s centreline and 6 inches above the finished floor. If a wide baseboard is being used, the water line and its escutcheon may end up straddling the edge of the trim, which is unacceptable. Either raise the stubout so that the edge of the escutcheon is above the trim or centre the stubout in the trim so that the escutcheon is flat against it. The second reason lies with the use of one-piece toilets. Their water supply connections are typically very low to the floor and some manufacturers specify a ½-inch OD supply line size which may require a specifically placed wingback connection within the wall. Owners must inform the plumbing contractor of any changes to the intended type of toilet to help mitigate these situations.

Any horizontal dry vent must be above the flood level rim of the highest fixture it serves, and if it is installed in holes that are drilled through a stud wall, it can be subject to possible penetration by drywall nails or screws if located at increments of 16 inches above the floor. These are the typical fastener locations for drywall installation. A good elevation for horizontal pipes of any kind, installed through studs, is midway between those increments, so 40 inches above the floor is a standard height for horizontal vents. As well, striker plates should be used to protect any piping that is within 1 ¼” (32mm) of the face of the stud. If the 40-inch height is chosen, and striker plates are installed, drywallers are less likely to pull the plates off the wall as they aren’t likely to interfere with their screws or nails.

The intended floor coverings in bathrooms can be an issue if not relayed to a plumber before rough-in starts. A correctly installed toilet floor flange will have its underside flush with the finished floor so that the top of the flange is above the bottom of the horn of the bowl. For instance, if a 3/8” (9.5mm) subfloor is to be placed onto the 5/8” (16mm) tongue-and-groove plywood so that sheet vinyl can be installed, the plumber should cut a ring of 3/8” wood material, matching the flange’s outside and inside diameters, and set the floor flange on it, screwing both to the 5/8” flooring using brass wood screws. The thickness of the finished sheet vinyl won’t appreciably affect the flange’s finished height and a single wax or foam gasket will seal the bowl to the flange adequately. When owners or general contractors change floor covering choice after rough-in has been done, it is sometimes difficult to achieve a leak-tight seal if the flange is set too low, or to have enough sealing material between the flange and the bowl if set too high. Again, choices of flooring material must be indicated and adhered to if any guarantees of a professional leak tight system are expected.

Concrete Construction

Commercial buildings are more likely to be of concrete construction than of wood. This means that block outs, sometimes known as “cans” for any holes or penetrations through floors and walls must be identified, located, and placed before the concrete is poured. To not do so may be very costly if a hole must be created by jackhammering or coring through concrete that has set.

Concrete construction has “pour” intervals which are:

• Footings and foundations,
• Floors and slabs, and
• Walls and columns

Reinforcing steel rods, known as “rebar”, are placed within all the above to ensure the integrity of the concrete, and these must be positioned to allow block outs to be placed in walls and floors that will create the required opening for pipes and other mechanical components. Also, there may be cables embedded in floors that help support the concrete floor area between the columns and walls. These are called “post-tensioned cables” due to their being mechanically stretched once the concrete surrounding them has set sufficiently. Any cans for pipe penetrations, as well as any cast-in-place inserts for threaded rod supports, should be located prior to the installation of rebar and cables, however, this is easier said than done. This is because the measurements needed to ensure correct “can” placement usually can’t be made until the formwork is in its final position, or “buttoned up” as it is called, and a few reference grid lines for measurement purposes have been set by surveyors. The same is not true for the installation of rebar, as its placement doesn’t normally require the same level of accuracy. Therefore, quite often, the rebar installers start their work before the other trades have a chance to make measurements and snap chalk lines for reference without the rebar being in their way. This has always been a cause of much anxiety and often aggressive confrontations between the affected trades and is due mainly to the practice of scheduling concrete pour dates that are unalterable. This means that all trades must get their work done before the pour happens. If rebar or cable placement conflicts with a “can” location, the rebar or cable must be moved, which may mean that the rebar contractor must circle back to remedy the situation. If a hole through a post-tensioned concrete floor is missed, it cannot be simply cored with a coring machine. To even nick the cable, which normally has around 50000 pounds of tension on it after being stretched, could be disastrous and life threatening to anyone in the vicinity. The floor must be x-rayed after normal working hours to find a space where the hole can be created, which may result in re-configuring the architectural layout in that area, incurring an extra charge to the plumbing contractor. Also, there may be electrical conduits embedded in the concrete that must be avoided. Missing a canned hole can be very costly. Therefore, a good working relationship between the general contractor, reinforcing contractor and the subtrades is paramount to ensuring a more stress-free working environment.

Once the concrete structure has been built, the same considerations exist as far as conflicts between the subtrades responsible for the finished interior and exterior of the building, as would occur in wood frame construction. Good plan checking and coordination between trades will ensure a smoother path to the finished product.