In my last post I noted that customers often give too little attention to the drawings of their site-built structures. This is particularly true of the basement layout drawings required for homes with a full or partial basement that contains some of the mechanical systems.
Basement Layout Drawings
When planning the layout of your basement, you and your GC will need to factor in basement stairs, chimneys, site conditions, garages, mudrooms, and other site-built structures, since each of these can affect the basement layout. For example, if the basement stairs come down on the right side of the home, then the two-car drive-under garage will probably need to come on the left. This means that the masonry chimney should go on the right, except the fireplace is in the family room, which is on the left. These kinds of conflicts happen all of the time, which is another reason why an experienced GC can be of enormous help.
Developing a basement layout plan is even more critical and difficult when you intend to finish the basement, or at least to use it in some fashion. You do not want a plumbing waste line hanging from the ceiling in your basement family room, or a water heater where you want to place a big screen TV. If you plan on finishing the basement, tell the GC, and then verify that his basement layout plans are compatible with yours. Here are some of the complications.
Basement Layout of Plumbing Pipes
Typically, the hot- and cold-water supply pipes will run across the basement ceiling and along the walls. The plumbing drain and waste pipes will slope down along the ceiling and walls to allow for gravity discharge to the septic or sewer system. With standard dimensional floor joists, all of these plumbing pipes, especially the waste pipes, will reduce the headroom in some places. If your home is built with floor trusses, the supply lines can be run through the webs of the trusses. The location of these pipes may affect where you can locate basement windows and doors. If you want windows or doors in a particular place, ask the GC to locate the plumbing pipes elsewhere. Expect to pay more for this new location, should it require more materials or labor than were included in the original estimate.
Basement Layout of Heating and Cooling Ducts
When a home is built with standard floor joists, the heating and air-conditioning ducts will have a major impact on basement layout headroom. The first-floor ducts will be mounted to the basement ceiling directly below the floor joists, reducing headroom by as much as a foot or even more. They will include a large main trunk down the middle and several smaller trunks branching off to the side. They will also affect the location of basement windows and doors. If you must locate the basement windows or doors in a particular place, the GC will need to move the ducts away from this area. If this relocation requires more materials or labor than allowed for in the GC’s estimate, it will also add to the cost. If the modular manufacturer can build your home with floor trusses, you may be able to minimize this problem.
Basement Layout of Heating Vent System
Similar issues apply to the venting of the heating system, whether it is done with a power vent, direct vent, or flue. The location of the venting system is determined in part by the location of the heating system, since they must be relatively close to each other. The venting system, in turn, significantly impacts the location of the basement windows and doors, house windows and doors, decks, porches, and bulkheads, since the building code prevents these from being too close to the exhaust. Choosing to place the heating system and flue in a particular location will affect many other decisions inside and outside the home. Conversely, choosing to locate the basement and house windows and doors, the deck and the porch in particular places will affect where you can put the heating system and flue. This is one reason why you should not finalize your modular home plans until you have also finalized your GC plans, including your basement layout.
Basement Layout Assumptions
One last consideration that often distresses customers. When a GC prepares an estimated price before you have complete plans or a detailed set of specifications, he will often assume the most direct, economical routing of all plumbing pipes and heating and air-conditioning ducts in the basement. These assumptions may not be best for you. But if you want him to relocate things, you should expect to pay more for the longer, less direct routing, since it will require more materials and labor. This is why it is such an advantage to complete all of your plans and specifications, including your basement layout, before you asked for GC bids, although this usually does not happen unless you work with an architect or home designer.
For more information about your construction drawings for site-built structures, see Designing a Modular Home, Selecting a General Contractor, and The General Contractor’s Responsibilities for Building a Modular Home in my book The Modular Home.