If demolition were an operation on your body, consider dealing with the mechanicals pre- and post-operative procedures. The first thing to know about mechanicals is what they are: plumbing (including supply lines, vent pipes and waste stacks), electrical and low/no-voltage wire, and HVAC (ducting and chases). Pre-Op
Cable and Phone. The easiest mechanicals to deal with are the obvious low-voltage stuff, such as phone lines, and no voltage, such as cable. They are often surface-mounted and can be moved and/or spliced easily. If you need to splice phone line, say to lengthen or otherwise move the line, you can bury the splice in the wall or ceiling. Or you can come out of the existing jack with a new line. It's worth pointing out, however, that a splice — even a good one — is the weakest link in the system. If you can retain access to the splice, should something go wrong later, you won't have to dismantle portions of a wall to locate it. Whenever possible, move these wires before you start big deal demo — pre-op.
Triage. For the heavier-duty stuff, the best thing you can do for yourself — before you tear up anything — is locate any mechanicals and decide what to do about them in advance. To explain this (and because every situation is different) I'll make up an example:
Say you want to take down a kitchen wall to expand the space. Grab a flashlight and tape measure and start triage on your house. Measure the location of the wall from the outside walls. Then head to the basement and (assuming you have visual access to the floor system above you) locate where your to-be-demoed wall is, again by measuring. If there are mechanicals in there, such as a waste stack or HVAC supply, you're quite likely to see them enter the wall through the bottom of the floor. It's kind of like taking an x-ray. Using a flashlight helps here.
This x-ray is crucial because A) it can tell you what's in there, and B) if you find several services in there, you'll have a very good look at the scope of the surgery you plan to perform — and may decide performing it isn't worth it to the patient or budget.
Also head upstairs. Look in the rooms above the room to-to-be-demoed for HVAC vents in the floors, walls and ceilings. If there is a bathroom above the wall-to-be demoed, you can be nearly certain there are supply, drain and vent lines running in the interior wall.
Use all this pre-op triage to make a decision about what your next steps will be.
Under the knife
The good news is that you can move mechanicals — where there's a will and a good sub-contractor, there's a way. But the moves must be planned. So say you decide to open up that wall after all and find it loaded with stuff. Here are some rules of thumb on what to do:
