The estimation of a residential project should never be taken casually because they can be just as complex and design-intensive as any commercial one. So don’t just assume you are simply taking off another “rope job.”

Today’s more modern residential jobs contain a whole new era of electrical devices, equipment and supporting materials. Higher end smart homes contain all sorts of special low-voltage control systems. They have really fancy lighting fixtures (did you carry enough labor?), niche lighting with remote ballasts, motion sensors, daylight controls, dimming systems and power outlets all over the place. And let’s not forget about the home theaters, which themselves can easily be a separate project.

Then there is all the equipment, which may or may not be just a single heating, ventilating and air conditioning unit; a water heater; and a garbage disposal. There may be multiple heating units, remote flash water heaters, more than one garbage disposal, pool and spa connections (don’t forget about the sauna), and two or three garage door lifters. Remember also the refrigerator, the freezer, the washer or the dryer.

There also are things on the outside of the house to consider, such as an electric ignition for the patio barbecue and fire pit, maybe a few pumps for the water features and possibly a connection to a solar panel array, which also has associated distribution equipment. And speaking of the great outdoors, landscape lighting can come with its own set of expensive materials and labor-intensive installations. Don’t forget to review the landscape drawings for these.

More power!

All of these fancy things require a lot of power, which is no longer a single 150-amp (A) residential combo-meter panel. Larger residences can have complete power distribution centers with 800A switchboards, multiple panels, a generator and an auto-transfer switch. Some even are powered with 480-volt (V) main services and have transformers stepping-down to the 120V systems.

Just like on a commercial project, it will be critical to labor these equipment items properly and carry enough support materials. Complex distribution systems can easily accumulate to hundreds of hours in labor and thousands of dollars in support materials.

How will they be run? What type of wire is allowed? Is conduit required? If not, do you really have a free and unfettered pathway from one end of the house to the other? How will you know for sure?

You should never assume that just because you are working within a house you can run all the wiring through the attic space or below the floor. You need to thoroughly review the architectural and structural drawings to learn all you can about your chosen pathways, wall types, barriers and access points.

Romex, MC or pipe?

One of the most costly assumptions an estimator can make on a residential project is that all the wiring can be done using Romex. While it is very likely Romex can be used, it may not be allowed or even applicable to many areas of the house, especially in a custom home or large mansion where walls and ceilings can often be glass, rock, decorative wood beams or other highly decorative surfaces.

I once estimated a project involving a 35,000-square-foot residence. It was like estimating an art museum. Many of the walls were constructed with rammed earth, which is a very expensive process using a special sand and concrete solution. When finished, the walls look like the natural rock formations in Utah’s Bryce Canyon.

As we got deeper into the project, we learned that conduit and wiring was not allowed to be installed in, through or even under the rammed-earth walls. It had to be routed around them. Many of our circuit and home-run routings were four times longer than they would have been in a normal house. More importantly, we couldn’t use Romex or MC cable, and every run was either in exposed EMT or PVC in a trench routed around the slab.

This simple realization saved us from making a huge mistake, one that affected both materials and labor costs.

But wait, there’s more

Adding to all of the electrical systems are the low-voltage systems: fire alarm, security, sound systems, telephone and data, and cable TV, which is probably the most important one.

All of these systems require outlet boxes and other rough-in materials. Is the electrical contractor responsible for this? What part? Rough-in only or do you install the cable, too? What about the equipment and devices? Will you install any of these, or will you get a “turn-key” quotation from a systems sub?

Just like on a commercial project, knowing your complete scope of work can mean the difference of winning a job with an accurate low bid or winning one with a losing number.

Next month, I will discuss specific materials used for residential projects and how they can vary greatly in both materials and labor. So stay tuned!

SHOOK is the president and chief estimator for his estimating company, TakeOff 16 Inc. He has worked in the electrical construction industry for more than 23 years. Reach him at 707.776.0800 and sfs@TakeOff16.com.