Maintaining Structural Integrity

Structural Integrity

• Before we can understand how to maintain structural integrity, we need to understand how homes are built.

• There are several different methods of home building, including:– Concrete Block– Log Homes– Manufactured Homes– Mobile Homes– Stick and Frame

Concrete Block

• Homes made with concrete or cinder blocks can be very challenging from a wiring perspective.– These homes lack a ready method to run wire inside

the walls– If the interior is finished with drywall, typically, the

builder will have installed thin nailing boards to facilitate the installation of drywall.

– There is insufficient room inside the walls to install wiring

Concrete Block con’t.

– Additionally, if the wiring were to be installed inside the walls, the limited space would not provide sufficient protection from damage due to picture hanging etc.

– Typically, these homes will have the wiring installed inside metal conduit.

– Outlets can be installed in the flooring, overhead, or conduit left exposed.

Log Homes

• Log homes provide a whole new level of complication for the electrician.– Aesthetically, seeing wires or conduit is not

appealing.– Drilling through the wood beams is a laborious and

sometimes impossible challenge.– New construction methods are using more:

• Floor circuits• Stick and frame interior walls• Engineered materials that allow for plumbing and wiring

Manufactured Homes

• Manufactured homes are generally stick and frame construction, however, most of the components are built inside a manufacturing facility and then trucked to the job site where they are assembled.

• There are some advantages and disadvantages as well as a variety of ways of different manufacturers design and build their homes.

Manufactured Homes Con’t.

• Advantages:– Quality control: It is much easier to control the

shape and size of components in a factory setting.– It can be built much faster since each assembly is

built by several people and is done in a set fixture.– Employees are generally more comfortable as they

are not exposed to the elements.– On-site assembly is very fast.

Manufactured Homes con’t.

• Disadvantages:– The shape and design of the home is limited by the size

of the walls and floors that can be shipped over the roadways.

– They are generally less aesthetically pleasing.– They typically depreciate (lose value) over time where

homes built on site typically appreciate (gain value) over time.

– The quality of materials is generally lower (thinner walls, lighter materials etc.) as the manufacturer has to keep within weight limits for trucking.

Manufactured Homes con’t.

• Wiring a new manufactured home requires careful attention to detail to maintain structural integrity.– Walls are thinner so less and smaller holes can be

drilled for wiring.– Lighter fixtures maybe required (lighter ceiling

fans, no heavy/fancy dining room fixtures etc.)

Mobile Homes

• Mobile homes have some unique characteristics.– The walls are extremely thin– Adding additional circuits or rewiring is made

difficult to impossible due to the excessive damage that can be caused to the structural integrity of the home.

Stick and Frame

• Stick and frame homes are the most common type being built in the US today.

• Floor joists are typically either “2x10” (actual size is typically1.5” x 9.25”) or an engineered joist (looks like a wooden I beam) and set on 16” centers

• Walls are typically “2x4” (actual size is typically 1.5” x 3.5”) and set on 16” centers

• Ceilings and rafters range from “2x6” to “2x10” depending on span and anticipated loads.

Stick and Frame con’t.

• For our purposes, we will focus primarily on this style of home.

• When wiring a new home, or re-wiring an existing home, care must be given to ensure that the electrician does not damage the structural integrity of the home, and ensure that the wires are installed to provide years of service.

Stick and Frame con’t.

• There are two “types” of walls in a stick and frame home:– Load Bearing– Non-load Bearing

• Load Bearing walls are those that are crucial to the structural stability of the home. These include:– Most (if not all) exterior walls– Interior walls that support the 2nd floor or roof

structures

• Non-Load Bearing Walls:– These walls are not bearing any of the structural

load of the home.– These frequently include:• Interior walls that are not along the center of the home• Walls that simply divide up space for privacy reasons

Stick and Frame con’t.

• The easiest way to determine which walls are load bearing is to look at the structure above or below.– Look for beams– Look for where floor joists meet or overlap– Look at the roof rafters and the point where

several load bearing members come together

So, what do we do with all of this?

• When wiring a home, either new or a renovation, we need to be careful not to damage the structural integrity of the home.

• Drilling holes can damage the structure if:– There are too many holes– Holes are too large– Holes are in the wrong place

Holes

• Holes for wires (in load bearing walls) must not be closer than 1.0” from each side. A 2x4 is only 3.5” wide, so:– Holes must be centered in the wood– Hole size must not be more than .5”– If more holes are required, the holes can be:• Drilled above and below• Ovals are also allowed

Running Wire Through Studs

Correct Correct Incorrect

Incorrect Correct

Wiring Through Walls

Wiring Through Attic

Wiring Through Basement