Building & Electrical Techniques

Building & Electrical Techniques

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Building & Electrical Techniques - 1

_____________________________________________________________________________ Updated 11/13/2018 -- Copyright © Insurance Schools, Inc.

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Building & Electrical Techniques __________________________________________________________________________________________________________

The Contractor

This section of the course covers the basics of building, construction, and electrical techniques

and consists mainly of definitions and calculations. When rebuilding or repairing a structure, a

contractor must be hired. The various types of contractors include:

A “contractor” is a company licensed to perform certain types of construction activities. In

most states, the general contractor's license and some specialty contractor's licenses don't

require of compliance with bonding, workers’ compensation and similar regulations. Some of

the specialty contractor licenses involve extensive training, testing and/or insurance

requirements.

A “general contractor” enters into a contract with the owner of a construction project and

takes full responsibility for its completion. Most general contractors are not licensed to

perform all parts of a construction project therefore, the general contractor may enter into

subcontracts with “specialty contractors” for the performance of specific parts or phases of the project such as the electrical or plumbing work.

A “subcontractor” is a general or specialty contractor who works for another general

contractor and a “remodeling contractor” is a general contractor who specializes in

remodeling work.

Concrete

Concrete is used as the foundation for most structures. The “foundation” is the supporting

structure below the first-floor construction, below grade (the ground) and includes the

“footers”. A “footer” or “footing” is a continuous 8" or 10" thick concrete pad installed

before construction begins and supports the foundation wall or monopost.

The concrete poured for a foundation is very important to the strength of the structure,

therefore, ribbed steel bars known as “rebar” or “reinforcing bar” are placed in the

concrete before it hardens. Rebar is installed in foundation concrete, walls, footers, and in any

area where concrete should be strengthened and comes in various thicknesses and strength

grades. “Foundation ties” are metal wires that hold the foundation wall panels and rebar in

place during the concrete pour.

Concrete is a fire-resistive material. Prolonged exposure to extreme heat causes concrete to

lose its moisture. The surface then flakes off in thin pieces. This condition is called “spalling”.


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Spalling also results from repeated heating and cooling during firefighting activities. Concrete

can shrink as a result of fire, and other shrinkage causes cracks to form.

Fire-damaged concrete can be repaired by cutting out the damaged area and replacing it. The

areas between the old and new sections can be connected by a “control joint”. This is a

tooled, straight groove made on concrete to "control" where the concrete should crack.

Areas of concrete that have spalling, can be scraped and resurfaced with a special overlay

such as stone. (Re-pouring new concrete over the old damaged concrete, will result in cracks

when the new concrete bonds to the old.) Stained and smoked-damaged concrete can be

cleaned with steam, sand, or chemicals. The concrete surface can also be painted or

stained to cover the discoloration from the fire.

Concrete comes in two forms - (1) ready mix and (2) mixed on the site. Ready mix is

delivered by large mixer trucks and poured into waiting forms. Concrete mixed on site is

prepared by stand-alone mixers and requires additional labor to mix it and haul it to the forms.

Concrete also comes in various formulas to suit different purposes, although the essential

ingredients are always cement, sand and stone. There are concrete mixes for heavy-use

locations, such as driveways and garage floors. There are also watertight mixes for foundations

and pools. The cost varies depending on the mix.

How to Calculate Concrete

Concrete is estimated by volume and its unit of measurement is cubic yards. There are 27

cubic feet in a cubic yard. To determine the amount of concrete you will need in cubic yards,

you will first need to convert all three dimensions to the same unit of measurement.

For example: A contractor would like to calculate the amount of concrete needed to pour a

slab that is 6 inches thick by 12 feet long by 12 feet wide. The steps to calculate this are:

Step 1. Convert the dimension in inches to feet.

6 inches ÷ by 12 inches = 0.5 feet

Step 2. Multiply the three dimensions together to find the number of cubic feet.

0.5 feet x 12 feet x 12 feet = 72 cubic feet

Step 3. Divide the cubic feet by the number of cubic feet in a cubic yard to find the number of

cubic yards.

72 ÷ 27 = 2.67 cubic yards.


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Framing the Structure

The type of construction in which the structural components are wood or depend upon a

wood frame for support is known as “frame construction”. A “framer” is the “carpenter

contractor” that installs the lumber and erects the frame, flooring system, interior walls,

backing, trusses, rafters, decking, installs all beams, stairs, soffits and all work related to the

wood structure of the home. The framer builds the structure according to the blueprints and

must comply with local building codes and regulations.

Lumber that is used for the structural members of a building, such as studs, joists, and rafters, is

known as “framing”. Lumber can be treated with fire retardant or chemical pesticides to

preserve it from burning, wood rot, or insects.

Methods of Framing

There are several different methods and materials used to frame a structure that you should be

familiar with for your state exam.

Stick built - A house built without prefabricated parts. Also called conventional building.

Post - A vertical framing member usually designed to carry a beam. Often a 4" x 4", a 6" x 6",

or a metal pipe with a flat plate on top and bottom.

Post-and-beam - A basic building method that uses just a few hefty posts and beams to

support an entire structure. Contrasts with stud framing.

Stud - A vertical wood framing member, also referred to as a wall stud, attached to the

horizontal sole plate below and the top plate above. Normally 2 X 4's or 2 X 6's, 8' long

(sometimes 92 5/8"). One of a series of wood or metal vertical structural members placed as

supporting elements in walls and partitions.

Plate - Normally a 2 X 4 or 2 X 6 that lays horizontally within a framed structure, such as -

• Sill plate - A horizontal member anchored to a concrete or masonry wall.

• Sole plate - Bottom horizontal member of a frame wall.

• Top plate - Top horizontal member of a frame wall supporting ceiling joists, rafters,

or other members.

Stud framing - A building method that distributes structural loads to each of a series of

relatively lightweight studs. Contrasts with post-and-beam.

Stud shoe - A metal, structural bracket that reinforces a vertical stud. Used on an outside

bearing wall where holes are drilled to accommodate a plumbing waste line.


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Beams and Joists

“Beams” support the weight of the structure and are made of either metal or wood. “Joists”

are beams that support a floor or a roof. The following are some types of beams and joists that

you should know for your state exam:

• I-beam - A steel beam with a cross section resembling the letter I. It is used for long

spans as basement beams or over wide wall openings, such as a double garage door,

when wall and roof loads bear down on the opening.

• I-joist - Manufactured structural building component resembling the letter "I". Used as

floor joists and rafters. I-joists include two key parts - flanges and webs. The flange of

the I-joist may be made of laminated veneer lumber or dimensional lumber, usually

formed into a 1 ½" width. The web or center of the I-joist is commonly made of

plywood or oriented strand board (OSB). Large holes can be cut in the web to

accommodate ductwork and plumbing waste lines. I-joists are available in lengths up to

60 feet long.

• Lintel - A horizontal structural member that supports the load over an opening such as

a door or window.

• Load bearing wall - Includes all exterior walls and any interior wall that is aligned

above a support beam or girder. Normally, any wall that has a double horizontal top

plate.

• Tail beam - A relatively short beam or joist supported in a wall on one end and by a

header at the other.

Calculating the Amount of Framing Lumber

Lumber is sold by the “board foot” which is defined as “one square foot that is one inch

thick”. To calculate board feet, you must multiply the thickness in inches by the width in

inches by the length in feet and dividing by 12 to reach the correct number of board feet in that particular piece of lumber.

For example: What is the number of board feet in a piece of lumber that is 2 inches thick, 4

inches wide, and 16 feet long?

2 x 4 x 16 = 128

128 ÷ 12 = 10.67 board feet


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Flooring

A rough floor that forms the base for a finished floor is known as a “subfloor”. The subfloor is

usually “plywood” that is laid over "floor joists" (beams) to support it. Then, different types

of flooring such as hardwoods, carpeting, tile, etc. is laid over the subfloor. The following are

some flooring terms you should understand:

• Plywood - A panel (normally 4' X 8') of wood made of three or more layers of veneer,

compressed and joined with glue, and usually laid with the grain of adjoining plies at right

angles to give the sheet strength.

• Roll, rolling – To “roll the floor” means to install the floor joists.

• T & G – A joint made by a “tongue” (a rib on the edge of a board) that fits into a

corresponding groove in the edge of another board to make a tight flush fit. Typically, the plywood used for the subfloor is T & G.

• Toe Nailing – To drive a nail in, at a slant. This is the method used to secure floor

joists.

Calculate the Square Yardage of Carpeting

To calculate the square yardage for carpeting and padding, the simplest method is to calculate the square footage of the room(s) (length x width) and divide by 9. However, many

contractors add 5% to the square footage of the room to allow for seams.

Simple Method Example: A contractor would like to calculate the square yardage for

carpeting the padding for a 12 x 12 room.

12 x 12 = 144 square feet ÷ 9 = 16 square yards

Add 5% Method Example: A contractor would like to calculate the square yardage for

carpeting the padding for a 12 x 12 room.

12 x 12 = 144 square feet + 5% = 151.2 square feet ÷ 9 = 16.8 square yards

Stairs

The “treads” and “risers” are the two main parts of a set of stairs. “Stair treads (also called

runs)” refer to the horizontal pieces that is “tread upon” with their feet. The depth of the

treads can affect the comfort and safety of the staircase.

The “stair risers” are the vertical pieces of the stairs. The “rise” of the stair is how high or low


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it is. The measurements of the “rise and run” in a staircase determines their safety and local

building codes will usually determine the exact measurements.

The typical tread/run measurement is 10 inches from the leading edge of the tread back to the

riser. Building codes generally also recommend that the tread/run be at least 36 inches wide,

and the riser be a maximum height of 7.75 inches.

Roofing

Types of Roofs

Gable - The upper portion of a sidewall that comes to a triangular point at the ridge of a

sloping roof.

Hip Roof - A type of roof containing sloping planes of the same pitch on each of four sides. A

hip roof contains no gables.

Gable Roof - A type of roof containing sloping planes of the same pitch on each side of the

ridge. A gable roof typically contains a gable at each end.

Skillion Roof - A Skillion Roof slopes from one side of the building to the other in a single

span and no ridge. As a result, the external walls are of varying heights.

Lean-to Roof - A roof with one slope only that is built against a higher wall.

Jerkinhead Roof - Consists of a Gable Roof with a truncated Hip Roof section at the top to

reduce the height of the Gable.

Dutch Gable - Is a combination of a Hip roof with a small Gable at the top and a

sloping roof below.

Gambrel roof - A type of roof containing two sloping planes of different pitch on each side of

the ridge. The lower plane has a steeper slope than the upper. A gambrel roof usually contains

a gable at each end, just like a standard gable roof.

Mansard roof - A type of roof containing two sloping planes of different pitch on each of four

sides. The lower plane has a much steeper pitch than the upper, often approaching vertical. It

contains no Gables.

Gazebo Roof - Often hexagonal or octagonal but usually symmetrical in their design.

Estimating Number of Shingles Needed

In order to estimate how many shingles you'll need, first you need to estimate the total square

footage of your roof's surface. Just measure the length and width of each plane on the roof,


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including dormers. Then, multiply length x width to get the square footage of each plane. Simply

add the square footage of each of the planes together to derive the total square footage of your

roof.

For example, this shed roof has one roof plane. Simply measure length (A) x width (B) -

A x B = 120' x 100' = 12,000 sq. ft. for the total square footage of the roof.

This gable roof has two planes. So, multiply length (A) x width (B) to get the square footage for

each plane, then add the two planes together to derive the total square footage of the roof -

• Plane 1 - 120' x 100' = 12,000 sq. ft.

• Plane 2 - 120' x 100' = 12,000 sq. ft.

• Plane 1 + Plane 2 = 24,000 sq. ft. for the total square footage of the roof.

Roof surfaces are measured in "squares." A "square" is an area of roof which measures 100 square feet. To determine the number of squares on the gable roof above, for example, simply

divide its total of 24,000 square feet by 100. Which means you will need 240 "squares" of

shingles to cover it.

The most common type of shingle, called a three-tab or strip shingle, is generally

packaged three bundles per square. There are 29 (12 x 36 in) shingles in each bundle.

If this is a new roof, you will also need 240 squares of underlayment (no underlayment is

needed if you are applying shingles directly over an existing asphalt roof). Underlayment usually

comes in rolls of four squares each, so covering 240 squares would require 60 rolls of

underlayment. Be sure to add 10% to all your material totals for trim allowance.

Slope

You will also need to know the slope of your deck. In order to determine this, measure the

vertical rise of your deck in inches over a 12" horizontal distance. If this rise is 4", then your

roof slope is 4 in 12. Roof slopes are always expressed with the vertical rise mentioned

first and the horizontal run (12") mentioned second.

Steep Roofs

To measure a steep roof, you will have to use an alternate method. To obtain the roof length,

measure the exterior walls plus the overhang for the length of the house parallel to the ridge.


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Next, throw a rope over the ridge and mark it on each eave. This will give the width dimension

to use in figuring your area. This should be done on each roof section containing a horizontal

ridge.

Number of Nails Needed

You will also need to know the number of nails needed for the job you are performing.

Generally, you should use four nails per shingle. With regular three-tab shingles, that would

require 320 nails per square. For high wind areas or when shingles are being applied to a

mansard, six nails per shingle are required (480 nails per square). This is based on 80 shingles

per square. Other styles of shingles may require more or fewer nails per shingle and may have

more or less than 80 shingles per square. Refer to the application instructions on your shingle

wrappers for the correct nailing pattern.


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Sample Roofing Designs


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Roof Angles

Glossary of Roofing Terms

American method - Application of giant individual shingles with the long dimension parallel

to the rake. Shingles are applied with a 3/4-inch space between adjacent shingles in a course.

ASTM - American Society for Testing and Materials - A voluntary organization concerned with development of consensus standards, testing procedures and specifications.

Asphalt - A bituminous waterproofing agent applied to roofing materials during

manufacturing.

Asphalt plastic roofing cement - An asphalt-based cement used to bond roofing materials.

Also known as flashing cement or mastic; should conform to ASTM D-4586.


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Back Surfacing - Fine mineral matter applied to the backside of shingles to keep them from

sticking.

Base flashing - That portion of the flashing attached to or resting on the deck to direct the

flow of water onto the roof covering.

Bundle - A package of shingles. There are 3, 4 or 5 bundles per square.

Butt edge - The lower edge of the shingle tabs.

Caulk - To fill a joint with mastic or asphalt cement to prevent leaks.

Class "A" - The highest fire-resistance rating for roofing as per ASTM E-108. Indicates roofing

is able to withstand severe exposure to fire originating from sources outside the building.

Class "B" - Fire-resistance rating that indicates roofing materials can withstand moderate

exposure to fire originating from sources outside the building.

Class "C" - Fire-resistance rating that indicates roofing materials can withstand light exposure

to fire originating from sources outside the building.

Collar - Pre-formed flange placed over a vent pipe to seal the roof around the vent pipe

opening. Also called a vent sleeve.

Collar beam - Nominal 1- or 2-inch-thick members connecting opposite roof rafters. They

serve to stiffen the roof structure.

Concealed nail method - Application of roll roofing in which all nails are driven into the

underlying course of roofing and covered by a cemented, overlapping course. Nails are not

exposed to the weather.

Counter flashing - That portion of the flashing attached to a vertical surface to prevent water

from migrating behind the base flashing.

Cricket - A peaked saddle construction at the back of a chimney to prevent accumulation of

snow and ice and to deflect water around the chimney.

Cutout - The open portions of a strip shingle between the tabs.

Deck - The surface installed over the supporting framing members to which the roofing is

applied.

Dormer - A framed window unit projecting through the sloping plane of a roof.

Downspout - A pipe for draining water from roof gutters. Also called a leader.


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Drip edge - A non-corrosive, non-staining material used along the eaves and rakes to allow

water run-off to drip clear of underlying construction.

Dutch lap method - Application of giant individual shingles with the long dimension parallel to

the eaves. Shingles are applied to overlap adjacent shingles in each course as well as the course

below.

Dry in - To install the black roofing felt (tar paper) on the roof.

Eaves - The horizontal, lower edge of a sloped roof

Eaves flashing - Additional layer of roofing material applied at the eaves to help prevent

damage from water back-up.

Edging strips - Boards nailed along eaves and rakes after cutting back existing wood shingles

to provide secure edges for re-roofing with asphalt shingles.

Exposure I grade plywood - Type of plywood approved by the American Plywood

Association for exterior use.

Fascia - Horizontal boards attached to rafter/truss ends at the eaves and along gables. Roof

drain gutters are attached to the fascia.

Felt - Tar paper. Installed under the roof shingles. Normally 15 lb. or 30 lb. Felt - Fibrous

material saturated with asphalt and used as an underlayment or sheathing paper.

Fiberglass mat - An asphalt roofing base material manufactured from glass fibers.

Flashing - Pieces of metal or roll roofing used to prevent seepage of water into a building

around any intersection or projection in a roof such as vent pipes, chimneys, adjoining walls,

dormers and valleys. Galvanized metal flashing should be minimum 26-gauge.

Flashing Cement - See asphalt plastic roofing cement.

Fly rafters - End rafters of the gable overhang supported by roof sheathing and lookouts.

Free-tab shingles - Shingles that do not contain factory-applied strips or spots of self-sealing

adhesive.

Gable - The upper portion of a sidewall that comes to a triangular point at the ridge of a

sloping roof.

Gable roof - A type of roof containing sloping planes of the same pitch on each side of the

ridge. Contains a gable at each end.


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Gambrel roof - A type of roof containing two sloping planes of different pitch on each side of

the ridge. The lower plane has a steeper slope than the upper. Contains a gable at each end.

Granules - Ceramic-coated colored crushed rock that is applied to the exposed surface of

asphalt roofing products.

Gutter - The trough that channels water from the eaves to the downspouts.

Head lap - Shortest distance from the butt edge of an overlapping shingle to the upper edge of

a shingle in the second course below. The triple coverage portion of the top lap of strip

shingles.

HEX shingles - Shingles that have the appearance of a hexagon after installation.

Hip - The inclined external angle formed by the intersection of two sloping roof planes. Runs

from the ridge to the eaves.

Hip shingles - Shingles used to cover the inclined external angle formed by the intersection of

two sloping roof planes.

Ice dam - Condition formed at the lower roof edge by the thawing and refreezing of melted

snow on the overhang. Can force water up and under shingles, causing leaks.

Interlocking shingles - Individual shingles that mechanically fasten to each other to provide

wind resistance.

Laminated shingles - Strip shingles containing more than one layer of tabs to create extra

thickness. Also called three-dimensional shingles or architectural shingles.

Lap - To cover the surface of one shingles or roll with another.

Lap cement - An asphalt-based cement used to adhere overlapping plies of roll roofing.

Mansard roof - A type of roof containing two sloping planes of different pitch on each of four

sides. The lower plane has a much steeper pitch than the upper, often approaching vertical.

Contains no gables.

Mineral stabilizers - Finely ground limestone, slate, traprock or other inert materials added

to asphalt coatings for durability and increased resistance to fire and weathering.

Mineral-surfaced roofing - Asphalt shingles and roll roofing that are covered with granules.

Pallets - Wooden platforms used for storing and shipping bundles of shingles.

Pitch - The degree of roof incline expressed as the ratio of the rise, in feet, to the span, in feet.


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Ply - The number of layers of roofing - i.e. one-ply, two-ply.

Quick-setting cement - An Asphalt-based cement used to adhere tabs of strip shingles to

the course below. Also used to adhere roll roofing laps applied by the concealed nail method.

Racking - Roofing application method in which shingle courses are applied vertically up the

roof rather than across and up. Not a recommended procedure.

Rafter - The supporting framing member immediately beneath the deck, sloping from the ridge

to the wall plate.

Rake - The inclined edge of a sloped roof over a wall.

Rake Fascia - The vertical face of the sloping end of a roof eave.

Random-tab shingles - Shingles on which tabs vary in size and exposure.

Ridge - The uppermost, horizontal external angle formed by the intersection of two sloping

roof planes.

Ridge board - The board placed on the ridge of the roof onto which the upper ends of other

rafters are fastened.

Ridge shingles - Shingles used to cover the horizontal external angle formed by the

intersection of two sloping roof planes.

Rise - The vertical distance from the eaves line to the ridge.

Roll roofing - Asphalt roofing products manufactured in roll form.

Roll roofing - Asphalt roofing products manufactured in roll form. 36-inch wide rolls with and

108 square feet of material. Weights are generally 45 to 90 pounds per roll.

Roof Flashing - Sheet metal installed at any break in a shingled roofline to prevent leaks. Also

around sewer vents, flue pipes.

Roofing tape - An asphalt-saturated tape used with asphalt cements for flashing and patching

asphalt roofing.

Roof jack - Sleeves that fit around the black plumbing waste vent pipes at, and are nailed to,

the roof sheeting.

Roof joist - The rafters of a flat roof. Lumber used to support the roof sheeting and roof

loads. Generally, 2 X 10's and 2 X 12's are used.


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Run - The horizontal distance from the eaves to a point directly under the ridge. One half the

span.

Soffit - The finished underside of the eaves.

Steep slope application - Method of installing asphalt shingles on roof slopes greater than 21

inches per foot.

Step flashing - Flashing application method used where a vertical surface meets a sloping roof

plane.

Top lap - That portion of the roofing covered by the succeeding course after installation.

UL (Underwriters Laboratories, Inc.) - An independent testing agency that checks

electrical devices and other components for possible safety hazards.

UL label - Label displayed on packaging to indicate the level of fire and/or wind resistance of

asphalt roofing.

Underlayment - Asphalt saturated felt used beneath roofing to provide additional protection

for the deck.

Valley - The internal angle formed by the intersection of two sloping roof planes.

Vapor retarder - Any material used to prevent the passage of water vapor.

Vent - Any outlet for air that protrudes through the roof deck such as a pipe or stack. Any

device installed on the roof, gable or soffit for the purpose of ventilating the underside of the

roof deck.

Woven Valley - Method of valley construction in which shingles from both sides of the valley

extend across the valley and are woven together by overlapping alternate courses as they are

applied. The valley flashing is not exposed.


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Windows

Additional terminology regarding windows that you will want to review are:

Sash – The frame that holds the glass in a window, often the movable part of the window.

Sash balance – A device usually operated by a spring and designed to hold a single hung

window up and in place.

Louver – A vented opening into the home that includes a series of horizontal slats and

arranged to permit ventilation, but to exclude rain, snow, light, insects, or other living

creatures.

A “window muntin” is strips of work or

metal that create a grid or latticework

appearance. They can be mounted on the

outside of window glass or they can be

sandwiched between double-paned glass.

Initially, they were used for additional support

for the glass, but today they are used almost

exclusively for aesthetic appeal.

Before it was possible to manufacture

large sheets of glass, supportive

“window mullions” were used to

create larger expanses of glass by

holding smaller panes of glass together.

Today, many window manufacturers

call all of these elements a grille or a

grids. Again, today these are used for

aesthetic appeal.


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Electrical Systems

Although residential electrical systems might appear complicated, the methods used in wiring

homes are generally straightforward and follow strict guidelines. The National Electrical Code

establishes those methods, and most local codes and electrical contractors follow them.

Entrance of Electrical Service

The wires that transmit electricity from the power company to residences are either above or

below the ground. Most homes use a weather head, which receives the wires from the utility

pole. Many newer homes have an underground cable running through a pipe called a “conduit”.

In both cases, the wiring passes through the electric meter before running into the service

panel.

Service Panel (Circuit Breaker)

After passing through the meter, the wires enter one of two types of service panels, a circuit

breaker or fuse box. The circuit-breaker panel and fuse box serve two purposes. First, they

distribute electricity into several branch circuits. Second, they act as safety devices by breaking

the circuit if an overload occurs, preventing the wiring from overheating and causing a fire.

These panels are rated by amperage. Adjusters need to identify the service panel rating when

scoping the loss because it significantly affects the cost of the loss. Amperage of service is also

often upgraded after a loss. The 70-amp fused service was standard before the invention and

increased use of many modern electrical appliances. Today, homes usually contain a 200-amp

service using circuit breakers.

Branch Circuits

Branch circuits are made up of wires running from the service panel to the outlets, switches,

and fixtures located throughout the house. They can generally supply different amounts of

electricity, depending on their amperage, which varies by the wire’s size.

With the exception of heavy-duty appliances, which should have their own circuits, most

residential branch circuits serve eight to ten outlets each. The National Electrical Code

recommends one 20-amp circuit for every 500 square feet of living area lighting. Appliances

such as air conditioners, electric ranges, electric water heaters, electric dryers often have their

own 220-volt circuit as opposed to the 110-volt circuits used for lighting and general usage.

Ground Fault Circuit Interrupters

Electrical shocks can be minor or fatal. The ground fault circuit interrupter (GFCI) was

designed to protect people from fatal electrical shocks. The National Electrical Code requires

GFCI outlets for bathrooms, kitchens, basements, garages, and outdoors. The GFCI monitors

a current’s flow through a circuit. When it senses a leak (ground fault), it shuts the power off


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to the circuit. If a person has become the ground for the leaking current, the person will still

get a shock, but the GFCI will prevent the shock from being fatal.

Wiring Types and Methods

Wiring types and methods significantly affect the cost of materials and amount of labor required

for repairs. Following are the most common types of wiring used to in residential construction.

• Rigid conduit

• Thin wall conduit

• Nonmetallic sheathed cable

• Armored cable

Wiring comes in two types - two wire and three wire. In a 2-wire strand, there is no ground

wire. There is only a black wire that has current in it (referred to as the “hot” wire) and a

white wire that is neutral. In a 3-wire strand, there is a green or bare copper wire in addition to

the hot wire and the neutral wire. The green or copper wire is the ground wire.

Rigid conduit is similar to water piping and is usually used outside or underground. It comes in

ten-foot lengths and various inside diameters. The pipe is threaded for coupling and connecting

to boxes. Conduit systems are installed before the wiring is threaded through them.

Thin-wall conduit is similar to rigid conduit in many ways. It is available in ten-foot lengths and

the same inside diameters. However, because it can be easily cut and bent because it has

compression fittings rather than threaded ones, thin-wall conduit is far more popular than rigid

for residential electrical applications. Another name for thinwall conduit is electrical metallic

tubing (EMT). Thin-wall conduit can also be nonmetallic.

Nonmetallic sheathed cable is one of the most popular methods of electrical wiring. It is both

less expensive than conduit and less time-consuming to install. Unlike the conduit systems, in

which wires are run after the tubing has been installed, nonmetallic sheathed cable is made up of individual plastic coated wires and a bare ground wire all wrapped in a flame-retardant, water

resistant plastic sheath. Connections must be made in metal or plastic junction boxes. Many

local building codes prohibit the use of nonmetallic sheathed cable in some types of residential

construction.

Armored cable is commonly called “BX cable”. Armored cable is not used as often as it once

was because of nonmetallic sheathed cable’s popularity. Armored cable consists of two or more

insulated wires encased in a spiral steel sheath. Like the other forms of wiring described, BX

has special connectors and fittings.

Structured Wiring

Most commercial buildings and many new homes are built with structured wiring to

accommodate audio, video, and data technology. Structured wiring (also known as

infrastructure wiring) consists of the wiring and components used for telephones, fax machines,


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computers, the Internet, audio equipment, security cameras, and video equipment such as cable

or satellite TV. Commercial properties often used fiber-optics cables to transmit data. Some

communities are installing fiber-optic cable so that residents can enjoy high-definition television.

Damage

Residential electric systems can be damaged by various causes, but fire, lightning and power

surges are the most common. The extent of damage varies by the type of electrical wiring.

Plastic sheathed cable can withstand less heat than metal conduit. Building inspectors often

require complete rewiring after a loss when it is not necessary. Adjusters should consider employing an electrical engineer or qualified contractor for an expert opinion, thus resolving

disputes and satisfying the building inspector. Likewise, upgrades may be required by code. If

this situation occurs, the adjuster must be aware of the potential coverage issue that it raises.

Glossary of Electrical Terms

Alternating Current (AC) – A flow of electric charge that undergoes periodic reverses in

direction. In North America, ordinary household current alternates at a frequency of 60 times

per second.

Ampere (A or Amp) - Unit of electrical current. Either how much electricity an appliance

will use, or a circuit (fuse, mcb, cable, connectors etc.) can handle. Fuses are always rated by

current as are cables. Each appliance will have an Amp rating or if only a wattage is quoted,

Amps = Wattage/Voltage.

Circuit Breaker - A switch like device with a pre-set current limit used to protect a circuit

from electrical overload. If the circuit breaker is activated (or tripped), it can be reset by

pushing a button - however the reason for the trip should always be investigated as it is an

indication of an overload, possible some form of fault.

Circuit Protective Conductor (CPC) - A name used for the protective earth wiring of all

metal parts of a building (see Earthing).

Conduit - A pipe or tubing used to house cable. In walls to switches and socket usually oval

and plastic in modern houses, or round and metal in older ones.

Direct Current (DC) - Unlike Alternating Current, the flow of electricity does not alternate,

it flows in just one direction. Normally used in low voltage electronic circuits and computers

etc. around the house and is usually derived from the alternating mains via a power supply.

Double Pole Switch - A switch which breaks (or makes) both the live and neutral lines with

one throw of the switch.

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Electrical entrance package - The entry point of the electrical power including - (1) the

“strike” or location where the overhead or underground electrical lines connect to the house,

(2) The meter which measures how much power is used and (3) The “panel” or “circuit

breaker box (or “fuse box”) where the power can be shut off and where overload devices such

a fuses or circuit breakers and located.

Fuse - A crude protection device which destroys itself (or 'blows') and breaks the circuit

should the current exceed the rating of the fuse. Once the fuse has blown, it needs to be

replaced - unlike Circuit Breakers/MCBs. Modern fuses are generally in sealed cartridges which

need to be replaced. See also Cartridge Fuse.

Fused Connection Unit (FCU) - A fused outlet from a mains circuit where the cable to the

fixed appliance is hardwired in (i.e. not a plug and socket) and contains a fuse for the appliance,

such as a cooker in a kitchen. See also SFCU (Switched Fused Connection Unit).

Fused Spur - An electrical supply using one feed cable to a socket taken off a ring main via a

fuse of lower rating that the fuse for the ring main. See also Spur.

Grommet - A small, round rubber/plastic washer with a groove in the outer edge so that it

can be located in mounting boxes etc. to prevent chafing of cables passing through.

Junction Box - A box containing terminal blocks for joining electrical cable.

Kilowatt Hour (kWh) - Measure of energy used equated to an hour - i.e. a 5-kW appliance

operated for 12 minutes will use 1 kWh, operated for 1 hour will use 5kWh, or operated for 5

hours will use 25kWh.

Ohms - A unit of electrical resistance. Resistance (ohms) = Voltage / Ampere (known as

Ohm's Law).

R-factor or value - A measure of a material's resistance to the passage of heat. New home

walls are usually insulated with 4" of batt insulation with an R value of R-13, and a ceiling

insulation of R-30.

Receptacle - An electrical outlet. A typical household will have many 120 volt receptacles for

plugging in lamps and appliances and 240 volt receptacles for the range, clothes dryer, air

conditioners, etc.

Riser and panel - The exterior vertical pipe (riser) and metal electric box (panel) the

electrician provides and installs at the "Rough Electric" stage.

Two Way Switch - Switches which can be used in pairs so that either can switch a light on or

off. Each switch has terminals allowing them to be linked using Three Core and Earth cable.

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Voltage (V) - The numerical value of the electrical potential between two points in a circuit.

Volts = Wattage/Amperes.

Wattage (W) - A unit of power - in electrical equipment defined as Watts = Volts x

Amperes. One watt is fairly small and household equipment will often be rated in terms of

Kilowatt (kW) - 1kW = 1000W.

Interior Construction

Most construction projects today use “drywall” instead of plaster to finish interiors walls. Drywall construction is a technique in which the interior wall finish is applied in a dry condition,

generally in the form of sheet materials or wood paneling.

“Sheetrock” (drywall, wall board or gypsum) are used to finish the interior walls of a

structure. Sheetrock is a manufactured panel made of gypsum plaster and encased in thin

cardboard. It is usually ½ inch think and comes in sizes 4 ft. x 8 ft. or 4 ft. x 12 ft.

“Green board” type sheetrock has a greater resistance to moisture than regular white

sheetrock and is used in bathrooms and other wet areas.

The joints between the sheetrock boards are covered by “taping” using paper tape and joint

compound, sometimes called mud.

Measuring Sheetrock (Drywall)

To measure how much sheetrock (drywall) needed for a room, you must calculate the square

footage of the room, and add the ceiling. For example, we have a 10 x 10 room with 8 ft high

ceilings so each wall would be 80 square feet. Then, we will multiply the square footage of

each all by 4 (because we have 4 walls), leaving us with 320 square feet. A 10 x 10 room would have a ceiling that is 100 square feet, so we add this to 320, to reach 420 square feet. The

sheets of drywall come in either 4 x 8 (32 square feet) or 4 x 12 (48 square feet).

If we purchase the 4 x 8 sheets, we would divide 420 by 32, we get 13.125, therefore we

would need to purchase 14 sheets of drywall.

If we purchase the 4 x 12 sheets, we would divide 420 by 48, we arrive at 8.75, or 9

sheets of drywall would need to be purchased.

Painting

When estimating the amount of paint to purchase, calculate the square footage of the room.

One gallon of paint is needed to cover between 350 and 400 square feet of finished walls

if rollers and brushes are used. A paint sprayer will use about 10% more paint.


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Cabinet Measurements

Standard size base cabinets are 36 inches in height and 24 inches in depth. Standard size wall

cabinets are 12 inches in depth but can come in varying heights. Therefore, when measuring

for cabinets, the walls must be measured in inches.

Depending on the style of cabinet, design items such as toe kicks, frameless doors, crown

molding, or frameless doors should be taken into account when measuring for cabinets.


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Review Quiz

PLEASE NOTE: The questions you need to prepare for the state licensing exam are

contained in the Exam Simulator portion of your course. You can access this invaluable

resource by going to our homepage at: www.insurance-schools.com and clicking the red

“Logon to my Courses” button in the upper right area of the page.

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http://www.insurance-schools.com/

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