Building Codes and Ordinances ARC 227 - Architectural Design ...

Building Codes and Ordinances
ARC 227
Week 5 – Construction Types
02.23.10
Instructor:
Rick Staub, AIA
Email: staub@pointonearchitects.com
Phone: 860-434-7707

General Building Heights + Areas
Review
The allowable sizes of buildings, both height and area, are a function of two things;
Use Group Classification
Building Construction Type – Chapter 6
The more “dangerous” a use group the less height and area allowed
The “better” the construction type the more area and height are allowable
You can increase either (or both) the area and height by providing sprinklers and/or open space
surrounding the building
Area Increases
Public Way / Open Space increase
Sprinkler Increase
Height increase
Sprinkler Increase -

Table 503
• Allowable building height and area are determined by the intersection of the Occupancy
group and the Construction type
• As occupancy is usually determined before heights and areas, the table will typically be read
by reading down the list of Occupancy groups until you find the corresponding group.
• Then reading across the table gives you the allowable heights and areas for the different
construction type.
• Construction Types
– Type I – Building elements are non-combustible
– Type II – Building elements are non-combustible
– Type III – mix of non-combustible elements(exterior walls) and combustible elements
(interior)
– Type IV – Heavy timber construction
– Type V – Any material allowed, typically conventional light wood framed
Note that the distinction between A and B categories of construction types is the associated
level of fire resistance. A categories have more fire resistance than B categories
A is protected construction
B is unprotected construction
Therefore type A Buildings of any construction type have higher allowable heights and
areas than type B buildings
The higher the level of of fire and life safety, the larger the and higher a building can be

Unlimited Area Buildings
Section 507
This section allows buildings of other than Type I construction to be unlimited area when certain
conditions are met. These exceptions overlay Table 503
507.1 –Groups F-2 and S-2 – One-story, non-sprinklered buildings may be unlimited in area when the
building is surrounded and adjoined by public ways or open space of not less than 60’.
507.2 - Groups B, F,M, or S – One-story, sprinklered buildings, may be unlimited in area when the
building is surrounded and adjoined by public ways or open space of not less than 60’.
Group A-4 - One-Story, sprinklered buildings, construction type other than V, may be
unlimited in area when the building is surrounded and adjoined by public ways or open space of not
less than 60’. May not even need to be sprinklered in certain uses where exits doors directly to the
outside are provide or the building is equipped with a fire alarm system with manual fire alarm boxes.
507.3 – Groups B, F, M or S – Two-story, sprinklered buildings, may be unlimited in area when the
building is surrounded and adjoined by public ways or open space of not less than 60’.
507.4 Reduced open space – the required 60’ open space may be reduced to not less than 40’ when
the following conditions are met:
1. For not more than 75% of the perimeter of the building.
2. The exterior wall facing the reduced space has fire rating of at least 3-Hours
3. opening in that wall be protected with fire-resistive ratings of 3-hours

Special Provisions – Section 508
Section 508
This section is devoted entirely to exceptions to the provisions of Table 503 and the other sections in
Chapter 5. These exceptions apply only when all of the conditions in the subsections are met. These
conditions are based on on specific combinations of occupancy groups and construction types.
Developed in response to conditions not addressed in previous years – these usually give the
designer greater flexibility in meeting the the requirements of the building program than will Table
3503 alone.
We annotate our code books Table 503 to include these provisions.
508.2 - Group S-2 enclosed parking garage with groups A, B, M or R above
This section may apply with an enclosed parking structure at grade with other uses built
above. Developed in response to apartment buildings using wood frame construction over a type I
concrete garage structure.
Allows the uses above to be considered a separate and distinct building for the purpose of
determining area and height limitations.
508.3 – Group S-2 enclosed parking garage with S-2 open parking garage above
Same principle as 508.2, allows use above to be considered a separate and distinct
building.

Special Provisions – Section 508
508.4 – Parking Beneath Group R
When a enclosed garage is built of type I construction or an open garage of type IV
construction your start counting floors above the garage portion.
508.5 Group R-2 buildings of type III-A construction
height can be increased to six stories and 75’
when some other considerations are met
508.6 Group R-2 buildings of type II-A construction
height can be increased to nine stories and 100’
when some other considerations are met

Types of Construction-Chapter 5
The IBC classifies all buildings into five broad types or categories of construction based on the fire
resistance capabilities of the members used in their construction.
5 types given Roman Numeral classification – ranging from type I to Type V – most fire resistive to
the least fire resistive
Construction Types
– Type I – Building elements are non-combustible
– Type II – Building elements are non-combustible
– Type III – mix of non-combustible elements(exterior walls) and combustible elements
(interior)
– Type IV – Heavy timber construction
– Type V – Any material allowed, typically conventional light wood framed
The five types of construction are subdivided into two additional categories – A and B, based
on the inherent fire-resistance or combustibility of the materials
Remember Table 503 - Height and area are predicated on the Occupancy group and the type of
construction. Its our job to work with the three variables when making initial code analysis.
The desired occupancy and size will determine the type of construction.

Types of Construction
The principle of fire-resistance is base on the desire to limit the spread of fire from:
One building to another
One area to another
One floor to another.
The idea is to divide a building into distinct zones with barriers to retard the propagation and spread
of fire – Compartmentalization.
The five types of construction determine the “Passive” fire-resistance that is inherent in the
buildings structure and envelope. Passive fire-resistance refers to the ability of a material or a
group of materials to resist the spread of fire.
Combustible materials can be layered or wrapped in fire retardant coverings to help resist the
spread of fire. The application of passive fire resistive materials may also increase the
performance of non-combustible materials, even steel loses strength when heated
“Active” systems refer to those consisting of fire sprinklers and alarms.

Types of Construction

Table 601
Table 601 defines the required fire-resistance of major building elements for each type of
construction.
The fire-resistance of building elements gives occupants time to leave the building in the event
of an emergency and allows fire fighters time to fight the fire.
A building may only be classified as a single type of construction.
Even if some building elements satisfy the requirement of another (higher) classification
The building as a whole need only to conform to the lowest type of construction based on
occupancy and size.
The building is to be looked as a whole system and considered in the aggregate
The local building official will examine the classification assigned by the designer and make the final
determination of class.
Categories of building elements are:
Structural Frame –columns and beams
Bearing Walls – walls that hold floor, roof, or point loading
Non-bearing walls and Partitions – walls that do not hold any structural load (except for
themselves)
Floor Construction – the diaphragm that composes the floor structure
Roof Construction - the diaphragm that composes the roof structure

Table 601

Table 601 -footnotes
Footnote a:
The definitions of what constitute a structural frame are contained in this footnote. Only those
elements framing directly into the columns need meet the protection criteria described
Footnote b:
This footnote recognizes that roof framing at interior bearing walls in Type I construction have a
lighter fire load than does the primary structure for floors
Footnote C:
The three conditions in this footnote refer to special provisions related to fire protection and
building element protection in roof construction
C.1 permits unprotected roof construction for roofs 20’ or more above the floor below,
except in Group F, H, M and S-1 occupancies.
C.2 allows the use of heavy timbers where 1-hour or less fire-resistance rating is
required.
C.3 allows the use of fire-retardant treated wood in Type I and II construction if the
building is not over two stories in height.

Table 601 -footnotes
Footnote d:
This footnote alls out trade-off provisions for the use of automatic fire-sprinkler systems to
compensate for the diminution of protection of the building elements of Type II, III, and V
construction.
Footnote e:
This footnote refers back to a specific provision for interior nonbearing partitions for type IV
buildings as spelled out in section 6022.4.6
Footnote f:
This footnote advises the designer to compare the requirements of both table 601 and 602 to
determine the fire-resistance rating for exterior bearing walls. It is possible that table 602 will
require a higher fire-resistance for an exterior wall than table 601. The most restrictive is
required

Table 602
Table 602 specifies the fire-resistance rating requirements of exterior walls based on fire-separation
distance as well as type of construction and occupancy groups.
It is important to compare ratings required in Table 601 and table 602
Fire separation distance –defined in section 702
“The distance measured from the building face to the closest interior lot line, to the
centerline of a street, alley or public way, or to an imaginary line between two buildings on the
lot. The distance shall be measured at right angles to the wall”
The fire-resistive requirements decrease with increasing distance between buildings.
they also decrease in relation to decreasing construction type requirements.
Table 602 also builds in assumptions about the hazard of occupancies relative to fire
separation distances – the principle is that increased distances offset the hazards presented by
various occupancies.
The amount of openings allowed in exterior walls is governed in section 7 under Table 704.8

Table 602

Type I and II Construction
The building elements of Type I and II construction are of non-combustible materials.
The definition of non-combustible is found in section 703.4 – it requires that to be considered
non-combustible it needs to meet criteria of ASTM E 136 – American Society for Testing and
Materials.
Type I-A Construction
provides the highest level of fire-resistance rated construction
requires passive protection for all elements of the structure
Type I-B Construction
similar to type I-A but permits a 1-hour reduction in fire resistance rating for the structural
frame, bearing walls and floor construction and a ½ hour reduction for roof construction.
Type II-A Construction
allows active or passive protection of all elements of the structure
Type II-B
allows unprotected noncombustible building elements

Type I and II Construction
Combustible materials in types I and II construction
the key to the use of combustible materials in a noncombustible construction type is
understanding that these uses are ancillary to the primary structure of the building. The
premise allowing the use of these combustible materials is that they will be of limited quantity
and used under defined conditions where they will not contribute in any large measure to
compromising the desired level of fire-resistance in the structure.
So, although types I and II call for noncombustible materials there are a number of exceptions
when all the requirements are taken together.
Section 603 contains a list of notes specifying which combustible materials can be used
Review section 603

Type I and II Construction

Type I and II Construction

Type III Construction
Type III buildings are a mix of non-combustible and combustible elements, having noncombustible
exterior walls and combustible interior construction.
these buildings are designed to prevent a fire from spreading from building to building.
The construction materials on the exterior of a type III building are required to be of
noncombustible materials.
Fire-retardant treated wood is allowable when the requirement is 2-hours or less

Type III Construction

Type III Construction

Type IV Construction
Type IV Construction
Came about to address “mill” buildings, or “mill”construction.
Heavy Timbers and GluLam
These buildings utilize heavy timber structural members and heavy wood floor decking inside
Exterior walls of noncombustible construction.
Criteria for “Heavy timber” Construction are based on past performance of historical construction
Type III buildings generally burn slowly under fire conditions. The Heavy Timber members begin to
flame and char at 400 degrees. As the charring continues it retards further deterioration of the
wood members by insulating the interior of the wood members.
No concealed spaces in the building elements are allowed
Lumber sizes are called out as nominal sizes, actual sizes are a bit smaller.
Floor Framing requires a minimum nominal 3” thick, and the floors are required to be held
away from the exterior wall

Type IV Construction

Type V Construction
Type V Construction
The least restrictive construction type.
It allows the use of any materials permitted by the code.
Conventional light frame wood construction is the most common.
Type V-A construction is protected construction and all major building elements must therefore
have a 1-hour fire-resistance rating
Type V-B construction is unprotected and required no fire resistance ratings except where section
601.2 and table 602 require exterior wall protection.

Type V Construction

Type V Construction