Class of Construction

Class of Construction

CLASS OF BUILDING CONSTRUCTION

 

REPRINT FROM THE INTEGRAL NEWSLETTER

The Class of Construction is the basic subdivision in the Marshall Valuation Service, dividing all buildings into five basic cost groups by type of framing (supporting columns and beams), walls, floors and roof structures, and fireproofing.

 

Class A buildings have fireproofed structural steel frames with reinforced concrete or masonry floors and roofs.

 

The primary feature of Class A buildings is the fireproofed, protected structural steel frame, which may be welded, bolted, or riveted together. The fireproofing may be masonry, poured concrete, plaster, sprayed fiber, or any other type which will give a high fire- resistance rating. Floors and roofs in Class A structures are normally reinforced concrete on steel decking or formed slabs resting on the  frame or poured so as to become integral with it. They may also be composed of prefabricated panels and may be mechanically stressed. Exterior walls will be curtain walls of masonry, concrete, steel studs and masonry, tile or stucco, or one of the many types of panels of metal, glass, concrete, and other materials. Interior partitions will frequently be of masonry or gypsum block although many movable and lightweight partitions are used. Included in this classification are Uniform, Basic and Standard Building Code construction, Types I and II (noncombustible) and ISO Classes 5 and 6 if the framing is protected steel. ISO Class 5 and 6 buildings with load- bearing walls and no interior framing and most low-rise buildings should be classified as Class C. This class is also referred to as Modified Fire Resistive or Two — Four- hour construction.

 

Class B buildings have reinforced concrete frames and concrete or masonry floors and roofs.

 

The primary characteristic of a Class B building is the reinforced concrete frame in which the columns and beams can be either formed or precast concrete. They may be mechanically stressed. It is a fire- resistant structure. Floors and roofs in Class B structures are formed or precast concrete slabs. The exterior walls will generally be masonry or reinforced concrete curtain walls or any of the many types of wall panels of concrete, metal, glass, or stone, etc. In some Class B buildings, the walls may be partially load- bearing. Interior partitions are often masonry, reinforced concrete or gypsum block, but many lightweight and  movable partitions are used where structural walls are not needed. Included in this classification are Uniform, Basic and Standard Building Code Types I and II (noncombustible) and ISO Classes 5 and 6 if the framing is concrete. ISO Class 5 and 6 buildings with load-bearing walls and no interior framing and most low- rise buildings should be classified as Class C. This class is also referred to as Fire Resistive or Two — Four- hour construction.

 

Class C buildings have masonry or concrete exterior walls, and wood or steel roof and floor structures, except for concrete slab on grade.

 

These buildings are characterized by masonry or reinforced concrete (including tilt- up) construction. The walls may be load- bearing, i. e., supporting roof and upper floor loads, or non-bearing with open concrete, steel, or wood columns, bents or arches supporting the load. Floors and roofs are supported on wood or steel joists or trusses, or the floor may be a concrete slab on the ground. Upper floors or roofs may be of concrete plank, steel deck, or wood. Bearing walls are frequently strengthened by concrete bond beams and pilasters. Included in this classification are Uniform and Basic Building Code Type III (noncombustible wall), Standard Code Type V and ISO Classes 2 and 4, and those Class 5 and 6 buildings which have load- bearing walls without interior framing and of low- rise (3 stories or less) design. This class is also referred to as Masonry or Unprotected Noncombustible, Joisted or Unprotected Masonry, or Ordinary or Unprotected One-hour and to include certain Two- hour or Mill construction (heavy timber).

 

Class D buildings generally have wood frame, floor, and roof structure. They may have a concrete floor on grade and other substitute materials, but are considered combustible construction. This class includes the pre-engineered pole- or post-frame, hoop and arch-rib-frame buildings.

 

These buildings are characterized by combustible construction. The exterior walls may be made up of closely spaced wood or steel studs, as in the case of a typical frame house, with an exterior covering of wood siding, shingles, stucco, brick or stone veneer, or other materials. Floors and roofs are supported on wood or steel joists or trusses or the floor may be a concrete slab on the ground. Upper floors or roofs may consist of wood or metal deck, prefabricated panels or sheathing. Class D pole (a subset of Class D) buildings are characterized by combustible prefabricated wood structural members. The exterior walls comprise an open-wood skeleton post frame and trusses, with exterior coverings of prefabricated metal panels or sheet siding. Wall girts span between posts, and there can be an in-fill of wood studs. Upper floors are supported on wood joists or trusses. The roof is supported by prefabricated trussed rafters with wood purlins or nailers. Ground floors are typically concrete slabs or dirt. Class D hoop arch (another subset of Class D) buildings are characterized by combustible, prefabricated, wood-post and tubular-steel, semicircular (hoop – Quonset shape), framed roofs that curve to a short wooden pony wall or to the ground. The roof and walls are generally covered with canvas or a woven vinyl tarp. Ground floors are typically dirt or can be a concrete slab. Construction Type V (wood-frame) of the Uniform, Type IV Basic and Type VI Standard Building Code are included in this classification as are ISO Class 1 buildings. This class is also referred to as Unprotected-protected One-hour Construction. Class D is further used to include all buildings that do not fit into any other classification.

 

Class S buildings have frames, roofs, and walls of incombustible metal. This class includes the pre-engineered metal buildings, including slant-wall and Quonset structures.

 

These buildings are characterized by incombustible construction and prefabricated structural members. The exterior walls may be steel studs or an open- steel- skeleton frame with exterior single or sandwich wall coverings consisting of prefabricated panels or sheet siding. Floors and roofs are supported on steel joists or beams, or the floor may be concrete slab on grade. Upper floors or roofs may consist of metal deck, prefabricated panels or sheathing.

 

Class S Slant– wall buildings (a subset of Class S) are characterized by incombustible construction and light, prefabricated structural members. They are not fire- resistant buildings. The exterior walls and roof coverings are prefabricated metal panels or sheet siding supported by an open- steel skeleton slant (modified A) frame. Ground floors are typically concrete slabs. Included in this classification are Uniform and Standard Building Code construction, Type IV (noncombustible), Basic Code Type V and ISO Class 3 buildings. This class is also referred to as Noncombustible and can be One- hour Type II construction.

 

In each class, there will be variations, combinations, and subclasses, but for purposes of pricing, the major elements of the building should be considered in selecting costs from the tables. Thus, if a building, which is otherwise in Class B, has a wood or steel truss roof, the costs for the Class B building may still be representative, or a Class C building may have concrete plank floors. Interpolations may be made if the appraiser feels the building overlaps two classes sufficiently or the Segregated Cost Sections may be used to modify the cost. In most localities, some buildings are built which are hybrids in construction, such as those with complete Class A framing, including columns and girders, but with wood floor joists and sheathing. In all such hybrids, the appraiser must judge whether to adjust the costs or interpolate between classes and qualities.

 

Those indicated are the classification before considering any adjustments for construction deficiencies or insurance rating purposes. For example, a building of Class 6 construction that is rated as Class 1 because of extensive insulation, not listed by UL, would still be valued as a Class 6 building.

 

CLASS OF CONSTRUCTION INDICATORS

 

CL

FRAME FLOOR ROOF

WALLS

A

Structural steel  columns and beams, Fireproofed with masonry, concrete, plaster, Or other  noncombustible material. Concrete or concrete on steel deck,

Fireproofed.

 

Formed concrete, Precast slabs, concrete Or gypsum on steel deck, fireproofed.

 

Nonbearing curtain walls, masonry,

Concrete, metal and glass panels, stone,

Steel studs and masonry, tile or stucco, Etc.

B

Reinforced concrete columns and beams.

Fire-resistant construction.

 

Concrete or concrete on steel deck, Fireproofed.

 

Formed concrete, Precast slabs, concrete Or gypsum on steel deck, fireproofed.

 

Nonbearing curtain walls, masonry, concrete, Metal and glass panels, stone,

Steel studs and masonry, tile or stucco, Etc.

C

Masonry or concrete load-bearing walls

With or without pilasters. Masonry, concrete

Or curtain walls with full or partial

Open steel, wood, or concrete frame.

Wood or concrete plank on wood or

Steel floor joists, or concrete slab on

Grade.

 

Wood or steel joists with wood or steel

Deck. Concrete plank.

 

Brick, concrete block, or tile masonry,

Tilt-up, formed concrete, nonbearing

Curtain walls.

 

D

Wood or steel studs in bearing wall, full

Or partial open wood or steel frame, primarily Combustible construction.

Wood or steel floor joists or concrete

Slab on grade.

 

Wood or steel joists with wood or steel

Deck.

 

Almost any material except bearing or

Curtain walls of solid masonry or concrete. Generally combustible construction.

S

Metal bents, columns, girders, purlins And grits without fireproofing, incombustible

Construction.

Wood or steel deck on steel floor joists,

Or concrete slab on grade.

 

Steel or wood deck on steel joists. Metal skin or sandwich panels. Generally

Incombustible.