8 Masonry And Ordinary Construction Flashcards
Typical brick size is
3 5/8x 7 5/8x 2 1/4”
For most bricks, three courses plus mortar joints equals what height
Eight inches
Concrete block
Aka concrete masonry units (cmu) most common concrete block is hollow
Hollow concrete block is produced in many sized but commonly in
Nominal 8x8x16
Most common stone masonry for construction is
Granite, limestone, sandstone, slate and marble
Brownstone is a form of
Sandstone
Masonry construction can be labor intensive and mortar can deteriorate. They can be made of
Brick, terra cotta, concrete block, stone, clay tile block, gypsum block, glass
Masonry units have no significant tensile strength their structural application is to support what type of load
Compressive
Allowable compressive strength of brick masonry
250 psi
A chunk of brick wall 8” thick measuring 4x4 feet would weight
Appx 1,267 lbs
The weakest part of a masonry wall can be
Mortar joints
Mortar is available in five basic types with strength ranging from
75-2500 psi
Compressive strength of brick
2000-20,000 psi
Compressive strength of concrete masonry units
1500-6,000 psi
Mortar is mixed from
Portland cement, hydrated lime, sand, water
Portland cement
Most common cement chiefly using calcium and aluminum silicates. Mixed with water to form paste that hardens. Known as hydraulic cement
Mortar once produced without Portland cement used what as primary bonding agent
Lime
Most common load bearing masonry walls are made of
Brick, block, or both
Gypsum block and lightweight concrete block are limited to what
Non load bearing partition walls
Masonry walls must be thicker as they get taller because
They need to support the compressive loads of the building as well as the lateral weight of the wall itself
Non reinforced masonry walls are usually limited to what height
6 stories
Steel framed buildings are typically built with masonry veneer because
It allows cheaper construction and stability at greater bullying heights
Steel reinforced masonry walls can have reduced thickness. A 10 sorry building can have a wall how thick
12 inches
Course
Horizontal layer of individual masonry units
Wythe
Single vertical row of multiple rows of masonry units, typically brick
Header course
Course of bricks with ends facing outward
Multiple wythes are normally provided for strength and stability. Sometimes in conjunction with block wythes. This design is referred to as
Concrete block brick faced CBBF
Stretcher course of brick
Bricks placed end to end
Bricks placed vertically on end
Soldier course
Headers are used to
Provide a horizontal bond between the wythes
Exterior brick wall is usually constructed with a vertical cavity between the exterior and interior wythes. Known as a
Cavity wall
Cavity walls are intended to
Prevent water seepage through mortar joints to interior and increase insulation. Requires metal ties
Masonry walls can be reinforced by
Placing vertical steel rods in a cavity between two wythes. Either brick or brick and block.
Reinforcement of masonry walls can also be accomplished with what
Buttresses, flying buttresses, and pilasters
Because mortar provides little tensile strength the individual openings in masonry walls must be supported by
Lintels
Lintel
Beam over an opening in masonry wall, made of steel, concrete or reinforced masonry
Lintels and to a lesser extend, arches, are most common means to supporting loads over masonry openings. Corbelling isn’t used only when
Where the Architectural styling makes it attractive
Parapet
Portion of the exterior wall that extends above roof line. Low wall at edge of roof. Found on exterior masonry walls and fire walls of buildings with combustible roofs
Parapet walls project how high
1-3 ft or more
Parapets, especially in front pose what risk to firefighters.
Collapse
Most basic and traditional type of masonry building
Where extrior load bearing walls support interior wood floors and roof rafters and joists
Ordinary construction is aka
Type III, masonry wood joisted
In many residential and commercial buildings wood joists are rest on a beam pocket which is
A pocket several inches into wall that is deep enough to suitable support the beam
When pocketed into a masonry wall a joist will be cut at a slight angle known as
Fire cut
Fire cut
Angled cut made in end of wood joist resting in masonry wall allowing beam to freely fall away from wall in case of failure of beam. Prevents beam from acting as lever pushing wall out.
Where a beam transmits a large vertical load to a wall,nether wall may be built out and increased in thickness to support it , known as
Pilaster
Fire resistance of masonry walls depends on
Type of masonry unit used and thickness of wall
Hollow block can crack and spall. Wall of fire rated cmu or brick a an have fire resistance time of
2-4 hrs or more
An officer must monitor changes or growth in masonry wall cracks because
Changes or growth can indicate impending collapse
Mortar can erode form elements such as rain by
Rain seeping in, freezing and causing expansion which causes mortar to crack or flake
Cracks in masonry can be caused by
Foundation settling or saggin interior beams from rot or damage
Structural deterioration of masonry walls prior to fire will contribute to
Structural failure under fire conditions
If masonry walls begin to bulge or lean out, a way of stabilizing it is with
Steel Tie rods, parallel to joists though the wall with bearing plates outside like washers, sometimes in shape of stars.
Tie rods in masonry wall may indicate repair however it may
Be a part of original design
Potential problems for steel tie rods
Heated under fire, expand, reducing strength and weakening walls.
Tie rods used for repair are generally
Less compatible with design of building, may just be form of steel channels
Not uniformly positioned or spaced on walls
Other indications of repair like mortar repair near tie rod bearing plates
Masonry walls usually collapse because of
Failure of interior beams by collapse, pushing against walls forcing them out.
Collapse zone of masonry wall is
At least the height of the building. Corners are safest.
Facia
Flat horizontal or vertical board at outer face of cornice, broad flat surface over storefront or below cornice. False front or mansard roof face
Mill construction
Exterior masonry, interior timber beams or laminated, classified as type IV
Two characteristics differentiating type IV from type III
Dimensions of wood members, and combustible voids not permitted
Dimensions and framing requirements for interior type IV members
Floors are 3” x 1” tongue and groove
Roofs are 2” tongue and groove or 1 1/8” structural panel or plank.
Non bearing interior partitions not less than two layers of 1” matched boards or laminated construction 4” thick or 1 hr fire rated.
Absence of void spaces in type IV is major firefighting advantage because
Can more easily get at fire
Not necessary to pull ceilings because there aren’t suspended ceilings
Advantages to mill type IV can be lessened when
It undergoes a change of occupancy, like conversion to residential units, leading to concealed spaces in partitions.
