CAREER INSTITUTE OF TECHNOLOGY
STUDYGUIDE
CHAPTER 16: COMPOSITE AND CAVITY WALLS
INSTRUCTOR: Mr. Brian Iasiello
USEFUL INFORMATION
1. Not only are masonry composite walls and cavity walls chosen for their
strength, but their resistance to rain, fire, and sound transmission keep
these two wall designs at the forefront of popular wall selections.
2. The designs for composite walls and cavity walls are similar. Both are
multiwythe masonry walls, two separate wythes of different masonry
units, with each wythe having different properties and strengths.
3. Tying the wythes together with joint reinforcement and insulating the
air cavity between them creates excellent exterior structural bearing
walls.
4. Frequently, aesthetically appealing low-maintenance brickwork is used
for the outside wythe and cost-saving concrete masonry units are used
for the inside wythe, also becoming the interior wall face.
5. Although similar, there are differences between composite walls and
cavity walls, affecting both their physical properties and selection in
wall design.
6. Successful performance of cavity walls and composite walls depends on quality workmanship and attention to details such as wire joint reinforcement, control and expansion joints, and flashing and weeps.
Terms
Adjustable Assemblies - Masonry wall reinforcement consisting of ladder-type or truss-type reinforcement embedded in the inner wythe with extended tabs or eye hooks to which rectangular adjustable sections are connected and embedded in the joints of theouter wythe.
Bearing Plates - Steel plates with welded anchors on their bottom sides embedded in the tops of masonry bearing walls to which structural steel beams or joists are secured by welding.
Bond Beam - A horizontal reinforced beam comprised of specially formed bond beam concrete masonry units, grout, and horizontally placed steel reinforcement bars designed to strengthen a wall, support loads above openings, or distribute imposed loads uniformly.
Cap - An architectural concrete or stone member for part of or an entire wythe that is terminated below the top of an adjoining wall.
Capital - An architectural concrete or stone top for piers and columns, protecting them from the weather and enhancing their appearances.
Cavity Wall - A masonry wall consisting of an inner and an outer wythe bonded with corrosion-resistant metal ties and separated by an airspace not less than 2” or more than 41⁄2”.
Cleanouts - Openings in the face-side of CMU walls, enabling the removal of mortar droppings before grouting.
Composite Masonry Wall - A masonry wall consisting of two wythes of different masonry units having different strength characteristics connected with corrosion-resistant wire reinforcement or brick headers and acting as a single wall in resisting forces and loads.
Control Joint - A vertical separation completely through a concrete masonry wall that is filled with an inelastic substance controlling the location of cracks caused by volume changes resulting in the shrinkage of block.
Coping - The projecting top cap of a wall.
Differential Movement - The unequal movement of the building materials in a wall system.
Drainage Wall Systems - Masonry walls designed to divert water from their air cavity to the exterior of the outer wythe.
Drip - A cutout in the underside of caps, copings, and sills preventing water from traveling back to and running down the face of the wall, causing water to drip beyond the face of the wall.
Expansion Joint - A horizontal or vertical separation completely through a brick wythe that is filled with an elastic substance permitting the expansion of brick walls caused by thermal movements or increasing volume of brick.
Fire Wall - A fire-resistant rated wall usually built within a structure from the foundation and extending above the roof to restrict the spread of fire from one part of a structure to another.
Granular Fill Insulations - Lightweight, inorganic, perlite or vermiculite granules treated for water repellency and used as wall insulation.
High-Lift Grouting - Grouting done once a wall is built to its story height or final height, whichever is less, in a single pour.
Ladder-Type Wire Reinforcement - Masonry wall reinforcement consisting of two or more longitudinal rods welded to perpendicular cross rods, forming a ladder design.
Load-Bearing Wall - A wall supporting its own weight and the structural loads, weights, and forces to which the structure is subjected.
Low-Lift Grouting - Grouting done in multiple pours as the wall is built.
Multiwythe Grouted Masonry Wall - A multiwythe wall whose air cavity is filled with grout.
Parapet Wall - That part of a wall extending above the roofline.
Rain Screen Wall - A masonry cavity wall containing protected openings permitting the passage of air but not water into the cavity, permitting equal air pressures of the outside air and that within the air cavity.
Rigid Insulation - Polystyrene materials produced from extruded foam or molded bead processes placed between the wythes of cavity walls as wall insulation.
Shelf Angles - Steel structural members on which brick are bedded for wall support.
Soft Joints - Horizontal expansion joints minimizing wall cracks by permitting both the expansion of brick masonry walls and the deflection of the shelf angles.
Through-Wall Flashing - Flashing extending completely across the air cavity separating masonry wythes and through the outer wall beyond the exterior face of the wall.
Truss-Type Wire Reinforcement - Masonry wall reinforcement consisting of two or more longitudinal rods welded to diagonally oriented cross rods, forming a truss design.
Wythe - A masonry wall.
STUDYGUIDE
A. Multiwythe Walls:
1. Two separate wythes of different materials
2. Each with different properties
3. Tied together with joint reinforcement
4. Great strength, resistant to fire and moisture, excellent insulator
B. Comparing Composite and Cavity Walls:
1. Composite Masonry Wall:
a) Built of two wythes of differing masonry units
b) Connected with corrosion-resistant reinforcement
c) Acts as a single wall
2. Cavity Wall:
a) Built of an inner and outer wythe connected by corrosion-resistant metal ties and separated by an air space
b) Different from a composite wall in that the outer wythe resists forces independently without transmitting stress to the inner wythe
c) Cavity walls and composite walls are similar in that they are both multi-wythe walls, but a 2" or wider air cavity is a distinguishing characteristic of cavity walls.
C. Controlling Moisture:
1. Cavity walls are drainage wall systems, as penetrating rain drains to the bottom and is diverted to the exterior.
2. Flashing and weep holes are required.
D. Insulating Composite and Cavity Walls:
1. Air cavities may receive insulation.
a) Granular fill insulations
1) Poured into cavities
b)Rigid insulation board
1)Polystyrene material adhered to the back-up wall
E. Wall Reinforcement:
1. Always corrosive resistant, such as hot-dipped galvanized or stainless steel.
2. Ladder type
3.Truss type
4. Adjustable assemblies
F. Accommodating Differential Movements:
1. Differential movement is the unequal movement of different building materials in a wall system.
2. Expansion joints allow materials to expand.
3. Control joints attempt to control crack locations.
G. Parapets, Copings, and Caps:
1. A parapet wall is that part of a wall above the roofline.
2. Coping is the projecting top cap of a wall.
3. A cap is an architectural member for a wythe terminated below the top of an adjoining wall.
H. Grout-Reinforced Walls:
1. Grout is a mixture of cement, water, and small aggregates.
2. It is used to strengthen masonry walls.
3. Grout is used in conjunction with steel reinforcing rods.