Fundamentals of BC_ Chap 10

Question 1

minimum recommended
separation between wythes of a cavity
wall

Answer 1

2 inches (50 mm).

Question 2

where insulation boards are inserted into the cavity, the remaining clear space between the face of the insulation ad the back of the outer whythe should not be reduced to less than x inch?

Answer 2

1 inch.

Question 3

Weep holes should be installed not more than how many inches horizontally in brick?

Answer 3

24 inches

Question 4

Weep holes should be installed not more than how many inches horizontally in concrete masonry?

Answer 4

32 inches

Question 5

Weep holes should lie immediately on top of the ashing in the wall to keep the bottom of the cavity as dry as possible.
Min diameter for a weep hole is?

Answer 5

1/4nch

Question 6

Ways to create weep hole:

Answer 6

1. A short piece of rope laid in the mortar joint and later pulled out, with a plastic or metal tube laid in the mortar,
2. or simply by simply leaving a head joint unmortared.
3. Plastic and metal weep hole accessories with insect screens are available for installation in unmortated head joints to prevent bees or other insects form taking up residence within the cavity.

Question 7

When the cavity wall
reaches the bottom of the cavity, it is
caught by a thin, impervious membrane
called?

Answer 7

a flashing and drained
through weep holes to the exterior of
the building.

Question 8

dampproofing

Answer 8

may be applied
to the cavity side of the interior
wythe of the wall.
In the event that water
does bridge the cavity, this coating
discourages seepage into the interior
wythe.

Question 9

The minimum recommended
separation between wythes of a cavity
wall

Answer 9

2 inches

Question 10

During construction, the cavity

must be kept free of

Answer 10

mortar droppings,
brick chips, and other debris,
which can clog the weep holes or
form bridges that can transport water
across the cavity to the inner wythe

Question 11

inevitably some of the mortar falls into
the cavity. Eventually, enough mortar
may accumulate at the bottom of the
cavity to block drainage holes. One
solution to this problem?

Answer 11

Is to place a
strip of wood on the steel ties in the
cavity to catch such mortar droppings,
then to pull out this strip and
scrape the mortar off it before placing
the next row of ties.
An alternative is for the
mason to bevel the bed joint with the
trowel, making it thinner at the cavity
face and thicker at the outside face,
before placing the masonry units in it.
This minimizes the squeezing out of
mortar into the cavity.

Question 12

cavity drainage materials

Answer 12

in the form of various proprietary
free-draining, woven, or
matted products have come into use.
These materials are inserted within
the cavity, either at the bottom of the
cavity or continuously throughout its
full height, to catch mortar droppings
so that they do not obstruct drainage
(Figure 10.5). 
Such products, though
helpful in keeping weep holes open,
may still permit mortar droppings to
accumulate, creating bridges that can
transfer heat and moisture across the
cavity. For this reason, they should
not be considered a substitute for
good construction practices aimed at
keeping the cavity as free of mortar
droppings as possible.

Question 13

Two general types of flashing are used in masonry construction

Answer 13

External flashings:
prevent moisture from penetrating into the masonry wall at its exposed top or where it intersects the roof.

Internal fl ashings (also known as concealed or through-wall fl ashings)
catch water that has penetrated a masonry wall and drain it through weep holes back to the exterior.

Question 14

Flashings and Drainage

Two general types of flashing are used in masonry construction:

Answer 14

External flashings
prevent moisture from penetrating into the masonry wall at its exposed top or where it intersects the roof.

Internal flashings
(also known as concealed or through-wall flashings) catch water that has penetrated a masonry wall and drain it through weep holes back to the exterior.

Question 15

The base flashing is normally turned up for a height of at least

Answer 15

8 inches (200 mm).

Question 16

internal flashing that is placed at

Answer 16

the bottom of the wall cavity.

Question 17

Where an internal flashing crosses the wall cavity,

Answer 17

it should be turned up 6 to 9 inches (150Ð225 mm) at the back face of the cavity and penetrate the inner wythe by at least 2 inches (50 mm). In this manner, water draining down the cavity is intercepted by the ß flashing and directed toward the exterior of the wall.

Question 18

c. At the outside face of the wall, the ß ashing should be carried at least how many inch?

Answer 18

3/4

Question 19

There are three general ways of insulating masonry walls:

Answer 19

on the out-side face, within the wall, and on the inside face.

Question 20

EIFS

Answer 20

exterior insulation and finish system
which consists of panels of plastic foam that are attached to the masonry and covered with a thin, con-tinuous layer of polymeric stucco rein-forced with glass fiber mesh.

Question 21

Expansion joints

Answer 21

inten-tionally created slots that can close slightly to accommodate expansion of surfaces made of brick or stone masonry.
open seams that can close slightly to allow expansion to occur in adjacent areas of material. Expansion joints in brick walls permit the bricks to expand slightly under moist conditions (Figure 10.21). Ex-pansion joints in aluminum curtain wall mullions (Figure 21.14) allow the elements of the wall to increase in size when warmed by sunlight.

Question 22

Control joints

Answer 22

are inten-tionally created cracks that can open to accommodate shrinkage in surfaces made of concrete masonry.
deliberately cre-ated lines of weakness along which cracking will occur as a surface of brittle material shrinks, relieving the stresses that would otherwise cause random cracking. The regularly spaced grooves across concrete side-walks are control joints; they serve to channel the cracking tendency of the sidewalk into an orderly pattern of straight lines rather than random jagged cracks. Elsewhere in this book, control joint designs are shown for concrete ß oor slabs (Figure 14.3c), concrete masonry walls (Figure 10.21), and plaster (Figure 23.12).

Question 23

Abutment joints,
sometimes called construction joints
or isolation joints,

Answer 23

re placed at junctions be-tween masonry and other materials, or between new masonry and old masonry, to accommodate differences in movement.

Question 24

Efflorescence can usually be avoided

Answer 24

by choosing masonry units that have been shown by laboratory testing not to contain water-soluble salts, by using clean ingredients in the mortar, and by minimizing water intrusion into the masonry construction.

Question 25

Below grade, masonry should first be

Answer 25

parged (plastered on the outside) with two coats of Type M mortar to a total thickness of 1/2 inch (13 mm) to seal cracks and pores. After the parg-ing has cured and dried, it can be coated with a bituminous dampproof-ing compound or, if a truly watertight wall is required below grade, it can be covered with a waterprooÞ ng layer, as discussed in Chapter 2.

Question 26

Mortar cannot be allowed to freeze before it has cured; otherwise, its strength and watertightness may be seriously damaged. In cold climates, special precautions are necessary if masonry work is carried on during the winter months. These include such measures as keeping masonry units and sand dry, protecting them from freezing temperatures prior to use, warming the mixing water (and sometimes the sand as well) to produce mortar at an optimum tem-perature for workability and curing, using

Answer 26

Type III (high early strength) cement to accelerate the curing of the mortar, and mixing the mortar in smaller quantities so that it does not cool excessively before it is used.

Question 27

The Þ nished masonry must be protected against freezing for at least

Answer 27

2 to 3 days after it is laid, and the tops of walls should be protected from rain and snow. Chemical accelerators and so-called ÒantifreezeÓ admixtures are, in general, harmful to mortar and rein-forcing steel and should not be used.