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15 Cards in this Set
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Cavity wall |
is a type of masonry wall construction in which a continuous air space or cavity is provided inside the wall. therefore it is actually two walls separated by an air space but joined through ties. Used to mitigate rain penetration through air gap, flashings and weep holes |
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What are some advantages of Cavity Walls? |
Reduction in amount of masonry used Improved thermal insulation (most important = ) Positive protection against rain penetration |
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What is essential to the design of a cavity wall on a foundation wall? |
A properly designed gutter installed between the foundation and the wall. Usually metal flashing forms this gutter and is shaped so that it turns up behind the outer wall and is carried into a mortar joint of the inner wall (mortar is omitted from the vertical joints of the bottom course, usually every third joint 'weep-holes') |
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It is essential that the air space be kept continuous. What is employed during the construction of the masonry wall to ensure mortar does not break the continuity of the air space? |
wooden strips collect mortar that drops into the cavity and is pulled up to allow installation of the next series. Fresh mortar may be removed by a hosed stream of water. There are other forms of "mortar dropping control" that are installed at the bottom of the wall. |
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What are the characteristics of good/adequate brick ties? |
strong, embedded far enough into mortar for anchorage (2.5"), corrosion-resistant (non-ferrous ties are more desirable), slope away from inner wall to encourage water away Corrugated metal strips are NOT acceptable for cavity wall construction |
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What are some shapes of ties and which is the most common? |
Most common: Z-shaped Rectangular U-shaped |
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NBC requires that ties in cavity walls be spaced.... |
more than 18" apart and not less than 36" |
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True or False: Shelf angles should be galvanized steel |
True, or stainless steel to resist corrosion |
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What can be done to precent water from passing along a door or window frame into the interior? |
Flashing, weep holes and proper frame designs (diverter strips, jamb flashing ) |
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True or False: Corners of cavity walls are particularly susceptible to cracking when a structural frame has been used. |
True, A vertical control joint is usually provided in the outer part of the wall approx. 3*4' from the corner. Also the outer part of a cavity wall should not be tied to corner columns of concrete. |
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Control joint are especially important for what part of the building where there is a greater tendency for movement? |
Parapets |
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What is the maximum height a cavity wall may be built above its bearing support according tot he NBC? |
36' |
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What is the minimum thickness of a cavity wall |
10 (254) inches, with the cavity not less than 2 (51mm) or more than 3 (76mm)inches wide |
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True or False, The NBC requires that lateral support, either horizontal or vertical must be provided for cavity walls |
True |
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What are the three essential requirements for cavity wall construction? |
1. Must have a gutter at its base to collect water rand drains to direct water out. 2. The two parts of the wall must be anchored together with ties that are corrosion resistant and strong 3. The wall must have a cavity free of mortar or other material that may bridge water |
