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15 Cards in this Set
- Front
- Back
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What are some factors which influence the problem of rain penetration through unit masonry? |
The degree of exposure of a building High buildings freely exposed (to wind and rain) buildings are most effected (low buildings are often protected/unexposed/have wide overhanging roofs) Properties of the masonry materials The care during design and construction |
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True or False: During a rain storm the air pressure at the outside surface of the rain-wetted wall is usually lower than the inside surface. |
False, It is usually higher than the inside surface. The rain falling on a wall is forced through the wall by this pressure difference provide there are available paths of travel. |
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What are some 'means' of water entry through masonry walls? |
Structural cracks from differential movements of building parts Unbonded areas between unit and mortar (often more important and are the most common) Brick itself Mortar itself (but these two are only in unusual circumstances) |
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What are the critical characteristics of the brick/mortar assembly to ensure a proper bond? |
The rate of water absorption of the brick The water retention of the mortar The ideal situation is when the mortar may remain plastic long enough to develop a good bond before the next brick is placed |
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True or False, To achieve as good a bond as possible, any mortar should be used as wet as possible. |
True, mortar of stiff consistency when laid produces a poor bond with the brick. |
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What can be done to remediate the suction of the brick when the brick has a high water absorption rate? |
Bricks can be wetted before being laid. |
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Does the bricklayers method of constructing the brickwork affect the bond? |
Yes, Better bonds are obtained when short mortar beds are laid out in advance of the work. And bricks should not be shifted once set. |
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What is the best tooling for mortar joints to resist rain penetration? |
Concave surface tooling (raked-out or flush cut do not provide as much resistance) |
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What is the function of control joints? |
To safely accommodate the movements of expansion or contraction of walls. eg "drying shrinkage" |
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Careful design of the building and the installation of proper flashings and caulking are required to ensure good performance when wind-driven rain strikes. Where are some common locations that should be flashed and caulked to avoid rain penetration? |
Flashing in the wall at spandrel beams Parapet wall flashing to isolate from wall below Caulking and flashings at windows and doors. Also, providing adequate drainage |
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Cavity wall |
Consists of two walls which are separated by a continuous vertical air space and are bonded by ties. Principle of operation is that rain may penetrate the outer part and flow down inside the face without crossing the cavity to the inner wall. |
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What is a design characteristic of ties to ensure water cannot pass along them to the interior? |
a "v" crimp in the middle |
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What are some causes of dampness on the inner surface of a wall and what are the essential parts of treatment? |
Causes: Direct penetration of rain Condensation Defective drains or pipes within or near a wall Defective flashings Lack of calking Rise of ground moisture into the wall from wicking action Treatments: filling of structural cracks, renewal of caulking, repair and correction of faulty drains and flashings, bonding remediation, permeable unit remediation |
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What can be done to remediate openings between unit and mortar? |
Brushing a paste of portland cement and fine sand into mortar joints OR Repointing - The mortar is removed do a depth of 1/2" (13mm) from the joint and replaced with fresh tightly packed mortar |
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What can be done to remediate very permeable units? |
Stucco Painting Colourless "waterproofer" All would have to be renewed periodically |
