This is the 4th and last part of the Architectural Details #1: Waterproofing through Design Solutions.Let's finish off with the last four design solutions that were discussed on the first part of this discussion.
Check the other parts here:
Waterproofing through Design Solutions Part 1
Waterproofing through Design Solutions Part 2
Waterproofing through Design Solutions Part 3
Capillary Break
Since water has the ability to pull itself through a narrow crack by surface tension and capillary action, it may enter a building connection through the gaps. It cannot, however, bridge a wide enough gap. Capillary action by water can therefore be stopped by providing an internal crack that is wide enough that water may not be able to bridge across. This is what we call a capillary break. The gap should be at least 1/4" or 6mm wide.
Wall Panels
Capillary breaks are added to both the horizontal and vertical connections of wall panel claddings. Large gaps are created in the middle to prevent water from bridging to the inside of the building.
Window Frame
Two capillary breaks were created in this aluminum window frame detail.
(Image taken from Architectural Detailing: Function - Constructibility - Aesthetics)
A Capillary break is also created by bending the parapet counterflashing. This will prevent water from getting inside the counterflashing and underneath the roofing membrane by capillary action.
(Image taken from Architectural Detailing: Function - Constructibility - Aesthetics)
Labyrinth
The labyrinth is created to stop any raindrop or snow from entering through the joints or gaps on its own momentum. It is simply creating a maze-like figure to architectural details which would break the straight path that a drop of water or snowflake may be traveling, preventing it from getting inside the building.
Below are other samples of labyrinth shapes used on common building assemblies used in wall panels, aluminum frames, door frames, etc.:
(Image taken from Architectural Detailing: Function - Constructibility - Aesthetics)
Rainscreen Assembly
The Wash, Labyrinth, Capillary Break, and Overhang and Drip details may prevent water from getting through the building which is driven by the forces of gravity, surface tension, capillary action and momentum but when air pressure differentials come into play, it's already a different story.
Air pressure differentials occur when air pressure on the outside of a building becomes larger than air pressure on the inside, or vice versa. When this happens, flow of air would transfer from the larger pressure to the smaller pressure until they are equalized, and more often than not, water is dragged in with the flow of air.
Below is an image where a rainscreen assembly was not used:
As air pressure becomes larger on the outside by gusts of wind or change in weather, air current may pump water inside and could cause leakage.
The solution to air pressure differentials is to provide a sealant or an air barrier on the inside which is seen on the image above. Now, if the wind blows and raises the air pressure on the outside, it will force air into the gap and inside the interior of the joint. Air won't be able to pass through the air barrier and it will stop right there. The pressure inside the joint and outside of the building will now equalize and there will be no more energy to transmit the water to the inside of the joint. Note that the air barrier should be placed after the pressure equalization chamber. This is very important because water will still be able to get through if it was placed before the pressure equalization chamber.
The capillary break on the joint now serves another purpose, as a pressure equalization chamber. The wall panels now are called a rainscreen. The whole assembly of rainscreen, air barrier and pressure equalization chamber is called the rainscreen assembly.
This principle not only works on wall panels and can be used on different situations. Some other applications of these are on window sills and door sills where the windows or doors are exposed to strong winds and storms.
Upstand
An upstand is simply a dam. This is used if placing an air barrier to create a rainscreen assembly becomes impractical. This may happen on door sills and window sills where gaskets and weatherstrips that acts as an air barrier are expected to age and wear which may lead to water leakage. Providing this upstand will serve as a backup in case the air barrier gives way. The height of an upstand is determined by the maximum expected wind pressure which is also a determinant of the height of water that may be pushed up towards the opening.
On the left is an image showing an upstand used on the sill of a sliding glass door.
(Image taken from Architectural Detailing: Function - Constructibility - Aesthetics)
To conclude the discussion on waterproofing through design solutions, using the solutions that were discussed alone may not be enough to ensure a water tight structure, a good knowledge of the situations, site orientations, the weather on the site and other details that may affect the project is beneficial to properly execute a good water proofing solution. This and the combination of the design details discussed will ensure that your building will be water tight for a very long time.
...go back to part 3
(Image above by Niffty.. on Flickr)
References:
Since water has the ability to pull itself through a narrow crack by surface tension and capillary action, it may enter a building connection through the gaps. It cannot, however, bridge a wide enough gap. Capillary action by water can therefore be stopped by providing an internal crack that is wide enough that water may not be able to bridge across. This is what we call a capillary break. The gap should be at least 1/4" or 6mm wide.Wall Panels
Capillary breaks are added to both the horizontal and vertical connections of wall panel claddings. Large gaps are created in the middle to prevent water from bridging to the inside of the building.Window Frame
Two capillary breaks were created in this aluminum window frame detail.(Image taken from Architectural Detailing: Function - Constructibility - Aesthetics)
A Capillary break is also created by bending the parapet counterflashing. This will prevent water from getting inside the counterflashing and underneath the roofing membrane by capillary action.(Image taken from Architectural Detailing: Function - Constructibility - Aesthetics)
Labyrinth
The labyrinth is created to stop any raindrop or snow from entering through the joints or gaps on its own momentum. It is simply creating a maze-like figure to architectural details which would break the straight path that a drop of water or snowflake may be traveling, preventing it from getting inside the building.Below are other samples of labyrinth shapes used on common building assemblies used in wall panels, aluminum frames, door frames, etc.:
(Image taken from Architectural Detailing: Function - Constructibility - Aesthetics) Rainscreen Assembly
The Wash, Labyrinth, Capillary Break, and Overhang and Drip details may prevent water from getting through the building which is driven by the forces of gravity, surface tension, capillary action and momentum but when air pressure differentials come into play, it's already a different story.
Air pressure differentials occur when air pressure on the outside of a building becomes larger than air pressure on the inside, or vice versa. When this happens, flow of air would transfer from the larger pressure to the smaller pressure until they are equalized, and more often than not, water is dragged in with the flow of air.
Below is an image where a rainscreen assembly was not used:
As air pressure becomes larger on the outside by gusts of wind or change in weather, air current may pump water inside and could cause leakage.The solution to air pressure differentials is to provide a sealant or an air barrier on the inside which is seen on the image above. Now, if the wind blows and raises the air pressure on the outside, it will force air into the gap and inside the interior of the joint. Air won't be able to pass through the air barrier and it will stop right there. The pressure inside the joint and outside of the building will now equalize and there will be no more energy to transmit the water to the inside of the joint. Note that the air barrier should be placed after the pressure equalization chamber. This is very important because water will still be able to get through if it was placed before the pressure equalization chamber.The capillary break on the joint now serves another purpose, as a pressure equalization chamber. The wall panels now are called a rainscreen. The whole assembly of rainscreen, air barrier and pressure equalization chamber is called the rainscreen assembly.
This principle not only works on wall panels and can be used on different situations. Some other applications of these are on window sills and door sills where the windows or doors are exposed to strong winds and storms.
Upstand
An upstand is simply a dam. This is used if placing an air barrier to create a rainscreen assembly becomes impractical. This may happen on door sills and window sills where gaskets and weatherstrips that acts as an air barrier are expected to age and wear which may lead to water leakage. Providing this upstand will serve as a backup in case the air barrier gives way. The height of an upstand is determined by the maximum expected wind pressure which is also a determinant of the height of water that may be pushed up towards the opening.On the left is an image showing an upstand used on the sill of a sliding glass door.(Image taken from Architectural Detailing: Function - Constructibility - Aesthetics)
To conclude the discussion on waterproofing through design solutions, using the solutions that were discussed alone may not be enough to ensure a water tight structure, a good knowledge of the situations, site orientations, the weather on the site and other details that may affect the project is beneficial to properly execute a good water proofing solution. This and the combination of the design details discussed will ensure that your building will be water tight for a very long time.
...go back to part 3
(Image above by Niffty.. on Flickr)
References:
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looking for water proofing methods for vintage home's. 1920 thru 1939.
architectual reference would be helpful.
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