Controlling Water/Air Leakage and Water Vapour (Part 1) Flashcards
There are 3 sources of water in exterior walls. Name them.
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Name the sources of water in exterior walls.
- Rain
- Groundwater
- Landscaping; i.e improper drainage slopes causing water accumulation in window wells, or sprinkler systems left operating over long periods of time.
Name the sources of water in interior walls.
- Vapour that condenses; i.e thermal bridging of a ‘cold’ beam
- Plumbing leaks
- HVAC equipment malfunctions
- Improper use of water
Name the source of water in construction.
The moisture content of new materials; i.e wood, concrete, firewood, fresh slabs, etc.
There are 3 conditions for rain penetration. Name them.
- Source of water
- Opening in assembly
- Force to drive water through
There are strategies to control rain penetration. Name at least 5.
- Deflect water away from critical areas
- Drain the water that has entered the wall
- Allow moisture that has entered to dry
- Choose materials that are resistant to water
- Seal openings where appropriate with sealants and gaskets ( although you cannot rely on this, they will wear out )
- Neutralize forces
True or False. Removing one of the 3 conditions ( Source, Openings, Forces ) eliminates the threat of rain penetration. All three are required simultaneously to have water leakage.
True.
There are 5 forces that cause rain penetration. Name them.
- Gravity
- Capillary action
- Surface tension
- Momentum
- Air pressure difference
Name the components of a detail pattern.
- Wash
- Overlap
- Overhang and drip
- Drain and weep
- Cold roof
- Foundation drainage
- Capillary break
- Labyrinth
- Upstand/dam
- Rainscreen assembly
What is a wash?
Slope surfaces to drain away from vulnerable areas, such as chimney cap and cricket, pitched gutters, pitched drains ( floor-to-slab )
Where?
- Window sills; away from window
- Parapet; away from roof membrane
- Roof; away from walls
- Grade; away from building
What is the rule of thumb for slopes away from the building?
10% / 10 feet
What is overlap?
To overlap a higher surface over a lower surface. ( ex. shingles overlap to aid in water flow off the building; exception: in cases of ice dams where the water could freeze and travel in the opposite direction )
What does flashing do and what materials is it made out of?
Demonstrates wash and overlap material used to intercept and direct water to desired drainage paths.
Materials include:
- Metals; such as, aluminium, galvanized steel, stainless steel, copper, zinc and lead.
- Membranes; such as, modified bitumen ( rubberized asphalt, i.e BlueSkin ), polyethylene, vinyl, and roll roofing ( NOT tape )
What are the requirements of flashing?
- Water barrier - doesn’t absorb water, only deflects water, has to be able shed water
- Terminations - the ends of the flashings have to be rigid to project water away; flexible to accommodate movement ( because they are installed where there are joints, the two parts might move differently )
- Durability - must resist UV rays, temperature changes, and handling during construction.
- Compatible with surrounding materials - chemical reaction between two materials, galvanic action, corrosion
- Buildability and sequencing - is the detail buildable?
- Maintenance ( vs durability ) - use high durability materials and maintenance becomes less of a problem. On the other hand, the more you are able to maintain a product the less concern you have with durability. ( don’t forget maintenance cost money )
True or False. We design under the assumption that water will always manage to get in.
True.
