Description: Through-wall flashing is used to divert moisture, which has entered the wall, to the outside, before it can cause damage. This flashing method is considered the most satisfactory method of preventing leaks except in areas exposed to earthquakes.
Through-wall flashing is used at all points where moisture may enter the wall, and in selected places particularly susceptible to water damage.
The flashing must typically rise at least 8" from the low point at the exterior face of the building to the high point inside the wall. Weeps spaced a maximum of 24" O.C. must be included. Use of pea gravel is recommended behind brick veneer. The ends of the flashing must be dammed to prevent water that has been caught from draining back into the wall.
Through-wall flashing is commonly fabricated by deforming the metal in such a way as to provide bond strength in mortar joints. All through-wall flashing should be set with a bed of mortar above and below the flashing in strict compliance with the flashing manufacturer's specifications.
On nailable sheathing, the flashing should be fastened with wide head nails or cleats. Nailing through flashing prohibits movement and should be avoided when movement is expected. The nail should be driven just above the upper edge of the flashing, allowing its wide head to hold the copper sheet. Nails or cleats should be spaced no more than 12" O.C.
The minimum recommended weight for copper through-wall flashing is 12 oz. using "High Yield", or 16 oz. using standard cold rolled copper.
Special Conditions: If copper flashing is used adjacent to other metals, proper care should be taken to account for separation of the materials. These conditions often arise at brick shelf angles, and under metal window and door frames. They are typically handled with the use of bituminous paint, zinc chromate or red lead primers on the contact surfaces.
Although copper flashing is not adversely affected by the corrosive alkalies present in masonry mortar, it's long term performance can be compromised by excessive chlorides. Therefore, chloride based additives in the mortar should be avoided.
See Detail 9.1I for more information on flashing special brick veneer conditions.
9.1A. Brick Veneer on CMU at Decking
This detail illustrates a condition where the top edge of the flashing is held by the CMU backup. This is the typical method of holding the flashing in a cavity wall.Download CAD File
9.1B. Brick Veneer on CMU at Steel Spandrel
This condition is similar to Detail A, except that the brick veneer is supported by a steel plate. The flashing detail is essentially identical.Download CAD File
9.1C. Brick Veneer on CMU at Window Head & Sill
It is particularly important to provide flashing at the head and sill of a window or door. Moisture can promote corrosion in the steel lintel, and may stain or damage the window.Download CAD File
At the sill, the risk of moisture entering the wall is especially high. Here, a backer rod and sealant are applied below the flashing to prevent moisture penetration. The ends of the flashing are dammed to prevent water penetration behind the sealant below.
9.1D. Brick Veneer on CMU at Grade
This detail shows the typical method for flashing a cavity wall at grade.Download CAD File
9.1E. Brick Veneer on CMU at Concrete Spandrel
Shown is one way of flashing over the shelf angle at a concrete spandrel. This detail can be used where the distance from the top of the concrete to the shelf angle is at least 8". If the distance is less than this, then a detail similar to Detail 9.1A should be used. If the distance is large, then a detail similar to Detail 9.1H should be used.Download CAD File
9.1F. Brick Veneer on Metal Studs
As with brick on CMU, proper flashing at window and door heads and sills is very important. With brick veneer on studs, the flashing at the head must be extended up along the sheathing and lapped by the building paper at least 4". The sill flashing detail requires that a backer rod and sealant be applied below the flashing. The flashing must be dammed at the ends. A bituminous coating or a strip of asphalt saturated felt should be applied to prevent contact between dissimilar metals.Download CAD File
9.1G. Typical Flashing Joint and End Dam
Wherever long runs of copper flashing are required, multiple sheets of copper flashing are used. Adjacent pieces are lapped at least 6" and sealed (see Solder and Sealants section for sealant recommendations). At the ends, the flashing is detailed as shown to provide an effective dam, preventing moisture from draining back into the wall.Download CAD File
9.1H. Brick Veneer on Metal Studs at Concrete Spandrel
This concrete spandrel condition can be used if there is a large distance from the top of the concrete to the shelf angle. The flashing at the shelf angle is inserted into a reglet cast into the concrete and held with lead wedges.Download CAD File
Dissimilar metals should not be in contact. A bituminous coating or a strip of asphalt saturated felt can be used to achieve this separation.
9.1I. Brick Veneer Flashing
The first detail shows the typical method of flashing a brick wythe. The flashing must extend up at least 8", weeps spaced a maximum of 24" O.C., and pea gravel are rec-ommended. The lower edge of the flashing should extend about 1/2" beyond the face of the brick, and have a downward bend to provide a drip.Download CAD File
The alternate flashing method shown is primarily for use with asphalt coated copper flashing. Because the coating exposed to the weather is likely to flow and stain the surfaces below, this flashing is held back from the face of the brick. With hollow brick, the flashing must fully cover the internal holes. The coating may also not be compatible with most currently available sealants. If this flashing material is used at a shelf angle, a proper seal below it may not be possible. For this reason it is recommended that the flashing be installed a brick course above the shelf angle.
The last two details show typical shelf angle flashing. These follow the same principles outlined in the first detail.
The detail on the left shows the copper flashing resting on the shelf angle. Direct contact of dissimilar metals must be avoided. This can be achieved by the application of a bituminous coating on the shelf angle or the insertion of a strip of asphalt saturated felt.
9.1J. Brick Veneer on Wood Studs at Window Head and Sill
The head condition shows a row lock course of brick. This detail is essentially the same as that for brick veneer on metal studs. The flashing is extended up the sheathing and lapped 4" minimum by the building paper. Weeps at 24" O.C. maximum must be included. The copper flashing must not be in direct contact with the shelf angle. A bituminous coating or a strip of asphalt saturated felt can be applied to the angle to provide a separation.Download CAD File
The sill condition for a wood framed window is considerably different to that of a metal window. The flashing extends from the inside face of the sill piece, under the sill, then down and under the brick sill. It should project out about 1/2" beyond the face of the brick below and be bent to form a drip.
The ends of both head and sill flashings should be dammed to prevent moisture penetration.
9.1K. Wood Siding at Window Head and Sill
The top edge of the flashing at the head is attached to the sheathing and is lapped a minimum of 4" by the building paper. The lower edge of the flashing is bent over the wood trim and turned down to form a drip.Download CAD File
At the sill, the flashing is turned up against and is attached to the inside face of the sill piece. Then it runs under the sill and laps over the siding below. A wood trim piece covers the copper flashing.
9.1L. Brick Veneer on Wood Studs at Grade
The bottom edge of the copper flashing is held at least 8" above grade to reduce the risk of moisture penetration from capillary action. The top edge is attached to the sheathing and lapped by the building paper a minimum of 4". Weeps at 24" O.C. maximum are required. The cavity below the flashing is filled with mortar.Download CAD File
A copper termite shield may also be required between the wood structure and the concrete or masonry.
9.1M. Wood Siding at Grade
This detail illustrates one method of flashing wood siding at grade. The top edge of the flashing is lapped by the building paper at least 4". The bottom edge is locked into a continuous 20 oz. copper edge strip which is attached to a wood watertable.Download CAD File
A copper termite shield may be required between the wood structure and the concrete or masonry.