# Thru wall flashing



## shazapple (Dec 3, 2010)

I'm trying to understand a little more about thru wall flashing, so I'm looking for peoples opinions on it, how they install it, and what they usually find when opening up walls...

I oversee the replacement of mostly flat roofing. A good deal of time the walls are brick, and there is either no thru wall flashing or membrane only thru wall. There will be leaks at the wall and I assume that the membrane has sagged and separated at the joints, but having never torn the wall open myself, I can't be sure. Does this typically happen? I hate to open up the wall at $100/foot unless I'm sure. 

When we replace the roofs we spec the metal/membrane thru wall, but we get a lot of complaints. The roofers say there's not enough room to work, the architects say the quality is poor, etc etc. I'm not sure if the roofers allow the masons to install the flashing, or what? They open up 3 or 4 feet of wall at a time so there are a lot of laps. 

On new construction I've heard thru wall tends to gather mortar which then blocks the weep holes. Makes sense, but again, I've never opened up a wall to see it myself. Would the larger (full brick height) weep holes get around this instead of the small tubes?


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## Pie in the Sky (Dec 21, 2011)

Shazapple, 

I saw no one answered this post so I thought I would give you my opinion and experience.

I have seen many walls opened up. They are typically full of mortar but the water that gets in has to come out somewhere. It usually makes its way down and into the building at the rising wall.

There are two main options in Brick walls. Full Wythe masonry where the brick is solid from the inside out and Brick Veneer where the Brick is only a rain screen. Full Wythe masonry typically has flashings but you’ll never see them because weeps are not necessary. Brick Veneer walls will have a through wall flashing (TWF) that should be made of copper. My Favorite is a copper laminate product where asphalt and fabric is laminated to each side of the copper sheet helping it hold in place within the mortar. This flashing should be set into a raggle in the structural wall (8”CMU usually), angled down a brick or two in length and run out the wall to the surface of the brick. Membrane through wall flashing will not last the life of the brick therefore it is useless. Weeps are located 2’ O.C. on all TWF’s. 

What you’re doing for replacement is correct. Always specify Copper flashings never accept membrane flashings. This method is no Fun, and should be done by a mason. We use an angle brace for support. I have specified this dozens of times. 50% of those times, it never happens. Where I live it’s a relatively Dry climate. They argue driving rain is not enough to penetrate brick and mortar that are both waterproofed. They may be right but Cracking is common in brick over its life. 

The bottom of the walls do collect mortar. There is a Product out there caller “Mortar Net” its shaped like dovetails to keep the cavity from being blocked. Another option is installing a product with a drainage channel.

A properly designed rain screen wall has an airspace with through wall flashings at the bottom with weeps and vents at the top of the walls. I settle for nothing less unless the owner wants to sign off on it. I’ve seen too many problems associated with it. Also Insulation is required in the US in a Masonry Veneer wall. 

PS, a lot of times Weeps are there but have been covered over by previous reroofs. Some investigation goes a long way. Another option is running the membrane up the wall to a lintel or the bottom of windows. But that’s not always the correct answer.

Let me know if you have any other specific questions.


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## Pie in the Sky (Dec 21, 2011)

A properly designed brick structure with Brick Veneer the mason installs the Copper flashing and a Prefinished reglet (provided by the roof contractor) below the weeps. Then the roofer installs the counterflashing. I like this because the counterflashing can be easily re-used at the re-roof.


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## smalpierre (Jan 2, 2012)

Rarely is a real reglet seen around here. Usually, we end up cutting with a grinder, install counterflashing, and sika-flex or vulkem it in there. (we use red-heads to mechanically attach, but seal the top which has a brake and is buried in the masonry)

As for copper - we use kynar 500 coated aluminum unless there's a reason to use copper.

Asphalt cements in their active state will eat copper - so I'm sure the asphalt coated stuff that was talked about earlier is somehow copper safe? I try to avoid asphalt / copper combinations, but if it's cured and no longer "active" as I've heard it put it's probably ok.

The other thing I'd worry about, is copper in conjunction with aluminum. Galvanic corrosion is a sure fire way to destroy metal.


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## Pie in the Sky (Dec 21, 2011)

Pierre, 

What your describing I would call a raggle mounted counter flashing. This is a legitimate detail. But it will only work for a chimney or a full wythe masonry wall. If the brick is a veneer, water will run behind the flashings and ultimately into the building. 

I would not use aluminum ever in Mortar, it corrodes, I guess the kynar coating can help but I wouldn’t do it. 

I have never heard of asphalt affecting copper. You say Cement, maybe roofing cement would? I’m not sure. But the asphalt coated copper is tried and true. I’ve pulled copper flashings out of 100 year old walls that were coated in asphalt and besides the black coating, the copper looked new. See composite flashings http://www.maconline.org/tech/materials/flashing/flashingtypes/flashingtypes.html 

The copper never touched the Kynar coated Galv. steel (not aluminum) so theres no issue with the metals. I’ve done this for a number of years, I’ve recently gone back on a number of my old projects and they looked great.

Shaz,
Below is a basis for what I was talking about:

http://www.copper.org/applications/architecture/arch_dhb/flashings_copings/wall_flashing.html


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## shazapple (Dec 3, 2010)

We use a similar method to the copper laminate method you mentioned, but it is made in the field. The base sheet is continued up and thru the wall and adhered to the CMU, then a heavy guage prefinished steel covered in membrane is held to the CMU with a termination bar. The membrane is the thru wall flashing and the prefinished steel is mostly just there to support it. 









Usually on the full wythe we will use a termination bar to secure the membrane to the wall and cover it with a reglet.


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## Pie in the Sky (Dec 21, 2011)

:thumbup: Looks like I could have drawn it...


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