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There’s a new type of flashing for window sills on the market now. It’s the Rissan 430 grey corner from Siga, which is a piece of pre-formed flashing tape that fits perfectly into the corners of door and window rough openings. I was lucky enough to get several Siga tapes and tools donated for my basement renovation and have been really impressed with them.* I’ll cover the full window flashing and air-sealing process in another post. Today, though, I want to focus on this one piece.
Standard method for flashing sills
Window flashing has come a long way in the past couple of decades. It used to be just wrapping the rough opening for the window with the water-resistive barrier (WRB). Then came the flashing tapes. Often they’re poorly applied and not integrated properly with the WRB.
The photo above shows flashing tape over the sill and up the jamb a little ways. Some builders stop there with the sill flashing and put the WRB over it and then some flashing tape up the jambs.
But the problem here is that empty square you see where the tape goes from horizontal to vertical. At the upper left of that square, water can get into the rough opening.
There are better ways
To avoid the empty square, we need to do some tape origami. That’s what Minnesota home builder Randy Williams did in the photo below. It takes extra time to do the fancy cuts and then apply the tape so it lies flat.
Tape origami with Siga Wigluv flashing tape. Photo courtesy of Randy WilliamsAnother way to go here would be to use a liquid-applied membrane. You could use only that material to flash the whole window, and…
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14 Comments
It's cool that you got sent some free swag, but the rest of us would need to pay $8.50 usd per corner. The value proposition is not there. Do some origami with 3m 8067
I guess the question would be, if it costs $8.50 per corner and takes 6 minutes to flash all four corners of a window, how long does it take to flash with the 3M tape?
To keep the math easy, let's say the origami techique takes slightly over 5 minutes per corner (21 minutes total) instead and the 3M tape costs $1 for the equivalent amount. So then it cost $30 extra to save 15 minutes. Or $120 to save an hour.
If the hourly cost to the homeowner for labour is $120/hour or higher, than this product is worth it. If it's less than that, then better to pay for the origami instead (assuming the install quality is the same in both cases).
I am available to origami corners for $119/hour!
Another issue with using products that are somewhat esoteric and somewhat expensive is how they affect workflow. Do you buy more than you think you might need so you don't run out, or do you run the risk of having to scramble to find the last few to finish a job?
I could see this making more sense if you do nothing but windows and could just keep a bunch on the truck all the time.
maxwell_mcgee,
Change the assumptions and you change the whole equation.
- The "origami" corners take me maybe 30 seconds each to cut. Installation time for them and the pre-made is the same.
- Common practice is to only do the bottom corners at the sill, not all four.
I'm just not sure it's something you can parse that way.
do you have any more pics/details of that window replacement with your brick veneer? i have a brick veneer home and like seeing all of the different ways a window can be flashed without removing brick.
If you are trying to stick with a single system it might make sense. I've been flashing with Zip, and find their stretch tape easy to use. It's nice to have a monolithic piece of tape that runs 3-4" up the side and gets the corners. But I've done a few windows with regular zip tape and then a 6" piece of stretch in each corner. Doing it that second way, you're at less than $1 per corner. Using 6" stretch across a whole sill, you're something like $8-12 per window. I have mostly 3ft wide windows.
That said, I'm slightly worried the stretch tape might let go. Having it under constant tension.
Tim_O
I use bow ties: https://www.youtube.com/shorts/SEfcmc2EXik?feature=share
For skilled, dedicated craftspeople, cutting bow-ties is simple and quick. Where I see this product potentially making sense is when you have a house or multi-family full of windows and relatively low-skilled/low-interest workers; it's harder to mess up than messing with origami, and one mistake could cost more than a building full of these corners.
Michael,
Partly why I champion them is they are one of my happy tasks. I really enjoy flashing window openings.
Are you implying that someone might... cut corners?
Sorry, I'll see myself out.
LOL
Malcolm, I can see that. I haven't quite reached that point but I do care about doing a good job. If only everyone thought that way.
Mike,
When I did spec. building for a decade or so I had a hard time making decisions about what made sense to do myself, and what to sub out. From a purely economic perspective it was relatively easy, but I also had to factor in how I wanted to spend my days. Did I really want to do the tasks I disliked, or was it worth taking a bit of a hit for quality of life? Some equations I made weren't based entirely on rational factors.
Malcolm, that seems rational to me.
A tile contractor I used to work with when I was building would do all of his own shower prep, then have his guys lay the tile. To me the tile setting was the fun part and I asked him about it. He said he was managing risk, he wasn't there to have fun. Or something to that effect.
The corner tape looks like a nice product to have in your quiver of products.
This particular install should have been done with fluid applied without question. All the irregular surfaces screams fluid applied.
There is a time and place for tape but this is not one of them.
Grace and Peace
Slick
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