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Installing foundation flashing over exposed rigid foam board insulation

Installing foundation flashing over exposed rigid foam board insulation

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  #1  
Old 09-17-20, 05:05 PM
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Installing foundation flashing over exposed rigid foam board insulation

I bought a ZLL house that has serious lack of drainage on the side yard, during the home inspection there was some water penetration in the crawlspace so as part of the purchase contract I had the seller re-waterproof the foundation all the way around the house. Their contractor left the exterior foam board insulation exposed under the siding so now I'm left to fix that this weekend before my landscaping contractor comes in to add a proper grade to the side yard and hydroseed.

I've been trying to find any articles I can about foundation flashing (lots of info about roofs and windows out there) but I can't seem to find a detailed description of how to properly install the aluminum foundation flashing I purchased or how to cut a corner out of the straight 10' sections. From what I understand I'll need to remove the bottom trim, slice a cut into the wrap under the bottom siding panel, and then slide the flashing up into the cut so it is behind and under the siding for any water to go down and out.

How do you cut the Z shaped flashing properly so it makes a clean corner and doesn't leak?

Exposed exterior foam board and mudpit side yard with no slope/drainage
 
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  #2  
Old 09-17-20, 08:20 PM
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This would be a lot easier to show you than to explain. But I'll try.

Let me preface this by saying there are left hand snips and right hand snips. Depending on which end of the z flashing you are working on, one will work better than the other. Also if you have "offset" snips, they work the best. The plain yellow handle ones kind of work but they will mangle one side of the cuts you are trying to make.

And we will assume that your foam is 2" thick and your z flashing is 2".

So let's say that you want to put the piece on under the window and you are going to turn that outside corner on the right.

The "back" of the flashing is the part that gets nailed to the wall. So get behind the back of the flashing. If the foam is 2", cut 2 1/2" of length off the back of the flashing. One cut straight down the back of it... then fold it down toward you... so that its just as flat as the horizontal part of your z flashing is. Then, snip it off at the bend.

Then, on the flat horizontal part, snip 1/2" off the length of it. Fold it vertical... and snip it off at the bend.

That will leave 1/2" "tab" of the small front vertical leg sticking out. So, using a pliers, (the proper tool is a Seamer) pinch that 1/2" tab right at the 1/2" mark and bend it 90 degrees to turn the corner.

Now that piece is ready to install. The vertical cut in the back should line up with the edge of your sheathing, and the tab you bent should turn the corner and hug the face of the insulation on the right side.

Now for the other piece. You will be cutting it to overlap the other one.

So using the other snips, get behind the z flashing and make 2 marks on the back side of it. A mark that is 1" from the end and a mark that is 2" from the end. Turn that mark into a line down the back using a square. Then cut on the 1" line, cutting 1" of length off the back of the flashing. One cut straight down the back of it... then fold it down toward you.. so that its just as flat as the horizontal part of your z flashing is. Then, snip it off at the bend. But this time, continue cutting along that bend an additional inch... right up to the other black line, to create another "tab". Then take your pliers and pinch that tab, and bend it toward you, so that once its on the house, it turns the corner.

On the front of the z flashing, snip just a slight angle, the least amount you can snip, off that front lip. This is just so that its not as sharp.

Then as you look down on the end of the z flashing, imagine that the end of the flashing has a 2x2 square on it. With your square, draw a diagonal line and cut a 45 degree angle on the horizontal part. The end of the flashing will be the starting point... and you are cutting back toward the base of the flap you bent in back.

That piece will lay on top of the other one and should match perfectly. But before you lay it on top and nail it on, you will want to run a bead of sealant (such as a clear roof sealant) all along the end of the first flashing. The second flashing will overlap it and squish into the caulking as you press it down.

And that goes for every joint of your z flashing. Overlap them a couple inches, but each time press them into a bed of sealant so that water cannot creep into the seam.

I'm sure that is clear as mud, but print it out and try to follow it. Once you do it once it will all make sense. Personally, I hate reading directions and I'm probably worse at giving them.
 
  #3  
Old 09-17-20, 09:49 PM
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Thank you for the amazing explanation, I picked up extra so I can always practice with a section until I get it down. Going to give it a whirl. Thanks again!
 
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Old 09-17-20, 09:55 PM
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Sounds good, let us know how it turns out!
 
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