flashing a flangeess winodow?

[mound]

how do you all like to flash a flangeless window?

[EatenByLimestone]

Last time I did it, I mounted the window in the hole with shims and then trimmed around it. If I was doing it now, the stick on flashing would probably yield another layer of protection.

[Stwood_]

I put J flashing on top. ensuring water rolls off the side of that, then tape the sides, then make sure the sill tapers downward on the outside.
Then caulk the sill in, and the bottom of the J flashing.

[Robert Adams]

Generally you don't. Flangeless windows are generally only used as replacement windows as you can't use regular windows. 

    You slide it into place then run a few screws into the framing from the inside of the window frame then foam it in. After the foam cures you trim the foam sticking out and caulk the joint between the window and the brick. I usually use OSI caulk as it is paintable and comes in colors. Great stuff but it is extremely hard to work with.
     
      Our house you could not caulk it and it be fine. The overhangs are big enough that the walls of the house rarely get any direct rain on them and windows almost never get even a few drops on them unless it's really windy.

[MstrCarpenter]

how do you all like to flash a flangeless window?

I assume it doesn't have factory applied casing either. I start with the understanding that all caulking may eventually fail. This means carefully considering where the water will go when it does. Minimizing how far in it can go is first, and then get it back outside before it can cause damage. Before it's installed, the R.O. has to be wrapped with flashing tape, Grace, or something at least as thick as Zip-wall tape. The bottom or sill framing, (which I pitch with a piece of bevel siding) should be first unless the flashing tape isn't flexible enough to wrap the corner without cutting a relief. In that case, do the bottom corners first, then the bottom, sides, then top. In an ideal situation, any seepage should end up on the outside of the siding. Now the window can be installed, shimmed, and secured. Next is the exterior casing. The root cause of some of my larger repair jobs were because the installer fit the casing perfectly to the jamb and only had to apply a tiny bead of caulk to seal the miniscule gap to have it look perfectly seamless. That would be great with painters caulk on the interior but not for weather proofing on the exterior. There are many great caulks with excellent adhesion and flexibility, we just have to give them sufficient surface area to adhere to and apply a nice thick bead so it can stretch, expand, and contract.  That's why I keep the casing about 3/16 away, use backer rod, a good quality caulk and am able to keep that gap sealed. The final precaution is to fill/insulate the R.O. with closed cell spray foam. It's a better insulator, sticks and seals better, and is waterproof. Just remember to use some sticks to keep the jambs from bowing 'til it sets.

Tom Silva showed how they sealed windows on the "This Old House" project they just completed. Even though they had nailing fins, (and he caulked the corners again) he still sealed to the window jamb itself. He's also instructed many times how, and why it's important to seal the R.O. properly.

[mound]

Thanks everybody!