Replies

1. GBA Editor
   Martin Holladay | Jun 29, 2017 05:37am | #1

   Tommy,
   The back dam goes behind the window. Here is a link to a GBA video that shows the process: Window Sills That Won’t Rot: Sloped Sill or Backdam?

   I am also sharing a screen shot from that video.

   .

   
2. 
   Tommy87 | Jun 29, 2017 11:51am | #2

   Thanks for clarifying Martin. So ideally, the backdam should run flush to the very edge of the interior sill?

3. GBA Editor
   Martin Holladay | Jun 29, 2017 12:24pm | #3

   Tommy,
   Q. "Ideally, the backdam should run flush to the very edge of the interior sill?"

   A. Yes. That way, it's easier to install the stool. (In other words, it's easier to trim out the window on the interior.)

4. 
   Tommy87 | Jul 01, 2017 01:26pm | #4

   Great, thank you Martin.

   Another question just came up.

   I got my windows delivered yesterday and the window flanges do not go down near as far as I expected (the bottom of flange only goes down 1" and the nail hole 5/8").

   I was planning on using 1/2" bevel cedar for a sloped sill pan but this would raise my window up another 1/2", which wouldn't allow for the bottom flange to be nailed into the sill (framing). Do you have any ideas to make this work so I can nail the bottom flange into the framing?

5. Expert Member
   MALCOLM TAYLOR | Jul 01, 2017 04:28pm | #5

   Tommy,
   That's an annoying surprise. Most flanges used to be 1 1/2" but recently more are going with 1 1/4", mainly so they can secure 2"x2's to the bottom to avoid damage. A 1" flange is a real headache to nail too.

   I guess the two best choices are to either use a flat sill with a back dam, or drill more holes closer to the bottom of the 1" flange.

6. 
   Tommy87 | Jul 02, 2017 11:48am | #6

   I know! Pretty upsetting to see a 1" flange. The windows are milgard. I got a few other brand windows and they are 1 1/2".

   My plan was to pre drill some lower holes but still seems like the hole would be too high up. Would it be an issue if I didn't nail the bottom?

   I was thinking of stapling as an alternative as well (to get even lower).

7. Expert Member
   MALCOLM TAYLOR | Jul 02, 2017 02:01pm | #7

   Tommy,
   The fasteners on the top and bottom are really only there to keep the window frame straight. It's only recently that manufacturers suggested nailing the top flange at all, and windows installed before that did fine.

   I bet staples would work. Or if you are using a rain screen (so protruding heads wouldn't matter) you could install pan head screws angled down to catch the sill.

8. 
   Tommy87 | Jul 03, 2017 04:02pm | #8

   Sounds good Malcolm. Thanks for the advise.

   One other thing- My windows have a 2" depth over the sill pan so my sloped sill pan will only be 2". The windows are cut out to use a 1/2" tall sill pan. Is there anything wrong with setting a window on a 2" (site-built) bevel with that big of an angle? Most I see are far less of an angle.

9. Expert Member
   MALCOLM TAYLOR | Jul 03, 2017 04:10pm | #9

   No. as long as the shims you use are the same angle it really doesn't matter.