Replies

1. 
   calvin | Nov 18, 2011 05:49am | #1

   John

   Hold the window to the outside.

   Either fab a pan of metal or form one out of a vicor type product (suitable for contact with vinyl if that's your window) and allow a tip to the exterior at the bottom of your box.

   Use treated plywood.

   Flare the opening at the inside to allow more light to pass through and to also give you better viewability to either side.

2. 
   glacierfergus | Nov 18, 2011 06:30pm | #2

   Are you making this your finished jamb extensions or just providing a good nailing surface?  I have done this for finished jamb extensions with very good results and a minimum of cost. I used the table saw to make a tongue to slip into the groove in my Andersen windows, and ripped the shop grade 3/4" oak plywood to width.  Then I edge banded each piece with adhesive backed oak veneer (bought a 250' roll to make it cheaper per foot) and trimmed and sanded it lightly.  Then I stained and finished them before installation, with one last coat of spar urethane after installation. I won't guarantee that this is the best way there is, but it worked, fit my skill level and looks really good after installation.

   If I misunderstood what you are asking, I appologize....

1. 
   calvin | Nov 19, 2011 07:21am | #3

   you probably have a better understanding than I do.

   I assumed no window in it, you are giving him jam extensions.

   I think you are correct.

1. 
   JohnWalker | Nov 19, 2011 12:57pm | #4

   various replies...

   Thanks for the input.

   The plywood boxes are just a nailing surface for the drywall or trim (and lining up the second RO!).

   I was thinking of pre-assembling the finish trim as a "box" and sliding it in exactly as suggested.

   Most of my windows are installed in pairs so although I do appreciate the comment about flaring the opening I think because they are paired I will just keep the framing shallow between them. That is, only the 2x6 pony wall between them.

   Good to hear that i am not completely out to lunch with this 1/2" plywood boxing thing.

   ***I was intending to hold the windows to the exterior surface, so in effect I end up with deep (interior) window sills. (Bringing them "in" is a very effective envelope failure detail here). Further to that I have 2" XPS and 3/4"(?) rainscreen strapping. Where the windows are I will have to hold the XPS back and provide a 2" thick "frame" for attaching the window fins to. That part is clear. Would you extend the 1/2" plywood box out flush with the exterior surface of the XPS? I am thinking of the drainage pan etc and ensuring it doesnt have any "bumps". (Also planning on using cedar bevel siding for the sill pan, with appropriate peel-n-stick.).

   Thanks

   John

1. 
   calvin | Nov 19, 2011 06:58pm | #5

   John

   It would be a thermal break to not run the plywood all the way out.