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· Registered
2 Posts
Discussion Starter · #1 ·
We are going to start replacing all of our windows in our new house that has 2x8 walls. The total thickness of the wall is about 8.5 inches. The windows we first got in are 4.5 inches thick so I think I need to add 4 inches of jamb extension on.

Does anyone know or have ideas for the best process for this?

Install jambs after window is installed or before?
I am really interested in doing a stool at the bottom and would like ideas for that if anyone has them.

The windows we are installing are integrity wood ultrex. We are doing a cabin feel throughout the house so we are just putting in clear coated pine/cedar so I don't have the option to use mdf and want to keep nails holes down to a minimum.

I think I posted everything but let me know if you need anymore info.


· Banned
17,249 Posts
My house has old lumber walls (thicker) & 3/4" sheathing outside & 3/4" cement-like board/plaster inside. So windows built for 2x4 walls did not fit my walls. I measure & used a table saw to cut my own extension jams
I'm so used to it now that even on my addition I ordered 2x4 windows & cut my own extension jams
I'd install them afterwards

· Tired & Dirty
84 Posts
if you want a stool you will have to put extention jambs on after window is in hole, if picture casing put on before installing window, that way you only have to shim up the interior edges, not sure how your windows accept extention jambs but I use Andersen 400 series and they have a plowed gruve* so glue and pin nailer work great.make sure the outside edge is solid for nailing the flange(not foam board) so jambs will be same thickness. I'm doing 6 awining windows in 8" concrete block wall now and it works very well. good luck on your project!

· Registered
226 Posts
Wait for the windows to be installed

then measure the distance from the window to the wall (if you are going to box out the opening like this scroll down the page to the window picture. If you are going to do a stool it is a different process.

Then build the box which is the head piece the sill piece and the two side jambs

Nail it all together

Lift it into the hole and shim around all sides

Apply your casing

Enjoy your new windows!

Pretty straight forward and remember don't build a yacht when all you need is a dhingy!

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