Anderson Extension Jamb Installation

Anderson phone support was a joke. I won't go into it.
Here's the jamb extensions: http://tinypic.com/view.php?picSu72fm
Never used jamb extensions. Extensions ordered separate from window. No paperwork with them. Anderson window instructions show a page about installing them. Also some info on Anderson web site. All docs show a solid flat side on all surfaces. Pic above shows a channel. Does channel face the RO or the visable side?
If facing the RO, what purpose does it have other than to weaken and promote splitting when nailed?
If facing the visible side all I can figure is to aid in nailing at an angle...as well as to weaken and promote splitting when nailed?
If you ask me it will look like crap if it's visable. The channel at the sill will end up being a collection place for any moisture/condensation. Window going in bathroom. Inside/outside temp difference can be 90-100 degrees mid-winter. Let's not go off on a tangent about ventalation fans, opening doors and all that.
Thanks, Al...
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Google gave me this:
http://www.hammerzone.com/archives/finishcarp/casing/jambextn/window/andrsn.html
Is this useful?
JK
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Nope. Found that. Note the ext jamb shown has no face channel.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

That channel - actually more of a culvert - is to facilitate nailing from the back side. The culvert - really more of an angled face with a relief cut - faces the framing, so it's hidden. That angled face - really more of a channel - facing the inside of the room, allows you to start the nail easily.
Extension jambs can be attached to the window prior to window installation, but that presents problems with extension jamb depth if there is any discrepancy in wall thickness. If the extensions are attached after window installation, it's pretty tough to get a nail started in the narrow space between the framing and the side of the extension - particularly since the nail is at such an angle to what would normally be a flat face of an extension jamb.
It's really not all that necessary in my mind as I typically pre-drill anyway and start the nails before I put the extensions in place. I also usually don't use store-bought extension jambs.
R
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

So you are saying either way is correct depending what poison you wanna pick?

The depth seems to be very close since the wall is pretty std - 7/16 sheathing + 5-1/2 stud + 1/2 drywall= 6 7/16". Jamb ext marked for 6- 9/16. I was thinking belt sander from the inside where necessary. But of course, ripping 1 or 2 16th's prior to install would be easier.

Yea, I can see that one just looking at it.

Do you do nailing straight into the narrow extension face with 3-1/4 finish nails (figuring 2-1/4 ext depth then straight into window jamb end face). Use trim screws on corners?

First timer on these. Figured I'd try it with OEM ones for simplicity. So much for that.

Thanks for the reply.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Of course. There are always alternatives. You'll find out after the fact whether you chose the right one or not. ;)

The numbers always work out - the actuality can be quite different. Heavy handed tapers, window not totally flush against the sheathing, etc. I rip 1x to rough sizes, gang cut them to length, test fit and scribe the outside edge with a pencil keeping the pencil mark a little over 1/16" above the wall surface, then cut to the line and use a hand plane to put a slight bevel on the outside edge. In other words the inside edge is slightly raised from the wall surface and tapers down towards the drywall. That insures that the trim sits perfectly flush, and meets at a tight edge at the extension jamb so there's no gap.

Something like that. The link that Jake provided is roughly similar to what I do.

I don't need the channel, I don't need the tongue, and there's enough work in tweaking the store bought jambs that I just find it easier to make my own. It's also a good place to get rid of scraps or use lower quality boards - you can always rip clear thin strips out of knotty wood.
R
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Site Timeline

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.