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lucasrcole 01-11-2011 12:47 PM

Window extensions and trim
3 Attachment(s)
This is my first time installing jamb extensions and trim using primed MDF for jambs and poplar for stool/sill and I'm running into a few problems. My windows currently have just a stool/sill and the jambs are just plain sheetrock and paint. Should I install the new extensions over the painted surface? If I do I ran into the "white" framing around my windows in some areas around my home are not wide enough and the 5/8 MDF boards are thicker than the white window frameing. Sould I cut out the sheetrock or simply trim down the sides to show a reveal on the window frame? I attached some pictures to help.

Jackofall1 01-11-2011 12:49 PM

I wouldn't touch that, it looks good already.

pyper 01-11-2011 01:10 PM

I would keep that as is, but I guess your desire is to put trim around the edges?

I wouldn't use MDF because it will get torn up. When you put up the casing, you'll leave a 1/4" reveal, which is another strike against MDF. If you paint it with water based paint it will suck it up and swell.

You probably need to remove the sheetrock in the offending locations so you can get the jams to fit uniformly. You could use thinner stock, but it will be harder to nail the trim to it. I use 3/4" plywood for jam extensions. I build the extensions on the floor, and then shim them into place. After they're up I use wood filler and sand paper as necessary.

lucasrcole 01-11-2011 01:49 PM

I think they look decent right now, however I also think my house looks to plain and I would like casing to bring things out...hopefully...

Your point with the MDF was my concern as well, however I spoke with a few builders at my local Probuild lumber and they all use MDF for paintgrade windows, baseboards and crown. If I had the extra money to spend and If I was going to live there for my entire life I would step up to a softwood/hardwood.

Back to my question, should I install extensions over the way it sits right now?

TheDoorGuy 01-11-2011 01:55 PM

Is the purpose of the extensions to compliment a casing installation
to give a consistent smooth wood look?

It looks like you will have a problem at the bottom of your side casings
because the stool "ears" appear to be too short for casing to die onto
without hanging out over the sides.

I agree with piper and jack ....Leave it the way it is and move on to
another project. Perhaps you could add an apron under the sill but it might be a problem getting the stain to match.

oh'mike 01-11-2011 01:58 PM

Peal the dry wall so your reveal is the same all the way around.

If you stick with MDF be sure to seal all edges before installation--condensation next to the window can puff up the MDF.

lucasrcole 01-11-2011 02:15 PM

Yes thats what I'm trying to do is have a clean look and I already know about the sill and I purchased poplar to make new (longer) ones.

TheDoorGuy 01-11-2011 03:03 PM

Gotcha....I understand now.
One thing you could consider would be to use the mdf and install it without a reveal.
I know it is not typical but if you leave the edge square after ripping (don't ease it with sand paper)
and bring the the casing right to the edge it will look fine. I do it myself with jamb extensions if
it makes sense for the particular project.

loneframer 01-11-2011 05:14 PM

Replace the sills and use the cornerbead as your Jamb. Set the desired reveal and trim it out. As long as the beads are straight, no one will ever know but you. Just hold your fasteners far enough back to avoid the bead(or the nails/screws used to set it).

lucasrcole 01-11-2011 06:15 PM

Are you talking about "mudding" out the drywall jambs and around the corner bead then sanding making it look like there is no texture as if it were wood?

If that is what your talking about I could do that on a few however the others the bead isn't strait...

Is the best/professional way to cut back the drywall about 1/2" and remove the corner beads then everything will be a normal extension/casing installation?

oh'mike 01-11-2011 06:18 PM

Yes,the best way is to remove the corner bead and peal the drywall off around the windows.

Joe Carola 01-11-2011 06:49 PM

The places where the mdf is to thick, why don't you just rip it down with a table saw? There's no need to take off the sheetrock and corner bead. The texture doesn't appear to be to thick where the ripped mdf would be wavy.

oh'mike 01-11-2011 06:53 PM

Joe--that makes sense--Brain fart here-

lucasrcole 01-11-2011 07:12 PM

I know this is kind of a personal preference but just to get your insight how much of the "white window frame" should I be leaving revealed?? a minimum?

That is a excellent idea Joe, so when I goto rip the mdf i'm leaving one half of the board full thickness and the other rip down as needed?? am I reading that right?

Joe Carola 01-11-2011 08:14 PM


Originally Posted by lucasrcole (Post 568112)

That is a excellent idea Joe, so when I goto rip the mdf i'm leaving one half of the board full thickness and the other rip down as needed?? am I reading that right?

I would rip the extension jamb the same size. Are you asking because some spots of the sheetrock corner are not square to the window?

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