Hello,

I have a number of window extension jambs that need replacing due to moister and them used oak plywood it seems. It has bubbled up in many spots and has what i believe to be some mold on them especially in corners and where the poly has bubbled up.

Questions
1. I have the casing removed and decorative pieces but how do i get these old extension jambs removed quickly? I see some screws where it holds the vertical piece to the horizontal and assume there are pocket screws perhaps holding this in place. I don't need to salvage these so if there is a quicker way too i am all ears

2. I have one window where i took the decorative pieces off and stripped the poly but the dark spots in the corners remain. i want to kill any mold that might be living there. Do i bleach it or how do i do this? I do plan on staining them again with similar stain.

3. Once removed, how do i best reattach these? if pocket holes do i do that again and what sort of spacing between pocket hole screws do i need?

4. Any issues using alder vs oak that is there now?

5. there is fiberglass insulation current. Can i used spray foam or why might that be bad if not?

Any help with this would be appreciated.
Thanks.

 

There is no way for us to know how they did it, we can't see it and we aren't there. Cut about 1/2" - 3/4" of drywall away from behind the trim (don't cut outside the area that the casing covers) then look for shims, and look for pocket screws... if you don't see pocket screws then they are probably nailed to the rough opening. You can cut these nails with a sawzall by running it around the outside of the jamb.

Dark spots from mold are often permanent. Best thing to try is an acid solution of oxalic acid crystals. It may take several applications. And the old finish has to be chemically stripped and sanded first in order for the solution to penetrate.

To use pocket screws you need to have about 3/8" of room around the jamb... more is better. The wider the jamb the more space you will need. And there is nothing wrong with shimming and nailing the jamb to the rough opening.

Use alder if you want, the type of wood doesn't really matter. But generally you want your casing species and extension jamb species to match because wood does not all stain up identically. You can use the same stain on 2 different pieces of wood and they won't necessarily match.

Foam is better at stopping air, whereas fiberglass slows air. If you use foam you need to use a door and window foam, then be sure you don't overfill the space. Windows are best insulated primarily on the outside half of the wall... around the window itself... not just the at the jamb. You can do both if you want. But many people will experience a draft coming out the joint between the window and the extension jamb if you insulate the extension jamb only, and not the window itself. It also makes the window noticably colder in winter if it has not been properly insulated and air sealed.

 

Thanks a lot for the reply. It was pocked holed in and I was able to get it off without alot of issue thankfully. Thanks for those tips.

I am going to attach a picture of one of the molded corners. I have checmically stripped the poly but have not sanded it. Do i only have to sand the black areas or the whole piece? Hoping so as I plan to stain it with the same stain.

I did a quick search of oxalic acid crystals and not finding much so wondering if i searched for wood bleach is that the same?

https://www.menards.com/main/paint/s...6491828&ipos=1




So when i get the black stuff chemically treated and ready to refinish how do i prevent this from happening again?

Some of the things I thought of were using like a marine grade poly and do all sides of the decorative pieces at minimum. Also, using solid wood vs a veneered plywood will help with the bubbling but not sure on if this will help keep the poll from flaking off?

 

Yes, the factory made Andersen jamb extensions are always installed with pocket screws. Didn't know that is what you had until I saw the pic.

I can't say ALL wood bleach is oxalic acid, but this commonly available one is. https://www.homedepot.com/p/SAVOGRAN...0142/300614433

You can likely sand part if it and get it to look better than it does now, then treat it. Those Andersen jamb covers suck up water like a straw from the ends. You could poly all 6 sides if you want... but that's not a perfect solution... you will scratch the finish on the sides as you go to install the top and bottom pieces. One thing that would help prevent that is to instead wax the ends using melted paraffin wax or use a product like Anchorseal2.

Best way to prevent it though, is to not let the wood get wet in the first place... don't leave the window open during a rain... don't let the window sweat in the winter because the moisture is what is causing the mold. That might mean lowering humidity in the house when its extra cold out or not shutting the curtains or blinds so that the heat from the house can keep the window warmer. And be sure they are kept locked when not in use.

You could also just get new jamb covers, they are readily available from Andersen... I order them all the time. They are like $15 per piece or thereabouts.