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Dr_Jim 05-06-2008 07:34 AM

Installing new window into existing wall, exterior question...
Greetings all, alot of good info here! I couldnt find anything related to my exact situation though so hopefully someone can help.

I am planning on adding a regular double hung window into our house.
The house is stick built, with T1-11 wood siding.
I understand the process pretty well from the inside, framing, headers...etc..etc.

Here is my problem. Everything I read with regards to flashing involves the flanges going over the weather proof wrap, then flashed in...ALL of this "under" the T1-11.
I am getting the sense that I cannot cut an exact window opening through the wall and get the flashing and such done properly. Its as if I must remove a larger area of the exterior T1-11...then install the window, flanges, flash it all and THEN somehow put T1-11 back into place?

Well,...patching the siding back around the window will obviously look like crap. And matching the stain will be impossible.

Perhaps a section should be removed from top to bottom and a foot wider than the window,...then replace the whole section after the window is installed? This would require putting back the section removed (cut at the vertical seams)....since again, using new T1-11 would look obviously different than existing siding.

I hope my quandry makes sense? I was initially hoping I could install a new window without having to rip up the exterior of the house! And I know I feel like I have alot left to learn!

Thanks to all..........

glennjanie 05-06-2008 11:03 AM

Welcome Dr Jim:
Cut the hole a little over-sized, slip a piece of metal flashing under the top of the opening, slip the window flange behind the flashing, move it back and forth sideways to work the side flanges in, renail the siding, caulk the opening with silicone and add brick mould trim to cover the unsightly opening. If the brick mould is not wide enough to cover, you could use some 1 X 4 trim boards. You haven't used any new siding to try to match, just paint the trim.

guyod 05-06-2008 11:16 AM

Do you have any type of sheeting under your t1-11? you might not have anything to flash. t1-11 is not like vynyl siding where water is allowed to get under it and the flashing would stop water from getting in the window. you need to stop water from getting behind it period you dont need a back up flashing.

If it was my house would frame out the window then create a window casing with 1x6's ripped down to fit. put some trim on the ouside and use a replacement window. chaulk every where with best silicone chaulk. if you want extra protection you can add a piece of flashing to the top of the window trim by cutting a line above the window trim in the t1-11 with a circular saw using a plywood blade. then side a piece of flashing in the slot and cover the top of the window trim and chaulk some more.

Dr_Jim 05-06-2008 11:35 AM

Thanks guys!

Guyod - That is a very good question! I assume I have something under the T1-11, but I am not 100% certain at all.
Could you actually just wrap the framing and then use T1-11 as your only exterior surface? They actually build that way? (I'm obviously a noob at construction)

glennjanie - I like the sound of that technique. That is kind of what I was hoping could work,....cut just the minimal amount over size necessary.
Wiggle - Jiggle the windows nail flanges into place nail into sheeting. chaulk it all, and use trim to cover it up.

Something tells me, that no matter how much I 'learn' on the internet about doing this, it's gonna be quite an experience once I start doing it 'for real'.

Any and all other advice appreciated!

glennjanie 05-06-2008 02:58 PM

Yes, Dr Jim it is a big project but I can already see the buttons on your chest begin to tighten and I'm sure you will pop a couple of them by the time you finish. Just think; a fine looking project you did yourself! It will be great!!!

Dr_Jim 05-06-2008 03:10 PM

Very true. I am also excited by the fact, if I pull this off, I would save the $1000, the local contractors want to do this. (and that is with me providing the window). And there are 3 windows we want to add,.....this would save alot of $$$ if I can DIY.

Thanks again all!

inspectorD 05-06-2008 04:40 PM

Just remember
Advice I give to all my students.
When it rains you need to be the water. Think of where it could get in ...and it will.
Always overlap every thing going down.
The best analogy I have is this.
You would not tuck your raincoat into you pants and caulk it with silicone, then tuck your pants into your boots and do the same. So don't do that when you install a window, and you'll be fine.
Good luck on your windows. Post some pics if you need to as you go, and we will fill in any DIY tips as we see them.:)

handyguys 05-07-2008 11:29 AM

I had a similar situation on an old cottage. The exterior walls were vertical bead board attached directly to a top beam, a middle rail and a bottom beam.

What I did was maybe not ideal but has held up fine (I think) for 5+ years so far. I say I think because I have not seen any leaks.

I framed up a proper wall with studs between the top and bottom beams with the rough opening for the window. Cut the rough opeig in the bead board. Attached the window. I then installed 1x4 trim over the nail flange (to match the style of other cottages and of the old windows). I caulked the back of the 1x4s before nailing them up, I caulked the flange before nailing up the window and I caulked the edges of the 1x4s after they were installed.

If I had it to do differently I would use some of the sticky black flashing material over the nail flange and under my trim boards. It was only available in 3' wide rolls when I did my project and was brand new on the market then.

Some of the other cottages have additional metal flashing let into the siding as guyod mentions. I did not do this.

I will be at the cottage in a couple of weeks and this post has reminded me to check on my caulk around the windows. I haven't inspected it since it was installed.

Dr_Jim 05-08-2008 05:37 AM


That sounds interesting as well!

I feel like this house has sheeting covering the studs and then the T1-11.
But I am note sure and will check.
Sounds like either way, I can basically cut a nominal amount of T1-11, and then use flashing, caulk and trim to seal it all up. Ofcourse, that is a "general" statement......but it appears I can do this without removing a huge section of exterior T1-11, or having to match in new T1-11.

guyod 05-11-2008 10:27 AM

T1-11 it is rated as an exterior sheathing. And is used because of that. it saves money and goes up quick. so if its original to the house thats probably all there is. handyguys way should work good if you use that special tape over the nail flange. some times the nail flange doesnt lay flat against the sheathing i dont know why but it happened a couple times to me were there was a bubble.

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