when you rip out an existing window but need to do a new construction window with a fin,what sort of Waterproof membrane or flashing do you use? is it a self adhesive that you only apply to the upper part of the opening or a bit on the sides as well?

 

When installing the new window, run a bead of caulk all the way around, under the nail fin. Then using the self adhesive flashing(6"+ wide), start at the bottom, sides overlap the bottom, top overlaps the sides, and the upper edge of the top should go under the housewrap. Top should also have aluminum flashing under the housewrap and down over the window edge.

 

Depends on the walls material: brick veneer, stucco, EIFS, cement board, wood siding, etc. and on the construction details of the particular structure - one of toughest situations is when you have two or more layers of cladding, for example vinyl over wood siding. When someone calls for a water intrusion inspection above a window or door two of my first questions are 1) has it recently been replaced and 2) has the house recently been re-sided or re-roofed?.

 

Bill,
first you put caulk around the window(silicone) then install the the window
. then run the adhesive over the nail fin and lay on the top and bottom of window..???
should there also be tyvek around the window already prior to using the membrane flashing?

 

Some membranes are known to have problems sticking to different house wraps, thus they have spray adhesives that can improve the results. Probably not appropriate for me to link you to another board, but they have a good thread on materials and related concerns. Send me a PM and I'll give you directions.

Bud

 

Not silicone, it often will not stick to PVC, which is what most nail fins are made. Siliconized latex(DAP 50 yr stuff), or similar is good. Run a bead around the nail fin, or where the nail fin will land on the house.

Yes, tyvek, felt, or something that wraps into the window opening, especially on the bottom. There are even special treatments for the bottom of a window opening. Keeping water out and off the house framing is VERY important.

And once the window is in place, don't forget to fill the air spaces with NON-expanding foam. I like DAP foam, or the blue can urethane stuff. And be gentle, you don't need to pack the opening, the foam will expand some.

 

Bill,
sorry for the confusion..if we have tyvek in the openings already; we then caulk around the WHOLE perimiter or just the sides?
then we put MEMBRANE TAPE OVER THE nailing fins and also along top and bottom? or is tyvek enough and no need for membrane tape?

 

Caulk all four sides on the nailing fin before installing, regardless of housewrap, then flashing tape, starting at the bottom as I outlined, then metal flashing at the top. I know this sounds redundant, but it is needed. You will cover up that part of the window and never see it again, if it is done right.

 

As was said...too many barriers to water intrusion..is just barely enough. Water leaking around a window may not be discovered for years. By then you have major structural damage.

House wrap, caulk, nailing fin, tape flashing, metal flashing, siding/trim, caulked joints. That should work....

 

Sorry to jump in on an old thread, but I've got a related question.

I'm getting ready to reside the house, and I know the Pella windows weren't installed quite right 19 years ago. When I pull the original siding off, I was going to leave the old tar paper (maybe felt? - It's probably original - 1955-ish) wrap and inspect the windows, and sheathing underneath. If all is okay, I was going to flash tape the nailing flanges and then put AZEK trim around the windows before siding.
Does the metal flashing at the top of the window go over the trim board, or between the trim board and the top flange of the window?
Also, will I need to use the adhesive to get the flashing tape to adhere to the old house wrap?

 

Metal flashing should extend past the top of the window trim. You probably don't need any adhesive since you aren't trying to meet a warranty requirement. The flashing tape is plenty sticky.


Hmmm.. after re-reading...better wait for chandler or someone...normally the metal goes over the top of the trim..but since you are adding to an existing install..it could be different.

Sorry to waste yer reading time...lol

 

In my experience, no flashing tape will stick to felt paper... at least not for long.

My recommendation would be to install the drip cap over the top piece of Azek, and ensure that the top edge of the drip cap is behind the WRB. (weather resistive barrier)

I think new threads are preferred, even on similar questions.

 

Thanks for the responses.

If the flashing tape won't stick to the existing paper, and I'm going to be putting on 1/4" P2000 insulation and taping the seems, should I just run this over the nailing flange, and then tape over with the flashing tape?