FWIW, mine was done the same way. Flashing, window then house wrap.

Mine was house wrap first then window flashing. I have excellent framers :). It took 4 guys 7 weeks to finish mine. I brought them drink and snacks almost every the other day though.

Mine was done the same way as yours and rpbc.

DuPont has always published installation instructions for both methods and both are included in ASTM E2112 Standard Practice for Installation of Exterior Windows ..... Many designers and builders prefer it for building sequence preferences and to avoid a potential path for water to enter the opening behind the wrap.

Ours was done like yours.

Here is the ASTM Standard kindly referenced by Sanford W.

But obviously too many words to be bothered with by builders who prefer the "that's the way we do it around here" standard.

The diagrams for ASTM Method A are basically the same as found on Tyvek's website as "installation Instructions for integral flanged window before water-resistive barrier (WRB) is installed"

To see whether the builder is following Tyvek's instructions, the owner could take some photographs. To begin with, consider the flashing tape that is supposed to go over the windows in exactly this fashion:

And that's only the start. I have my reservations.

I am going to have rigid foam on my walls, are you? I'd like to see closer photo(s) of that flashing and DOW product you mention. Grace Vycor is a good product. Depending on design, I may be forced to use house wrap after installing the windows. House wrap is most effective if it's tied *in* with the flashing and tape, but I firmly believe you can do just as good of job or better by proper flashing detail prior to house wrap. This topic is very interesting to me and I would like to know of any houses that had rigid foam on the exterior, because that turns it into a different ball game.

For what's worth, Grace has always recommended using Vycor as the OP's builder has with full full perimeter flashing to the sheathing.

It doesn't look like the Vycor was used full perimeter - just on the bottom. I can not tell if the sill is covered (proper way) or if the product is only folded over the sill by an inch or so. Now is a good time to assess the quality of work by looking at the window sill corners! See how good of job they flashed them prior to window install.

Mine took two days ago. House wrapped has been a month and windows were installed last week.

From the looks of OP's pic, the Vycor serving as sill pan flashing does not run far enough to the interior. Perhaps just as concerning is the blue tape does not appear to have very good adhesion with the plywood. The roof to wall flashing above the window needs a closer look too.

With houses14 pic, it does not appear the sill pan flashing laps the tyvek/wrb but it could be behind the layer we are seeing. Cant say Ive seen that head flashing detail before either. My guess is an attempt to cover up the original job or it could just be a nice redundancy.

Worthy, would it be hard to find that BSC picture source? Kind of surprised by that one. The weakness is the reverse lap of the tyvek tape, though its a better reverse lap transition than the blue tape Iam sure. There appears to be a possible wrinkle taped over. Looks like a solid flashing job but I dont think Ive read that particular article.

Springtime Builders,

Thanks for your insight!

It is a nice redundancy from framers team as you mentioned.

The choice of materials is puzzling. The blue Dow Weathermate Straight Flashing is HDPE film with a butyl adhesive and is designed for use on polystyrene foam insulating sheathing. The Grace equivalent is Vycor Pro. The sill flashing Is Vycor Plus with a modified asphalt adhesive. Dow's sill pan or a full depth recommended installation of Vycor is missing

Good adherence of flexible flashing to bare sheathing requires careful rolling or even vigorous rubbing. There should not be any loose flashing nor should it be easy to remove it.

The odd pairing of materials and sloppy installation is troubling. I would ask the installer what design instructions or standards were being used. Don't wait to see the final housewrap installation.

For this type of installation a house wrap "apron" is installed below and under the sill flashing but it has been omitted.

It might be possible that the outer half of the paper backing of the flashing remains and the house wrap will be slid under it. That would be pretty odd but nothing this installer does would surprise me.

The original question was about installation sequence but given this sequence I don't see any recommended installation method being used.

Here are the Grace Vycor Plus installation instructions for windows before wrb. Note the provision for laying the sill flashing over the wrb and the use of Vycor to seal the window flanges to the sheathing . wrb tape would be used to secure the wrb to the flashing. In the photo this is reversed. I still think the installer intends to slip the wrb under the flashing as improbable as that seems.

I wonder if the paper backing has a split down the middle they could adhere half under the window and leave the paper back on the outside part so they could later adhere it to the outside of house wrap if that wasnt done yet.

Was that Grace Plus instruction set for installing a window that is bumped out with firing strips?

Not uncommon for this subject but those Grace instructions leave significant room for error IMO. They skip any mention of sloping sill or backdam which I can understand but the glaring lack of info is between step 3 and 4. Vycor does not have too much flex to it and with no instructions on the proper way to pull it out and over the corners, most installers will cut it to fit in the corners which leaves the most vulnerable area of the window installation open for water damage. Iam sure this is why they conveniently avoided this important area of detail.

We always avoid cuts or seams in the sill pan area and prefer more flexible tapes that can be pulled over the corners and attached with large crown staples or button caps.

Perhaps even worse is what's taking place in step 6. It sure looks like the picture is showing something different than what the text explains. It looks like they are taping over the bottom flange, a classic no-no.

The split backing is what I was referring to. The Dow flashing has a plastic film liner and I don't believe it is split.

The Grace instructions are only for the basic flashing that complies with published industry standards. The company has made it clear for the last 10 years that it recommends using their preformed VYCORners at the sill ends.

The instructions obviously do not call for the sill flange to be covered and in the photo you can see the printing on the flange warning to not cover it.

For easier to understand instructions see the Tyvek instructions for this method linked above by Worthy.

@worthy or whomever - what is the cheaper alternative to ordering tyvek's flex wrap for the sill. Especially when using Vycor Plus?

I really like Zip's new stretchy tape but still on the high end. Forti flash and protecto wrap's asphalt based tapes are more stretchy than vycor but still need fasteners at the outside corners. Its also wise to use a thinner more tenacious adhesive tape to flash over those tapes top edge. You can use horseshoe shims, button caps or whatever to create space between the bottom flange and tape behind it to achieve similar drainage gap that you would get with the tyvek flex product.

I dont like Vycor's method, its solid if done right but still creates a seam on a horizontal plane where water can pool (sill pan). Sloping the rough sill will help with this and most sill pan situations. I think the most recognized published guidelines are the ASTM 2012 that worthy linked to and the vycor seems to fall short of this in regards to slope and backdam. And I still think picture #6 of first vycor diagram post adds to the confusion and wrongful practice of sealing or taping the bottom flange. Dont do it!

My comments were not intended to recommend a window flashing method or start a debate about flashing materials and details but to help the OP understand how unusual and possibly inappropriate the flashing shown in the original photo are.

Wasn't anything against you good sir. Just want people installing quality windows in a quality manner. I think your posts are a positive contribution for that.

I think the OP's builder has a good idea but doesn't know how to detail it. It is only in home building that a loose housewrap would be considered an integral part of waterproofing a wall opening.

A little late but my builder is only putting flashing tape on the outside and insisting this is good enough. I am very concerned with leaking later on and having no protection from any water that may get through .