Lately I have been finding an epidemic of improperly installed replacement vinyl windows; or, if they are “properly” installed the installations are not working out as planned.
I am talking about windows where the old windows have been removed and new windows are installed in the same opening.
There are correct ways and wrong ways to do this.
There are ways to do it that are considered “best practice” and installations that are “less than ideal.” These poor practices are a little bit more like trying to make a silk purse out of a sow’s ear as they say.
In homes where the siding runs right up to the window frame—as in older metal frame windows that have no wood trim around them—the siding must be cut back to allow for proper removal of the old window as well as to properly flash and attach the new window in the old opening.
What I am seeing over and over is where the glass is removed from the metal frames and then the frames are collapsed so that the nail flanges can be withdrawn from behind the siding. This accomplishes the desired goal of removing the window but also results in less desirable consequences. The window wrap flashings and/or house-wrap will be trashed by the extraction process and gaps will be created in those protective materials that will be vulnerable to water intrusion after the new window is installed. How can proper repairs be made to this damage without taking the siding off?
Once the old window is removed, the trick is to get the new window flanges back in behind the siding.
This is where the magic comes in, because it essentially cannot be done.
The window installer simply scores the plastic nail-flange on the new window with a utility knife and snaps the flange off. Even more magical is that there are actually vinyl windows that can be purchased that have no flange to begin with. If you can buy windows without a flange that tells me there must be some magical way of sealing around them so that they do not leak.
Then again perhaps not.
Without a flange the new window can then be installed up against the interior trim. Screws are then installed through the jambs of the window to hold the window in place. The gap between the window and the original siding is then caulked; the installer collects his check and is off to screw and glue the next unwary client.
If you have ever visited the installation instructions of a window with a flange, you will see that it is actually quite a complicated process to install the window properly. The window opening itself has to be sealed and wrapped with flashings. These flashings, on all four sides of the window, are installed such that every layer overlaps the layer below it—including the house wrap. A bead of caulk then gets installed all around the window and the window is set in the caulk and the flange is nailed. After this another layer of flashings is installed—each layer lapping the layer below and the top layer goes under the building wrap across the top of the window. The bottom flashing materials that runs behind the bottom nail flange is made to likewise lap over the top of the building paper/house wrap.
The gist of all of this, as you have probably gathered by now, is the idea that all layers of materials lap over the layers below it—all of which is finally lapped by the siding which, depending on the type, also laps each other. In this way any water that finds its way into the wall structure can follow the surface of the house-wrap all the way to the bottom without getting into the wall structure. At least this is the theory. The resistance to water penetration with such an installation is great—even related to moisture vapor moving through into the home around the window as a result of negative pressure within the home.
So now we go and buy a window without a flange and install it in a manner that seemingly violates all of these protocols and then cross our fingers and hope for the best. This might not be such a big deal in a house where the window is merely being fitted into an existing frame that is theoretically all flashed properly behind the wood window installation, but it is certainly less than ideal.
When the installation is done where the entire old window is removed and the new window is merely inserted and caulked, we are certainly asking for trouble down the road. If the caulk is relied upon to keep water out, and the integrity of the house wrap and the flashings of the opening is questionable, all bets are off on keeping water out of the house structure long term. This method of installation is far from “best practice.”
Proper installations typically requires either cutting the siding back so that the window can be installed with proper flashings and the nail-flanges intact, or the siding must be removed and then re-installed. Obviously this ups the cost of the installation of your new windows. Sometimes proper installation requires adjustments of the interior trim as well—thus further increasing the costs of the installation of your new windows.
In light of these considerations it is not hard to understand why some installers would take shortcuts—-why some homeowners would take shortcuts. Add to this that if the windows are being sold as part of improving “energy efficiency” it may be necessary for the short cuts to be taken in order to meet the window seller’s claims of eventual “payback.” Hopefully everyone knows by now that new windows will never pay for themselves in energy savings. You change them out for comfort, sound control, because the original ones are no longer functional and energy efficiency in the sense that you will safe energy, not because they ever stand a chance of paying for themselves.
In doing research for this post I found it interesting that in some cases the window manufacturers seem to care less whether there is a flange or not and leave the weather-tightness to the installer. While this seems contradictory to the lengthy “how-to-install” instructions that comes with the windows, one has to think about how many more sales of windows come into play when they don’t care how they are installed and hang the problems that develop with improper installation on the installer. Of course logically it should be the responsibility of the installer—but I do think they are getting mixed messages.
Without proper flashings and nail flanges, we are relying on caulk alone to keep water out of the wall structure. Even the best caulks don’t last as long as will be necessary to adequately protect the home. Differing rates of expansion and contraction between the window and the siding materials will typically result in cracking of the caulk over time. Cracks in the caulk mean that water will have a pathway into the home. It also means that moisture will have a pathway to be drawn into the home when the home is under negative pressure. That means moisture laden air will be drawn into the wall structure regardless of whether it is actual water or not—merely humid air can thus represent a problem. Both scenarios are not good for the long term health of the home especially in really hot humid climates or really cold humid climates. At one season or another, this is true of most homes in the US.
In this picture we can see paint failure and unevenness of the siding of the recently replaced window. Elevated moisture was noted by moisture meter behind the siding in these areas of obvious damage. The flange was not present and the jambs had been screwed in place.
So how can you tell if your windows were installed without the flange?
If you have new windows and no changes to the siding were made—this might be one clue.
If you have new windows and no changes to the wood exterior trim were made—this would be another clue. This next picture shows the original wood trim wrapped by new trim installed on top of the siding.
New windows with screws in the jambs would also be a good clue.
If you can slip a knife into a crack between the siding/trim and the new window and you don’t hit the flange of the window within a 1-1/2”—this would be a good clue as well. As in this three year old window in the next picture—where the caulk has already failed—the 3” knife at full depth along the side of the window should have hit the plastic flange before the knife got this far in. This is clearly a window without a flashing and yet may be an approved installation according to the manufacturer of the window. Is it “best practice?” Certainly not in my opinion.
Things that are cost effective in the short run are often not cost effective in the long run.
New wood trim around the windows is a pretty good clue that the flanges are in place but even this is no guarantee. Trim installed on top of the siding is another clue that the flange might not be there. This is not always true either however, because it is a common to find trim installed over the siding even when the windows are properly installed (I can argue that this is also less than ideal but that is a topic for another post).
Installation of windows without flanges has created enough window installation failure issues that some jurisdictions now require permits to install replacement windows and the windows have to be installed with proper flashing details.
Verification that the windows have been properly flashed and that the nail flanges are still in place is a good idea. Windows installed without a flange are almost always, to some degree, going to be a gamble and vigilant maintenance of caulk seals will be essential.
By Charles Buell, Real Estate Inspections in Seattle
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30,000 years ago Neaderthals built multilevel homes having discovered the infallibility of the overlap concept. (Probably from scaling fish:) I suppose they used a little good clay mud once in a while to seal something but no more than they had to.
Today reportedly larger human brains are too often turned off & listening to caulking being marketed.
Subsequently an incredible percentage of exterior workmanship is not overlapping things & instead uses a product, caulking, which has a short life & which is as likely to trap water in as keep it out.
The Neaderthals are snickering & you & I have job security!
Wow,just had windows replaced a week ago by window world,and installer said he was going to replace with flanges,but was told to cut them off,over $1500.00 dollars spent,on 3 and 1/2 windows I,m pissed.It may be court time.
I moved into my 1970’s house a little over a year ago – about three months later I had new vinyl windows put in. Prior to that I never heard loud noises from above, but since, I have…almost gunshot loud.. a friend told me he thinks it is the way the windows were installed – not far enough back so weight is not securely on sill… have you ever heard of this?
Sorry, I have no experience with changing windows doing this.
Is there any way to cover these window flanges up so they don’t show with the screws we already had wood siding up
Typically the siding has to be cut back to cover the flange
I’m on the east coast so a lot of 60 year old (my house) to 100+ year old stock and this is pretty much the standard installation method because so many houses are full 4 inch brick siding around stick framing. What I’ve found in mid century homes at least is that the original steel frame windows w/ flange went in after framing was done then the masonry was done last creating a brick opening that is smaller than the rough opening like with siding. Of course though removing brick to temporarily enlarge the opening enough to get a new flanged window in is a much different animal than cutting back/replacing modern siding so no one even considers that an option. What you end up with is typically a no flange window with the vinyl sill resting on the brick sill on the exterior side and vinyl quick trim down to the stool on the interior side, plus screws through the jambs like above. I had a large horizontal slider put in and it took about 12 hours for all the weight of that glass to sag/bend the quick trim and deform the jambs, had to go back behind the install and build the bottom of the rough opening up to carry the weight. Then they clad the gaps between the window frame and the brick with aluminum coil held in place with caulk. We call it “caulk and walk.”
And don’t get me started about insulation and air sealing. These guys will all tell you that foam is bad for any number of made up reasons. At least in the old days they jammed all that fiberglass in to stop most air infiltration.
I knew literally nothing about windows before getting mine replaced so if you’re reading this thinking “wtf” I was there too. The last thing I’ll mention is spend the extra money to go with a manufacturer that isn’t going anywhere. I had a lifetime warranty or whatever that came with my Vista Windows which is worthless now that they don’t exist lol. At least now I know I can absolutely do the job the right way myself next time it needs done (hopefully not for a while!).
TL;DR what this blog says is exactly right, and it’s even worse with brick exterior. There’s a right way to do it, this (screw and glue/caulk and walk) ain’t it.
This is so helpful but I’m still confused by all the different terms my potential installers are using. I’m looking to replace 1970s aluminum windows with vinyl windows. One swears ‘flush fin’ installation (putting vinyl frame over the aluminum frame) is my best option. Another said ‘fin set’ (completely tearing out aluminum frames) is way better than ‘screw and glue.’ Who’s right??? Thank you!!! Dara
I would have serious reservations about any installation that does not remove the original windows and allow for use of the nail flange on the new windows—unless the house is brick veneer. Other types of siding can be cut back to allow for proper sealing of the opening, installation of the window with a nail flange and then final trim to cover over the nail flange. This is also the easiest way to remove the original aluminum windows. Installation of windows without a nail flange should be “last resort”
It has become very necessary to grasp both the science of window installation and of window construction. Avoid a very expensive mistake and check the materials being delivered, especially for vinyl windows. Stand the closed window upright (protect the fin) and splash a bucket of warm soapy water onto the panels (Not too hot for vinyl windows). Observe for 1) run off 2) run through 3) seeping at corners or on bottom, 4) fogging or bubbling between or behind panes, 5) noises (bubbling, squealing, hissing, crackling) and 6) abrupt (post production) alterations to feature profiles or component finish.. You probable won’t want a window that doesn’t keep water out even before it is installed.