Bad Window Replacement: Top 10 Installer Screw-ups
When good windows happen to bad installers
WARNING This article contains profanity, which is not gratuitous but rather fundamental to the art, as well as being a true and accurate expression of my frustration with aspects of the window industry. We can put a man on the moon, so why do we sometimes do bad window replacement?!?
The window industry is so big and non-uniform that you can find window installers of every skill level, from ignorant to brilliant, and anywhere in between.
This is because of a gaping absence of uniform installer certification and a widespread ignorance of important construction principles, even at the management level. You will be hard pressed to find a window company that provides a uniform training curriculum to their workers.
I continue to be appalled when I see bad window replacements that involve good windows installed with fundamental errors that result in window water leaks, air leaks, poor operation, caulk failures and even structural failures. What is going on? Did nobody in the company from owner to apprentice figure out the basics that are needed for a successful window installation?
In the absence of good training, too often the brilliant workers just figure it out for themselves and care enough to do an excellent job, and the ignorant workers do bad window replacements that are doomed to fail without much caring for the result.
While it may sound like I am beating up on the workers, and to an extent I am, by far I am laying most of the responsibility for bad window replacement at the feet of management and the window industry. Window installer curriculum and training must come from above. First, management and the window industry must determine the concepts that are important, then they must require workers to learn and implement it.
When the window replacement goes bad, the hapless customer is often faced with a three-way finger pointing exercise where the window supplier, the window manufacturer and the window installer each blame one another for the bad window replacement. The customer spent good money for windows and got bullshit instead.
Window people! Is this who we want to be? Let’s be better!
So in the interest in industry improvement and personal catharsis, here is my list of…
Top 10 Window Installer Screw-ups
#1. Not tying to the Tyvek!
In most buildings built in the last 20 years, there is a “membrane” inside the wall that acts as the primary weather resistive barrier (WRB). Often this WRB is DuPont Tyvek, a waxy paper-like sheet that resists air drafts and incidental water but allows water vapor to escape.
A fundamental of WRBs is complete continuity with all elements in the wall including window and doors frames. The Tyvek or other WRB must be sealed to the window frame on all sides or the building envelope will be violated. Yet when clients complain of bad window replacements that leak air and water, too often I find that the connection between WRB and window is missing or incomplete. The incorrect open space between the window and the WRB provides a wide-open passageway for air and water to enter the building.
Here’s how DuPont says Tyvek should be used.
#2. No damned end dam!
Imagine a gutter with the end missing. Water will spill out the end, right? Well, window systems have gutters too, but they are called sill flashings or subsills. Just like gutters, they need to have something at the end that prevents the water from running out and into the wall cavity. The water should drain, or weep to the front only.
Gutters or flashings or subsills are needed beneath window openings when 1) there are multiple windows in an opening, or 2) when there are trim pieces or receptors that might admit water into the system. Avoid penetrating these with fasteners!
End dams are needed anywhere there are gutters, flashings or subsills. End dams are also needed to terminate the ends of masonry flashings. So why are these critical features missing or incomplete in so many buildings?
#3. Shi**y shimming!
Shims are small pieces of plastic or wood that act as spacers between the window frame and the surrounding structure. Usually there are fasteners, such as screws, that pass through or near the shim to anchor the window in place. Shims are usually evenly spaced at the bottom, sides and top of the window.
Shims at the bottom of the window also carry the weight of the window. These must be spaced according to manufacturer instructions to distribute the weight so the bottom of the frame is not distorted.
Shims around the window also create a space where caulk can be installed with a caulk joint sufficiently sized to handle long term movement. Shims at the sides of the window keep the frame square. Without shims at the sides, the rectangular window could become a parallelogram over time, which is very bad for performance. Shims must support much of the front-to-back depth of the frame so the frame does not twist out of position over time.
Some windows, such as double hung windows, have a special need for shimming at both jambs at the height of the meeting rail, so proper weatherstrip compression is maintained.
#4. Crappy caulking: Cleaning!
Caulk is a fundamental part of window installation. It is the stuff that seals between other stuff and maintains water and air tightness. In order to work, it must stick. So why do I see window installers apply caulk to dusty, dirty surfaces, where it will have no chance to achieve a good bond?
You have to clean the surface, also known as the substrate, before caulking. Using isopropyl alcohol (not denatured) with a wet rag/dry rag method will produce a reasonably clean surface for caulk adhesion.
#5. Crappy caulking: No tooling!
Most caulks also need to be tooled in order to stick. Tooling is similar to buttering bread. In fact, good caulkers have a series of metal spatulas of varying width for tooling caulk joints of any size. These spatulas look look a lot like cake decorating tools. Sometimes they are cake decorating tools.
When a caulk joint is properly tooled, it has a pleasing, continuous concave surface. It shows that a skilled worker applied the caulk. When a caulk joint is not tooled, the joint is bumpy and uneven. Its life expectancy is reduced. It was installed by someone who needs better training and practice.
Continue to Part 2 of Bad Window Replacement: Top 10 Installer Screw-ups
My condensation problem does not seem to be any of the ones listed here. I have condensation where my double hung sashes meet in the middle. It is on the top sashes. I know my windows are improperly installed. None of the sashes seem to fit properly in the window frames. Most of the windows, you see daylight along the top sashes, along the sides where the two sashes meet. Of course the window company is blaming me for the misalignment of the windows, I am using them wrong. The windows have been installed three months. Is this condensation because of the way the windows are installed? I feel cold air over this area (the place where the two sashes meet). It is 36 here right now and I do not see any condensation this morning. We keep the temperature at 65 in the house. Now yesterday morning it was in the 20’s and all windows had condensation except the kitchen sink window. That window is on a deep covered porch and I have never seen condensation on it even though I can tell you the sashes do not fit its window frame tightly. Thanks for your information.
The area you refer to is called the meeting rail. It can be a big leaker if the two rails are misaligned and cannot be tightly sealed.
Hi Mark,
I bought a house and the windows were not shimmed properly.
The glass has pulled away from the frame. (a little)
How much will it cost me to have the windows reinstalled and shimmed and caulked?
Thanks,
Patty P
Costs vary a lot by area. Google “window installation” plus your zip code and start making calls.
Great article! Always remember to use tempered glass in a window adjacent to a door or inside a shower or bath. Tempered glass shatters into small, blunt pieces when broken instead of dangerous glass chards.