Residential window installation has come a long way. History and experience along with testing, have given window manufacturers, qualified builders and construction experts a whole new "window" of knowledge on how and why install windows with the current techniques.

Historically, windows in residential construction were installed directly on the framing of the structure and sealed with caulking around the final exterior trims. The same was true for replacement windows where an older window would be removed and a new one installed in its place. The new window would some times be installed directly on top of the siding edges, fastened and sealed with caulking around the trims. This would be the extent of water or weather proofing of the windows and trim edges.

Of course this all changed few years back (early in the nineties), when moisture related issues were single handedly creating mold problems all over the nation. Add to the moisture issues a little of media scare tactics, and you had construction experts trying to identify all possible methods of preventing water intrusion into homes.

Undoubtedly, windows and their installation was one of the sources of mold problems, as the installation techniques in the past assumed that caulking itself would prevent moisture penetration. Everyone forgot to acknowledge that most home owners will not take good care of their homes and perform annual maintenance and re-caulking of the exterior trims around the windows.

Thus, the industry came up with a set of installation techniques and procedures to help prevent moisture related problems with residential construction due to the window installation. These techniques have been adopted by all window manufacturers and current codes either make specific mention of the installation procedures and/or refer to the manufacturer recommendations for proper window installation.

Unfortunately, even with all the information out there on how to install windows properly, there is still the wide spread practice of doing it wrong or half way when compared to window manufacturers instructions.

As of the writing of this article, I have been able to watch construction of several structures where the water proofing materials or flashings are improperly installed. What is more troublesome to see, is that construction foremen, contractors and even building inspectors are continually neglecting to check on the installation of the windows as the projects are being built.

Some home owners expect that a structural (home) inspector will catch the improper installation of windows when they inspect a home for sale. Unfortunately, all standards of practice regulating home inspectors clearly detail that property inspectors will not perform destructive investigation or move items to expose concealed areas. Since a home being inspected already has the siding installed, a home inspector will never be able to see the flashing or procedure used for the window installation of a home. 

How can you tell if your windows are installed correctly? Well outside of you watching the home being built, there is no guaranty that the windows would have been installed properly. The only way to verify this is to actually remove portions of the siding around the windows to visually check the flashing and weather proofing. This carries the additional task of having to replace any portions of the siding removed and/or damaged during the removal process. Some times with the additional expense of having to hire a licensed contractor to perform the work.

So what is the big deal about the window installation? Current techniques recommend that flashing or water proofing be installed in the proper sequence when installing a window. This sequence is extremely clear and every window manufacturer recommends it. When the flashing is installed improperly, the chances of water penetrating into the framing and the interior of a structure are increased exponentially. Of course if proper caulking is present around the windows on the exterior, this is minimized a bit. However, current construction practices have builders NOT performing any type of caulking of any of the trims and siding joints throughout the exterior of residential construction and most home owners are never aware of the potential problem.

Below are some photos of current construction (fall 2007), where improper and proper window water proofing is demonstrated. Unfortunately, for the improper example on the second and third pictures, the lower section of the water proofing below the windows is clearly on top of the lower window flashing. Current installation calls for the lower window flashing to be installed on top of the water proofing to allow for drainage in the event of a leak, as shown on the first photo.

In part two of this topic, we will discuss the proper installation procedures and provide links to most of the well known window manufacturer's instructions. In addition, we will look at the current codes regulating the window installation and water proofing.

Correctly Installed Window/Flashing

 

Improperly installed water proofing over lower window flashing instead of under it.

workers stoped for lunch right in the middle of installing the siding around the window with improper flashing.