Improperly Installed Windows Can
Cause Severe Water Damage To Your Home…

Bottom Line: If Your Contractor Or Remodeler
Cannot Tell You What The “4 D’s” Are
You Need To FIRE Them On The Spot… PERIOD.

Proper window flashing and proper sealing of the window cavity is critical to a properly functioning window. Window flashing is never really given much thought, because they are usually visually unimportant – remember that 90% of the installation occurs behind the walls, where you can’t see – and they are monetarily unimportant because they represent a very small part of the overall cost of a window installation.

But, despite the fact that window flashing gets very little notice or attention, window flashing is by and large the most important items in terms of the safety and weather tightness of a home. In fact, if the window flashing is poorly designed or is haphazardly installed, or both, it will prove to be the most costly error that can be made on a home.

In fact, Don Hazeldean, a very respected Canadian architect, discovered about 10 years ago that the prime cause behind a “leaky home” is primarily bad flashing practices. According to Mr. Hazeldean, next to a major fault in the foundation, a fault or oversight in window flashing is the most costly error in the entire home construction process.

Mr. Hazeldean took over 10 years of research and investigated the essential purpose(s) of flashing. These essential purposes were identified and the principles behind them were then encapsulated in a simple but complete conceptual phrase, the “4 D's.”

In short: the 4 “D’s” clearly explain the four design principles that should exist in each and every flashing.

In fact, “The 4 D's clearly explain sound flashing design. The phrase and the principles behind the 4 D's have been adopted by the NZ Building Code, by weather tightness experts around the world and are now taught in building training establishments.”

Here Is An Excerpt From That Report:
What Are The 4 D's?

The 4 D’s stand for four design principles that must be followed when using and installing window flashing:

• Deflection prevents water and moisture gaining entrance to the building structure as the first line of defense
• Drainage should any moisture penetrate behind the flashing (occasionally) this water should have a pathway via a drainage system which will eventually and harmlessly disperse this unwanted water to the exterior.
• Drying to assist in the removal of any moisture that does (occasionally) breach the first line of defense: deflection. There should exist a suitable amount of fresh airflow to remove the moisture by evaporation
• Durability the flashing material and design should be tough enough to endure for the life of the cladding and therefore maintain the weather tightness protection.

Deflection of water is the number one priority of flashing. If water cannot get into the building structure then there is no need for drainage or drying. In fact, for true “window professionals,” Drainage is solely a backup safety practice.

In other words, we install drainage as a “worst case scenario,” such as in the event that a wicked storm hits Kentucky, any water that happens to penetrate will simply “drain” away. This is extraordinarily important when you consider that we get quite a bit of rainfall and snow here in Kentucky.

If water does happen to penetrate behind the flashing, then Drying will assist the removal of moisture but this will depend on the dampness in the air and the weather. This is particularly important when installing windows in our area given that Louisville, Kentucky is prone to the extremes of weather.

For example, if the weather is predominantly wet over long periods, as can happen during torrential rainfalls like it did in Kentucky in August of 2009, then the drying aspect will be very low and even negligible; thus only reaffirming the importance of installing flashing correctly.

That is why we do everything in our power to make sure that the window flashing is installed perfectly.