Window flashing is affordable, simple to install, and may save you a significant amount of money by shielding you from the expensive effects of water damage or fines for non-compliance, irrespective of the type or material you select.
Flashing, however, is misinterpreted by many builders. When it’s necessary, why you might install it, and the consequences of not doing so are all unclear.
In this simple guide, you’ll discover:
- What flashing is and why it’s essential
- When flashing is necessary
- The potential consequences of not using flashing
- A straightforward method to safeguard yourself
What Does Window Flashing Mean? and Why It is Important
Flashing comes in a wide variety, yet they all serve the same function. Flashing is intended to keep rainfall from destroying your home’s interior construction textiles and to waterproof windows.
Homes in USA typically have a timber frame with external cladding, such as weatherboard, brick veneer, or another material, sandwiched between the cladding and the timber with a waterproof building wrap.
In order to stop moisture from seeping into the interior of the walls, flashing redirects rainfall in conjunction with the building wrap.
Considering this, flashing is crucial for two main reasons:
- Without flashing, rainwater can gradually leak inside a house, causing twisted plaster, mold growth, broken frames and floorboards, and other problems. Flashing shields a house from the expensive effects of water damage. Flashing significantly lowers the possibility of water seeping into the house or construction materials.
- State building authorities, such as the VBA in Victoria, may penalize you for not flashing. Flashing is required in all residential windows in Australia according to the recently revised National Construction Code. Inspectors will apply severe and costly penalties if your windows do not have flashing fitted.
Window Flashing comes in Three Primary Varieties:
“DC” or damp course: damp course In essence, flashing is a huge, thick polythene sheet that is affixed to the window.
Z-flashing: a folded metal component makes up this style of flashing. Usually found in homes with lightweight construction, it is installed on the head of a window rather than the sill or the jambs.
Self-adhesive: You can buy self-adhesive flashing and attach it between the window and building fabric yourself if the window you purchase from a manufacturer or supplier does not have flashing already attached.
When is it Required to Flash Windows? What Prerequisites Must Be Met?
Every window in a house with lightweight construction cladding or stone veneer needs flashing of some kind, no matter where you live in USA. As on 10 Jan 2025 this is a definite and unambiguous requirement for adherence to the recently revised National Construction Code.
This is where part of the misunderstanding arises.
Although flashing was previously stated in the Code, it was frequently done so using ambiguous language, such as “flashing is necessary where required.” The following prescriptive guidelines are now provided by the Code:
1. When Building Using Masonry or Brick Veneer:
Flashings must be installed on the top and bottom (or head and sill) of an opening, as specified by the Code in Clause 3.3.5.8. Furthermore:
- Installing the flashing requires that it protrude at least 150 mm on both sides of the aperture.
- The flashing needs to be placed 300 mm above the aperture and no more than one course below the sill brick course.
- At least 150 mm above the entrance, the flashing needs to be cranked up in the cavity.
- The flashing needs to be set into the masonry veneer at least 30 mm.
- The flashing needs to be fastened to the wall or window frame.
2. In Wall Cladding made of Wood or Composite:
According to the recently amended Code, flashing must be installed on an opening’s head, jambs, and sill as well as on its sides and top. Furthermore:
- The flashing needs to be at least 100 mm long on both sides of the aperture.
- The flashing needs to be fastened to the wall and window frames.
- At the top and bottom of the opening, the flashing needs to drain to the exterior face of the wall or cladding.
- The flashing must cover the ends and edges of the opening’s framing and be firmly fastened at least 25 mm beneath the cladding.
Additionally, the flashing joins need to:
- Overlap in the flow direction by at least 75 mm.
- Be firmly secured at no more than 40mm intervals.
- Install a sealant in between each lap.
How Flashing Functions
The purpose of flashing for windows and doors is to divert water across consecutive overlapping layers of flashing material, much like shingles do on a roof. Fashing is usually installed in two sections around a window or door frame:
Applying flashing tape in a particular sequence across the window’s sides on the house’s outside wall.
A sill pan that either extends out or butts up against the bottom of the window, and a drip cap that fits over the top of a window. Note: brick homes might not need them.
What Happens if Someone Doesn’t Comply?
Failure to flash a window can lead to one of two possible outcomes. Both will cost you money and/or time, so neither is good.
1. Rainwater can enter your house without flashing and severely damage the materials.
Over time, water seeping into building materials can cause mold growth, bloated floors or lumber, and warped or cracked plaster in your walls. Repairing the damage will probably be expensive and time-consuming, depending on its severity.
2. A state-based building authority or an independent inspector is likely to find you non-compliant if you don’t flash.
This probably means missed time and money for construction. It is really inconvenient for homeowners. Why?
How About New Windows?
Many window replacement businesses would insist on removing some of the siding material from the home, removing the flashing material that was already there, and rebuilding it from scratch if money was no object. This is a labor-intensive process that would likely treble the installation cost.
Of course, window makers are aware that different people install windows in different ways. In order to guarantee that their products are installed correctly, each manufacturer will outline the necessary flashing technique for replacement installation.
Although the procedure for removing and replacing windows is very similar from one house to another, there are some variances. For example, if pre-existing problems are discovered within the home’s walls while a window is being replaced, the procedure must account for fixing all of the difficulties that are discovered.
Fundamental Process:
- The outdated window will be taken out.
- The flashing will remain in its current state if it is undamaged.
- After that, the window will be shimmed level or plum
- The entire window will be pumped with insulating foam.
- We will make a sloped top cap, capped sides, and a sloped bottom cap to suit.
- Caulking will be applied to the cap edge where it meets the brick or siding.
- Caulking will be applied to the inner cap edge where it meets the window.
Choose a business that gives and is dedicated to a lifetime warranty on the installations they are performing to make sure your windows are being installed correctly.
Conclusion
Every window installation must include window flashing, and the advantages of adequate waterproofing last for decades. Unless you want callbacks, you only have one chance.
The aforementioned window flashing instructions are relatively generic ones for window installation; your job is probably even more complicated than the code minimum.
