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Faux Siding and 'J' Channels and the Leaks Caused

Steel Siding, Aluminum Siding, and Vinyl Siding come in several configurations but they all have one major flaw in design. That flaw is in the use of water collecting ?J? Channels. Decades ago, the metal exterior cladding products brought the ?J? Channel to the fore for exterior trades. These channels were thin and low profile, but the inherent problems with leaks were evident to the tradesmen that followed the exterior cladders. 'J' channels are even improperly used on Fiber Cement Siding!

Note: The actual examples below are not indicative of every siding job with 'J' Channels.  All photos below are from the same area on the same wall of one house.  This is the northeast side of a home located about 2 blocks from the NJ shore.  This is an extreme example of what can happen on an open, and unprotected wall without overhangs.

J channels on WIndows and Doors channel water under siding. The use of these 'J' Channels has long been helpful in interior applications, such as drywall and interior cladding terminations. Materials could be cut, capped, and butted cleanly to adjoining materials in a neat, fast, and appealing application. This idea has been inappropriately applied to exterior wall cladding construction.   Look at the photo to the left:  A common problem is the water that is trapped behind the siding from the velocity resulting from water collecting 'J' Channel on a round window.  Large Patio Doors are also a problem with the width of the water collecting 'J' Channel.  Rain water is collected and directed behind the siding, along with any dust or material that resided on the wall. J Channel Collect Water and sends it behid the siding

The focus of siding installations has mostly been on aesthetics and functionality was something that was left for the subsequent service call. Leaks in siding, as we have documented on this website several times, are usually not realized right away.

Many damaging affects of the use of the water collecting ?J? Channels have been realized years after initial installation. When mold, insect infiltration, and rot have taken over, walls can begin to stink, structures can begin to sag, in extreme circumstances, and insects have a field day.

Mold and Mildew growing under siding because of leaking J channels? J? Channels cause water to enter behind the siding, along with any dust that may be present on the wall.  Dust, along with the organic components of the wall substrate can become food for an organism that may have been harmless while on the surface of the siding.

These photos of organic growth resulted from the accumulation of moisture and dust that washed behind the siding at the window and door heads and down the channels and into the locks. The overflow of material and organic growth shows itself seeping out at the locks. Mold and mildew thrive in warm and moist environments. 

mold growing under siding because water and dust enters in the J channels.
mold spores   The use of ?J? Channels to hide the expansion and contraction provisions in the Siding itself has made for even larger channels. The channels are made very large, because the gaps in the siding left for thermal movement are large. A 1? ?J? Channel is now the norm, and this replaces the smaller channels of old. Larger channels mean more water collection. The vertical walls of a home shed enormous amounts of water in the face of a storm. Many gallons of water flow down the vertical surfaces to meet the penetrations in the vertical planes: Window and Door Heads are normal obstructions to this massive flow of rain water.  Just like a gutter on every window and door, these water collecting channels collect the rain water and channel it behind the siding. Now Seamless Siding has hit the scene with even larger expansion rates and larger channels.  The bigger the ?J? Channel, the bigger the water retention and leaks associated with this methodology.
mold spores  
example of how water enters and collects in j channels

Some in the industry claim that all that is required is an underlayment that will keep the water out of the substrate after it has entered behind the siding.? This can be the case, but for how long? Below we have a link to the ?Weather Barrier Statement.?? This statement, made in writing by the Vinyl Siding Institute, and makes it very clear that if you have siding installed with ?J? channels on your home, underlayment must be used to keep the rain water out of your home.

The major push for housewraps and weather barriers has been largely caused by the industry that has been put on notice regarding the expectation of precipitation entry under the siding. This is sometimes a big mistake if the entire wall system is not first considered, especially on older homes. This crazy dilemma is, in part, caused by ignorance. Part of the onset of the problem was in the mindset that came with the cover-all mentality. With little experience and minimal tools, a newcomer could start out covering over existing homes in a neighborhood in a seemingly harmless endeavor of exterior ?upgrades.? In many cases, and years after these products are installed; however, the real damage is realized. The siding, along with the underlying materials must be removed in order to gain access to the rotting structure of the home. Manufacturers have notified the trades with the "Weather Barrier Statement" and the designation of the siding as only a "Supplemental Rain Screen."The installer of your siding is on the hook if the siding job leaks, if he can be found.??




A simple answer is not to use any product that ?bucks water.? Bucking water is an age old roofing term that, essentially, means that materials should be lapped as to allow the flow of water off of the plane of the roof and flashing details. Why has this simple truth been abandoned in much of the Siding Industry?


Below is a new age window with incorporated channels, manufactured for "easier" installation.?

window with j channels
proper siding with true water shed The photo to the left shows a proper window trim application.  This is a simple, low-tech application, just like the true tradesmen of old used to employ.  No ?J? Channel is used in a true watershed application that disperses rain water & debris off the building.  True Watershed.  Water rolls off window and door heads.

Read about Mold behind Siding caused by interior moisture, house wrap and new age paint.


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Website written by, Robert Wewer