Saturday, July 13, 2013

New Specifications For Shingles On Low Slopes

Never go below 4" Rise Per Foot for roofing Shingles.  Have we all not seen enough damage from poor specifications?  No matter what manufacturer specifications say, just say "No."
Bob Wewer - Damage from low slope shingle installation

It seems that the old timers had a lot more on the ball than the modern construction gurus of today. It has been for a long time in this era now that low sloped roofs have been cladded with asphalt shingles.  In the designation of "low slope," here I am referring to the subject like an old timer from centuries prior.  It used to be that in the old days (like the 1800's to early 1900's and before asphalt shingles) when primary natural cladding was used on steep slopes.  These steep slopes were no lower than 8" rise per foot.  This dividing line caused the use of metal roofing on lower porch roofs, etc.

There were no low sloped shingle applications.  There was no "ice and water" underlayment either.  There was only the primary water-shedding or waterproofing material and the construction methods were superior to today in regard to precipitation protection.  The rooftops lasted longer and functioned better.

Even with the current array of lower sloped roofs and specifications by manufacturers that have blurred the lines between steep and low slopes, we can still do the job right and without nonsensical methodology.    The link above (at the top of the page) leads to a page that demonstrates the problem within our industry of acceptance of faulty specifications.  An absolute line has to be drawn at four inches rise per foot as the limit for roofing shingle use.  This is far lower than what the old timers would have accepted and we should realize that there is a definite line that should not be crossed when specifying a product that relies solely upon lap and slope to shed water.

by Bob Wewer

Bob Wewer - Underlayments Have Become All The Craze In Roofing & Siding

The Underlayment Craze

It started in the mid-80's. On the rooftop, roofers were required to use a new type of underlayment called “Ice & Water” underlay. The roofers of old would sometimes use 90 lb. or a heavier underlayment at the eaves and up to a point 24” inside the eave wall to protect for ice damming events. This sticky underlayment is applied to the plywood and it eventually melts itself to the roofing shingles, sealing around nail shanks to provide a seal at the eaves that protects against ice damming. These products represented a boost to the manufacturers' bottom lines as profits increased because of the increased sales of these underlayments.

The real cause of ice damming on rooftops is the “hot-spots” associated with poor ventilation. The spotty areas of interior heat combined with the sun would cause uneven melting of a snow covered roof. Once the runoff reached the eaves it would freeze similar to a bridge roadway freezing before the connecting roads. The overhangs are cold and suspended in air while the attic areas are warmer. This is caused by a lack of proper ventilation which tends to even out temperatures on rooftop planes.

The use of these products increased in popularity. The tradesmen of the rooftop are generally young and with the influx of foreigners into the workforce, the expert to journeymen passing of proper roofing disciplines was lost in the same era. Manufacturer specifications were looked upon for direction as building codes are vague and the makers of the products specified the use of the “Ice & Water” underlayments at every critical juncture of the roof. Even on chimneys and rakes and where the heavier underlayment would conceivable transfer its runoff to the lesser felts (or tar-paper). The underlayments became more important than the primary shingles in the specifications and in the minds of the installers!

There had been a lack of proper discipline in the applications of metal flashings for years. The loss of transfer of information came with the many workers in the trades being from other countries. Soon these underlayments were looked upon as roofing systems, themselves. They were specified even by manufacturers for roof slopes down to 2” rise per foot (low slope) under asphalt roofing shingles. By trade standards and for years, for roofing shingles it was always anything under a 4” rise per foot was considered “low slope” and a sealed roofing system was used. The crowd went along with the new specifications only to find that problems emerged. Bob Wewer - Low Slope Shingle Failure   The underlayment did not work as specified. The fingers were pointed and the leaky roofs were blamed on the installers that installed them per spec.  See Bob Wewer - Mold from leaks 

Soon it was realized that proper flashings were compromised because the “Ice & Water” underlayments were used and roofers would just haphazardly install sub-par flashings. The underlayment became more important than the proper and fitting old world specifications.

Now the siding arena was suffering a similar fate with the cladding of side walls that leak. The products made with channels that collect and allow water behind them had to be underlayed with significant products to prevent water intrusion. Housewraps with perm ratings were invented because of the moisture vapors that push outward in the winter. Condensation was a problem with the necessity to install a formidable underlayment, so a permeable underlayment had to be used.  See Bob Wewer - Siding Leaks

This idea of a permeable underlayment was the answer to provide protection for liquid moisture while allowing moisture vapor to escape. The problem with this scenario is that when the temperature variables are added into the equation, the idea does not work well. The comparison has been made that if you were to open your window on a cold winter's day and place a pot of boiling water on the window sill with the screen closed, the exiting moisture would be stopped by the screen, beading up and running down onto the sill. The screen is many, many times more permeable than any housewrap. So the perm theory does not work in the real world. Making sure your home is air-sealed and a proper vapor retarder is on the inside of the wall, on the warm side of the insulation is the answer.  Bob Wewer - Mold In Wall

In the above image, moisture from inside the home was slowed down by the underlayment and condensation occurred.  The "perm" rating has little to do with reality. 

The argument will be made, as it has been, that the wall must be allowed to dry out and trapping moisture is wrong. The wall can dry from the outside, in the northern climates. Never in 35 years have I torn open a wall to find, what is referred to as “reverse condensation” in the Philadelphia climate. The condensation always shows on the outside of the wall.

Flashing tapes similar to “Ice & Water” were developed to “flash” windows from the onslaught of water that is channeled under the siding. Such emphasis was put on underlayment that again, the proper installation of wall cladding and head flashing was lost to the new age. The main problem with these window flashings is that when an opening is not sealed (with foam insulation or batt insulation and a proper vapor retarder) it will emit interior moisture vapor that condenses on the “flashing” tape.

The bottom line here is that proper installation techniques have been lost to an over emphasis on underlayments. Underlayments should only be looked upon for temporary cover while construction is underway, or at the very most supplemental protection in the case of devastating weather.   Many will scoff and argue but this is the way it was in the old days when installers knew what they were doing.     These are those who have had their ideals skewed by bad industry practice.  A case in point is the shingle manufacturers specifying low sloped roofs to receive asphalt roofing shingle cladding because of the stickt ice and water underlayments.  Low Sloped Shingle Specifications by Bob Wewer

A story of interest:  Moisture Inside Walls by Bob Wewer discusses how interior moisture migrates through walls to condense and cause confusing issues.

by Bob Wewer