I’ve had this Q & A page at JLC online on my to do list for a while now to post up here for you all…while the discussion is about drainage problems on low slope roofs, the photo they use is a deck over living space with tile on it and ponding water. And of course, decks over living space with tile or pedestrian traffic coatings on them are roofs as well, just that we walk on them too.
Frank discusses how a roof deck can pond water even when it’s “built to code” from loads placed on the deck. Recommended reading for designers, architects, builders, waterproofers and anyone interested in increasing their knowledge and skills.
Q. Can deflection of a low-slope roof cause ponding? How can this be avoided?
A. Frank Woeste, P.E., professor emeritus at Virginia Tech, responds: Historically, structural designers and builders have assumed that a design slope of 1/4 inch per foot (1:48) is sufficient to prevent ponding action, thinking that the installed roofing system will maintain at least a 1:48 slope in-service as required by some roof covering systems. However, in many cases and for different reasons, ponding on limited areas of low-slope roofs is common. That’s due to roof deflection, which over time can cause water to collect in some areas of a roof where the design slope for drainage is not adequate, and in fact changes from a “positive” drainage slope to a “negative” slope (see photo below).
DOWNLOAD THE PDF VERSION OF THIS ARTICLE. (666.96 KB)
In a search today for something entirely unrelated to decks, I stumbled upon the news that a Homeowners Association in Diamond Bar CA had been red-tagged and the residents ordered to leave their homes because of deferred maintenance leading to structural concerns. The order to leave has been rescinded after the first engineers report declared the property and immediate hazard and recommended evacuating units was found to be lets say “over cautious”. There are 155 condos at the property on the first and second floors. The second floor units have balconies while first floor units have a patio.
Several structural engineers reports on the conditions found at The Village at Diamond Bar came to the conclusion that “while there are substantial deferred maintenance issues that should be addressed throughout the complex property, the condition does not create a widespread and immediate danger to the life or safety of all occupants of the individual units as previously recommended via a report by Khatri International, a structural engineer hired by the Diamond Bar Village Homeowner’s Association.“
“The deck that we had off the house,” she said. “It was a two-tiered deck, and it was redwood, and that’s what brought down our house.” Corey and Danusia Larsen of Malibu CA of the Woolsey Fire that burned over 600 homes.
I’m still trying to find it but I remember seeing a quote from a firefighter in California describing wood decks as organized kindling. That quote sticks in my head and won’t budge. I’ve reviewed hundreds of pictures of homes that are burned and often you can see the outline of a wood deck or the remnants of…
To me the ideal fire resistant home would be stucco or concrete or Hardie board with a metal or concrete roof any decking on it would be a division 7 traffic coating that is fire rated for use in California fire zones.
I subscribe to Milwaukee’s Red Tool Store and get frequent updates on sales and new tools. One new tool from them is their combination concrete screed and level. They have concrete screed/level combo’s in 24″, 48″ and 72″ lengths. The levels range in price from $49.00 to $149 at Red Tool Store https://www.redtoolstore.com/collections/layout-tools
Does anyone doing concrete deck coatings out there have one or two in their tool box? Drop us a line and let us know how you like yours.
Fire Chief Blame’s Wood Decks as Cause of Fires Getting Into The Home , Advises Getting Rid of Them
WildFire and WUI experts such as Stephen Quarles of UC Berkeley, Jack Cohen of University of Montana and many others agree, attached wood decks are a danger to homes that are otherwise fire hardened. Stucco homes with tile roofs have burned in nearly every wildfire when ember showers from the fire being whipped by wind land on the deck ahead of the fire actually reaching the home. The wood deck ignites, items on the deck and under it ignite, and can then climb the walls into the attic area.
This video discusses fire hardened homes and why they still burn-often from wood decks igniting and entering the house.
Well we have the perfect alternative to the problem with wood decks-Division 7 Pedestrian Traffic Coatings. Our manufacturer’s listed here all have at a minimum a Class A fire rating as a roof covering. Meaning they resist ember storms wood decks can’t.
Not only do they resist ember storms, but our deck systems also waterproof space below and provide an easy to maintain surface that needs an occasional cleaning and resealing.
Dex-O-Tex published a case study a few years back on a home with Class A Dex-O-Tex Weather wear on the decks. The home, in Glendale CA, was subjected to a wildfire along with it’s neighboring homes. After the fire burned through, the only home left standing was this one. Read the case study here Dexotex case study fire resistant house
With deck season in full swing, now is the time to consider building your next deck with unique, beautiful, waterproof and fire retardant deck systems from DeckExpert.com manufacturer’s.
Search our site for your perfect deck and learn more here.
The deck waterproofing industry needs to speak up!
From the California Building Standards Commission-
Notice is hereby given that the California Building Standards Commission (CBSC), Exterior Elevated Element (EEE) Subcommittee will solicit technical expertise on the items listed in the attached agenda and the link below. The public is invited to attend and provide their input or comments. For questions on this notice, please contact CBSC at (916) 263-0916.