Tag Archives: professional deck builder magazine

Excellent Q&A From Frank Woeste via Journal of Light Construction – Drainage Problems on Low Slope Roof Decks

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.

Drainage Problems on Low-Slope Roofs

By Frank Woeste

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)

Who Should Inspect Deck’s & Balconies?

 “Leys makes a good argument that even the other groups identified in the draft bill—general contractors, architects, and engineers—aren’t qualified to perform these inspections, despite their skills and training.”

Andrew Wormer Editor Professional Deck Builder Magazine

If California’s Senate Bill 721 is adopted without modification by that state’s legislature, periodic inspections of enclosed balconies and similar structures on multi-family buildings that are higher than 6 feet above the ground would be required statewide. This is a common-sense measure, especially in light of the Berkeley balcony collapse in 2015 that killed six students. But as Bill Leys points out in an interesting post on PDB’s LinkedIn group, one of the groups that would be authorized under the law to perform these inspections, make repair-or-replace recommendations, and certify that repairs have been properly completed are structural pest control licensees.

Read the rest of Andrew’s editorial by clicking here 

Read my opinion by clicking here