Flat Roof Parapet Details Explained (For Architects + Contractors)

Parapets in a flat roof assembly are often a source of leaks, moisture issues, and air leakage, as they are the intersection between the exterior walls and roof plane that are exposed on three sides to weathering, in addition to interior air leakage. Parapet walls must effectively transition the flat roof membrane to the weather resistive barrier on the exterior walls, using a series of flashings and membranes to ensure water-tight and air tight connections between dissimilar materials. Parapet walls must be designed to resist and shed bulk water, prevent air leaks that can deposit moisture into the cavity space, and be constructed to remain durable throughout the service life of the building. Water control layer continuity between the flat roof membrane terminations, the flashings at the parapet wall intersection, and the connection to the weather resistive barrier is the most critical factor that will determine the durability of the parapet and its ability to resist rainwater penetration and air leakage.
Link to the article on Best Practice Details for Flat Roof Parapets: asiri-designs.com/resources-1...
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Other Flat Roof and Parapet Articles and Resources: asiri-designs.com/resources-1...
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[@ASIRIDesigns]

*Get my climate specific guides to flat roof design available here:* asiri-designs.com/shop

[@kellyfowler1809]

Excellent information, once again! We're builders, but this flat roof is new to us. I bought your cold weather package, even though I'm in zone 4 in Northern Arizona, since we used to more foam in Utah where we usually build. We connected the 4" polyiso layer on the roof with the 2" foil-faced polyiso layer on the wall by going up and over the parapet so it's fully encased in foam. The parapet structure was fully sealed with Prosoco joint & seam and R-guard MVP before adding the foam. Then we added an 18" strip of high temp peel & stick membrane over the foam on the parapet top and down the sides 6". Our roofer is stopping the deck TPO at the inside corner of the parapet and then running a separate piece of TPO up and over the parapet to the outside wall, which also overlaps the roof deck TPO by 12". The parapet TPO is fully adhered, the rest is mechanically fastened. We air sealed the roof deck seams with Zip tape the joint & seam filler. The peel & stick between the foam and the TPO is required by the manufacturer to "protect" the TPO since we're using metal coping over it. I'm not sure how the peel & stick under the TPO matters - I really hope this all works. Would love your input. Thanks.

[@DrawerdonBelfort]

I cannot begin to express how thaknful I am that you have all this content. I'm beginning construction on my adobe style home and your website has been a GOLDMINE thank you so much!!!!

[@frame223]

Great information, Thank you

[@XYZ-Drafting_and_Designs]

Great explanation. Thanks

[@ticklemezellmo]

My parapet wall and likely the roof as well was not constructed properly, and there's water infiltration and possibly condensate issues. To have it fixed properly, should I talk with an architect before I get a contractor?

[@SteveP59]

Well explained

[@AardvarkArchitecture]

Great video and info!

[@ASIRIDesigns]

Thanks so much!

[@1truthseeking8]

​​@@ASIRIDesigns Do you cover insulation of and moisture control of shipping container homes? Looking to purchase either a ~ Marine shipping container (Corten steel), or a ~ preinsulated Freezer Shipping Container "Marine" (Corten steel) given that both of these have flat roofs so to speak, AND a continuous IMPERMEABLE METAL surface: (mostly impermeable -- imperfections, holes for windows, doors, plumbing, electrical, etc that might not be perfectly sealed, screw or bolts that also may allow moisture movement despite our best efforts) ....a tremendous amount of spray foam insulation could be applied to the exterior and whatever layers on top of and cladding/siding to protect that... But then what about the floor, AND the walls and ceiling inside the container? Initially we "want/wanted" to install a flat on both sides: milled log floor,wall,and ceiling of about 6 to 12 inches (depending on total R-value achieved with all other layers = our goal was a total R-value of around 50 to 80 as we intend to be moving it (we are CDL holders so we would keep then on Semitrailers, likely a double drop or other low trailer as we wish to have a HC / High Container 9'6" or higher interior if we find a custom/larger container [oversized load are no problem for us] as the taller and wider is just a nicer internal liveable experience, AND allows for the thicker milled log wall,floor,and ceiling without much perceived loss of space === thermal mass is part of the desire for using milled logs on interior) EDIT: We would be in 3 entirely different environments over an entire year each in rotations: south Florida, Arizona/New Mexico, and Alaska... So we "need" to account for all the major environment challenges, which pretty much exist in Alaska alone, sea spray/salt from the ocean being around a less than a half mile from coast in Florida and Alaska for a couple of the years and no where near the coast for other years.... Thus the preference for Marine/Corten steel... ... because this would be a FULL TIME RESIDENCE as opposed to a "week/weekend camper or RV like usage...the quality of life within is VERY important, such as: near ZERO chance of moisture trap/condensation aka MOLD, and near ZERO chance of "off gassing" of spray foam/not using spray foam inside ...or off gassing of very much of anything else...we were concerned about termites,ants, mealworms, etc as they are known to EAT foam board, and the only Foam Board that claimed to be "resistant" and explained HOW this was achieved said: it was via a aromatic/fragrant deterrent!! ...1. who knows what effect that has on anyone that might be or become sensitive 2. Who knows what long term health effects are from exposure 3. Who knows how long it would last ...given so many "unknowns", it also brings to mind whether one should even bother with such concerns? i.e. simply use rigid foam board where it is appropriate and "if" ants, termites, mealworms take up residence eating it, tear it all apart and redo ??? Or are there other methods to safely and EFFECTIVELY preventing and Eliminating such concerns? Obviously using milled log of any thickness for interior would be a BIG problem with any ants, termites, mealworms...not to mention the off gassing of their fecal waste which is nothing to dismiss as it is quite an irritant to health/immune/allergy/sensitivities/respiratory, etc... I am familiar with Boron/Boric acid, but it is not perfect and is claimed to have been "ineffective" in situations, and i am unfamiliar with what potential problems it could create with various materials... I am also very much interested in "Shou sugi ban" (burnt wood) and using it on the milled log interior ...this i do not have any practical experience with, but like the various looks of different applications/degrees of... ... thanks in advance for any direction you can point me in or where to get started with your assistance?

[@juanortega3231]

Need to learn how to frame this

[@Armineh11]

CAN i HAVE A PDF OF YOUR DETAIL?