Roof Overhang Or Parapet

The assembly is straight forward but what complicates matters is that the roof needs to be vented.

Roof overhang or parapet.

Consider alternatives to using a parapet because of the high risk of failure when compared with other possible options if this guidance is not followed. My flat roof has a fall in it and surrounding it all is a parapet that is probably 600mm high at its highest point. The roof was circa 300 square metres and the new section of roof accounted for approximately 25 of the total roof area. They are essential for framing and shading windows reducing splashback and getting rain to fall far enough away from the foundation.

Historically so many problems have occurred with parapets that we have a name for it. Overhangs for each roofing profile. Roof overhangs might look relatively routine but there is a lot of design thinking that goes into creating the optimal dimensions for each one. Failed lap joints to the deck and the parapet wall up stands.

A parapet roof is simply put when a building s outermost walls extend upwards past the roof around the edges most often by a few feet. Normally you would find the venting at the soffit the underside of the roof overhang but that s not possible with the parapet. Parapet walls which can be added to one or more walls differ from facades and mansards in that they have no projection. Flat roofs come in many shapes and sizes which include parapet roofs roof decks and green roofs to name just a few of the options available.

1 their major function today aside from confusing architects is to protect the edge of roof assemblies from wind uplift forces. Parapetitus they have a long history which of course is not always clear that allows me to embellish without threat of peer review reversal. A well designed roof overhang is much less likely to lead to rain penetration and will offer better weather protection to the underlying wall. Flat roofs can be used to create box shapes cantilevered into daring overhangs or can be planted to create usable vegetated gardens.

They re wall panels below the roof line that extend above the roof line to a given elevation. While a roof parapet wall may seem like a small detail in the grand scheme of the entire building design it can actually change the dynamic of an entire roof both in terms of cosmetic detailing and safety. Typically they are added at the high eave and both endwalls of a single slope building to hide the roof slope. Like any roof with batt insulation the venting is an important part of the system.

For example corrugated sheeting has a 100mm maximum overhang when unstiffened and 200 to 300mm depending on wind load category and steel grade when stiffened by the attachment of a continuous supporting.