Minimum Thickness Of Flat Roof

The minimum slope for a flat roof is 1 4 per foot or 1 4 12 but some owners or insurance companies require a minimum slope of 1 2 per foot.

Minimum thickness of flat roof.

Tapered polyiso panels are manufactured in standard 4 by 4 sizes with a minimum thickness of at its low edge and maximum thickness of 4 for a single board. That will suffice on a roof with rafters set 16 inches apart with minimal roof loads. The definition of a flat roof according to bs 6229 is having a pitch less than 10 o to the horizontal however some in the industry would consider up to 15 o as their definition of a flat roof. Minimum thickness most roofs will be sheathed in plywood at least 3 8 inch thick.

A flat polyiso underlayment board often referred to as flat fill is used beneath continuing repeating tapered panels. Out of interest you mentioned furring pieces for slope. Flat roof drainage up until the early 1920s was still essentially to the outside the perimeter which required a minimal fall in one direction. Tony thanks for that very useful.

However over the last few decades new and advanced materials have been developed. 8d ring shank nails should be used instead. Although there are certainly many times and places throughout the history of architecture where flat roofs have been used the flat roof has been intrinsically tied with modern architecture since it emerged from the modernist style in the 1920s. The typical thickness range for sheathing is 3 8 to 3 4 inch.

Sheathing should be a minimum of 19 32 inch thick. A classic flat roof is either almost completely level or has a very slight pitch of 3 in 12 inches or less. The idea is to provide positive drainage toward roof drains so there is no ponding water 48 hours after a rain storm. Thickness or rating 1 the thickness or rating of roof sheathing on a flat roof used as a walking deck shall conform to either table 9 23 14 5 a.

2 the thickness or rating of roof sheathing on a roof not used as a walking deck shall conform to either table 9 23 15 7 a. Others would treat even steeper pitches as flat roofs. Influential architects working in the early 1900s such as walter gropius and le corbusier saw ornamentation and traditional styles of architecture as. Never attach roof sheathing with staples.

Most flat roofs are typically not as long lasting or durable as sloped ones because the latter shed snow and rain a lot quicker.