Flat Roof Joist Definition

Some roof designs lack joists depending on how they are designed using careful manipulation of other structural members to achieve the desired level of strength and stability.

Flat roof joist definition.

Live load is weight of furniture wind snow and more. Timber flat roof construction usually consists of structural joists topped with a decking of plywood or a similar sheet material. If that same joist had gypsum ceiling l 240 the allowable deflection is 0 6. They are nominally 2 inches thick actual width usually 1 1 2 inches and come in a variety of widths from 8 to 12 inches.

1 ft 0 3048 m. They are ideal for long spans including continuous spans over intermediate supports. Dead load weight of structure and fixed loads 15 lbs ft 2. Joist is a term used in construction for load bearing planks that run horizontally or nearly to horizontally to ground.

The major difference between the warm flat roof and the cold flat roof has to do with the air flow between the roofing timbers known as joists that help to hold up the roof. Joists and rafters must be strong enough not to break when loaded. Wherever possible joists should span the shortest distance of the roof plan. Joists are traditionally made from timber.

I joists are used extensively in residential floor and roof framing. 1 psf lb f ft 2 47 88 n m 2. Note it gives the allowable deflection based on a fractional span quantity so a larger denominator will yield less deflection. To determine the dead load value for a given floor or roof system the weight of all permanently installed materials in a given component are added together.

The pitch is governed by the roof covering and the required rate of rainwater discharge. Because i joists are straight and true it s easier for builders to avoid crowning and maintain a level framing surface. See the table below. Unlike stiffness live loads and dead loads are added together to determine minimum design values for strength.

For example the allowable deflection of a 12ft span floor joist with plaster l 360 is 0 4 12ft divided by 360. In the warm flat roof construction there is insulation packed into every possible space where air can flow. A roof joist is a structural member which provides support for the roof and distributes its weight so that it is even. Depending on the building design finished ceiling surfaces may be affixed to a ceiling joist at the bottom of the roof triangle giving a flat ceiling between the opposing building walls or the ceiling may be affixed partly to the under side of rafters and partly to the under side of rafter ties giving a cape cod type ceiling design.

2 are indicated below.