Flat Roof Joist Detail

1 enter joist details 1 1 span and joist spacing.

Flat roof joist detail. Joists are placed on edge spaced at 400 600mm centres supported by external and internal load bearing walls. Downspout strap detail 1 4 dia. This demo version is fixed at 1m clear span. Trada and approved document part a give guidance on sizes of joists for flat roofs relating to spans and loading.

This detail for cmu installation only. Nail to backer block and joist with 2 rows of 10d nails 6 o c. The construction of the flat roof is similar to that of the timber upper floor. Continuous ceiling joists or collar ties span from rafter to rafter.

On a basic level flat roof construction comes in the form of roofing timbers or joists as they are more commonly known or steels that are laid across two uprights walls in most cases. Minimum r value of exterior ci determined by total r value of insulated assembly see also. Figure 3 i joist cantilever detail for balconies 1 1 2 x l4 minimum 4 maximum where l is length l of cantilever 2 x 8 min. There is no need for bearing posts under the ridge board which is nonstructural.

Detail for attachment to metal panel siding or fascia. 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. The full version allows any size. The flange material is typically laminated veneer lumber lvl or solid sawn lumber and the web is made with plywood or osb.

In a typical roof framed with dimension lumber the rafters rest on the exterior wall top plate at the lower end and bear against a ridge board at the top. This is the distance between joist centres. I joists are comprised of top and bottom flanges which resist bending united with webs which provide outstanding shear resistance. Cantilever nails may be used to attach backer block if length of nail is sufficient to allow clinching.

X 5 8 bolt brass alum. The steels or rsj s rolled steel joists are often built into one or both walls to give added stability to the roof structure. Usually 400 450 or 600mm but any value can be used up to 610mm max. Continuous insulation on top of sheathing exterior ci with fiber fill in joist cavity this is how to detail an unvented roof assembly for flat and low slope roofs.

Flat roof joist calculator.