Flat Roof Rafter And Joists

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.

Flat roof rafter and joists.

Notches are not to exceed 0 125 of the depth of the joist and are to be located between 0 07 and 0 25 of the span from the support. Understanding the difference between them is essential for those working in the construction trades while basic knowledge is useful for homeowners if repair and maintenance issues arise. Span calculator for wood joists and rafters also available for the android os. There is no need for bearing posts under the ridge board which is nonstructural.

Rafters attached to ceiling beams. Roof rafter span use this table to determine the maximum lengths of roof rafters based on species and grade of lumber spacing dimensions load and slope. The size of rafters for a flat roof depends on the horizontal span of the building the type and grade of timber used and the load on the roof. Continuous ceiling joists or collar ties span from rafter to rafter.

The rafters in a flat roof serve as ceiling joists for the space below. Timber to be covered these span tables do not apply to timber which is fully exposed to the elements. Assuming that your builders have chosen to use wood for your house s frame your roofing joists ceiling joists rafters or trusses will be made from long planks of wood placed parallel to one another at evenly spaced intervals along the length of your roof. Span tables for flat roof joists to bs 5268 7 2 imposed loads of 0 75 kn m for maintenance and snow load are applicable where there is no permanent access no fixed ladder or staircase and most areas where the altitude does not exceed 100 metres refer to bs 6399 3.

They are nailed securely to exterior wall plates and to each other. Cb200 20 beam span table used w 6000 rafter span width of frame 8441 purlin span rafter spacing p 1963 maximum purlin spacing the cb200 20 beams as purlins easily achieve the span and spacing required therefore we can potentially look at using a smaller beam for the purlins i e. These span tables apply only to flat roof and roof with a slope of up to 10 degrees. Also available for the android os.