An essential part of planning a patio roof or gazebo project is determining the number size and spacing of rafters beams and posts according to the loads they will carry.
Single span vs double span roof.
Three spans was considered representative of any additional number of spans say 4 5 6 or more.
The use of only 1 2 or 3 span conditions for steel decking is a legacy from pre software times.
Rafter span tables use these tables to determine lengths sizes and spacing of rafters based on a variety of factors such as species load grade spacing and pitch.
Rather the span is based on the rafter s horizontal projection.
In areas with mild climates patio roofs are generally designed for loads of 30 psf pounds per square foot.
The span would be 11 5 3 4.
With simple single span joists that are overlapped at the center beam or girder the reactions are equal at each end of the joists.
Roof its classification.
Two spans less conservative.
The single roof is a type of sloping roof.
Visit the roof framing page for more information on cutting roof rafters and visit the roof pitch calculator for determining rafter lengths based on rise and run.
Thanks for the input.
Three spans represents the best most optimistic case.
Double span decking uses surface material that is long enough to bridge the gap between two joists hence the term double triple span decking uses surface material that spans three joists.
The result is that you can use smaller sized stock be it conventional lumber or i joists for multiple span continuous joists than with simple single span joists.
18 open span doubled or tripled 2x12 s.
Ok just to clarify i am talking about doubling or tripling the 2x12 s that span the 18 direction and then hanging single 2x12 s spanning appx.
Single span construction refers to a beam or slab which is simply supported assumed pinned at its ends.
Metal decking plans call for joists to be 24 inches apart so a double span deck plank is at least 48 inches long and a triple span deck plank is at.
Of course single span is conservative.
Single roof is defined as a roof having only a single slope on each side of a central ridge whereas in shed roof it has a single slope but without a central ridge.
The result of joining two or more gabled roof sections together forming a t or l shape for the simplest forms or any number of more complex shapes.
So consider a simple gable roof on a 24 foot wide ranch framed with 2x6 exterior walls and a 1 1 2 ridge.
Maximum rafter spans for a patio roof.
For heavy roofs or in.
Gable ridged dual pitched peaked saddle pack saddle saddleback span roof.
But with the continuous joists the center beam.
