What you see is the result of weight and time and gravity.
Rafters and roof ridges are normally under deflection.
Deflection criteria default deflection criteria for the following members.
Collar ties rafter ties tension beams structural ridge beams.
Allowable deflection is generally expressed as a fraction of the span in inches.
This article describes and illustrates the different types of support that prevents roof sagging and wall bulging at buildings including definitions of collar ties rafter ties and structural ridge beams.
Roof beam double span.
If the sagging appears in the plane of the roof that is up and down between the ridge and the eave and from side to side the sagging is probably due to deflection and creep of the rafters themselves figures 8 and 9.
Supporting roof and floor.
Deflection is the immediate sag produced when an object is set on a structural member.
Ridge beam double span.
Ridge beams are required by code if the roof slope is less than 3 in 12 irc section r802 3.
Some of these can support the roof and prevent ridge sagging and wall spreading.
This roof is composed of rafters which meet a center ridge beam.
Removal of the lateral bracing necessary for a roof rafters that are framed without a ridge beam will make the ridge dip noticeably as in the photo below.
Typically for better performing floors minimal defection is desired.
Structural defects undersize roof rafters or trusses that have had their center web members removed to make room for attic storage can cause a roof to sag along its span.
The route taken by the weight of the roof through the framing members to the soil is called the load path.
You have probably seen this and it is most likely due to roof deflection sag and creep.
In homes with conventional ridges the rafters support the weight of the roof and transmit the roof load down through the walls to the foundation and finally to the soil.
Ridge beam sizing is based on the span of the beam between supports and the amount of roof load supported by the beam.
The center beam is probably not terribly thick.
Duration of load is 1 15 snow tributary length 12 0 exclude outer 6 ft of rafters which bear on outside walls the ridge beam.
Deflection criteria for rafters roof beams joists and floor beams.
A ridge board is a non structural member that serves as a prop for opposing rafters to rest against and connect to.
Ridge beam single span.
