A detailed discussion by theoretical structural guys will help on this, particularly for the characteristics of wood. Ridge Board Is a plank that supports the top end of the rafters, maintains spacing, and helps the roof structure to work as a connected system. It can be under the rafters to support, or the rafters can tie into it for support. Put the rafter in steep slope and failure may be wholly compression, not tension. Transfers the roof load to the gable ends or a post and supports the rafter ends at the ridge. In addition the stress diagram in the rafter under a failure test that may not be pure triangular compression or tension as typically diagrammed for bending. The inclination puts added compression in the rafter, in addition to that caused by bending. When it comes to analyzing the stresses in the rafters, it is not just calling bending the critical factor before failure. More likely than not, the joinery in the roof system of a timber frame is often loaded with tension and so special consideration is needed to make sure everything is held together. Put in more of these at lower heights and you can get away with a lighter rafter, effectively. The tie beam in this case has a 2 inch locator or stub tenon and has a diminished housing going into the rafter. The first, and often preferred, method used by engineers employs pieces of all thread and extra large washers to hold everything together. That effectively reduces the length of the rafter as a beam carrying load. In this detail we show a collar tie to rafter connection in two ways. However, under loads the rafter tends to sag and this puts the tie into compression. The writer gives these collar ties a function of tension in case of uplift. Here is an explanation that I don't agree with. I agree with JAE's three options as stated in his post above.īA RE: Collar + Rafter Ties Roof Framing - No Load Bearing walls needed, right? msquared48 (Structural) 21 Apr 20 09:02 The type of wood would not change the fact that a 2圆 cannot span 26'. It is quite possible that the existing roof could support the existing ceiling by means of wire or wood hangers, but this would rely on competent nailing and splicing of the bottom ties (ceiling joists), which may or may not be the case. Collar ties are common in residential roof construction. I do not know the type of wood the rafter ties/ceiling joists are made from-perhaps I can look for a marking.I believe you are correct in the two comments highlighted in yellow. The spanned length is somewhere around 25'. I'm fairly confident it's not needed except possibly to support the ceiling drywall and plaster. There is an interior wall but believe it is non-load bearing and in-place to provide space for more kitchen cabinets, refrigerator, and oven.
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