Michelle!!!! I don't know if you'll ever see this comment. I've had you sub before in Residential codes and you were fantastic. THis video with our new Structures one instructor is difficult so far. THis video saved my homework life!!!!! Thank you!!!!
I'm trying to build a screened in porch on top of an existing deck and trying to calculate the linear load on the joist to know if I need to add deck beams. This was helpful but it would be great if it showed the assumed material sizes i.e. 2x6 or 2x8.
David Sanders there are 2 types of horizontal bracing: collar rafters and tie rafters. Collar rafters keep the Rafters (diagonal wood) from detaching from the Ridge Board in the center. Tie Rafters (ceiling joists) keep the outside walls from bowing out. Neither of them really support any weight. I'm also learning all of this and hope this helps.
Excellent explanation. Also, please include another video to explain how to evaluate the roof load on a hip rafter beam which is not uniformly loaded, but rather triangularly loaded in reality.
Thanks for the clear explanations. This video is the closest so far to helping me understand how much load my roof can bear. Question: does the number of trusses and studs change the load-bearing quality of the roof?
If I understand your question correctly, yes. If the rafters/trusses are spaced closer together, their tributary area is less, so the uniform load they can withstand will be higher. Therefore, the roof can withstand more load as a whole. This applies to studs in the wall as well. As the number increases, the tributary area decreases for each stud, so the allowable uniform load can be increased since it’s applied over a smaller area.
Correction: For the example of the rafters with the ridge beam, (i.e. the one with the three tributary areas), the ridge beam calculation is 8' x 19' = 152 sf and not 104.5 sf, therefore, the ridge load is 152 sf * 40 psf = 6,080 1b. The error here is the introduction of the 104.5 sf tributary width into the ridge calculations. The 104.5 sf tributary width is appropriate for the calculations of the load that is carried by each of the two exterior walls. This is: tributary area = (4' + 1.5') x 19' = 104.5 sf; wall load = 104.5 sf * 40 psf = 4,180 Ib. Total roof load = 4,180 Ib + 6,080 Ib + 4,180 Ib = 14,440 Ib. Just saying to clear up the confusion.
So if I have a shed roof 12' x 24' long with rafters to a ledger board screwed to a vertical wall, is the ledger considered a supporting ridge carrying 1/2 the shed roof area ( two tributary loads, 6'x24' to ledger and 6'x24' to the beam at the birdsmouth) or is the beam carrying the entire load (one tributary)
If the roof is a shed style with one wall 12 ft and the other wall 8 ft high, Does all of the roof load fall on the lower wall? Or half? Thank you for your help and useful video
yes!I we now see 14,400 lbs.spread outon on walls...but what do we do with this number?I know a 2x4stud walls are adequate to support this,as we have been doing this since 1870.So..
