Roof Framing Looks Worrisome
Kim O'Brien
12 days ago
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Comments (12)
Mark Bischak, Architect
12 days agoKim O'Brien
12 days agoRelated Discussions
hip roof framing
Comments (5)quote" does this design needs some sort of bracing at the beam corner (lateral bracing) because all the load is then concentrated at the corner and going downward and outward. "quote Most definitely yes. The load is always going downwards and outwards. That's why your man wants a brace under the ridge where it meets the hip rafters. Make a mental picture of a triangle with weight on the top. The weight bearing down is all pushed to the sides, therefore your birdsmouth (BM) fastener (nail) is taking all the stress. This is dramatically reduced with a brace going straight down to a ceiling joist. As settling may occur the load is placed on the ridge brace. With an open air cathedral ceiling using the roof decking as your ceiling you have no ridge or purlin braces help distribute the load. That's why you triple cut the BM. It redistributes the load to both the fastener and the intersect of the inner plumb cut of the rafter and the beam. This allows the fastener, rafter, and beam, not just the fastener, to absorb the load. On standard roof framing this load is divided by the total number of hip,jack, and common rafters. When you go to the look like I have you gave up the number of rafters to divide the load by and dropped that number to either 4 hips or 4 hips and 2 commons. By placing the rafter inside the beam your quadrupling the amount of contact area to the beam and sending all the stress to the beam itself. The beams must be securely fastened to each other at the corners. I use a combination of large L brackets and nailing strips to fasten the beams to each other. I do this on the outside so they'll be hidden above and behind the soffit. This look is still achievable on your project. See ya, Kelly...See Moreroof framing: stick vs. truss
Comments (10)"The vertical cross-gabled portion is the addition." It's deceiving, as pictured, or is "C", the addition actually wider than "D" and "E", as it affects the roof tie-in. "It will be 11' wide and 15' deep" Aesthetically, the matching and maintaining a uniformity of roof framing, except when addressing specific architectural elements is desirable. "Is the use of trusses a matter of quantity? Or construction design?" Quantity. As a matter of practicality, in a small addition, combined with the roof tie-in you'll not save anything, one vs the other. "Question #2. What's the math/geometry that tells you whether the roof portions intersect at the peak or lower down?" The aesthetics are generally the governing factor. Another aesthetic to consider is matching the eaves and facia. "I'm assuming the proper thing to do is match the roof pitch and it intersects where it intersects." And how you address the ridge intersection. "So, if I've got a 6/12 roof and the addition is 11' wide (outside dim), the peak would be 11 x 6/12 = 5'-6" high? And if it's 4/12 pitch, then 11 x 4/12 = 3'-8" high?" Actually, at 11' the ridge will be directly above the 5'6" dimension, so with a 6:12 pitch the ridge will be roughly 33" above the ceiling or top plate. Since, as pictured, the addition is wider than the main dwelling/building, the ridge will be above the main ridge. So you have a couple of choices; you ca stop the new ridge directly above the existing, creating a gable end, you can stop the ridge back from the existing ridge and frame a hip section that conforms with the main roof, or you can continue the ridge past the existing ridge and create the gable there or shorten the extension slightly and create a "flying dutchman."...See MoreA-frame roof
Comments (11)I apologize for my misinformation. Clearly I am not very knowledgeable in my terminology. This would certainly not be a do-it-yourself project for us. If we got to the point of drawing up plans, we will involve a contractor. We live very far out of town, though, and I haven't wanted to ask contractors to come out to quote two different options on a project that likely won't happen for another year or two. We have been told that the roofing cost will be high because of the pitch. That is why I was wondering if the lesser roofing cost associated with the pitch of new dormers would help to offset the framing costs. I wasn't looking for specifics but simply an idea of how these would compare. Thanks for your input....See MoreStick or Truss Roof Frame?
Comments (4)In order to compare two structural systems you must describe them in more detail. I suspect the trusses are at 24" o.c. and the rafters are at 16" o.c., otherwise the two methods would have the same sheathing span and the same resistance to sagging (assuming the sheathing is the same). Obviously, the sheathing material is very important. The edges of OSB do not return to their original thickness and tend to lose bending strength after getting throughly wet so OSB requires the immediate installation of underlayment (over a dry deck) or the use of Huber Zip sheathing or the use of AdvanTech or the use of plywood. In any case, roof sheathing should always be thicker than 1/2" (now often 7/16"). But IMO the most important reason to use rafters is the ability to use the attic space. The desire to do that is so common in New England that I've only seen roof trusses in multi-family construction and tract house developments. I always platform frame the attic floor and rest the rafters on a plate at the edge of the platform in order to increase the height of the eaves and the ridge. This detail is especially important for one story houses. I also insulate the rafters and seal the attic space. I also double up some rafters for future dormers some of which are added during construction when the owners see the upper level space and the view from it. Good design is mostly about recognizing opportunities and an attic is an obvious one.....See MoreT T
11 days agoAnnKH
11 days agoJoseph Corlett, LLC
11 days agoT T
11 days agoKim O'Brien
11 days agoMark Bischak, Architect
10 days agorockybird
10 days agoT T
10 days agores2architect
5 days ago
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