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floridagramps
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# Posted: 3 Dec 2013 06:00
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My daughter is asking me to build her a 12x16 cabin with a sleeping loft over a porch on the gable end.............old western style cabin.
My experieince is limted to having built an 8x12 chcken coop using roof trusses that I built on site. I have no experieince with ridge beam construction.
Four questions:
-is this too complex for a 72 year old novice w an 18 year old helper?
- are rafters connected to ridge beam w metal Simson connectors? Rafters and wall studs will be 16" OC
- I am thinking of T&G pine planks for aesthetic reasons insead of plywood for the roof which will be covered with asphalt shingle. Strong enough?
- Do I need to use 2x6 rafters or will 2x4 suffice. To be constructed in a no snow area in Los gatos California
Your suggestions appreciated
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VTweekender
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# Posted: 3 Dec 2013 07:19 - Edited by: VTweekender
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I would use the 2x6 with a 2x8 ridge board......It will actually be easier for you with using the ridge......build your walls, then set a post in the middle of each end wall on top your double plates , the ridge board will sit on top these posts.....you can adjust your height of the ridge board that you want by using the height of the 2 posts under the ends of your ridge board......fasten the ridge securely to top of these posts.......you will be able to find the angle to cut the top of rafters with the ridge board in place as well....use a notch cut to set the bottom of rafters onto your wall top plates, leave maybe 8" overhang on the bottom.
Pic shows the post that was set under ends of ridge board to hold in place before rafters went up...
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razmichael
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# Posted: 3 Dec 2013 08:44
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No expert here but is there some confusion between a ridge beam and a ridge board? 2x8 sounds like a ridge board! Couple of links picked at random:
Ridge Beam
and from
Ridge Beam and Board ....
RIDGE BEAM
The engineering principles are pretty straight-forward for a ridge beam. The sloped roof joists span between two pinned points; one at the envelope of the structure on top of a framed wall or a header, the other at the peak of the structure on top of the ridge beam. (The ridge beam could also be flush with the joists.) The ridge beam is typically a larger member (like a 4 x 12) and carries the gravity load of the roof joists just as the bearing wall or header does at the envelope.
RIDGE BOARD
The engineering principles of the ridge board are a bit more complicated. Because the ridge board is a smaller member (typically only an inch thick, sometimes even less) it is not a structural member and doesn't carry the gravity load. Its only job is to provide a connection point for the roof joists on each side of the roof. This means that the gravity load is being carried through the roof joists out to the bearing walls. The gravity force at the peak of the roof pushes down and out, requiring a tension member to hold the assembly together. To resist the gravity force pushing out, each joist needs a tension member or the headers at the perimeter need to act as lateral beams spanning between the tension ties.
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razmichael
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# Posted: 3 Dec 2013 08:50 - Edited by: razmichael
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By the way - the only reason I would consider myself a semi-expert on this (the most dangerous type) is that I used an LVL ridge beam in my build to allow for a completely open loft and ceiling.
IMG_1881_P.JPG
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MtnDon
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# Posted: 3 Dec 2013 10:35
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Quoting: floridagramps -is this too complex for a 72 year old novice w an 18 year old helper?
Depends on the 72 yr old and his abilities. If you can learn the basics of how to correctly do the job, the theory, then it is a matter of having the physical ability. There are 20 and 30 year old who can not or do not want to learn the correct methods so IMO at age 67 I say the only age limiting factor is the physical one.
Working on a roof requires surefootedness. Just be sure you are comfortable with that. A easier roof would be a shed style. No ridge at all, the loads bear only on the walls that support the rafters. The rafters have to be much larger.
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The mention of a beam also caught my eye. Beam and board are 2 very different things as razmichael first pointed out. World of difference. You will see examples of projects that use ridge boards when they should have a ridge beam. They all will not fall down right away, but the two different types should be used correctly.
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No snow load but what about seismic?
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razmichael
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# Posted: 3 Dec 2013 12:08
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VTWeekender, when I stated
Quoting: razmichael 2x8 sounds like a ridge board!
I realize that this looks like I was implying your description was wrong - sorry - you are clearly describing a ridge board! Bad wording on my part.
Quoting: MtnDon Depends on the 72 yr old and his abilities
Floridagramps - my crew consisted of me (55) and my father-in-law at 72.
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VTweekender
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# Posted: 3 Dec 2013 13:00
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raz, nope I didn't take it that way, I edited my post to say board instead of beam, I used wording ridge beam originally before I edited because the OP used wording "beam", and I figured I wouldn,t confuse him by using "board"...lol...now we are all confused!!!
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razmichael
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# Posted: 3 Dec 2013 13:09
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Quoting: VTweekender I edited my post to say board instead of beam,
That explains my confusion - I thought I was going crazy!
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SandwichBear
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# Posted: 3 Dec 2013 13:13
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You can do it. I am finishing up my first tiny house - an 8'x12' - and learning to cut rafters was part of it. At first it was frustrating, and then it was very rewarding. Folks on this forum were helpful when I had a question.
I used a ridge board. I used 2x6 rafters and a 2x8 board. I used Simpson hardware that I installed on the ridge board before lifting it into place. I used two temporary (and rather flimsy) supports to hold the board while I went up and down a ladder with one rafter at a time. I did this all by my lonesome, and it would have been much easier with some help.
I am as novice as they come. The biggest thing I built previously was a set of shelves. I have a good feel for tools from being a bicycle mechanic, and I tend to obsess over details when I am learning about a new subject. But I'm just a 31-year-old goofball with a new hobby/obsession. If I can do it, I'm sure that you can. If you can climb a ladder with a rafter and you're steady on your feet, then the math and measuring should be a minor hurdle.
I did find myself questioning the strength and precision of my work as I was building. After the sheathing, insulation, wall covering are installed - it's very sturdy, and I'm proud. Follow instructions, work carefully, and you will succeed.
Do it!
Best luck
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rockies
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# Posted: 3 Dec 2013 17:33
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http://www.motherearthnews.com/diy/build-this-cozy-cabin.aspx#axzz2mSAFDcad
This is the article that I based my "Cozy Cabin" designs on. It is 14 x 16 with a 4 foot deep sleeping loft over a porch (which I don't really like) but the article has the framing all laid out for you. It's a very sturdy cabin, but personally I find sleeping lofts over porches to be a poor design choice. The problem is that you basically have 4 surfaces surrounding you as you sleep that are exposed to the outside temperatures (two gable roof planes, the loft floor and the gable wall). The most expensive and time consuming things to build are the foundation and the roof, so why not pull the lower 14' porch wall forward and create a 14 x 20 cabin and have the loft over inside space? I designed my cabin so that it can be added on to in the future (livingroom bumpout, screen porch, pantry, mudroom, etc) but it can also function well at just the basic 14 x 20 size.
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Borrego
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# Posted: 3 Dec 2013 21:49
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You can do it, just tie yourself off when on roof. I would suggest that you may save money, time and kill 2 birds with one stone if you were to use 5/8" T 1-11 ply with grooves down for your roof sheathing.. stronger, faster and same basic look from inside........
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jrbarnard
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# Posted: 4 Dec 2013 09:00
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i made a dual 2x8x32 beam and never had experience. I have 4 supports, one on each end at least 4x4, 1 6x6 under the loft (the end of it inside the cabin...8ft from the end) and one about 8ft from the far end. a 14 ft long cedar post.
Let me post a couple pics
Also added 2x6 rafters each 16 ft long
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toyota_mdt_tech
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# Posted: 29 Jan 2018 10:45
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Build all rafters identical, after you get it figured out ie pitch run etc. This includes plumb cuts and birds mouth, leave rafter tails alone, do not worry about the plumb cuts there just yet. Then set up gable end rafters they will come together at true center automatically if the rafters were build all identical, same for other side. Then slide the ridge in between the ends where the plumb cuts but up. If your building was built square and it should be, all other rafter plop right in vs measuring centers then custom building each rafter one at a time.
I learned this from Larry Haun, the efficient carpenter. Watch his youtube videos and get his book "The efficient carpenter". I have use this method with perfect success twice!
Then you can add in the ridge support beam at the gable end walls to carry that load all the way down to a foundation. I would avoid a window or door opening/header in that area in your design.
Then you can figure in overhang after all rafters are set in place, mark the 2 end rafter tails on each side, chalk line them, then with a cool tool like a "squangle" mark the rafter tail plum cuts from the chalk line and bob them off. They will be in perfect alignment for your facia board. I use a heavy board, then cover with trim, I like the HD stuff.
A squangle is a cool tool, it not only can be set and locked for your plumb cuts, it also has a part that is used for marking the birdsmouth cut (sometimes called a seat cut too) too.
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socceronly
Member
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# Posted: 14 Mar 2018 15:31
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What about buying parallel cord or scisser trusses? You still get to use trusses and don't lose the head room?
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KinAlberta
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# Posted: 14 Mar 2018 21:17 - Edited by: KinAlberta
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Also: Oddly I never see this discussed, but any thoughts on running the joists right out to the eaves to meet the rafters at the outer edge vs stopping the joists at the wall and having the rafters (everything) intersect at the wall.
The former will provide a larger volume through greater headroom and width for a given slope and since it’s a loft the joists will be larger anyways.
More for the loft: lessons from others mistakes:
How to Reinforce 2x6 Ceiling Joists to Handle Heavy Loads - Fine Homebuilding
http://www.finehomebuilding.com/2011/02/09/how-to-reinforce-2x6-ceiling-joists-to-han dle-heavy-loads
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ICC
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# Posted: 15 Mar 2018 00:12
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Quoting: KinAlberta ...any thoughts on running the joists right out to the eaves to meet the rafters at the outer edge vs stopping the joists at the wall and having the rafters (everything) intersect at the wall.
That is not normally done as it introduces some complications.
A conventional rafter with birdsmouth connects to the wall top plate and transfers the downward force directly to the wall framing. The horizontal outward forces are restrained by the correct number of nails used to tie the joists to the rafters and the wall top plate.
Rafter tails connecting to the ceiling or floor joists that extend past the wall framing will have the downward vertical load applying a bending force to the extended joist. Those bending forces are not taken into account in the standard tables. It would probably be possible to do the calculations and have corrective factors much as there are corrections or adjustments that are done when the rafter ties are raised into the lower third of the roof rafter - ceiling joist triangle. It is a complication though.
The downward force on the extended joist would also produce a corresponding uplift force inboard of the wall framing. That might not be a problem if the joist was one piece. However, if the joist was two pieces, as is sometimes the case when there is a load bearing interior wall, then the uplift forces would have to be taken into account. An engineer could do that but tables that we have do not take that into account. Complications.
There also may be more risk of water damage and rot to the joists extended out from the walls if something in the roof waterproofing barrier fails. Or if water is blown in by strong horizontal winds.
Just thoughts that spring to my mind when presented with the suggestion.
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ICC
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# Posted: 15 Mar 2018 00:33
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OTOH, it is relatively common to see buildings in Europe, centuries old buildings, with upper floors that overhang the lower. Sometimes three stories with each overhanging more. Those were done for various reasons and we have many examples to see today. Keep in mind that failures aren't seen because they have fallen down or been torn down.
However, we are back to reasons we do not have much like that is simply that the standard tables and codes have not addressed that type of construction and so if we wanted to build something like that we need an engineer. Engineers cost extra, so we don't do that ordinarily.
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KinAlberta
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# Posted: 16 Mar 2018 09:22 - Edited by: KinAlberta
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Yeah it was a practice around here as well on some old, old houses. (Visible in old houses where there is a full 8’+ exterior wall from bottom of door to soffit/eave (plus larger space above windows and doors and the soffit. Sometimes a small window above the doors and clearly not 9-10’ interior walls).
As for the little unsupported triangular area, I’d guess that little vertical braces or plywood triangles could be added to put the load directly over the wall.
Or along the length of the wall, run a 2x? something support along in the gap. That space would have to be filled anyway especially with a wall where the loft is built.
One other thought is that this pure triangular rafter style would increase the area for insulation etc and the interior roofline could still meet at the walls.
Where there is open beam / cathedral ceiling something would be necessary since there wouldn’t be any ceiling joists.
By the way what are the proper names for these two styles of rafter design?
https://www.wwpa.org/western-lumber/design-application/spans
Large image Raised-heel truss:
http://boulderlibrary.net/img/1312/image420.jpg
Modified/modernized:
http://boulderlibrary.net/habitat-for-humanity-international/page/9
Raising the Roof: Raised-Heel (Energy) Trusses
“RAISED-HEEL TRUSSES PROVIDE A COST-EFFECTIVE WAY TO MEET MORE STRINGENT ENERGY EFFICIENCY CODESâ€
http://www.norbord.com/na/blog/raising-the-roof-raised-heel-trusses
5 Ways using Raised Heel Trusses will Save you Money
http://www.norbord.com/na/blog/5-ways-using-raised-heel-trusses-will-save-you-money
Raised-Heel Trusses - APA – The Engineered Wood Association
https://www.apawood.org/raised-heel-trusses
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