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Pocketpower231
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# Posted: 22 Feb 2016 22:20 - Edited by: Pocketpower231
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Pocketpower231
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# Posted: 23 Feb 2016 20:27 - Edited by: Pocketpower231
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rockies
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# Posted: 23 Feb 2016 21:36 - Edited by: rockies
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Well.......some of the people on the site may be a bit.....surprised?.....at the personal "term of endearment" you've chosen for your spouse so they may not feel like responding. Just a guess.
In any case, I'm assuming that you'll be using anchor ties set into the tops of the concrete piers in order to bolt the beams to them? I think that 2x8's are too small for the beams and joists. I would go with 2 x 12's.
Try to make sure that any point loads from the roof and second floor transfer all the way down to a pier (locate the pier under that point and double up the joists). Also, I would use a good thick plywood for the subfloor ( probably 3/4" T&G) rather than OSB and glue and screw it to the beams and joists.
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MtnDon
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# Posted: 23 Feb 2016 21:46
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Quoting: Pocketpower231 9 of the 10" sonotube concrete piers spaced 8' apart
I don't follow that math when thinking 16 x 24 floor. I get 4 piers down the long side. With "2" x 8" x 8' for the floor joist" that indicates a center beam which is 12 piers total. ???
Eight feet between piers is likely too much for two - 2x8's.
Piers are not recommended as being a really great foundation. The design of your cabin needs to begin with the snow load and the frost depth. Snow load in the UP can be 70 psi, maybe more.
Piers have many faults, unpredictable stability is one. Not being approved by any building code in the country is another.
A interactive snow load map can be found here... Scroll down to your state. Michigan is listed. You only get "so many" free clicks on the map per day.
Sorry, I have no handy frost depth links for MI. The local / county offices should have that information for you. While talking with them ask about building permits and any zoning requirements.
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Pocketpower231
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# Posted: 23 Feb 2016 21:58 - Edited by: Pocketpower231
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Quoting: MtnDon I don't follow that math when thinking 16 x 24 floor. I get 4 piers down the long side. With "2" x 8" x 8' for the floor joist" that indicates a center beam which is 12 piers total. ??? Eight feet between piers is likely too much for two - 2x8's. Piers are not recommended as being a really great foundation. The design of your cabin needs to begin with the snow load and the frost depth. Snow load in the UP can be 70 psi, maybe more. Sorry, I have no handy frost depth links for MI. The local / county offices should have that information for you. While talking with them ask about building permits and any zoning requirements.
Your right , my math was flawed , there should have been 12 not 9 piers. the span calculator is reading a max span of 11' 11" for the type of wood going to be used, you dont think 8' is safe? snow load would be about 60 psi for mackinac county mi a gambrel metal roof will help shed snow, frost depth is 42" and i was planning on using 6 ft tubes for 24 inches of height off the ground. The building permit is pretty easy to attain, it is only going to be 384 square ft but the U.P wants people to move to it so getting a pass is not going to be hard. i just have to be honest with them about it and they will work with me, it's when you try to be sneaky is when they get riled up and less willing to work with you.
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MtnDon
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# Posted: 23 Feb 2016 22:37 - Edited by: MtnDon
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Quoting: Pocketpower231 the span calculator is reading a max span of 11' 11" for the type of wood going to be used, you dont think 8' is safe?
The AWC calculator is for floor joists (and rafters, ceiling joists) across the building width. The 8 feet I am referring to is the 8 feet between the piers down the long sides. Those are girders or beams, not joists. Those are supporting the entire sidewall loads which include the roof and snow load, the upper loft floor as well as the main floor joist loads.
Maybe you have already ascertained that the permit will be easy, I don't know. As you say 'work with them and they will work with you', but if there is a permit office they also have a rule book. I would not assume and I would recommend asking about a pier foundation. Go down to the office with a drawing and see what they say, before getting too involved in planning and designing. Could save time, money and frustration later.
Ask if there is a MI specific online code book available. MI uses the IRC2009, it seems. They may have amendments unique to the state or county.
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MtnDon
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# Posted: 23 Feb 2016 22:40 - Edited by: MtnDon
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...it must have been something I said...... and I refrained from any comment for a day because I knew it would sound critical... damned if I do, damned if I don't?
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rockies
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# Posted: 24 Feb 2016 21:31
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No, it was me. I, too, felt a little uncomfortable mentioning "it" since "it" wasn't really bad and was simply the "personal term of endearment" used between two private people. Still, most private nicknames should probably remained private. Still, it's too bad he deleted the entire message since that provides the info needed to answer his question. Hopefully he wasn't offended.
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Pocketpower231
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# Posted: 25 Feb 2016 00:13
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Quoting: MtnDon ...it must have been something I said...... and I refrained from any comment for a day because I knew it would sound critical... damned if I do, damned if I don't?
Quoting: rockies No, it was me. I, too, felt a little uncomfortable mentioning "it" since "it" wasn't really bad and was simply the "personal term of endearment" used between two private people. Still, most private nicknames should probably remained private. Still, it's too bad he deleted the entire message since that provides the info needed to answer his question. Hopefully he wasn't offended.
No I just got rid of it all, now i have to retype it. Mtndon I did think that 2x8 would be fine for the beams, If not then what do you suggest? I want to be as cheap as possible on the materials but not on the construction. rockies suggested 2x12, would it be better to run 2x12 for the beams and 2x8 for the joists? I also am pretty set on the pier foundation, the ground is very stout and full of rocks and not very level, My build spot is off of a main road about 7 miles by trail or 3 by boat, getting a concrete truck is not going to happen , 40 bags of concrete is doable by boat though. I could not see getting hundreds of cinderblocks there with out doing a bunch of trips. Also I was planning on doing the j hooks into the tops of the pier's for anchors, 6x6 beams secured to the j hooks and the beams on top of them . doubling or tripling up on joists under load points was going to be done. I was thinking the .700 t&g osb flooring for the subfloor. I guess I wasnt to specific on my first post. Any insight is appreciated.
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deercula
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# Posted: 25 Feb 2016 08:33
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How many trips will it take you to haul all of your materials to the site by boat? If you use the "trail", can you get them there by truck and trailer?
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MtnDon
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# Posted: 25 Feb 2016 10:32
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OK, I just try to point out that pier foundations don't meet code accepted building practices. A pier foundation is more prone to develop problems. So we'll leave that part of the questions.
If piers are the way you go, IMO, you may be better off if you discard the center row of piers and the center beam. A sixteen foot clear span is possible with dimensional lumber floor joists. When it comes to repairing any pier movements the task will be simpler if you don't have to deal with a row under the center of the cabin. Just my opinion.
DougFir, 2 x 12 #2, 16" OC can easily span 16 feet.
TABLE R502.5(1) of the IRC is for girder and header spans. That can be used to help size the beams that will be supported by the piers down the long walls. The left column lists various combinations. Across the top are the columns for various building widths and snow loads. Use the 20 foot wide columns for your width. The numbers can be extrapolated for the 16 foot but if you use the 20 foot values you have a safety factor.
I would use the 70 lb snow load columns myself. Even a 12/12 pitch metal roof can accumulate deep snow if the conditions are right. Why take a chance and design/build with a lower load and then be faced with possible future worries when the grand-daddy of all blizzards comes along?
If you keep the loft loads light and use proper rafter ties to keep the walls together you might be able to get away using the "roof, ceiling and one clear span floor" selection in the left column. If that loft will be loaded up with beds and bedroom furniture I'd use the section with two floors.
"roof, ceiling and one clear span floor" = 3 - 2x10 for beams with piers on 6'10" centers. Or 3 - 2x12 with piers on 7'11" centers
".....two clear span floors" = 3 - 2x10 on 6'7" centers or 3 - 2x12 on 7'8" centers.
Or lots of other combinations. Note that making a beam or a joist deeper (taller) gives much more strength/stiffness than it does to make the beam or joist wider by the same amount.
Then hang the floor joists between those built up beams using steel joist hangers. 3/4" or thicker T&G subfloor is good. Note that you lose a little width with the T&G sheets so 4 sheets width does not produce 16 feet. Plan ahead for that so you are not in the position of having a narrow strip of subfloor along one wall.
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