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optimistic
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# Posted: 15 Oct 2012 11:16pm
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Hey all,
I am closing in on my target - finding a location near my house to keep the flatbed trailer I'll buy so I can build my tiny portable cabin on it.
After comments by people here over the weight I made a detailed spreadsheet with weights to see how much weight my 24ft by 8ft (almost 13' high) cabin will approx' weigh. In my current design I have about 6300lbs which should be fine with a 24' trailer that can carry around 10k kbs (9 with the trailer weight itself - about) but it is not easy to find ones who are low (bed under the line of the top of the tires), 24' long, and used (less expensive).
I might have to buy a new one which in case I do - I should try to get the weight down to be able to buy the more standard 7000lbs GVWT trailers - once I have the cabin on my land I will add supporters to it which will make my load capability much higher but I most get it there first... so -
According to my calculations - the single heaviest part of my cabin will be the 1/2 OSB sheating (roof included) at 1700lb, then the 2x4s at 900lbs. I started looking into alternatives to this materials but I would love to hear from you guys on material options.
I am aware of the economics of these - being more expensive than just getting a higher rated trailer - but at this point, when I have a plan and price for conventional 2x4&osb build, I want to also know the alternative, enabling me to buy on the spot.
Things my 'alternative material' research came back with -
1. most likely my only other 2x4 option is metal studs but I believe the ones who are readily available (HD/Lowes) are not meant to support loads. The ones that do - come in many different sizes and gauges so I have no idea what I should get.
2. I found several alternatives to sheating:
a. SIS by dow - which is very expensive but I am not sure of real price
b. press-board which should be much lighter
c. or even keep the 2x4 for my framing but use good bracing techniques (read about those but not sure which one is really good) then just cover with 1 or 2" foam - which at least will bring down my sheating figure.
Would love to hear from you!
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MtnDon
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# Posted: 16 Oct 2012 12:44am
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Where did the weights you used for the calculations come from? I ask because my local suppliers of stud and #2 grade 2x4's have different species over any given time span. Sometimes they are Douglas Fir, sometimes S-P-F, sometimes ???... There is a huge difference in weight between a DF and the S-P-F for example.
Re the SIS.... Homedepot can special order it.... can't remember the price but IIRC it is not cheap. One big attraction for a contractor is the labor savings as it does several tasks at once.
Not sure what product you mean by "press board".
Other forms of bracing... no other method is likely to offer the rigidity of an OSB or plywood panel. Diagonal bracing, metal or wood, do have code approvals but do not have anywhere near the same rigidness. I can't find the bookmark I have that compares.... If I get lucky I'll post it here.
There are aluminum framed flatbed trailers available. Just a thought.
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MtnDon
Member
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# Posted: 16 Oct 2012 12:57am
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Wall Bracing
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Martian
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# Posted: 16 Oct 2012 07:22am
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Check out used boat trailers. I recently sold an aluminum I-beam, 10,500# capacity, three axle w/disc brakes trailer for only $3000. It held a 32' boat and was 8'6" wide.
Tom
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GomerPile
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# Posted: 16 Oct 2012 09:32am
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How often will you need to move it? I moved mine one time and it cost $250...
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TheCabinCalls
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# Posted: 16 Oct 2012 12:25pm
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I mentioned it in your last thread. Why can't you install the roof once you get onsite? Since it is the heaviest and highest parts.
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optimistic
Member
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# Posted: 17 Oct 2012 08:39am
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thecabincalls - the roof is not the heaviest and it will cause me some issues to do that...
Thanks don. I do rather use osb so hopefully I'll find a good trailer that I won't need to worry about.
I am a bit confused as to the weight on the trailer because there are axles ratings, tire rating, and ball rating. So even if I find axles that can carry the load I also need to make sure the tires can as well?
Also, if the ball, for example, can carry 5000lbs then is that makes my limit lower or higher? as weight will be distributed among the axles and ball?
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toyota_mdt_tech
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# Posted: 17 Oct 2012 09:00am - Edited by: toyota_mdt_tech
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How many axles on the trailer, rule of thumb, if its a std axle, about 3500 lbs. Tandem, 7000 lbs, but you must deduct the weight of the trailer for payload. A 5000 lbs ball means its probably limited to just that. A tandem axled trailer, should have a 2 5/16" ball with large shank.
How about having a foundation put in place, use the trailer to haul building material or even pre built walls etc. You could lay down the flooring. Then pre fab your walls, haul them all in, with help, set them up. Then come back with trusses/rafters and roof sheeting. Use the trailer to haul the pre fab'd parts.
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groingo
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# Posted: 17 Oct 2012 09:53am
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Might want to check those numbers again, my 10 by 12 barn style shed weighted just shy of 4000 pounds.
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MtnDon
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# Posted: 17 Oct 2012 10:30am
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Quoting: optimistic I also need to make sure the tires can as well?
Yes, and in addition, check how old the tires are. The date of manufacture is coded and molded into the sidewall. There is no hard and fast rule on how old a tire can be before it us unsafe to use, but the estimate ranges from 5 to 6 or up to 10 years from manufacture date.
Determine tire mfg date
Aging info
I have never had a tire fail due to age, but a friend had a 12 year old tire explode after he had a flat and installed the original equipment spare. People who buy old RV's with great looking tires are often unpleasantly syrprised by tire failures.
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optimistic
Member
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# Posted: 17 Oct 2012 09:04pm
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Good news & bad news:
The good - I am going to look at a trailer tomorrow that can carry 14,000 so I am good on the weight issue I believe even though.... ->
The bad - I didn't complete the roof calculation as it turns out.
If I will build a 26ft by 7ft cabin (with max width of 102" - so overhang cannot exceed this) then how many rafters I need? (I want to calculate weight.
Thanks for the links don. I am going to use it tomorrow when I look at the trailer. They guy said he put new tires on it. We'll see...
I will put my spread sheet here tomorrow so I can be corrected if I made any mistakes.
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Rob_O
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# Posted: 17 Oct 2012 10:22pm
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Quoting: toyota_mdt_tech How many axles on the trailer, rule of thumb, if its a std axle, about 3500 lbs. Tandem, 7000 lbs, but you must deduct the weight of the trailer for payload. A 5000 lbs ball means its probably limited to just that. A tandem axled trailer, should have a 2 5/16" ball with large shank.
Addendum to above info:
The number of lugs on the wheel will let you know how much weight each axle can hold. 5 lug axles are rated at 3500 lbs, and a trailer with a pair of them will haul around 5K. 6 lug axles are rated at 5K and a pair of them will handle 7500, 8 lug axles axles are 7K rated and handle 10K for the pair
These numbers are typical for the trailers you see hauling construction equipment, your travel trailer frame will be a little lighter per ft^2.
These rules are not absolute, my 16' travel trailer has a single axle with the wide 5 bolt pattern and a 2 5/16 trailer ball. Not sure exactly what it weighs but it's more than you should put a single axle!
Hope that helps, good luck with the project!
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MtnDon
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# Posted: 17 Oct 2012 11:59pm
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I forget if this is a flat roof, or a shed roof with a low pitch from side to side. Or if this is to be a low pitch gable roof. ??? Makes a difference; can anyone remind me? Also what is the average snow load in the area of NYS where this will be placed.?
If anyone can tell me those the calculations for what material and how many is easy.
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optimistic
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# Posted: 18 Oct 2012 07:36am
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Rob -- Then from your numbers the trailer itself weighs a whole lot? (dual 7,000 - instead of 14,000 only 10,000)?
Don - I want a low pitch (3?) gable. Snow loads in my area = 55
I saw one roof that was built without a ridge?? is that possible?
(ridge is that long piece of wood that is essentially the highest point of the roof and it is the entire length of the house plus over hang, right?)
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MtnDon
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# Posted: 18 Oct 2012 11:18am
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Quoting: optimistic low pitch (3?) gable. Snow loads in my area = 55
Using that southern pine, #2, 2x4 can span 4'8" when on 24" centers, which makes it okay for a gable roof. Doug Fir is 5'4"
(The span of a rafter is not based on the measurement along its length. Rather, the span is based on the rafter's "horizontal projection". This is the horizontal distance from the inside surface of the supporting wall to the inside surface of the ridge board. So consider a simple gable roof on a 24-foot wide ranch framed with 2x6 exterior walls and a 1 1/2 ridge: the span would be 11'5 3/4".)
Quoting: optimistic I saw one roof that was built without a ridge?? is that possible?
That would be a flat roof or a shed roof. Rafter ends on walls. Rafter span then would require 2x6 as even select structural doug fir 2x4's can span to only 7'5", with the 2x4 on 12 inch centers.
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optimistic
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# Posted: 18 Oct 2012 08:22pm
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I know this is way ahead of time to discuss but just in general - why not make a shed roof which is almost flat? something like 2/12 or 3/12? Or just a flat roof?
I want to use metal roofing and according to Fabral (a metal roofing company) the minimum pitch is 2.5/12. So I can do this but I wonder if I can push the envelope even more and do a flat roof period.
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optimistic
Member
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# Posted: 18 Oct 2012 08:29pm
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Another thing - what will be more space efficient - gable roof or shed roof?
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MtnDon
Member
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# Posted: 18 Oct 2012 09:34pm
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With an overall height restriction a flat or near flat roof may offer the best use of space. No cramped side angle spaces as a gable will produce.
Theoretically if you placed ice and water shield over the entire roof sheathing and then installed roll roofing or metal you would probably be safe. Probably. No guarantee. And a slight pitch to one side would be much better than totally flat, IMO. If using metal roofing I'd also want butyl rubber sealing tape at each overlapping seam / panel joint. Roll roofing is glued down with roofing tar / cement.
(ice and water shield is a sticky backed membrane that is usually used along eves in snow country. Grace manufactures an excellent ice and water shield.)
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silverwaterlady
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# Posted: 19 Oct 2012 02:54am
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Any idea on the cost of your cabin?
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optimistic
Member
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# Posted: 19 Oct 2012 02:10pm
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I just came back from looking at that trailer. It's an adjustable trailer 25ft-36ft with two 7,000lbs each torsion axles. The guy is a car dealer and he puts two large SUVs on it on a daily basis and it pulls it without any issues. It has 4 new tires, electric breaks, and new LED lights. The diamond plated floor is a bit rusted but the I beams look in good shape.
I think found my trailer. He wants 1800 for it and will deliver it to my location for free. Now I just need to find a warehouse/land to park it in.
Don -
I just got off the phone with an engineer from Fabral. He said that I can do a 1/12 pitch with one of thier models and that I should get this taping thing to put in between the panels. I will order panels which are the exact width of my roof to avoid width seams.
For rafters:
I use this site to calculate max spans -http://www.awc.org/calculators/span/calc/timbercalcstyle.asp
2x6 of DF no.2 at 24" on center, with 55 snow load, will be able to span 7ft6". My span will probably be just under 7' so I think I am good on that.
Silver - I need to finish running my numbers in the next few days so I will post it.
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optimistic
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# Posted: 19 Oct 2012 02:55pm
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could it be that 15 2x6 boards of Douglas fir no.2 at 100" long weigh 170lbs? seems too little.... (non-treated)
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capthook
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# Posted: 29 Oct 2012 02:14am
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Hello All...
Out of curiosity, how you considered using SIPs for your walls/roof/floor?
Mike
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