Roof Plans

Cabin roof

Cabin roof

I guess the first roof related decision for a shipping container builder is whether or not to even have one.  Considering that I have three connected containers, am in Wisconsin with ~50 psf snow loads, and that the inner walls are removed,  I felt a roof was a good idea.  In designing the roof I needed to consider the style, pitch, overhang, roofing material, and structure.

Style:

A flat roof is tempting with shipping container buildings, and that’s what you see a lot of, in addition to no roof, in artists drawings of them.  A flat roof in Wisconsin just doesn’t seem right though, and would be somewhat out of place in the country.  Shed roofs are attractive, at least to me, easy to build, and would definitely fit in around here.  Unfortunately, even with a minimum 3:12 pitched roof, I would not be able to get the amount of shading I wanted with the roof peak on the southern side.  This left the gable roof, which is OK with me since it fits in well around here – I was looking for a steel pole barn sort of appearance anyways.  It’s also nice to have room under a roof to run wires, install stacks, store stuff, whatever.

Pitch:

I would love to have a 12:12 roof pitch.  There would be a LOT of space underneath, my solar panels could be mounted flat to the roof, and any snow would just slide right off.  Unfortunately, I also need enough overhang to completely shade my south facing windows in the summer as I don’t plan on having any air conditioning.  A 12:12 pitch would not extend out far enough and still have clearance for the doors – at least not in the style of roof I wanted.  The best I was able to accomplish was a 4:12 pitch which will be adequate.

Overhang:

SketchUp shadows

SketchUp shadows

I’m going to bring up my favorite tool again – Google SketchUp.  SketchUp has a great feature that enables you to design the perfect overhang for your specific building and location.  If you set the coordinates and orientation of your building, you can see the shadows as they will appear for any date and time.  For the hottest months of the year, almost no direct sunlight will enter the south facing windows of the cabin.  Conversely, the coldest months will allow all of the sunlight, and warmth, to come in.  The overhang I needed to accomplish this was right around 3 feet.

Roofing Material:

This wasn’t too hard of a decision, as a metal roof just seemed appropriate for a shipping container cabin.  A metal roof has so many advantages over shingles, especially in regards to the ease of framing and installation.  I did choose to go with galvanized panels mostly from an appearance standpoint, although coated steel would probably be more durable.

Structure:

Roof framing

Roof framing

Since I was using metal panels, a combination of rafters and purlins would be an efficient choice.  Several friends tried to talk me into trusses instead of rafters, but I really don’t like the look of them, access under the roof can be difficult, and the steel support beams that are in the way would have required some expensive custom trusses that would not have saved me much money.

The rafters themselves are dual 2×8’s four feet on center.  Note that for the snow loads this cabin could experience I needed to use Doug Fir lumber which just barely meets the limits.  Any more snow load, or a lesser grade of lumber, would have required dual 2×10’s.  If I had chosen dual 2×10’s I could probably have increased the spacing to eight feet, although that would have required the purlins to be oriented vertically either on or between the rafters.  As it is, the purlins are 2×4’s laid flat every 2 feet.  I could also have used single 2×8 rafters every 2 feet, but I like the more substantial appearance of the dual 2×8 beams.

Rafter attachment

Rafter attachment

I probably/hopefully over-designed the roof just a bit, but with a cabin this small the extra cost will be minimal.  Each set of rafters is connected at the top by two 5/8″ plywood gussets, and connected to the top plate with four steel angle plates that have eight 1/4″ SPAX lag screws each.  Two of the middle rafters have 2×4 rafter ties on each side to help prevent any possible rafter spread.  The top plates at the eaves are dual 2×8’s attached to the containers with welded angle plates, while the top plates at the gable ends are dual 2×4’s.

Two additional roof details are the chimney opening and protection from animals.  I,m planning for the chimney to be at the peak of the roof, and I hope this will minimize the amount of flashing that is necessary – we shall see.  To protect the “attic” of the cabin from nesting birds, red squirrels, and insects, there will be blocking between the purlins on the gable ends in addition to insect screen on the gables and eaves.  There are also foam closures between the end purlins and the metal panels, and ridge vent material at the peak under the ridge cap.  Aside from protecting the attic space, this should also provide for adequate ventilation in the summer months.

Opening for chimney

Opening for chimney

Sealing of roof

Sealing of roof

19 thoughts on “Roof Plans

    1. Steve Post author

      Don’t worry, I’ve got lots more to post. I’ve had some delays because of the spray foam insulation company I hired. I will talk about my problems with them next week when it gets finished.

      Reply
  1. Ricky

    Hey, I love the work you are doing and i hope one day i could do the same on my great-grandmother farm also! I understood about make your roof like the others so it doesnt stand out but have you though about away to collect the rain water/ melting snow and filtering and cleaning it to be used for everyday usage? I seen that being done all over with conventual and new container homes to reduce the print of the property!

    Reply
    1. Steve Post author

      Ricky:

      Collecting rainwater would be pretty easy with just some some gutters and a storage tank. The bigger problem is storing the water so it doesn’t freeze during the very cold winters here. I know I could bury the storage tank, but that’s getting a bit too complicated for me. If I was in the south, I would definitely have a cistern – it’s the easiest way to provide water to a cabin.

      I am fortunate though in that my water table is pretty high. There was an old well and hand pump nearby until someone stole the pump – I’m sure it’s in a garden somewhere being decorative. A shallow well and a hand pump will work just fine for me here.

      Steve

      Reply
      1. Aunt Raven

        There are some good hand pumps on-line. Check out “Buffalo pumps” Or this one at http://www.survivalunlimited.com/deepwellpump.htm
        which is a sleek modern style that harmonizes with your cabin, and would probably not invite theft for a “quaint garden ornament”. That said, I myself would encase it in a lockable, concrete-foundation pump house /shed. Some hand pumps produce enough pressure for a shower, if you like cold showers.

        Reply
    1. Steve Post author

      Raven:

      The best manual pump I have found is the Simple Pump. It’s made of aircraft grade stainless steel, is removable to prevent theft when you’re away, and can be upgraded to a 12VDC motor powered unit later on. The only drawback to the pump is it’s price, about $1,500 for the complete system.

      Simple Pump

      Steve

      Reply
  2. elliot

    Hello,
    Great blog, I’m eagerly reading it all in its entirety! Quick question: did you have any plan to use the space between the roof and the containers as an attic for storage? Seems like you could get to it easily with a quick cut to the top of one of the containers. Anyways, awesome work so far! Your posts and pictures have solved most of the questions I’ve had with container design.

    Cheers,
    ~Elliot, New Zealand

    Reply
    1. Steve Post author

      Hi Elliot:

      My only thought for the “attic” space would be for storage. If I ever run out of storage space inside and need to go up, I will install one of these:

      It’s a high security roof hatch and can be welded into the top of a shipping container. They run about $500 and up depending on size. The only downside would be the appearance on the inside. I would probably install it in my bathroom/storage room.

      Steve

      Reply
      1. mike

        how did you attach the roof structure to the top of the sea containers. So that wind was not a factor in causing the roof to blow off from wind gusts or a sustained wind? as i’m in Georgia and we frequently get wind as a factor on structures that are bulit.
        thanks for your time
        Mike

        Reply
  3. CRB

    Thanks for all the detail. Still have some questions as how the top plate were attached to the containers? Welded angle brackets, what size and what distance were they place O.C.? Placed on the Interior of the plates?
    Thanks again.
    CB

    Reply
    1. Steve Post author

      CB:

      The top plates were attached to the containers with welded angle brackets on the interior side, although I don’t have the size or number that I used. In my case though it’s probably a moot point. Since I insulated the roof of my containers on the outside with spray foam insulation, the top plates are basically “glued” to the roof along the entire perimeter.

      Steve

      Reply
  4. Larry

    This has been VERY COOL to watch and still enjoy coming to your site for more information. I’m looking into the details of mounting the various roof ing parts to the container. I have been building a cabin using a shipping container, ONLY because of its security features, as you’ve stated.Would you send me any detailed information, including any additional pics thatyou might have.
    Anything you could send would assist me and any engineer in adding a roof to my container.
    Thank Again!

    Reply
  5. Ian

    Greetings from Ireland Steve. What a great site you’ve created here. I’ve just found it and have pulled out my container plans to update with all your advice, so thank you.

    I’ve some initial questions which I hope you can help me with. Brief background: my plan is to build a two container (16×20) studio in the garden of my home, learn a little then go bigger with a permanent multi 40′ as soon as I find the right piece of land in a/surrounded by woodland etc.
    Hope to beat the awful 30 year life crippling bank mortgage system that has become the norm in Ireland these last ten years!!!

    I’d love your opinion on my plan:
    1) reusing the internal walls removed for the roof, incl. other bits such as door and window cutouts to complete the size needed for an overhang. Like you, I feel a metal roof is the way to go for a container, just a different colour/tone but then to buy one when I’m removing sides seems odd (to me).. What do you think?
    2) I’d love to increase the pitch and open up the roof then to use the attic space, maybe showing the rafters/trusses (in which case I’ll spray foam the inside of the roof, not the outside. I’m worried though about lossig then the air tightness/vapour barrier that comes “free” using containers. Any thoughts on how to achieve the space without the compromise (but mindful of budget)?

    Thanks in advance and once again great site!!

    Ian

    Reply
    1. Steve Post author

      Hi Ian:

      Sorry for the late reply. While I think it would be possible to reuse the roof panels for roofing, you would probably have to beef up your rafters to deal with the extra weight. Typical steel roofing panels are much lighter in weight than the walls from a shipping container. In the US at least, lightweight steel roofing panels are relatively inexpensive. They can also be custom cut to whatever length you need which makes installation a breeze. I’m not sure I would give up the ease of installation just to reuse some scrap container panels. Mine are still stacked under my cabin waiting for some unforeseen project.

      As for opening up the ceiling, I think that would negate one of the greatest benefits of shipping containers – their air and water tightness. At that point you might as well build using traditional materials and use metal panels as siding.

      Steve

      Reply
  6. Larry

    I’ve enjoyed reading your site many times, it’s great, and it always gives me more ideas!
    I’m working on mounting a mono type roof on my container and would appreciate more detailed info and especially pictures on the top plate mounting brackets that you welded on your containers.
    Again it would be greatly appreciated.

    Reply
    1. Steve Post author

      Larry:

      Unfortunately I don’t have any pictures of the top plate mounting brackets. They were actually an unplanned addition for me. The builder I hired to help with the roof didn’t want to drill and lag bolt the top plates to the container box beams around the perimeter – this would have been my first choice.

      It is all a moot point anyways. I consider the mounting brackets I used to have only been a temporary attachment. By spray foaming on the exterior of my roof, I essentially glued all of the top plates to the container around the entire perimeter of the cabin. If I didn’t have the spray foam, I would definitely want to lag bolt the plates to the box beams.

      Steve

      Reply

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