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Need advice, gotta get a real roof on my cabin offgrid im living in it

 
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Glenn Herbert wrote:Yep, a good kiln and the right clay to fire in it makes all the difference... as well as the knowledge and experience to fire it well. A novice is going to spend a huge amount of time and energy getting up to speed, not practical for a single project (unless it is in the tropics where drying is easy and frost is irrelevant).



Point taken. My apologies.
 
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If I can get the top off and use it as a floor of room 2 on the downhill side, I have no clue how to connect them strongly so the settling problem is accounted for... If I convert it to 16 x 16 in this way I would need larger rafter boards than 2 x 4 I assume.


Great tips. Metal roof and hardie board siding... I maybe could get a helper in sept to do some of the heavy lifting. How can I fix the settle issue ? I'd prefer to be able to make it a single building. Maybe open a door between the two. I may do the framing on the second out of 2x6 studs but otherwise just another 8 x 16 room. I may also close the northern facing window (by the door) for better thermal efficiency. I planned to just plywood and frame up the hole, this ok?

My first thought is to use the two posts I just made on the downhill side to hold the ends of a 10 foot 2x6 flat (it's sitting on 2x4 now between pier and framing for wedging it even do it would be simple) and lay the across to two more piers(is that enough?)  then use these to build/lay the floor framing on. If I built 3 walls (one downhill and two end walls) and leave the shared wall (putting a door in)  I would have two barely connected structures. The roof would partially tie them together, but what else could or should I do to reinforce that connection structurally
 
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If you are connecting the two floors at the same height, you can use lag bolts, carriage bolts or structural screws to hold the rim joists together where they meet.  The settling will be more impacted by the footings.  If they settle, the building settles.  So by connecting the two floors together down the middle you have supported half of the new floor from the existing downhill footings.  Then you just need good footings for the downhill side of the addition.  Mind you, if the new footings are all properly done and the old footings on the uphill side are not properly done, the old ones can still settle.  But since it's not a $250,000 house, you may be fine if you watch for settling and then add shims to unsettle any problem spots.

Frost heaving (if you get frost and the footings aren't deep enough for it) may be a harder issue since it comes and goes with the seasons.  Versus settling which just kind of slowly happens in one direction only (down).

With the bigger roof you may want to go up to 2x6 rafters.  I'm not sure what your code would say but I'm pretty sure 2x6 would be strong enough.  My 1960s house has 2x6 rafters and it's 28' wide and it has to hold up several feet of snow.

If you do rafters, you need to connect the ceiling together as well as the floor.  The weight of the roof and snow will be pushing down on your rafters and trying to spread apart your exterior walls.  So the ceiling joists are used to complete the triangle and hold the exterior walls together.  So when you build the ceiling of the cabin just use 16' long boards that span the whole width or get two 10' boards and overlap them in the middle and connect them securely to simulate a 16' ceiling joist.

If you do trusses, they will span the ceiling and become the ceiling and you don't have to worry about it.  Standard trusses will be made like a bunch of triangles in a W shape.  So there won't be much storage space in them.  For a few dollars more you can get trusses made that have attic space built into them.  Or you can get what are called scissors trusses that will give you a cathedral ceiling.  Or you can do some of each and have a cathedral ceiling in one half of the cabin (over the gathering space?) and storage/attic trusses over the bedroom/kitchen/bath side.

Plywood and studs to fill in the window is just fine.

You can remove more than just the space for a door on the downhill wall of the current cabin.  If you have rafters and ceiling joists you may want that central wall to help hold up the ceiling.  But it could be a beam with big passageways between the old cabin and new addition.  If you use trusses you can remove that wall entirely and have an open concept.

Good luck!!!
 
Dustin Nemos
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Great advice! I think I need to do rafters I can't carry anything to heavy up the hill, 16 footers are doable in spurts, as for the piers I have been doing them 18 inches deep with a few gravel sized rocks in the bottom and 8 inch round, these will be much longer what do I need to do there? Just throw in some 2 foot rebar? Or longer?
 
Mike Haasl
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Sometimes trusses can be pretty light.  Much lighter than folks realize.  They are often made of 2x4's and even 2x3's so they are deceptive.  But their size and floppiness can make them awkward to carry.  

Some people have been known to make their own trusses on site.  Building inspectors probably wouldn't like to see that though.

Either way, a nice 16x16 building would be pretty sweet.  Enjoy the ride
 
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For a 16' x 16' total building size, I would be totally comfortable using 2x6s for rafters and ceiling joists (which would effectively be the bottom part of site-built trusses, if you connect the joints securely). 2x4s would be about adequate for the ceiling joists in this layout, but not allow much insulation if you put in an attic floor. I would just go with 2x6 and rest easy.

As for joining the two parts of the structure, after lagging the floor sections together, I would extend the plywood wall sheathing continuously across the joint. Simply adding a sheet spanning the junction, or removing a couple of feet of the existing sheathing (back to the middle of the next stud) and running the replacement sheathing onto the new framing, will make the walls into continuous planes that will give considerable resistance to gapping from differential settling.
 
Dustin Nemos
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So with luck I'll be moving ahead on building the second half of cabin, making it 16 x 16

I bought materials for another 3 piers at the lowest slope and there will be significant gap there, how high up can my concrete piers be? How much rebar? Ongoing to ripoff roof and use it as floor of second half (hope no rain!) and build up 3 walls from that point attaching to existing downslope wall, I'm going to stagger plywood over gap and then proceed to sheathe and roof. Help me not screw these piers up please


Trying to put together materials lists for this project as well. I am shopping lumber on Craigslist but wanted to get the 18 foot 2x6 s for the ceiling joists of roof, I think I'm right in using 2x6x10' for the rafters for a decent slope and space inside. How many of the longer boards will I need? Anything longer than 10' I'll have to order from Home Depot I figured I would get the 18 footers (1' overhang on both ends) for joists and a ridge beam 2x8x ?' ( do I go longer than building this way too? So 18 foot ridge? I have books for figuring out the cuts and online calculators for the slope. Would appreciate help on the parts list
 
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Dustin Nemos wrote:I could take that floor ceiling off, it's only caulked a bit to bugproof. I don't know that I could get trusses carried up there though!


As for framing I do know how to frame windows and doors with proper headers and footers although my friend failed to do them correctly here I couldn't fix the door it's already installed and the windows are an abnormal size I've been thinking I would reframe them to standard sizes when I get to windows and siding. I just don't understand how the siding goes to the window hole and I don't understand how to properly flash windows and all that. Basically I can frame everything but the roof and I think I can handle that off the videos I found.


This might give you a bit of an idea. You might want to skip the first 3 minutes or so. Actually, although they use store bought everything, you might get some useful ideas out of the whole series as it's a tiny house build (8.5' x 24' on a trailer).They just give overviews in the videos, but it might be enough to give you direction. They also have free plans: http://www.ana-white.com/2016/06/free_plans/quartz-tiny-house-free-tiny-house-plans



They talk about doing the roof here.
 
Mike Haasl
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Hopefully someone else with more rafter experience will chime in.  But my belief is that your ceiling joists should just be the overall width of your stud walls (to the outside edge of the studs).  So likely 16' is long enough.  The roof rafters have to reach from the ridge down over the top plates of the walls and then overhang.  It's common to overhang the walls 12-18".  So I believe you'll need longer rafters than 10'.  Maybe 12'.  The pitch of your roof will help determine that.

The ends of the roof are the tricky parts.  I'm used to trusses and making "fly rafters" for them.  With a conventional rafter roof I'm not sure how you get the roof to be longer than the building.  I'm guessing books or the internet or other permies can help.

Keep in mind that for the ceiling joists, if you leave the center wall in place between the two halves of the building, the ceiling joist can be two 10' 2x6's (or a 10' and 8') that are nailed together and resting on that wall.  That may save some $$$
 
Glenn Herbert
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16' overall is definitely long enough for ordinary ceiling joists. You can use continuous 16' members, or join two 8' members with splice plates. I would investigate the cost for 16' vs. two and a quarter 8' pieces, as well as the logistics of carrying the pieces to the site. Continuous 16' joists would add a little strength to the overall structure to resist differential settling.

You showed a truss/rafter calculation site earlier, so you can figure the length you will need for any particular roof pitch and overhang combination.

The ridge in your case does not have to be one continuous piece, it can be two 2x6x10' or an 8' and a 10' (depending on your desired gable overhang) spliced together and supported in the middle from the interior wall. The ceiling joists will hold the rafters together, such that you could even do without a ridge, but it will be easier to keep alignments with a ridge to work from.

For the concrete piers, there is no practical limit to the height for you, so don't worry about it. Dig down the same distance as your other piers, and make them as tall as needed to meet the new floor framing. One or two rebars full height should take care of the relatively tiny load here.
 
Dustin Nemos
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Thanks guys. About rebar can I stick any out the bottom if it's too long, or the top to rest some boards on, perhaps put a hole in the board and sit it on rebar sticking up from pier?
 
Mike Haasl
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As Peter V said, the rebar needs to be completely encased in the cement.  Just cut it to length with a hack saw...
 
Dustin Nemos
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So can the structure rest on the column without being attached to it? I couldn't find any 2x6 attachments
 
Mike Haasl
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It should really be attached to it.  If you haven't poured the column yet, embed a threaded J rod in the cement with the threads sticking up.  Then you can bolt a post base onto it.  If you already did the cement work, you can drill a hole in the top of the cement and epoxy anchor a piece of threaded rod into it to mount the post base.  They are usually sized for a double 2x rim joist.  Around the perimeter of the addition you'd ideally have a double 2x8 or 2x10 that the floor joists all attach to with joist hangers.  So that double rim joist would sit on this post base just fine.  Or if you want, the cement column can just go above the ground a bit, put the post base there and then have a 4x4 that goes from the post base up to your rim joist.  Then the exact height of the cement isn't as critical.  If you need to just attach a single 2x8 to the post base just use a scrap chunk of 2x8 to fill up the space on the post base.  Hopefully this makes sense....
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Dustin Nemos
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So I'm laying a 2x6 flat on its 6" side atop both columns to create strength under the uphill side of the new rooms floor, (sitting on the other piers I did after jacking it up) I still plan to lag bolt the floors together but wanted strength under neath it as well. This I figured would save me pouring 6 columns and only gave to do 3 on the downhill/outside wall. I planned to build the floor on top of these two 2x6 which stick out 8' from the old wall (which has the 2 columns under it)


Couldn't find anything to imbed for holding a 2x6 flat, but I could just go a bit shorter on columns and then add a 4" piece of 4x4 into a micro column then put these on top, how about this?
 
Glenn Herbert
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A 2x flat will add essentially nothing to the strength of the system, aside from keeping the piers it is attached to from sliding apart (which the floor framing would do anyway).

What are you trying to do with this 2x6, beyond holding the piers in line?
 
Mike Haasl
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Ok, I'm afraid we're all confusing one another here.  Do you have new pictures of your progress?  That could help us know what your posts look like now and what the existing floor looks like.  A pic or two of the underside of the existing floor could be a good thing to have as well.

IF the existing floor was framed correctly and has a good rim joist system, the new floor structure should be able to be lag or carriage bolted to it.  You shouldn't need a 2x6 under the floor to support it and you shouldn't have to tie the new floor to the existing posts.  As Glenn stated, a 2x6 on its side is pretty wimpy.

Here's a picture of how I imagine you could attach the new addition to the existing structure.  First, let's talk about the existing floor.  In this picture it is resting on a continuous foundation.  The sill plate is a 2x6 on its side but it has the full support of the cement underneath it.  That allows the floor joists to sit on the 2x6 instead of buying a bunch of joist hangers.  Due to that continuous foundation, the rim joist (labeled "house rim") is only a single 2x8.  Since your foundation is three posts, the rim joist should probably be two 2x8's or 2x6's sistered together.  In effect they become a 4x8.  That way they can carry the load from post to post.  On your existing structure the floor joists (labeled "house joist") should be attached to the double rim joist with joist hangers.  They may have just nailed the joists to the rim which might be fine for an 8' span.

Now for the addition part of the project.  The existing footings on the downhill side of the building should be able to carry the added load of the uphill half of the addition.  All you need to do is tie the two floors together.  I'd do it the same way they did this deck (picture).  Attach a ledger board with a bunch of lag bolts, structural screws or carriage bolts to the existing rim joist.  You don't need the flashing they show since you shouldn't have any rain inside the house.  On the downhill side of the addition use the cement posts and post bases and maybe a 4x4 to get the support up to the elevation of the new floor.  Put a doubled up 2x8 beam across those three posts.  Then use joist hangers to install floor joists between the ledger board and the downhill beam.  

Someone else may be able to comment on if you can just nail the joists to the rim joists instead of using hangers.
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Glenn Herbert
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With an 8' total floor width (maybe 7'-6" actual joist span), you *can* just nail the joists in place. Joist hangers would be stronger, but not totally necessary, as long as you use enough nails (probably as many nails as you would be using to fasten the joist hangers in place, and then lock the joists into the hangers).
 
Dustin Nemos
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Here's so far. I wanted to use the 2x6 to level things/give a platform to lay the floor out on before bolting to existing floor rim joist, and I wanted to give something under the floor supported by the uphill existing columns from under to give more strength than just the lag bolts.

Note: I did not double rim joist on existing cabin didn't know that was necessary
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Mike Haasl
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Ok, things look pretty good to me. Thanks for the pictures!

Will your flat 2x6 be sitting on top of your beam on the downhill side?  The most efficient use of lumber would probably be to put a double 2x8 beam in your post bases, add a ledger board to the existing structure and nail/hanger joists between them.  The flat 2x6 has probably done everything it can for you once it's traveled a foot under the addition.  I do like how it helps support the ledger board.  Extending it all the way to the downhill beam would be ok but probably doesn't add much strength.
 
Dustin Nemos
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It's basically only for Strength under the lag bolts and for leveling up the floor, I was going to sit some 4x4 on the posts and screw them to those metal pieces and then sit this 2x6 on that for level the build the floor stop that. Putting the rim joist directly in the metal would result in an uneven floor
 
Mike Haasl
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Ok, I think I follow and that should be fine too.  Good luck!
 
Dustin Nemos
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Awesome. Thanks everyone. Moving on to next steps as lumber is bought
 
Dustin Nemos
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Say I wanted to do the knee wall method and do a mini second story. How would there ceiling joists work for a roof like that? They would have to be he shorter kind that don't rest on the first floor but go higher up, yes? Looking for thoughts - this might allow me to skip tearing off the ceiling of existing building and the mad scramble to get everything built before rain and bugs destroy my existing cabin.
 
Dustin Nemos
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Bump. I am moving ahead with leaving the existing "floor" on top and trying to match it on the other side, looking for options in terms of putting a roof on top that will leave space open for moving about, i.e. - no ceiling joists or not the usual kind as they would be in the way of walking on the "floor".   What do I do?
 
Mike Haasl
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I was hoping someone else with more experience would chime in but here are my thoughts.  

If you were willing to remove the ceiling, I think the attic storage truss would be the easiest (first picture).  The bottom chord of the truss holds the walls together and is the floor of the attic.  Downside is getting through the floor of the attic to access the attic.  Normal truss spacing is 2' on center so you need to make a narrow staircase or pull down attic ladder to get up in there.  On my cabin I did half of the building with these trusses and the other half with scissor trusses.  Then you could look down from the attic storage area (like a loft) and access it from the scissor side where it was a cathedral ceiling.

A second option would be to use scissor trusses or parallel chord trusses (second picture).  You could build the wall of the addition to be the same height as the top of your existing ceiling and then set these trusses on top of it.  You could leave the existing ceiling there and you'd have a half loft.  Or you could add a ceiling over most of the addition and then you'd have a bigger attic.  Basically the existing ceiling and any more ceiling you add would not be load bearing and would just be there for a ceiling/floor.  There might be options with "raised heels" to increase the headroom.  When I built my cabin I worked with a truss guy and pointed as he clicked to design the truss the way I wanted.

A third option would be to install a beam down the ridge that is supported at the two ends of the cabin.  Unlike a ridge board, this is supported at the ends and it carries half the weight of the roof and snow.  All the rafters you attach to it are supported by the beam and the weight won't spread the walls of the building out.  Then the ceiling would not be load bearing and can be added to or left as a loft on that one side.  This requires a sturdy post system in the end walls to support the beam and carry the load directly down to the ground so that is the downside.  But you can build it with lumber yourself.

There might be more options but this is what comes to mind.  The steeper the pitch of the roof, the more storage you'll get in the loft/attic.  But the harder they will be to carry up there and the harder the roofing will be to apply.  My vote (fwiw) is to put in parallel chord trusses with a 8:12 pitch.  Then put a ceiling over half of the addition.  Add a cute staircase or ladder to get up there and use part of it as a loft and part as storage.  With that pitch and a 16' wide building you should be able to get close to 5' or more of headroom at the center of the attic/loft.
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