Will this fall down?

[mojo43]

Hi, I am trying to design our little 9X12 shed (with a loft) to figure out what we want, but I am not sure if what I have designed will work.

I was planning to use 6X6 PT poles and notch out spots for the floor and loft. I was planning to nail tongue and groove boards on the outside to the 6X6s.

Here is a sketchup drawing that I have made. My first concern is that I am not sure if there are enough 6X6 poles to handle the weight of the roof, loft and floor. My second concern is that I want the loft to have a bit more room so it would start 2 feet lower than where the roof touches the walls. Is this possible to build without it falling down?



Any help would be appreciated!

[MountainDon]

So in the illustration the wall are we looking at a 12 foot wall or a 9 foot wall? It sort of looks like a 12 foot wall, but then the roof ridge is running 90 degrees what would be expected.

Where is this? Snow? Soil is what? Which direction do the planned main floor joists run; parallel to 12 foot wall or 9 foot wall. Ditto the loft joists and the rafters? Are those simply transparent walls or something like an expanse of patio slider doors or ... ?   I need more info so I don't fill in the blanks incorrectly. Can't speak for others on that.

[mojo43]

Hi MountainDon, it seems you are helping me on a different forum. Thank you once again!

We are looking at the 12' wall and the climate is cold and snowy and sometimes hot. The building will be built on a slight slope with moist earth for soil and will be built with poles as per your suggestion on the other forum.

I was thinking that the floor joists were going to run parallel to the 9 foot wall as well as the loft joists and the rafters. The transparent looking walls are two 5 foot wide patio sliding doors. Here is another shot from a different angle.



I still have a lot of blanks to fill. I am pretty new at this, but I wanted to see if I was already off track with something that will fall down?

[MountainDon]

Ah. Ottawa area. To do a proper design the snow load (lbs per sq ft or kg per sq meter) needs to be known. The reference materials I use stop at the 49th parallel.    On the south side of that line up there it looks like 50 or 60 PSF.   

They may also differ some in what practices are accepted/required. Which brings up the question; will the bldg inspector come calling? 9x12 to meet some quirky bldg rule? Call it a shed, not a cabin?   

I would swing the roof 90 degrees unless there is a compelling reason to keep it as illustrated. That would place the roof loading on the longer walls. Maybe increase the pitch some?

[MountainDon]

The "window wall" might be a problem. Best practices state that each one of the 4 walls should have one full 4x8 panel of exterior structural sheathing securely nailed to the framing. That adds great rigidity to the structure. Building we see with glass walls usually have had design input from an engineer. I'm not one.

The building is probably ok with 6 posts on concrete pad footers at frost line. Unless you load it up with a water bed or something. 

How much height would there be above the glass door wall? Perhaps there's enough area above the glass to provide bracing?  Especially if the back wall was mostly sheathed.  Like I said; but I don't know for certain.   

[mojo43]

It's 9X12 so that there is no building permit needed. Would swinging the roof 90 degrees increase the load it can take? I guess it would be three feet less width. The pitch unfortunately cannot be increased unless I raise the loft as well as anything over 5 feet high counts as square footage. I was trying to get the loft at 5 feet high and down to two feet on the sides for maximum room.

The back wall will all be sheathed and there would be approximately 3 feet above the patio doors. The reason that the roof is that way is for aesthetic purposes as well as I figured it would take load off of the wall that has the patio doors. I am not sure if this is true though?

Thanks for the help...

[MountainDon]

OK, I understand the roof / loft height.   
Yes the roof is more pleasing to the eye oriented the way it's illustrated.
Properly sized headers over the doors would take the loads if the roof was the other way, though.   

One of the issues in play here, is the same issue that comes up every time a design comes along with a dropped loft floor. That is the absence of rafter ties at the wall stud top plate or at least in the lower third of the rafter triangle. It gets a tad more complicated with the roof turned from what's normal.

How big is the loft floor intended to be? Half as in an end or less or more? 
How well do you want it insulated?

The way it's drawn a well secured good size connector from the top of each corner post, down the 12 foot side, would help hold those wall tops together.    But would that be enough with a potential 60 psf snow load? And how to fasten. maybe someone will have some ideas to contribute?

The two 9 foot wide walls could be framed between the posts to support the rafter tails; it's the outward horizontal force that needs restraining.

[MountainDon]

Could you determine your snow load? Plus the soil bearing capacity?   The county/township or whatever the local governing body is may be able to supply that info or at least point you in the right direction....

[flyingvan]

To answer your question, "Will this fall down?"  The answer is a resounding yes---unless it burns down first.  You goal as a builder is that your structure makes as many trips around the sun as possible before it does.  Just get some dead trees, hit them with hammers just right, and you end up with a house that can fight gravity for a long time

[MountainDon]

Ground Snow Map, Canada

see page 5 for map

[Don_P]

To answer your question, "Will this fall down?"  The answer is a resounding yes---unless it burns down first.  You goal as a builder is that your structure makes as many trips around the sun as possible before it does.  Just get some dead trees, hit them with hammers just right, and you end up with a house that can fight gravity for a long time

Van your response is reminescent of the old builder responding to a concerned homeowner who kept asking when the log house would stop settling "When the ridge is resting on the ground" 

If the center posts extend up to support a ridgebeam the loft kneewall thrust problem is solved. I wouldn't notch the posts, I'd use simpson type hangers or can you weld? The open front wall would be easier to brace in steel.

[mojo43]

Hmmm, maybe this is more of an undertaking than I anticipated. I have built small sheds before, but nothing like this. Maybe I could take out one of the patio doors....

[MountainDon]

Ridgebeam      How is it I can be so blind to the obvious at times?  

[mojo43]

The only problem with extending the center post is that it is already a 16 foot post. I am not sure I will be able to find anything longer than that. Can I add to the post in some way in order to extend it?

[MountainDon]

Yes, Don_P is the expert on best practice to do that. Need a good footer for that too.

[mojo43]

How big is the loft floor intended to be? Half as in an end or less or more? 
How well do you want it insulated?

I forgot to answer this question: The loft floor is 9'X5'9 and I am not sure if I am going to insulate just yet. I really wanted to have a wood look from the inside as well as I didn't want to lose the space taken up with insulation.

[Don_P]

We can lose the expert part, I'm just an old and in the way carpenter. This is stepping outside of the cookbook, you are on your own, this is just opinion. Just one door and a section of wall will certainly make it stouter. You can special order longer posts, you can also build up posts. What you asked about is splicing a post, I've got pics of some awesome historical work but its really engineer territory. But, with the loft floor acting as a stiffening diaphragm, we can look at it as platform framing above the loft floor, splice or begin anew at that point, just like a wall stacked atop a floor. I'm drawing what might seem like fine lines, here's what is going on in my mind. If the posts are buried within the walls the wall sheathing braces them to a very large extent. I don't want you defaulting to short posts under the cabin that are poorly braced, we all should know better than that by now. I also don't want anyone thinking you can splice or build up just any post, these have bracing from both directions by walls and floors every 8' or so. Hopefully that doesn't confuse you or a reader with a different situation  .
One insulation option is to wrap and strap the exterior with sheet foam, 1x's, and exterior finish. However you do need some form of studding or some mighty hefty siding to span 9' without framed walls between posts... rethink dimensions based around true wall thickness, you'll have room for at least some insulation. Did you find your snow and wind load info and how far between grade and the bottom of the floor?

[mojo43]

Thanks for the info Don_P and MountainDon. I updated the design a bit. I am still looking into the snow and wind load...

This is the back of the shabin


This is the front. I used 2X6s for the headers

[flyingvan]

Don----regarding 'expert' status, let me ask you a question based on a true local experience-----say you have a bank to cut at a certain angle.  The soils engineer with a PhD from a respected university says the ground will support a cut angle of X, while the backhoe operator who has run his backhoe, mostly in the immediate area, for decades---disagrees and says it will only hold a much shallower angle.  Which opinion would you go with?

[MountainDon]

OK, I'll lose the expert word; but you do have more practical experience than myself and many others and from what I have seen I trust your word and work more than I trust what many so-called carpenters where I live charge money for. 

[flyingvan]

 Believe me, I've made my share of mistakes.  I wish you'd hurry up and invent a board stretcher for all the times I continue to make a cut exactly 1" off.  "Good decisions come from experience.  Experience comes from bad decisions". 

[Don_P]

I've been called as an "expert" witness before, the word sounds an awful like "fresh meat" in my ears  .

My question would be whether the phd talked to the equipment operator, an open mind. If it all happened on paper without any experience behind it that is not a good thing, and it happens. The flip side of that is the great pride some tradespeople take in their ignorance. Look for good critical thinking skills tempered by experience. They don't have to agree with what you want to hear but it does need to make rational sense. Either way it's a human equation.

There is one more actor, the one I probably encounter most. A friend dropped by this morning to pick up an oak beam. He had the prints for their current job, a $400k carriage house. They've just poured 42 yards in the footings, 3000lf of steel. We were talking about something similar and he said "yeah the porta john guy was trying to tell me how to do the footing". No book smarts, no experience, just a skull full of packing peanuts to keep his eyeballs in place.

The odds are with the phd, I've seen him fail by ignorance or by following the engineer's creed too close (an engineer's job is to do with one dollar what any damn fool could do with two). I wouldn't ignore the experienced tradesman but he only see's a failure, he can be deep out there in his safety and not know it till he crosses the failure line, that happens in construction regularly, we had a church roof under construction collapse here a week ago, thankfully at night. I went by, I know they ignored the engineers, it was plain what they thought, and it was wrong. That can be bad because there is a line of bad thinking behind him. During Andrew some contractors lost their entire body of work while others fared much better. They didn't know how deep they were into their safety till the exam. And be very careful when that third guy opens his mouth. He might know his stuff, but the odds aren't good at all.

Inch syndrome, I know it well  We had one homeowner going "well we could use the board stretcher but they get thinner when we do that and I don't think you'd be happy."

[MountainDon]

Inch syndrome

How about getting confused (me) and being off by three inches; 26 for 29 or vice versa. Happens at times when I'm reading the tape upside down.   

[flyingvan]

Remember that 10 out of 5 people have some level of dyslexia (also 78% of all stats are made up on the spot)

   If the engineer had recommended the more conservative slope his opinion would have been followed.  The decision was to go the more conservative route----it cost some flat space but everyone slept better (maybe even the engineer)
   I don't know any good carpenters that wouldn't consult span tables if supporting a live load.  A good carpenter will also consider loads from all directions--compression, sheer, etc