Building on platform vs hanging floor from posts

I’m planning on building a roundwood/pole barn house on sloping ground. I wanted to hear y’all’s thoughts on using wood piers to create a floor/level building platform versus having the poles extend from the footings all the way up the height of the structure, and hanging the floor from that with either timber frame joinery or metal fasteners (sorry if I’m not making sense; I mean hanging it the way you might hang a loft floor off your posts in a pole barn).

On the one hand, most everyone seems to first build a platform foundation and then put the timber frame structure on that. I imagine this is because the measurements and anssembly are much easier once you have a level building surface.

My concern, though, is that I’m in hurricane/high wind country, and doesn’t making a floor/platform structure separate from the main walls and roof create an additional hinge point? Or is the danger of this/advantage of having a single post span footer-to-roof negligible when you properly secure the structure to your platform?  

What you are describing is called "ballon framing" as opposed to "platform framing."
Balloon framing is an acceptable method, but it doesn't necessarily make for better wind resistance.
In platform framing the structural sheathing on the top level extends past the floor platform framing and is attached to the vertical walls below that floor platform. This ties the wall above to the wall below and eliminates the weakness in the hinge joint. In platform framing without structural sheathing, metal straps are often used to tie the two level together. These straps are also used in conjunction with structural sheathing to increase wind resistance (lateral) and uplift resistance.

Either one can be made to meet any wind load you need. Most houses are platform framed because it is faster and easier with modern lumber and tools and work crews. It is also much easier to build complicated non-rectangular floor plans.  The wind shear strength relies on the sheathing, so don’t skimp there.

Pole framed allows you to build the shell and roof and get it dry and warm before you even start working on the interior framing. Great if you are DIY and want to work inside for the winter or rainy season. Cheaper overall for a simple rectangular gable roof, but adding architectural details gets very expensive very fast.  All the wind strength can be built into the posts.  Multistory building needs fire blocking to prevent chimney effect to stop fire traveling up the wall cavity.

For a roundwood/pole barn building on a platform would be unusual.
That kind of building is usually reserved for building with dimensional lumber.
The main advantage of a pole barn is the footings for the poles are the foundation for the building.

William Bronson wrote:For a roundwood/pole barn building on a platform would be unusual.
That kind of building is usually reserved for building with dimensional lumber.
The main advantage of a pole barn is the footings for the poles are the foundation for the building.

The footings are of critical importance here. Depending on the total height of those poles and the square footage of the walls, the lateral forces could become quite substantial.
All that lateral force needs to be transferred to the foundation, and that foundation needs to be large enough, and deep enough to resist overturning.
This is another reason why conventional foundations and platform framing are so widely used. That continuous foundation and stem wall provides exponentially more lateral resistance than a pier foundation per cubic yard of concrete.
I built quite a few pole barn type buildings over the years. Most of them were simple structures used for horse stalls (we called them mare motels).
One building I remember was about 5000 square feet and open sided. The roof peak was around 20 feet tall. The piers for that building were 48 inches deep and 36 inches in diameter.

The comment from R Scott is something I agree with.
I have built a number of 'pole framed ' homes and they work very well on steep slopes and as R Scott says, assemble quickly but take time to fit out.
I believe with the issues you have with hurricanes, pole framing would be a great place to investigate,
I dont witness hurricanes / cyclones , but I am astonished when I see the stick frames mess left after one I am amazed anybody builds that way.
I have done a bit of research about this topic and I am surpriced to see some variations on what are described as pole houses.
I have worked with large round poles 12 inch buried into the ground connected with 2 x 8 , 20 or 12 inch deep beams bolted and set partially into the poles with a flat / skillion roof attached to similar beams .
I have seen homes which I dont consider pole houses, built with concrete slabs, 6 x 6 poles timber framed wall between large 6 x6 inch square poles and roof trusses across the walls.
This is a good book 'Practical Pole Building Construction With Plans for Barns, Cabins, & Outbuildings' to consider
pole building

John C :
Any idea how those 6x6 timbers are affixed to the slab?
Do they use a sill plate?
What do they use for infill?

William Bronson wrote:John C :
Any idea how those 6x6 timbers are affixed to the slab?
Do they use a sill plate?
What do they use for infill?

There are many cast-in-place post bases available from Simpson and Mitek. The posts should bear on a concrete footing which is typically poured with the slab. The post anchors are embedded in the wet concrete with bent rebar hooks.
Simpson anchors: https://www.strongtie.com/castinplacepostbases_postbases/category

Uh, duh, I should have thought of that!
I've always  figured using these set into the tops of concrete piers, it never occured to me to use them in regular slab.
In fairness to myself, it's still hard to understand the practical benefit of post and beam on top of a slab, especially when the posts/beams are only 6x6.

William Bronson wrote:Uh, duh, I should have thought of that!
I've always  figured using these set into the tops of concrete piers, it never occured to me to use them in regular slab.
In fairness to myself, it's still hard to understand the practical benefit of post and beam on top of a slab, especially when the posts/beams are only 6x6.

I really like post and beam construction, especially when the structural timbers are left exposed on the interior. It's such a nice balance between rustic and contemporary.
One of the primary benefits is the ability to add-on a new room or add an opening for a new window or door. All of the roof and second story (or third story) load is carried on the beams and posts. The infill framing between posts is non-load bearing and can easily be removed without the need for vertical shoring.
IIRC, a 6x6 post is good for somewhere around 20,000 pounds of vertical load. It may be more, but that's a lot of vertical load.

So, let's take an example of a single-story house that is 30 ft wide by 50 ft long and see what that means. (see attached photo)
If we put a standard gable roof on that house, the bulk of the load is on the long walls. Rule of thumb for roof loading is 15 pounds per square foot of dead load and 20 pounds per square foot of live load. (snow load only comes into play when the area the house is in has a ground snow load of more than 20 pounds.)

So, the roof load along the wall line is 15+20=35 P/SF X 15 feet (1/2 the width of the house) which equals 525 pounds per linear foot.
If we space those 6x6 posts at 10 feet on center, each post is taking 10*525 = 5250 pounds on each post.
Minimum allowable soil bearing capacity is 1500 pounds per square foot. 5250/1500=3,5 sq ft of footing roughly 8 inches thick. Probably with some rebar mat to disperse the weight.
So, each footing under a post would need to be about 2 feet square. That's not really big.

If you lived in an area with a ground snow load of 30 pounds, the footing size only increases to about 26 inches square.
Of course, all of these footings need to be deep enough to be below frost depth.

6 x 6 inch square poles are usually set into steel 'stirrups' set into the slab or even strip footings.
In Australia 6 x 6 would often be red gum or  jarrah timber which is durable.
With good timber hard to find I have used 100mm x 100mm hollow steel columns set into the concrete foundation.
And even steel roof trusses since they are easy to work with and easily obtained.