Hybrid foundation?

[MushCreek]

I posted on here recently about building on piers, and I'm not that excited about the idea. I really would like at least a partial basement. My house design is a cross shape, with a main center section, and a wing off of each side, one for the living room, the other for the master bedroom. How about if I put the basement under the main section only? The LR and BR don't have any plumbing, so that's not a problem. I could put the two wings on piers. Do you see a problem with uneven settling? What could I do to be sure the wings didn't settle differently then the main section? Or is it not worth whatever savings there might be?

[PEG688]

  How about if I put the basement under the main section only?

  The LR and BR don't have any plumbing, so that's not a problem. I could put the two wings on piers.

  Do you see a problem with uneven settling?

  What could I do to be sure the wings didn't settle differently then the main section?

   Or is it not worth whatever savings there might be?

 

  #1: Stairs into the basement , maybe only a bulkhead access?  ( exterior stairs).

  #2: You might have that issue , but,

  #3:   with over sized piers with large foot prints / footing you could combat that.

  #4: You'd lose some fairly cheap basement space seeing you'll be digging a big hole already the excavation fees wouldn't be to much different.

   But if that added basement space isn't that critical I'd say you have a  pretty good idea.

   

 

[Don_P]

I like it, you have a big hunka something stable to work off of. The best way to assure even settlement, if this is an issue with your soils, is a continuous beam/footing under everything. That is also the prescriptive minimum if it matters. That eats into some of the advantages but is cheaper than walls above those sections. Ever notice most decisions are not "either this or that" they are some point along a long line of choices? This is one of those kind of decisions. If you do go with oversize footings the minimum thickness is equal to or greater than the width projection between the column and outer edge of the footing to avoid "punch thru".

One thing to think about might be long continuous joists running across the building and out to the piers on both sides. The loading on a joist with equal spans, spanning continuously across 4 supports is 13%, 36%,36%,13%, The load on the outer piers is roughly half of what it would be with 3 simple spans and it would help tie the building together, I'm thinking about long TJI's if it could work into your plan, just something to consider.

[MushCreek]

Those would be long TJI's- 44 feet. Do they make then that long? Our soil is described as sandy loam, but it has the usual South Carolina clay component. Not the real slimy mucky stuff- there's a fair amount of grit to it. I'm building into a hillside, so a walk-out basement is a natural. I really want at least some basement; I'm just looking for ways to cut costs. The reason for the shape of the house is primarily for ventilation. We love to have the windows open as much as possible, and the climate there is conducive to that. My design allows for windows on 3 sides of each of the major rooms, with closets, bathrooms, and stairs in the middle. The view (mountains) is out the back, and my layout allows the living room, kitchen/dining, and master bedroom each to have the view. If there's any interest, I'll post a floor plan sketch. I have questions about framing to figure out; maybe y'all can give me some ideas if you see it. My original plan was to have a half story upstairs for the main gable- time and money will be the final determination for that. I wanted access to an upstairs deck over the back porch for a better view and maybe some star gazing. The upstairs could be a master suite until we are too old for the stairs.

I've wandered a bit here, but another reason for not having basement under the entire house is that I'm thinking about ICF for the basement, which ain't cheap, and then there's the issue of covering it with something durable, yet authentic to the style of the house (farmhouse). Lattice and brick or stone pillars would do nicely for the sections on piers.