How to raise the floor in a split-level?

[bruffc]

SITUATION: We have a front to back split-level home, so really the house is kind of like a two story home but the front entry door and 2nd living room are in-between the top and bottom floors. I would like to raise the floor of the 2nd living room up 4 ft so the floor would be the same height as the upper level in the house. I don't think this should be a major ordeal as there is already a floor there (it's just 4 ft to low) and the existing space under the floor is a framed in sub-basement. I know I'd have to re-work the air return vent, heating/cooling vents, electrical outlets, etc but these items are already there - they'll just need to be raised or moved. I would have to figure out something for the windows as raising the floor 4 ft would cut the windows in half but I can sub-contract out this part of the job.

QUESTIONS:
Does this sound like a do-able plan?
Are there any items that I'm forgetting about?
Would I have to remove the existing floor or can I frame in a new floor on top of the old floor?
Would it be more structurally sound to build the new floor up from the sub-basement to the new height and eliminate the exisitng floor?
If I run new joists across the room then how would I tie them into the exterior wall studs? There is a header running down the middle of the house so I could use joist hangers to tie one side of the joists to - can't I?

We received a decent quote on the whole project but we haven't been able to get ahold of that contractor for the last 3 months. I do have his detailed quote though so I know approximately what materials to buy .

Any advice would be appreciated, thanks.

[LCHIEN]

1) what about the ceiling? already 1-1/2 stories high shared with the second story hopefully?
2) I would not trust *anything* from a contractor who doesn't return calls for 3 months.

[bruffc]

Good questions about the ceiling height. The upper level and the 2nd living room already share the same ceiling height. I have some pictures of the house during construction and the electrical drops down from the ceiling so I would just need to raise the outlet boxes. The vents are in the floor though so I'd have to splice some duct work raise the vents.

I was hoping to leave the existing floor as is so I could have a crawl space for additional storage but it sounds like I would need to remove the floor in order to create new headers??? If I understand correctly, by removing the floor then I'd have access to the sub-basement, the existing floor is "pony wall" framed so I would mimic this "pony wall" except 4 ft higher????

Do you think I'd be able to re-use the existing carpet once the floor is raised, (the carpet won't be there forever but it'd be nice if I could re-use it for a couple of years)? Also, how hard would it be to re-do the stairs? The stairs have some squeaks and the railing isn't very sturdy so I thought this would be a good time to re-do these. I'd like to be able to bolt the railing posts to the joists below the floor instead of those square brackets that are screwed to the step which the builder used.

Thanks again.

[LarryG]

Floor Framing: First of all, just to be sure we're clear on terminology, "pony wall" is just the term for an infill-type wall that's shorter than a full floor. Sometimes it's between the foundation and the first floor (think: older, This Old House type houses with shallow basements and first floors that are several steps above grade), sometimes its between an attic floor and the roof framing (think: "bonus room" above garage of modern-day two-story homes).

I would think that leaving the existing floor in place will be far easier, and should present no structural issues. If you're saying there's an intermediate wall or girder in the basement that's supporting the floor, say at approximately the middle of the span, all you'd have to do is build your new pony wall directly atop that ... basically, just recreate the existing floor, except four feet higher. As long as the bearing walls line up above each other all the way down to the foundation, you'll be golden. (Technically, you'll be increasing the load on the existing footings, with the weight of the new floor and whatever you store in the new crawl space you will create; but the sizes of modern residential footings usually have lots of reserve capacity.) It's neither required nor practical that the walls supporting a given floor have to be continuous all the way down to the foundation. All you have to do is make sure they "stack" atop each other.

Carpet: As long as the rooms are the same size and shape, you ought to be able to do this just fine. You'll need new pad, but that's cheap.

Stairs: Could be easy and cheap, could be difficult and spendy. It all depends on the design of the stair, what needs doing, what you want it to look like, etc. I would certainly agree that if this area needs work, this would be the time to do it.

[JeremyM]

Something I would definitely be thinking about is all the dead air space.

Are you going to be cooling and heating that 4' of space between your old floor and new? Are you going to have fresh air going into it and recirculating?

Personally, I wouldn't want a pocket of dead air like that. Yes, I know some subbasements are dead air, but most have some vent to the outside. Got any buddies that are HVAC men?

Otherwise, you've gotten good advise on the structure. Pony walls or stripping some drywall and attaching to the studs.

Just some random thoughts.