My floor plan- how do I frame this?

[MushCreek]

I'm going to post a rough sketch of the basic floor plan I've been tinkering with for over a year now. It's a cross gable, with the main gable being 20 X 38, and two 12 X 16 wings. The primary reason for this is that it affords ventilation, with the three major rooms having windows on 3 sides. We like the windows open whenever possible! This will be deep in the woods of the SC mountains, so there is a view in all directions, but the main view is out the back. With this layout, the parlor, kitchen, and master BR all have the view. I'd like to have a room upstairs in the main gable, to provide access to a deck over the back porch. My concern is in how to frame the upstairs over the opening into the parlor. I'd rather not have a beam or anything visible defining the opening to the parlor, since it is only 12' deep. The upstairs would be a 1/2, with maybe a 4-6' wall height at the eave. Is it practical to support that 16' opening into the parlor? I'm also planning a basement, but possibly under the main gable only, so support on the first floor is not a problem. While we're at it, does anyone see any screaming flaws in this design for a couple empty-nesters?

[Don_P]

If that's a full masonry chimney I'd continue foundation over there and tie it to the main footings. Might as well put in a basement woodstove over there at that point. If it's a lightweight zero clearance type chase then piers would be ok.

I did muff it last night, with continuous joists the piers carry 13% of the floor load. As individual joists, lapping at the main building, the outer piers carry 16.5% of the floor load, so maybe a 20% lightening of the pier's load but not half. From your description I would call that a 2,000 psf bearing capacity soil, your inspector should be able to provide or confirm that number if asked politely.

I'm not understanding the second floor, if you can open the picture in paint and outline the scond floor in a red line it would help my visualizing it.

The parlor could be open using a structural ridge beam to hang the rafters from. It will require an adequate post at each end, carrying the post load down to adequate footings. Is there somewhere you can tolerate a post? Just thinking on the fly... if the chimney is a wood chase and if it could be moved to dead center of the floorplan it could be the support post with LVL ridges going all 4 ways out to the gable walls. It would certainly change the focus of the room though 

[MushCreek]

I'm not real worried about the fireplace for now. I outlined the second floor- it's the size of the entire main gable. As you can see, it's supported all around the perimeter, except for the opening for the parlor, and the doorways for the master BR, closet, and bath, but there's intermediate support there. All first floor ceilings are flat. The red outline is also the proposed basement outline, which solves the problem of supporting the first floor. Depending upon cost, I may put a basement under the whole thing. I could then support the first floor with load bearing walls/columns in the basement as necessary. I'm trying to avoid a visible support at the opening to the parlor, to give the impression that the parlor extends all the way over to the stairwell, making it seem bigger. Otherwise, that area becomes a big hallway.

[PEG688]

The ground floor pretty simple use 20'  I joist across the main area , the one the foundations under. I'd use two beams under that floor one right under the parlor side stairwell wall , one under the master bath area , make sure this beam is off set from any major plumbing fixture mainly the crapper thats the one that will give you trouble .

The reason for the beam under the stair well wall is to make it a bearing for that floor area above. Run a beam , maybe a exposed GLB hang or if it's a exposed beam , set the 2nd floor joist on it . maybe run that beam to a "T"  at the kitchen wall and use it to change directs on the joist above the kitchen area to reduce span down to what about 13' if you run from the end wall back to the "T" beam area at the stairwell head.


There's a few other ways you could do it but thats my first take on it. Beam and joist size could be done by the lumber yard and or beam and I joist provider.

   

 
 

[Don_P]

sure the ceiling can have a flat unbroken bottom plane, that just sounds like a flush girder across the parlor end. There would be a built up girder, probably several plies of LVL's that will sit on top of the parlor walls at the corner.
Are the walls along each side of the stairs in the basement? are they on the main floor? I'm wanting to use them as load bearing walls if so. Running the joists over the kitchen dining the short way would allow them to be lighter but the thrust from the roof needs to be restrained some other way if this is done. The wings bracing the middle area provide restraint in that area so the joists could run either way.

This is one doodle, I'm not thrilled with it yet; Trying to keep the load on the 20' girder low, it will have roof load coming down on it as well. Notice the flow direction I gave the stairs coming down from the second floor into the kit/din area... I could span the ceiling better and still have headroom going down the stairs that way but I'll bet I'm basswards there. More info and another round?

[MushCreek]

The wings will be one floor only, so I can use trusses over them for roofing. I had planned to platform frame the main section, partially because I want 10' ceilings on the first floor, which would make for some pretty tall walls to deal with when framing. If the second floor is a platform, does it matter which way the joists run? While we're at it, when building a true second story on a platform, what keeps the walls from thrusting out? I know I need collar ties for the rafters. I plan a 12/12 roof pitch, and only need an 8' ceiling upstairs, so if my knee walls are 4', my collar ties will span about 12'- that should be plenty. I assume some support also comes form the ridge pole? I've only built with roof trusses in the past, so I'm new to this kind of framing for a roof/2nd floor. If I do build the second floor, the 14 X20 room at the back would be an MBR; with a bath on one side of the stairwell, closet on the other. The front part could be storage or even trusses, whatever is easiest/cheapest.

I have no problem with having load bearing walls around the staircase all the way to the basement. The stairs are there anyway; I don't care if they're walled in. It would make more sense, though, to have the stairs go up from the foyer end.

Further explanation of the positioning of the house on the lot- The garage is the same side as the road, but you can't see the house from the road, it's on the other side of a small hill. The driveway comes in from the left, and makes a 90 degree turn, facing the house. The view is NNE, not the best exposure, but our main concern in SC is keeping cool, not keeping warm. We like cold weather- our house here in FL got down into the 50's this year (inside).

[OkieJohn2]

That floor plan reminds me of one from a Taunton press book from years ago, I am pretty sure it was from "More Small Houses".  I no longer have my copy of this. 

[PEG688]

One note about "I" joist hangers the top mount type tend to squeak to high heaven. Even if you glue the joist into the seat of the hanger. I like to avoid hangers where ever possible.

YMMV.

The other thing about "I" joist is they tend to be bouncy / they deflect. The chart / span tables will give that deflection amount on them but most people tend to want to save money and think " How  bad can it be?" then after try to figure out ways to add support to reduce the bounce.

     
Some things to think about when using "I" joist.

[MushCreek]

I've heard that they are bouncy as well. I'd be happy with a beam and regular 2X joists for the first floor, or maybe even steel joists. I don't know if they are bouncy or not, though. I've gotten pricing on stamped steel joists, and they're not to bad. They have holes for ducting and wiring, too.

[PEG688]

"I" joist are bouncy when you over span them, and it really not over spanning it's spanning to the outside limits of the product. Sales / marketing ideas can run counter to good building practice. By maxing out products to end limits they have given the product some bad attributes / history , sure it "saves" a few bucks going in but ................ if you get my meaning.


 

[MushCreek]

As a life-long toolmaker, I tend to overbuild everything. When a span comes close to a limit, I go up to the next size as a matter of course.

[PEG688]

As a life-long toolmaker, I tend to overbuild everything. When a span comes close to a limit, I go up to the next size as a matter of course.

That works for regular lumber but it , IMO , does not quite make it with the engineered joist. You don't quite need to cut the span in 1/2 to get a stiff floor but it's closer to 1/2 than 3/4 , so about 5/8 , or a 3/8 reduction is a better rule of thumb.

The sales guys get into all kinds of math contortions with floor loads / dead / live loads , Vs deflection per joist , OC of joist , sub floor thickness , yadda yadda yadda.

But if you take a chart and reduce  the span by about  one  3rd you'll have a good floor.



G/L PEG

[Don_P]

You asked how thrust is restrained upstairs. One way is that the ties are allowed to be raised 1/3 of the distance between plate and ridge. It typically requires a deeper rafter to account for the increased bending load in span., Then recycle back through to see if that is an acceptable kneewall. In this ridge board or risdgepole type of construction the ridge is simply something to nail the rafters to, it is not figured as support.

The second way is to use a structural ridge beam with the rafters hanging from it. The ridge beam needs to be sized adequately and supported down to the ground. If the ridge beam cannot sink or sag the rafters hanging from it cannot thrust on the walls. So there's the two main approaches. I'd try the upper approach first and if doesn't do what you need then try the other.

Actually I joists are stiffer than solid sawn. We can span further with them, they have little mass. The term bouncy can be taken two ways. It is often more like a snare drum than a trampoline, it's easy to excite that taught light drumhead. In those cases more mass can help, but typically if you size them using the "improved deflection" chart, basically what PEG is doing, they work well at span lengths like this. "Deeper is cheaper", depth improves a horizontal member faster and cheaper than making it thicker if the design allows it.

I don't see either approach affecting joist direction on the main and second floors. If there is a post at each end of the master side of the stair wall as mid supports for crossbeams they could run the long way in three sets 12', 14', 12'. Shorter spans, more hangers if this all wants to be smooth ceilinged.

Soo, which way do you want to run 'em? Think about plumbing and heating runs maybe.

[Don_P]

No siding today, I doodled over another liesure pot of coffee this morning. One thing to check early in design is that the stairs work.

You had said you wanted a 10' ceiling. I assumed that the 2nd floor would frame with 2x10 depth, this should yield a 130" overall rise. There was a 14' long hole drawn. First I divided the rise in increments of risers until I got an acceptable rise per step. With 17 risers the rise is about 7-5/8". That would mean there are 16 treads, so 168" overall run/16=10.5" tread. A tad steep but they work. Maximums are 7-3/4 rise x 10" run.

[MushCreek]

Wow! Nice work- thanks! I'll have to check the SC code- they follow IBC 2006. We wouldn't have to have all of the stairs within that opening- I don't mind if there's a bit of slanted ceiling under the stairs in the kitchen. So we could add another step or two. And I don't HAVE to have 10' ceilings, although I would like them to be at least 9'.

You can only move the collar ties up 1/3? If I have a 20' span @ 12/12, that's only 40", which added to my 48" kneewall is only 88". I'd probably plan on going up at least a foot more with my kneewall to 5'. As it turns out, the left side of the stairwell is on the gable centerline, so it would be easy to have ridge support there going all the way to the basement, if I decided to go the ridgepole route. Knowing me, I'd probably do both!

I'll have to think about joist direction more. Despite having a subfloor, I've been advised to have my hardwood floors cross the joists at right angles wherever possible, and to fasten through the subfloor into the joists. I need to look at what makes sense as far as laying the flooring.

[MushCreek]

I'm bumping this up for more discussion. I've done some more sketching, and found I could make the main part of the house 16' wide, and still do everything I want. I also extended the parlor wing enough so it can be a discrete room. This allows for a beam across the opening, and maybe even a couple posts for appearance and support. Basically, I'm looking at a 16 X40, and two 14 X 16's, one on each side. I'm thinking the smaller sizes will make everything more manageable for a one to two man crew, and the spans are pretty small.

When you calculate the linear feet of wall, you realize just how inefficient a design like this is. As is, there are 168 linear feet encompassing 1088 sq ft. As a square, the same square footage is only 132 linear feet, or 20% less. Aside from the obvious increase in building materials, do you think I'll be paying heavily in increased heating and cooling loads? I'm planning a lot of insulation- 6" walls, plus a barrier layer of foam on the outside, and heavy attic insulation. Am I fooling myself in thinking that the small spans will really make it easier for a small (often one man) crew? Somehow, if I think of it in terms of building 3 small buildings, instead of one big one, it seems less daunting. I like this style, both for its looks, and for the aforementioned cross ventilation. One more change I'm making is to drop the roof pitch to 8/12, and the side walls are increased to a full 8' upstairs. This eliminates any valley work, since the wings are only one story.

Thanks to the ongoing economic situation, I'm having to keep re-thinking my design. 3 years ago, the money I would have gotten from the sale of my current house would have allowed me to pay someone else to build my dream house, and there would have been money left over! At the current asking prices for houses around here, I would have enough to build my original plan- if I did most of it myself. But those are asking prices. As selling prices drop, I keep trimming the square footage, and I've actively considered putting the whole house on piers to cut costs. Next stop will be a single-wide, up on blocks. I'm also keenly aware that many, many people are in worse shape than I am right now, and that I should quit my whining. I'm just trying to figure out the easiest and cheapest way to build a functional and interesting house. Thanks for any input!

[Don_P]

I'm a little lost on the posts and beams but it all sounds ok on the face of it. I just finished framing a 20' wide solo and have done several 24 wides by myself. The dimensions aren't really that big. If you outsmart the inanimate objects there is actually very little that you can't do singlehanded. I set some 8x10 rafters solo this winter. Didn't set any speed records but it was as much fun figuring out how to do it as doing the actual lifting.
I notched in and set this 10x10x24' one Saturday by myself after the help was whining about it. I sure don't want to talk you into anything dangerous though. The main thing is to think through stuff and don't get hurt. It never hurts to have the cell on you when working alone either  .

[MushCreek]

Having the right equipment and knowing how to use it is the key. I moved my machine shop 3 different times single-handed, with equipment as heavy as 3500 lbs. , and no forklift. It takes longer, but you can do it alone, and safely. That being said, a co-worker of mine died in a fall off of a ladder working on his cottage in the country. I never did hear the exact circumstances, but it will remind me to be careful! I'm thinking of renting an off-road man lift for my roofing and other off-the-ground stuff.

[archangel]

I'll never understand the reasoning of putting the fireplace on an exterior wall.
Most of the thermal mass is outside!

I seems to me that it would be a good idea to have it all inside the building adding thermal mass and allowing any heat from any part of the fireplace to remain inside the house.

[MushCreek]

True- an outside wall doesn't seem to take advantage of thermal mass. The old capes in New England were almost always center chimney, and the chimney/fireplace structure was massive. I think the idea of putting them on an outside wall comes from people adding them to a house that never had one, and it is (or seems to be) easier than cutting a hole in the middle of the roof. For myself, I like to be able to sit by the fire and look out the windows.

[MountainDon]

Unless the plan is for a heavily built masonry fireplace and chimney I don't think it matters at all if it is central or not. Most folks use insulated chimneys and zero clearance fireplace inserts. Those don't act much like the heat sink a masonry unit would be.