We’re building a cape that is 1 1/2 stories (4′ kneewalls upstairs). Its my impression that balloon framing the load bearing walls using 13′ 2X6s would be better than platform framing it. A couple of builders I was consulting with thought not. One suggested using triple top plates on the second floor to stiffen things. THe other said the collar ties would do the job.
It just seems to me that the floor joists in a balloon frame would do a much better job of keeping the walls from spreading.
Thoughts?
Replies
Collar ties won't do a dang thing for you to prevent that kneewall from spreading out. You need either ballon framing or qa structural ridge, or a combination of both.
Triple top? maybe do something, but have things engineered if yiou want it to stay put. Chinscratch ingineers don't count.
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piff,
I think the ballon framing point is a good one. Why break the studs at the floor? But at any rate, you say no to the collar ties. Since the rafters start on top of the four foot knee wall, a collar tie would be "more" effective than in a classic case (ie say rafters runing from a 12 foot high ridge to the floor where the collar would be in top third in that case). In the 1 1/2 case teh collar tie could be well into the bottom third. NO?
All said, why not ballon frame anyway. And be sure the design has the collar ties low enough. Or, what the heck, ridge beam.
Jackofall,
I would do it with ballon and use a structural ridge, both, for redundant support.
Bu there would also be some tie supporot in the cieiling joists, which you and others here have been calling collar ties. They are not collar ties when they are in the lowere third of the roof system, though, whuich is where they need to be to yield any significant strength. In that position, they are called rafter ties, and they ned to be fastened adequatly to resist outward thrusting forces. An engineer defines what is adequate. A few sixteens is not up to that task.
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piffin, you are right in that I ahve frequently been think of rafter ties as functioning as collar ties. Ridge beams do solve many issues and gives you freedom.
I think it's a great method for story and a half , the house I live in now(1940's) is framed that way and I'm planning to build a new house in two years or so using the same methods. I think it will use less lumber and be structurally superior.
I'm currently converting a 1914 three story balloon frame into a five suite condo building and here the balloon framing works against me because of the need for fire blocking at the ceiling and floor planes.
They built that one with 23 foot studs and 32 foot long floor joists!
cheers ...........Rik.......
23' studs and 32' joists, back when men were men.
<23' studs and 32' joists, back when men were men.>
32' joists!
And trees were trees.
Edited 12/19/2004 7:42 am ET by rez
I plan on building a 1-1/2 story cape one day......
Piffin, what is wrong with building your 2nd floor deck
putting rafter plate on top of deck, then raftering off of that
You wouldn't need a structural ridge, just your ceiling joists at
8' height or whatever. There wouldn't be anything to spread
as your 1st floor walls would be tied of with the 1st floor deck.
Edited 12/19/2004 6:13 am ET by butch
My house is built that way. I think the original poster wants to have the rafters set much higher than that so there is more floor space available. Then the baloon framing makes sense because of the outward thrust. That will also cause the shape of the cape to be out of proportion, so I would probably nix the idea and go for a 2 story myself, although it isn't a bad idea for a 1 3/4 story cape.
That makes sense
I was reading it different
Proportion of the 1 1/2 is quite nice. An photo is attached. THese things are all over the Maine coast. This is essentially what I'm hoping to reproduce.
That is a very nice looking house, but here the capes are pretty short, and are called 1 1/2 story, although they are really just one story with small attic room(s) upstairs. I suppose what you show is really 1 1/2 story though. I would think baloon framing is the way to go, but I'm not qualified as an engineer. A lot of the material these days is not of the same quality as it once was. Actually none of the lumber is as good.
My sister and bro-in-law lived in a story and a half house. I wouldn't have really called it a cape, more of a farm house. Big porches. It was ballooned framed. The ridge of the ~90 year old house had become swaybacked and the exterior walls that were (supposed to be) parallel to the ridge were bowing out. The 24" O.C 2nd floor joists which were real 2x8s (I think) had already been sistered two times. They were exposed on the 1st floor ceiling. There was a significant amount of floor bounce in the second floor, which I would guess spanned about 20'. An engineer was called in to prescribe a fix. Then a second opinion was hired. The house was condemned and they were mandated to move out before snow season (NE Penn). My conclusion: Story and a half houses should be built with structural ridges unless the ridge is supported in several mid-span places down to the foundation by other significant means. You draw your own conclusion.
Question: what is the generally accepted practice for supporting 2nd floor joists at the walls on a modern balloon framed home? Let in ledger? Framing anchors? Matt
Was there a continued ongoing movement in the sway and walls bowing out that was noticable as to cause the calling in of the engineer and the second opinion?
Was it the request of your bother-in-law for the services or was that also a mandate from the city?
I guess what I'm inquiring is how the city got involved in the first place as to condemn the house while your kin were living in it. I'm guessing it was a rental?
The property (120 ac) belongs to the local university. BIL is the caretaker. The house was the caretaker house. Not sure who called the engineer in to start, but I think it was because of the floor bounce. Not sure how it ended in condemnation but maybe it was because it was kind of a public facility. BIL & Sis were fine with it as they got a new house out of the deal. The old one had it's charm, but I felt like it was like camping out when staying there. Many old houses from that era have a few cool architectural elements, but this one never did and the unmatched plywood kitchen cabinets, unlevel floors, and old leaky pot bellied stove were pretty rudimentary for a full time home. I love old houses, but this one was a POS and structurally unsound. You could easily see the bow in the walls and the ridge. I would have enjoyed taking the first coupla hits with the track hoe bucket.Matt
We let in a ledger and hang to it with joist hangers rather than setting on top og it. Either way works. The thing to keep in mind nowdays tho is to install fireblocking.
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That is a story and a half Greek Revival, not a Cape Cod house
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I have a question or two.
First, how do you ensure your walls are square when you ballon frame 1 or 2 of them?
Whats the benefit of ballon framing? The negatives?
Whats the biggest determining factor on choosing to ballon frame or not?
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Edited 6/30/2005 10:09 am ET by sailfish
square any two walls by squaring the lines you set the bottom plates to. After laying out lines square to each other on the deck, plumbing the walls up from thiose lines results in walls that are square to each other, if you have straight lumber.Benefits? I suppose the guys of the 18th and 19th century had their own advantages in mind when they did so many this way. I'd gues that for them, one advantage might have been fewer pieces overall to cut. Remember they were using hand saws and chisles with elbow grease.
We already discussed above here the structural advantage of ballon framing for certain styles of building. Disadvantages - we now recognize that the open bays from sill plate to wall top allow free air flow that adds to chimney effects fanning any fire that might find a waay into the wall. A house will go up in flames much faster and burn hotter that way, so fireblocking is now required to be added at regular intervals to prevent flame spread and act as draft stops.
longer 2x4s are more expensive than eight footers too.The only time that I balloopn frame is when the second floor has a short kneewal that might be pushed out by the lateral forces generated from the roof rafters when a structural ridge is not practical. Off the top of my head, this has happened with me more often when building garages with overhead storage or apts.
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Good stuff.
My guy is somewhat insistant about balloon framing the 2nd story gable ends. I can't figure out why??? He had asked to have me order the trusses with out gable ends and instead go with the scissors throughout (ends included) cuz he was going to ballon frame. He said it was "stronger" than the alternative??? I'm leaning heavily against this and ordering the trusses with the ends gable.
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Might be a terminology lapse here. I wouldn't comment further without seeing the whole design
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Butch,
There is no concern with the walls of the first floor spreading; like you said, the second floor joists will hold them in place.
The concern is that the 4'-high walls of the second floor will spread. The rafters apply both a downward and outward force where they hit the top of the 4'-high wall. Visualize this framing interface as a long piano hinge and you will understand the issue.
There was a FH article about this a few years back.... if you were really interested you could probably find it online.
Man I just got prosperoood
Just spent a few minutes replying and when I hit post it went to a page
that said this page is unavailble.
Let me try it again,
This is a great forum for those who have a great command of the written word
and that is why I do more reading than posting.
But, I misread the initial post and thought he was refering to a 4' knee wall
in 4' from the outside wall and not a 4' wall at the outside plate line above the
first floor ceiling joists. Does that make sense? Now maybe I'm on the same
page as everybody else is.
Take a look at the picture in post #10 of this thread and it will all be clear.
BTW I am planning a couple of A dormers on one side of this roof.
I'm on your page now, too! It's hard to describe three-dimension problems with words alone.
butch, I think the poster wants four foot walls even with the outside walls of the first floor. Your plan, which I personally prefer the looks of, would have the knee wall set several feet inside the first floor exterior walls.
No?
OK I'm going to summarize what I'm getting from all the posts.
It seems that collar ties that are below the 1/2-way of the triangle in conjunction with balloon framing will solve most if not all of this problem. But maybe not so:
Add a structural ridge as a reassurance but to avoid having a mambo beam it probably needs some kind of post supporting it in the mid-section. This post has to go 17' (13' inside the triangle + 4' of kneewall) down to the floor on the second story (thats quite a long post!). This point load then needs to be carried by a wall in the first floor. FInally that first floor wall better be over a beam in the cellar.
If I can pull all that together, I will never see so much as 1/16 of inch of roof sag even if snows 5 feet of slush!
The thing that puzzles me, is that you see these 1 1/2 story farmhouses/capes (whatever you want to call them) all over the place. Around here they were mill-workers houses. In Maine, I assume fishermen built them and lived in them. In the midwest I would guess they were built and occupied by farmers. I've never seen one with roof sag or wall spread. These guys didn't have Microlam beams or degrees in engineering. THe trim packages on the ones in Maine show more than a passing interest in carpentry though, so maybe these lobstermen knew a thing or two.
One big difference between common construction of today and 100 years ago is room size. In times past stick framed roof configurations could more readily be given midspan support because the "open floor plan" was not in vogue. Matt
Many architectural books call this type structure, "vernacular". Given the Greek revival detailing, the picture shown could be called a "Greek vernacular".
Structurally, these were built with center walls dividing the floorplan that supported the ridge board, and with balloon framing.
the carpenters were quite skilled in yonder ages, possibly more so than today. The houses built by unskilled fishermen or jacks of all trades have long since fallen down.
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The houses built by unskilled fishermen or jacks of all trades have long since fallen down.
Might you be referencing that old ramshackle place across the street from the end of your drive that you should have gotten and redone? :o)
What ever happened to that house?
Edited 12/21/2004 2:05 pm ET by rez
glass in the windows is still holding it up
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Yeah, ifn I'd only "read" the subject of this post I would have been on the
same page as everybody else
Balloon Framing 1 1/2 story cape
Happens more often than not. As long as everyone remains calm it is part of the fun. The conversations snake all over the place. Some people get burrs under there saddles, but most don't.
what you are refering to is a cape, not a 1-1/2 story in my thinking. The balloon frame is needed when the outside walls are partway up, say 44" tall. what you describe would have the kneewalls as interior walls, non-structural.
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I helped a friend frame his house about 8 years ago using just the method you describe. I think he used 14' 2x6's to give him a 9' ceiling height downstairs and a 4' plus or minus kneewall upstairs. It was surprisingly easy and quick for the two of us to build the walls this way.
The knee walls seemed much stiffer, while we were working around them than what I would have expected if we had platform framed them.
We cut all the notches for a let-in 2x6 ledger with the studs flat on the floor. We clamped them together and cut the notches out with a circular saw. Then we raised the walls and went back and nailed in the ledger. Itwas simple then to set the 2x10 floor joists on top of the ledgers and nail them off to the studs.
The only real difficulty was making sure that the stud layout was dead on and that we had spaced everything properly so that all the joists would work. We didn't sheathe the walls before raising because we were afraid that they would be too heave for the two of us to lift.
A triple top plate won't do much for you but would not hurt. You need to focus on taking the outward pressure off of the wall. Either collar ties at a specified height as determined by an engineer or architect, or a structural ridge beam are required. You could have the collar ties left open as a design element or drywall your ceiling to them which would provide for greater insulation. A structural ridge beam though would solve all of your problems.
I had an (real) engineer design a system for me for a very similar application. A 5' knee wall with 2x6 collar ties set at 8'. However, there were dormers on both sides and where the ties couldn't go their full distance we doubled them up and he spec'd in 4 3/4" through bolts at each of those connections. We also had to use 2x12 rafters to get the width for the connection, on a 8/12 roof with a rafter length of 16'. We had to use 18' 2x6's in most places. Hindsight being what it is, I think a structural ridge would have been quicker and cheaper. When in doubt, find an engineer. Mind you, this p.eng is a cut above the rest imho for creative solutions and not way overbuilding. 2.5kpa snowload factor.
ian
My structure will be 26' wide and 32' long with 12/12 pitch 2X12 rafters. So with the ridge running in the long dimension what kind/size of structural ridge should I be looking for? Our snow loads are 40psf here in western Mass.
The designer I hired was the one who told me triple top plates would do the job and nixed the balloon frame, I eventually gave up waiting for him to finish the design so I'm finishing it. I'm really not looking to pay yet another person to fart around with my design. I'd rather put the money into the structural ridge and a few other (possibly overdesigned) features if necessary.
Whats the best way to attach the rafters to one of these ridges? I presume nailing with 16D nails isn't the way to go. Given the 12/12 pitch I'm guessing there must be a nice rafter hanger that is available for this application.
thanks
You will need to have at least one post (and preferably two) for a structural ridge of that length or else you will need a HUGE ridge. I probably would opt for balloon framing and collar ties at 8 ft . The collar ties would be in the bottom third of the rafters and would counteract the out thrust. I would probably not use 2x12 rafters for the 13 ft span either. 2x10's or even 2x8's are adequate for this span and a lot cheaper.
In any event do not use the guy who suggested tripling the top plate. We have used 2x10 double plates in the case of a ten foot room in place of a structural ridge and we have used steel beams bolted through the plates for longer spans but these were unique situations unsuited for a structural ridge or collar ties. A triple 2x6 plate 32 ft long would do nothing to hold the roof up.
Do you have any stacked bearing walls or posts in your design that would divide the 32 foot span of the ridge? You must be able to, unless you are building this thing to house a squash court.
If you are starting with a clean sheet of paper, you should see about doing this. Then an LVL ridge can be sized to take your worries away. One load path down from about mid-span will make your ridge span only 16 feet, and an LVL can be readily sized.
Don't worry about a window being centered in a gable wall and fouling your ability to get a post under the ridge end. You can header over the window, and post up under each end of the header.
With a structural ridge, you can platform-frame the house, and won't need to be concerned about your kneewalls kicking out. They will be handling the downward load only, coming from the half-spans of the rafters.
The main ridge of the cross-gable roof shown in this pic, is structural. Look at the size of the window in the gable that has a header over it to pick up the ridge end load.
View Image
Edited 12/20/2004 1:14 pm ET by Gene Davis
Gene (and all),
I've got a situation with a 1-1/2 story house where there is original balloon framing. However, due to large first-floor windows (both regular windows, and rectangular bays), the nice, long balloon studs are necessarily interrupted over the window openings. What's left at the top are relatively short studs connecting the top plates to the header over the windows.
I've noticed that some spreading of the "second" story half-walls has occured directly over the large, first-floor windows. Is there anything I can do to prevent further spreading that wouldn't require major structural work (like adding a ridge beam)? I have an opportunity to do some structural work over the first-floor window headers since that area is going to be remodeled.
Any ideas would be appreciated. Thanks.
"I've got a situation with a 1-1/2 story house where there is original balloon framing. However, due to large first-floor windows (both regular windows, and rectangular bays), the nice, long balloon studs are necessarily interrupted over the window openings. What's left at the top are relatively short studs connecting the top plates to the header over the windows.
I've noticed that some spreading of the "second" story half-walls has occured directly over the large, first-floor windows. Is there anything I can do to prevent further spreading that wouldn't require major structural work (like adding a ridge beam)? I have an opportunity to do some structural work over the first-floor window headers since that area is going to be remodeled."
I'm trying to picture where your ceiling joists tie in in this scenario. I'm imagining they are low, relative to the center of the short studs, allowing the top plate to bow out more in the window sections.
I once read a case study where this sort of spread problem was fixed by building structural top plates. Basically, the plates were pulled plumb using cable winches, then a length of steel angle was bolted over the top plate to resist the lateral forces.
There was also something in FHB recently about building an odd cathedral ceiling structure that use steel to reinforce top plates.
On this particular house, the balloon framing extends up about 32" above the second floor. On the main floor (which has nine foot ceilings) there's about 22" of vertical surface between the ceiling and the window heads. The floor joists (between the main and upper floor) are 2x8s.
Before reading this thread, I hadn't thought of the possibility of strengthening the top plates against horizontal loading. It's an interesting way to tackle the problem.
Here is a rough graphic of your structure, showing a structural ridge.
The pic shows posts in red, with one at mid-span. The post can be out away from a wall, and be visible "just as a post," or of course, it can be buried in a parition wall.
Not shown, are how the posts are in the main floor framing, to transfer the load paths down to the foundation (walls, piers, footings.)
Shown in blue, are your short pony walls that support the rafter ends on their top plates. They can be framed atop the floor frame platform.
You don't need to balloon frame, nor do you need collar or rafter ties, if you do the structure like this.
Thus speaketh me, a bona fide structural engineer, with my old sheepskin up on the wall, in a frame.
Gene: thanks for the diagram. From looking at my plan I can send a post down from about the mid-section of the ridge and land it on a wall in the first floor. I could then insert a 4X4 in this wall at the point of bearing and stick in an extra lally column/conc pad in the cellar right under the 4X4.
I kind of wonder what kind of post I'm going to use to go 17' from the ridge to the platform on top of the bearing wall though. This goes through a closet on the second floor so I won't have to look at it.
I need the collar ties for insulation of 2nd floor ceilings and have windows in the center of both 2nd floor gable ends so I'll have to header the load down.
Dave, all you will need is a 4x4 parallam (3.5 x 3.5) or a triple of 2x4s at the upper floor walls, and the same for the lower floor where it bears underneath. From the main floor down to the spread footing under the basement floor, place a 3.5 inch lally column. Your lumberyard can size your ridge.
Happy framing. Happy holidays.
It's 25 below here tonight. I hope you are not framing tomorrow.
dave
If you don't want to put out any more cash I suppose that's your call but a few hundred bucks to get a peng to design you a roof system is money well spent.
Bird's mouth over the ridge or cut a bird's mouth to fit a normal joist hanger and keep the top of rafter flush with top of beam.
A copy of your local code book should have tables of max beam spans and you'll need a post in there as well. Do I need to say that the post should bear all the way down to a footing? If not, my apologies for assuming the worst. If so, I definitely reccomend hiring a pro, a capable framer will save you $ and headaches.
regards
Ian
truehaven: You say "get a peng to design". What is a peng? Professional Engineer?
yes
I ment p. eng
I would think the balloon frame would be a better design in this case. Platform framing would create an awkward 'hinge' situation.
Need for a structural ridge depends upon the ceiling design, and whether it would make for good collar ties. Interior walls can also be designed to resist roof spread, so your interior layout is a factor.
Another way to fight spread is to engineer the plates to resist lateral forces.
It may also be possible to use 'scissor' trusses on top of your balloon frame to fight spread. Maybe our resident truss man will comment.
Thoughts?
Having waded through the posts, what occurs to me is that this is an excellent case for a timber frame with infill studs. Or infill SIPS, if you have a mind to.
Why?
Because the timber frame obviates many of the arguments. The frame brings the structural member up to where the roof line begins. The roof rides on purlins between the frame rafters, which takes the "xxx ties" (will not start that argument, here, again) out of the equation, too.
That makes the dormer layout much more critical, though.
Its funny watching this problem evolve from my initial designers/builders saying "collar ties are fine" to 'you should probably timberframe it".
Now that might open a timberframe vs. stick frame debate and I definitely don't want to go there.
"collar ties are fine"
Like the collar versus rafter tie definition flame wars are not bad enough <G>?Occupational hazard of my occupation not being around (sorry Bubba)
Collar ties are meant to keep the ridge area of the roof from spiltting wide open during a severe weather event. Ceiling joists that tie the lower rafter ends together prevent the walls from spreading over time due to the forces of gravity. In in the absence of either, something else significant must be substituted, and that does not mean triple top plates :-)
Let me make a guess here - you live in an area where building code is not heavily enforced and engineering is not required.
Get an engineer's stamp on your house plans and have a nice day.
Matt
I am in the styx of western Mass. I think the state probably has one of the tighter building codes. I think this because its one of only 3 states that won't allow non-direct-vented wall heaters, for example.
In fact, the guy I was using as my designer used to be the building inspector for this area; he's a very well respected builder. He's no structural engineer but he's got a quite a few houses standing plumb and square that have been built over the years. In the end though, it was pretty clear he'd rather be out building than sitting at his computer messing around with someone's layout.
26' wide 12/12 pitch 4' walls That would put your rafter ties right at the bottom 1/3 at 8' ceiling. 13' total rise on your planned house. Should be adequate. I work on these houses all the time. Most don't even have a ridge, just the rafters meeting at the top. 2x4 rafters about 2' on center some are 19" apart and some are 28" apart. The one I am working on now has 1 20 spike each end of rafter tie. No lean out on 2x4 4' walls. The only time I see sags on these houses is from water damage and neglect.
Why not a engineered truss?