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in ireland, architect’s are not used to building stick frame, so i would like your input.
i’m building a 1.5 storey house. the architect is proposing a platform build. but the second floor exterior walls are only 20″ high. then by the regulations, the kneewall is a further 3′ into the house. will these small external walls not topple over, or is ther something else i should do to prevent this?
appreciate the suggestion’s guys
good stuff
Replies
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eddie, you should be fine if you , 1. are using panel sheathing such as plywood and have a full sheet start at your top plate and run down over your second floor rim and on to your first floorframing. If you use your rafters tied into your exterior (20") wall and your interior pony wall they will provide some lateral bracing. You can also run a diagonal brace from the top plate exterior wall to the shoe plate of your interior pony wall which would provide better bracing if you are not using a sheared roof sheathing, ie using skip sheathing for the roof rather than plywood.
With out knowing framing details and specs, I wonder why you cannot just frame the full heigth and ledger your floor rim, aka, balloon frame? But then that seems to be the underlying question you have.
walk good
david
*I would want to do it balloon frame or with a structural ridge supported on the gable end walls.Simpsons harware makes some brace mounts for this kind of application too if they are available over there but that seems like the expensive way to correct a poor design. Has he had an engineer review it? Or have you?Architects are well versed in "Documentation 101" so they can blame the builder if something goes awry. Ther could be some fine print that says, "Builder shall make diligent effort to certify...Blah, blah, blagh"
*I suspect you'd have to have a structural ridge beam to keep from having outward thrust at the walls. You could always brace them back to the wall that's 3' in if you wanted to.
*eddie.. properly built, this detail sounds great...with your 12/12 pitch that means the kneewall is going to be almost 5' high... and the back of your closets will be almost 2' high...good use of space..lots of tricks and structural details already mentioned to make this work..i like structural ridges..and the balloon framing would be cool too.. but i bet this architect is way ahead of us...like i said earlier.. your plan has all the earmarks of a classic New England Cape Cod...
*mike, have you got a thing for 'capes'?thanks for the responses though.so how would you 'properly build' this detail then?enlightenment please
*just the way the other guys described it.. but 1st , i'd ask your architect.. i think he knows..anyways , the bearing walls would be balloon.. from the 1st floor deck to the bottom of the roof bearing platethe 2d floor joists would sit on a ledger let into the balloon framed wall.. the roof would sit on the double bearing plate on top of the wall... and the ridge would be structural at each gable and one or two or three midpoints
*mike, would this mean that the ridge would need to be bigger then a 2x?would a 2x ledger be big enough, and when i let it into the wall, would i let the floor joist's run in beside the stud's?thanks
*eddie.. a structural ridge is just that.. it's "structural" in that it acts as a beam.. it has to carry the live and dead loads imposed on it.. so someone has to do the beam calulations...the moment is DOWN as opposed to a conventionally framed roof where some of the moment is OUT and some is DOWN.. which is why everyone was calling for a structural ridge.. no outward thrust on the short walls... sometimes a 2x will be all of the "structure " you need , sometimes it won't..the ledger has to comply with your code...usually a 1x8 ledger will be fine.. but it has to comply with good engineering and code..
*mike, the ridge beam was called for with platform framing.but if i balloon frame, will i need the structural ridge?i ask for your opinion only, so i'll know, no strings attached. i will be checking all this with an engineer, but would like the knowledge to know what to ask, know what i mean.good stuff
*eddie.. draw a moment diagram.. show the forces.. the rafter forces are down and out.. working on the moment arm of the 20" wall.. if the studs are extended thru the 2d floor platform AND are strong enough to resist the outward thrust for EXTENDED DURATION, then you could balloon frame it without a structural ridge...if they are just 20" walls (NOT an extension of the first floor studs) then they will probably just tip over.. i'm not an engineer.. but these calcs are all available in most code books.. and simple structural design books... your jurisdiction may require a Professional Engineer or Architect to run the calcs and attest to them... with my building inspector i can show him the math and teh references and he might accept them.. in the bigger towns they'd just tell me to go away...and hire a PE...
*Eddy, Are you building in Ireland? My BIL just built a 1 1/2 story house there similar to what you are describing but with block walls(unreinforced). The architect simply used steel beams to hold up the roof at the ridge and at points 1/3 up the roof. This also allowed the builder to use smaller rafters. This would work with a framed building as well, though a structural ridge would suffice.
*mike,i like the idea of the non-structural ridge, if it is ok.my exterior walls will be 2*6 , and at balloon framed will be 12' tall, with ground floor ceiling landing at 9'6". with the joist's running into the stud bay's, and being nailed off to the stud's, how well do you think this would operate, for the life of the building.
*eddie , i have no idea...i'm not a structural engineer , i'm not familiar with the materials available in Ireland, or the techniques you guys use.. ..i don't know what weight /sf you roof system will be.. nor what spacing your studs will be on, single plate vs. double plate.. yada , yada , yada.. if i were building it for myself , i'd design it to suit.. probably just the way you will wind up doing it.... i still want to know what your architect / engineer have to say and the local codes that applyyou've got enough info now to have a pretty good discussion with them..so go get 'em tiger !
*thanks mike
*Two similar examples I have seen recently.1) A Barn with a second floor. Ballon framed as described, Second floor plate height about 4'6". Width of the building about 25'In order to eliminate the structural ridge board the engineer required2x8 ballon frame walls.2) A second floor remodel that had ballon framed 2x6 walls and about2'6" second floor plates. Only 22'wide No Structural ridge, but when converting this space to living space the inpsector required Bolted2x10 collar ties that ended up about 25% of the way down from the top.You can do it with ballon framing, but the structural ridge might end cheaper by the time you are done.
*thanks dave.would i still platform the top end of the gable wall, or balloon the whole gable wall - fairly hard to handle?thanks again
*Why eliminate the structural ridge? Do you want the structure to last? Design a rational load path to the ground. Do not attempt to use "magic" to hold the building up, in order to save nickels and dimes.Dave [email protected]
*We have as an afterthought buy the homeowner, put 2' tall walls on the front and back. We braced them down through the deck ply wood to the side of the floor joists. We cut out a rectangle in the floor just big enough to accommodate a 2x4 at 45 degrees. It was an unfinished area over a garage. The building inspector didn't have a problem with it. I don't remember if we went every 48" or 32". Been a while since we did that job.