residential framing questions

huangyhg

residential framing questions
everyone,
i have a friend who is building an addition to his home.  the framing contractor did a few thing that the building inspector is questioning.  as a structural engineer (i do not have too much experience with residential framing though),i am looking for some additional opinions.
here are the problems:
1.  the contractor staggered the roof rafters 8" o/c, and thus dd not provide collar ties. he also did not cut a few of the rafters at the proper angle to correctly meet the ridge board, and placed shims in the space.  the building inspector is concerned over there being no collar ties, and the shims.
2. the inspector is also questioning the stagger in the rafters (says they should be a max of 6.5").
3. in the basement, due to not placing the basement wall in the correct place or something, the contractor notched the ends of all of the floor joists where they meet the sill.  the ends of the rafters are notched at a depth of  2.5" and 7" long, with only 4" bearing on the sill.  the max span is 16' (the other end of the joists are correct.)joists are doubled/tripled under bathroom and partition wall.
what does everyone think?  i thank everyone in advance for their help.
mark e. reme, pe
well,
from where i am,
1.  depends on the design but generally, you would need collar ties.  no shims.
2.  he's probably right, must be in his building code. i don't believe they should be staggered at all (personal preference).  nys requires they meed the ridge board and collar ties or gusset plate.  is this a ridge board or a ridge beam?
3.  from the nys building code, "notches in solid lumber joists, rafters and beams shall not exceed 1/6 of the depth of the member, shall not be longer than 1/3 of the depth of the member and shall notebe located in the middle 1/3 of the span.  notches at the ends of the members shall not exceed 1/4 the depth of the   
none of those are good.  depending on where you are, and since you mention a basement, my guess is that you have some level of snow load on the roof, there will be a fair amount of lateral thrust, so the collar ties are necessary.
poor fit-up at the ridge beam is not good either.  the shims are useless and likely won't stay in place unless fastened.  depending on load, you could exceed the allowable stress on the wood perpendicular to the grain.  further, the attachment would not likely be good.  you didn't note whether he used rafter connectors or just toe-nailed them.
joist notches likely exceed code allowable.  further, they are at the point of highest shear.  not good in either case.  also, since they bear on masonry, are they either pressure treated or isolated?

i agree with ron here.  
depending on the design, collar ties may or may not be required.  if there is a large ridge beam, no, but if it is a ridge board, yes.
generally, i do not like notching the ends of any members as it incurs horuizontal splitting and a corresponding shear and section modulus reduction, both affecting   
i hope your friend hasn't paid the carpenter.  he is lucky to have a good building inspector.  give the inspection report to the carpenter with a notice of termination and find a competent builder.
while i agree with the result of hokie66's comment, you have to be a bit careful how you go about it to prevent a lawsuit for non-payment of the contract (yes...you can get sued by the contractor for non-payment even if he has thoroughly screwed it up).
first, get a hard reference for violations of the building code or accepted practice for each of the inspector's deficiencies, not just the fact that the inspector doesn't like it.  that's not good enough. i'm not sure where you're located, but there's a building code that applies.  in addition, the building code references other documents that are incorporated into code by that reference, such as publications of the american forest and paper association that show proper wood framing techniques, span tables, etc.
the collar tie is a little different. that's a design feature.  if plans were drawn for the structure that show no collar tie, then the designer has to justify that by proving that lateral thrust is accommodated, either by essentially no deflection of the ridge beam, by lateral resistance of the wall, or black magic.  even a rigid ridge beam does not remove all the lateral thrust and it could be argued that you still have sufficient lateral thrust to cause problems without a collar tie or ceiling joists.
as for the offset rafters...that makes no constructive sense...yes, theoretically it divides the load path from one side to the other, but who cares?  it also induces lateral bending in a   
the best answers require the best problem description, you did pretty well, but we are still lacking sizes of members to help with specifics.  
as dermott suggested, the roof question can best be answered if we know the size of the ridge member, plus how it is supported (thus a ridge beam or board).  you can rest easier if it is a ridge beam (properly supported at each end by properly sized posts.)  if it is a ridge beam of appropriate depth and thickness i think the only thing that needs to be repaired are the poorly cut rafters.  the contractor will likely figure out how to reuse these members if possible, take note of how he repairs this roof area.  a well done shim doesn't concern me as much as a missing collar tie if it is needed.  if the bearing area of the rafter is in full contact with the use of shims, i think that would be alright... but i didn't see it in person.  it might be difficult to cut the correctly angled shim to really give full contact of the rafter to the ridge   
im supprised people still do ridge board + collar ties construction.  i dont see that anymore on new construction.  people either go with trusses or ridge beam.  i dont think i will ever specify ridge board & collar ties.
never, but never question engineer's judgement
all of the above comments are valid.  it is unfortunate that these things occur and the owner must be forced to accept a product less than designed.  assuming, of course, that the design drawings properly showed the contractor what to build, and did not presume that anyfff"> contractor would know the right way to construct a wood-framed building.
the 2005 nds (eqn 3.4-3) provides the means to calculate allowable shear for a member notched at the bottom.  it does not specify a maximum notch - using this equation and diarmud'sfff"> 1/4 depth maximum, the resulting allowable shear force is 56.3% of that for a full depth member.
i disagree with mike's statement though ("... and section modulus reduction, both affecting member strength.  the deflection will also be greater.") - section modulus is not as critical at the end of a simply supported member, and i doubt that deflection (controlled by i) will be measureably increased.  horizontal splitting will be a concern if the   
rhtpe:
i stand by my statements here.  
in general you are correct, but, depending on the application of the load and the extent of the horizontal crack, the bending and deflection can be affected.  particularly with transfer beams.
mike mccann
mmc engineering
to msquared48:
in this forum we tend to cover this kind of a problem in general terms.  my statements really apply to joists in general.  i think you would agree that a careful examination of all notched members is in order, particularly those used to carry loads other than uniform loads.
there are many 200+ year old structures in new england still standing that have the ends of