Replies

1. 
   Sasquatch | Aug 27, 2004 04:31pm | #1

   Unless you are significantly overbuilt, removing any structural member does have an effect.  Some rhetorical questions: What is the configuration of the collar ties?  Is your second floor let into the studs?  Are you using hangers?  Is the entire second floor suspended just by nails?  That sounds pretty shaky to me.  When 350 lb cousin Ralph falls off of the piano in the center of the addition, he might end up on the first floor.  I just assume your engineer knows what he is doing, so it must be my interpretation that is deficient.

   I am a retired engineer myself, in residential construction for a change, a challenge, the satisfaction of helping folks get something good for a reasonable price, and the benefits of a physical job.  I love this job and being my own boss.  I am also very opinionated regarding certain aspects of framing.  Having said that, I am still learning when it comes to practical application of principles vs book knowledge.  Please don't tell your engineer that I said he is wrong.  I am sure you and he have a much better understanding of the situation than what I can glean from your message.

   Les Barrett Quality Construction
2. 
   csnow | Aug 27, 2004 05:00pm | #2

   If the floor joists are just hanging there, and not nailed into the sides of the studs, I doubt they are doing much to prevent spread.

   Perhaps they are notched to hang on the ledger.  In that case they may have some big nails through into the top of the ledger which may do something to resist spread. 

   How much they can contribute also depends on how far the joists are from the top plate. Does it have a full height upstairs wall with ceiling joists?

3. 
   kclarson | Aug 27, 2004 10:52pm | #3

   Brian, I am a Structural Engineer currently working as a Building Inspector for the city.

   I think I can help with your question some but I'll have to make some asumptions regarding the exact construction and your location.

   First, collar ties are not intended to help prevent spreading forces on the walls...they are for uplift at the ridge. Tie joists such as roof ceiling joists will help resist the spreading forces that the roof places at the walls. I am going to assume that it's a 2 story place with 8' below and 8' above with a floor kinda hanging there in between.

   This floor does several things and one of them is to brace the exterior wall studs. An unbraced 2x4 (or 2x6) wall that is 16'-0" or more in height has very little resistance to wind loads...placing a floor at the mid-height of the studs breaks this up into 2 adequate spans of 8'. The floor will also help to resist some of the spreading forces at the top of the wall. Our code (2000 IBC and IRC) limits the maximum stud height to 10' for 2x4's spaced at 24" o.c., 12' for 2x4's spaced 16" o.c. or less. 16' for 2x6 at 24" o.c. and 18' for 2x6 at 16" o.c. These can be modified with the proper design and these member sizes may need to be increased depending on your wind region.

   If the floor ledger is simply nailed to the wall studs, I would seriously conside getting some support under it...this is a poor design even if your engineer gives it the big thumbs up

1. 
   homebaseboston | Aug 28, 2004 02:47pm | #4

   That's good to know re: collar ties... has been an incorrect assumption of mine for some time.

   Lurch, the second floor in this case is not full height, that's a good point... in fact, that's part of the reason we're cosidering removing it.  It's just about a 13' run from the first floor to the top plate.  The ledger is let into the face of the studs by about a 1/2 inch, and I don't think it's nailed off to the studs but will have to look.

   It might also be worth mentioning that this is at least a 100 year old structure.  Basically a small addition attached to a main house... which is over 160 years old.

   I really appreciate the insights from the engineers and 'engineer minded' :) in the group... many considerations I hadn't thought of.  Haven't had the engineer in yet... so this is more about looking at feasibility and thinking it through... so thank you again.

   Now, I guess my only question is:  Assume that the second floor does have some 'spread resisitance' application.  What are some potential solutions if we do want to take out some, or all, of the floor?

   Very much appreciate your thoughts.

   _____________________________HomeBase__________________________  LLC

   Brian Roberts, Manager

   Edited 8/28/2004 7:59 am ET by homebaseboston

1. 
   DANL | Aug 28, 2004 03:38pm | #5

   I'm not an engineer, but I would just take part of the floor out at the same time I was putting the new floor in (if there's working room). If you took out two or three joists starting near an end wall (the other walls can't get away too far with the end walls right there) and then go right below that and place the new joists and work your way to the center from each end, that should work. Temporary cables could also be used to tie the thing together while you work.

1. 
   homebaseboston | Aug 28, 2004 04:34pm | #6

   Actually... I'm thinking to take the floor out entirely and make at least part of the room "cathedral"._____________________________HomeBase__________________________  LLC

   Brian Roberts, Manager

1. 
   DANL | Aug 29, 2004 04:33am | #7

   Oh. Pete's message, just below your reply to mine, has a good idea, since you are taking the floor and joists out entirely. If you replace the joists with beams that are a decorative element, it could look nice as well as maintaining structural integrity. One thing he said that I hadn't really thought about is that the full floor structure acts like a diaphram and does more than just keep the walls from bowing. I don't know that just beams across would resist twisting as well--or racking. I guess the though that the wall sheathing prevents racking and you'd only get twisting in an earthquake.