HumbleChief

Floor Structure Strategy...

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Another in a long line of questions regarding floor structures.

 

In this case I have 2 floors that are now framed with 14" TJI's and the engineer thinks 16" TJI's will be better in the long run and allow us to use less costly steel and for other reasons.

 

So I need to go in and change the framing from 14" TJI's to 16" and maintain all the floor heights etc.

 

What's the best strategy?

 

 

Plan here

 

TJI Heights.plan

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Larry,

 

Do you want the Floor Elevations to remain constant or the Ceiling Heights to remain constant?

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Assuming that the Ceiling Heights are to be maintained, you need to change the Floor Structure Definitions only.

 

If you want the Floor Elevations to remain constant then after updating the Floor Structure Definitions - start at the top floor and set the absolute floor elevations for all rooms to the desired values.  This will push the floor structure below down and the ceiling height below will be lower.  Doing this for each floor except the 1st Floor.

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Larry,

 

Do you want the Floor Elevations to remain constant or the Ceiling Heights to remain constant?

I think both Joe, if I understand your question. I want the first floor elevation to remain which would push the basement level down to accommodate the new TJI's? And leave the 10 ft ceiling heights in the first floor.

 

Then I'm thinking the second floor would move up to accommodate the new TJIs and leave that floor at 9 ft high, which I assume would move the roof structures up as well?

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Just change the Floor Structure Framing Defaults and then Rebuild all the Framing.  That will leave the 1st Floor at its current elevation, all ceiling heights will be correct and all floor elevations will be moved up appropriately.  You will have to have "Rebuild Foundation" ON so that the Basement will move down.  You will also want "Rebuild Roof" ON so the Roof will move up.

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Just change the Floor Structure Framing Defaults and then Rebuild all the Framing.  That will leave the 1st Floor at its current elevation, all ceiling heights will be correct and all floor elevations will be moved up appropriately.

I'll give that a try, thanks Joe. Have an appointment now but will try later.

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I always do a back-clip elevation and tile the views so I can watch what what's happening as I make the changes. 

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When I have to change the depth of a floor system I've found the easiest way is to change the framing defaults to the new depth. Everything under the *0* is not affected (basement). I then use the *all off* layer so nothing is showing. I then turn the roofs on and select every roof that is above the 2nd floor subfloor. I raise them all at once the amount of depth I increase for the 2nd floor system only.

Done!! No selecting each and every room or rebuilding roofs that you manually built or altered.

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Why is this set up that way to begin with? I could never get that part. If I put a basement with 2 stories above and I want to change the basement height, it should move all the floors up without changing anything other than pushing everything up the height of basement wall. If I want to change the first floor ceiling from 8' to 9' it should bump the upper floor with the roof up 1' without changing anything above or below.

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That's the conundrum, Greg. There have been many threads on this subject, with two current ones if you want to follow the discussion. How you describe it is the "bottom up" approach many of us are sooooooo familiar with. But CA, apparently, works "top down," which is counter-productive to the way I think. I don't know if I will ever understand it.

 

Mike

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Greg:

 

I'm with you - Chief should be able to do this auto-magically

 

Lew

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Why is this set up that way to begin with? I could never get that part. If I put a basement with 2 stories above and I want to change the basement height, it should move all the floors up without changing anything other than pushing everything up the height of basement wall. If I want to change the first floor ceiling from 8' to 9' it should bump the upper floor with the roof up 1' without changing anything above or below.

That's a pretty logical way to look at the structure and I can wrap my brain around that way of thinking very easily - however - you know the rest of the story.....

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I have always worked with the Main Floor height as "0". The basement has always gone down a - amount and the upper floors go up a + amount. This top down approach is giving me headaches but if I make a sketch with each floor level I can usually work it out. Definitely counterintuitive though.

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Sherry, I always "think" better with a pencil and sketch pad close by. I can't tell you how many times I resort to those (with a Construction Master IV handy) to solve the "structure tab."  :) Computers are great, but what are we going to do when the power goes off?

 

Mike

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Mike

I always have my Construction Master close by for the Dbx's too.

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..... :) Computers are great, but what are we going to do when the power goes off?

 

Mike

I go play golf.

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