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Old 07-17-2007, 05:58 PM   #1
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Floor joists for 2nd Floor Addition

We would like to pop the top of our small ranch (put on a smaller second story addition). The current ceiling joists for the first floor are 2x6 on 24 inch center. The structural engineer says that we must remove these joists and use 12" I-Joists instead to create the second story floor. This means that all the ceiling on the first floor that is under the addition will have to come down. Is there a way in which we can save those joists (and the first floor ceiling) by adding more structure to create the appropriate floor joists for the second story.

The first floor is about 1100 sq ft. The addition is about 500 sq ft. The addition will run from the front of the house to the back of the house. The roof will be taken off only where the addition will be. We will be adding more posts to the basement to reinforce the the steel I beam. We will also be adding more 2x4 studs to a wall on the first floor that runs the length of the house (side to side and perpendicular to the floor/ceiling joists). THe front to back span of the house is about 30 feet. The current joists run from the front to the back of the house.


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Old 07-17-2007, 10:20 PM   #2
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Originally Posted by poptop View Post
Is there a way in which we can save those joists (and the first floor ceiling) by adding more structure to create the appropriate floor joists for the second story.
Unless your existing ceiling is falling down or wavy or sagging , then your Engineer is 100% wrong. I do Add-A-Levels all the time and never take out the ceilings unless there's some areas that need to be for the stairwell or something else. Other than that they stay in. Get a new Engineer.

Years ago we used to sister the joists right next to the ceiling joists sitting the new joists on the existing top plates., but in my area everything is 16" centers. Later on we used to put 2x4 blocks on the top plates and sit the new joists on top of those. The only problem either way was that you had to remove all the wiring , plumbing and anything else that ran perpendicular to the joists so that we could add the new joists.

Now we cut back the existing ceiling joists 1-1/2" and add a box around the whole perimeter the same height as the ceiling joist and sit the new joists on top of a 2x6 nailed flat on top of the existing ceiling joists.

This way nothing is in your way and your existing ceiling, electrical , plumbing doesn't get touched, you will have the new plumbing to deal with if your putting any bathrooms in.

I'm just giving you some examples of how you do it without touching the existing ceiling. There are many other things you have to consider when doing AAL's on the first floor.


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Old 07-18-2007, 04:57 AM   #3
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I don't understand why the structural engineer wants to rip off the ceilings and then jump up to 12" engineered I-joists just to construct a 2nd story onto a "small ranch".
Adding on a second story (like what is being discussed here) should not involve much more than what Joe C. has described.

Maybe there's more to this story pertaining to the structure?
Sounds like it may have something to do with the existing layout of the flooring and where the load bearing walls are (?)

Whatever the case, maybe you should talk to another structural engineer....
- Build Well -

Last edited by AtlanticWBConst.; 07-18-2007 at 05:02 AM.
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Old 07-19-2007, 06:46 AM   #4
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It's never a bad idea to get a second opinion. Keep in mind that these guys are signing a serious liability... they dont always value engineer with their reputation if you know what I mean. However, it IS possible that there are few load bearing interior walls and/or suitable beam for the added 2nd level load and he wants all of the loads transferred completely to the outside walls and hence directly to the foundation. This may turn out cheaper than changing the configuration of the first floor, changing a beam, etc. good luck and let us know what eng. #2 says.
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Old 01-11-2008, 07:57 PM   #5
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A forty to fifty year old ranch might have 2x6 joists that are probably bellyed. If you are adding a floor then you need to put new joists in, or over or next too. The joists need to be rated for the new live and dead load and any center wall collar load. If the second floor does not fall from within a foot or so of the existing bearing end walls (front and back or left and right sides) then the new second floor will bear more on the existing collars or new floor.
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