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Best Way To Build A Floor Over Existing Ceiling & Rim Joist--Remodel 2Nd Story Addition?

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Hi, 

This is something that comes up all the time in remodels:  I would like to show framing for the following.

 

Second story addition over existing ceiling framing:

  • Leave existing ceiling / attic floor--2x6 or 2x8; (existing ceiling will be blocked at rim joist).
  • Add new rim and TJIs on top of existing ceiling framing.  Not between existing ceiling because often ceiling joists change direction.

 

Question is:

 

What would be the fastest way to have Chief generate this automatically?

  • Do you think I could add a floor between with 1/4" ceiling ht, then add a third floor as my second floor?

 

What would be the most stable approach?

 

 

Thank you,

Barry

 

 

 

 

 

 

 

 

 

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I would do the floor, zero height or maybe 1 1/2" if adding plates(or whatever)and then add another

floor for the second floor, which to chief would be the 3rd floor.

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I would do the floor, zero height or maybe 1 1/2" if adding plates(or whatever)and then add another

floor for the second floor, which to chief would be the 3rd floor.

 

Dennis's method is doable,  I have done it.....  problem,   think about how your stairs will display on first and third floor...  will they show on third floor,   yes you if you use ref set or  cad lines or blah blah blah,.....

 

My method (or second method)  take a look at pic,  why now design the floor structure with the ceiling built in.....  you will need to add the 2x4 pad on the ceiling joists to support new floor joists.  Not sure what the down side to this second method is.  One downside to my method would be lack of control of joist direction. Suppose you want joists going one direction and new floor joist going second direction.  If that were the case,  I would not use joists for existing ceiling joist bay,  I would leave empty and then come back later and add a ceiling or roof plane to create joists for sections cuts.

 

Maybe Perry will pipe in,  he has probably had more experience with this situation.

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Dennis's method is doable,  I have done it.....  problem,   think about how your stairs will display on first and third floor...  will they show on third floor,   yes you if you use ref set or  cad lines or blah blah blah,.....

 

My method (or second method)  take a look at pic,  why now design the floor structure with the ceiling built in.....  you will need to add the 2x4 pad on the ceiling joists to support new floor joists.  Not sure what the down side to this second method is.  One downside to my method would be lack of control of joist direction. Suppose you want joists going one direction and new floor joist going second direction.  If that were the case,  I would not use joists for existing ceiling joist bay,  I would leave empty and then come back later and add a ceiling or roof plane to create joists for sections cuts.

 

Maybe Perry will pipe in,  he has probably had more experience with this situation.

Thank you Dennis and Scott!

I will play with both methods to familiarize with attributes and issues.  I probably will need to control joist direction..  Scott... the last part of that sentence...leave empty and come back later and add ceiling or roof plane.    Do you mean...pop in a roof plane where the old ceiling is to generate joist ends for the cross section after I generate 3Ds?

 

All I really need is a a big empty space between the top and bottom plates that looks good from the outside and acts correctly from the inside. I can fill in my own framing.  

 

Thanks again, very helpful...

Cheers! Barry

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 ......   Do you mean...pop in a roof plane where the old ceiling is to generate joist ends for the cross section after I generate 3Ds.......

 

 

Yes,  that wouldbe purpose 

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All I really need is a a big empty space between the top and bottom plates that looks good from the outside and acts correctly from the inside. I can fill in my own framing.  

I did this once and used the method Scott describes with a second floor structure built into/under the second floor. If you want a big empty space you could create an air gap the size you need and fill in framing manually.

 

You could also manually draw in any joists you need to run in another direction or note your floor plans with the proper joist direction. Sections are very easy to notate as well without necessarily trying to get the model perfect.

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I don't know why go through so much trouble... We would just sister up the ceiling joist, subfloor (or take them out completely) and off with the second floor you go... Did dozens of add-a-level and never build another deck on top of ceiling joist... never did it that way or see anyone doing it that way.

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I have been doing 2nd floor additions since 1974 like this, I adjust the 2nd floor, floor, by creating a floor with 2 framing layers built right into the floor DBX. You can then add your floor beams as needed, works quite well except the direction for the existing ceiling joists are parallel with the floor joists. I just fix up the sectionswhen needed. This method creates a great duct space and you can put any size beams you want with worrying about floor depth problems. Framers and homeowners also love it b/c you can frame with disturbing the existing as much. You also don't have to re-wire all the existing electric runs and gas lines.

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I don't know why go through so much trouble... We would just sister up the ceiling joist, subfloor (or take them out completely) and off with the second floor you go... Did dozens of add-a-level and never build another deck on top of ceiling joist... never did it that way or see anyone doing it that way.

Greg,

 

I was introduced to the technique by a local builder and was a little skeptical but quickly saw how practical it was. It allows for so much flexibility when running new electrical/mechanical/plumbing and doesn't disturb the underlying framing. A great technique that should be considered for any second story addition.

 

I think I even remember Perry advising on how to get it done in Chief as well.

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I did build a 2nd story on a good size ranch house this way.  As Larry mentioned it saved rerouting the existing electric etc, did not have to mess with ceiling pops.  It was basically a piece of cake.

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Sorry guys, never had any issues whats so ever, not with the need to reroute anything (don't even know what is there to reroute if nothing is above there except a few lights) or never had any problems to run new wiring, or anything else... If you going up with the whole first floor area, all you need is one wire up there, a junction box and you run all your wiring for the second floor from that, your HVAC is going in the attic so there is no need to chop anything on the first floor. If you going up over one area, lets say a split level and you going over cathedral or regular ceiling, there is nothing up there, we get this rooms up in: day 1 demo framing, sheeting, day 2 we install roof...  its a walk in the park to erect another story without the need to build up anything. 

 

With that said if you going to do that, you might as well pack the plates up, eliminate the ceiling all together and do your typical floor assembly, at least you end up with a taller ceiling...that would make more sense vs. building a whole new deck on top of the existing ceiling.

 

I guess it all comes down to each its its own.

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In the past I have done it Greg's way too but usually inside an exist attic so we don't want to lose head height , but I like this idea for a Full new storey . How Perry has it set up looks pretty simple too, so basically you add 3X8 rims all around ( and wherever needed) and then just frame the new floor ?

 

Do you have an old plan you wouldn't mind / can share Perry with this technique, looks really interesting.

 

Thanks M.

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I have been doing remodels since 1979 here in CA.  Like Perry,  I have done thousands of remodels.

 

 I usually rip off the ceiling and then build the floor.  I have done Perry's method maybe 4 times at the most.  How to do it is typically up to my contractor and most of the time they say rip off the ceiling.

 

I think Perry's method makes a lot of sense if you want to save the electrical runs etc.  

 

Both methods have their pluses and minuses and  both methods are good.

 

I find it interesting that Perry and I,  both of us very experienced,  do it differently due to......  what......  where we live?  The contractors we associate with?  Who knows.

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I have been doing 2nd floor additions since 1974 like this, I adjust the 2nd floor, floor, by creating a floor with 2 framing layers built right into the floor DBX. You can then add your floor beams as needed, works quite well except the direction for the existing ceiling joists are parallel with the floor joists. I just fix up the sectionswhen needed. This method creates a great duct space and you can put any size beams you want with worrying about floor depth problems. Framers and homeowners also love it b/c you can frame with disturbing the existing as much. You also don't have to re-wire all the existing electric runs and gas lines.

Thank you Perry and all!

 

Yes, big help.  This is the info I needed to first frame auto, then make adjustment to framing direction manually.   

 

Side note:

Ripping off the old ceiling can work sometimes, but is often much more costly, that's why we do it this way--as well as ease of plumbing, hvac and electrical for the new space.  You can't tear off lath and plaster ceilings without affecting the rest of the walls, so it works well in older houses.  

 

Cheers! Barry

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Scott, electrical runs are not being effected, and if something needs to be moved its not even an issue, and looking at that floor assembly you end up with 2' of floor cavity, now you have to deal with draft stopping  and everything else and in general its just wasted space. and wasted material on the exterior... if you have a house lets say 300 ft x 2' you looking at 600SF of siding, sheeting, etc just to wrap that floor system, its a  waste of money.

 

Nothing against anyone, you guys do what your contractors ask you to do. Around here its unheard of to do anything like that...

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Greg,

 

It's probably closer to 300 sqft extra siding because you would have to do a 12" height even if you took out the ceiling and didn't add the 8" space between the Floor Joists and the existing Ceiling Joists.  But then you would have to redo all the lighting and ceiling finish anyway. 

 

The cost is difficult to figure without knowing all the parameters.

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But now that I play with this, I see why it's hard to change joist direction because both floor joists are stacked on top of each other.

 

Question:

 

what's does the ceiling structure change?  I placed 17 into ceiling structure and it doesn't seem to change the cross section?

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Sometimes depending, you can also use a ceiling plane for the existing ceiling, but there is some tweaking with that. And you can control the direction.

Greg, nothing up there ,really, what is everything underfloor, we got slabs out here there is no underfloor to put anything.

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It is, of course, dependent on each specific project and the case where we did it we used beams to span certain areas that allowed us to open up large areas of the living space and to ignore a lot of questionable very old framing in the attached garage, and its associated footing/foundation. We just basically went around the questionable old stuff with an entire new structure. Worked out pretty sweet, but of course won't work in every case.

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Joe,

 

If I'm redoing the whole thing, the whole place gets gutted, because when you dealing with homes built in 20's, 30, some of them have brick lined walls, etc.and over a certain % area of the total house area in most places is 25% over of total area, you have to bring everything to new code... therefore all ceilings, walls must be down, all old wiring has to be removed, etc. 

 

If you doing one room addition, and customer don't want anything disturbed (never happened yet), we take the roof off and syster up the joist and put the second floor plywood. No matter how you looking at it, you don't have to disturb existing electric because you need a home run for the new addition and 95% of the time it will be ran on the outside therefore nothing gets disturbed. Also 95% of the time customer wants to upgrade everything below the new area.

 

Here is a few pictures from 2 jobs I just completed. One, the L shape we sister up the joist, and the second one one story addition on the back we raised the plates to match the floor height, so the ceiling beams get cut out to make the ceiling higher and new framing is going in from there. 

 

 

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Perry,

 

I thought he is talking about second floor addition, so there is no underfloor, there is only ceiling and the attic... this is what I'm talking about. 

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Greg

ok ,so you try to sister the new f.j. to the old c.j. with the electrical laying on top of the old c.j. You have to re-route the electrical, there is no way to do it using your method unless you are using 2x6 floor joists. Also, Gas lines usually also sit on top of those ceiling joists, do they magically just go through those f.j.. You also can't notch them that much, what gives. I have built hundreds of these and drawn thousands.

I was looking at your photos and we just couldn't do that here also, your method creates to much of a hinge effect crippling that up like that. everything around here needs to be held down.

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Perry, If its one 2 rooms its no big deal, if its the whole second floor added, everything is rewired. If its sheetrock, its nothing to it. I'm only 54 years old, I'm not gonna say I been doing this as long as you have,but I have about 70 New construction homes under my belt, and about the same # of complete home renovations and additions... Been at it almost 30 years, and I never seen with another floor cavity on top of the ceiling.

 

If you think about it,  If everything below is not being disturbed, you will not have anything new being installed in that new floor system, there is nothing even to be rerouted in the existing ceiling other than a light fixture  so there is no need for all that just because of the ceiling light? If someone got a problem with a few lights, they should be making hamburgers not building house. 

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Down here in Oz (or at least my work, and I have done hundreds of these), the owner usually stays in the house (95% of the time) while the upper floor is constructed.

So it makes for a very clean job to leave the existing ceilings and framing and build a new timber floor platform over the existing ceiling.

The other consideration is waterproofing the job asap.

We remove the roof, build new floor platform (new floor framing and flooring).

We then cover the whole floor platform with a custom welded poly tarpaulin that stays for the whole building time and the new walls are just built over it.

At the end of the construction, the tarp is cut out room by room around the walls and taken away - rubbish and all.

This process provides minimal disturbance to the owners living there - the only real disturbance is when the stair opening is cut through and that doesn't happen until the roof goes on and the new upper floor is waterproof.

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I am surprised 25% is consider enough for a total gut..... think it used to 85% here and they lowered it to 65% a few years back , though I am not as lucky as you Greg as far as Wiring etc  and it only being a few ceiling fixtures which is why I was interested in this Idea. I guess even adding a 2x6 on the flat over the existing Rim and reframing would work too , if you didn't need to beef up the structure with 3x8 to make the engineer happy. 

 

Typically Perry since we aren't on Slab the Gas line is in the basement ceiling here and I suspect Greg's is the same looking at his pics.

 

M.

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