Second Story Strategy to Preserve Existing First Floor Roof Framing?

[HumbleChief]

We are adding a second floor to a mid century modern home and the builder wants to preserve the existing roof framing and interior finishes and place the second floor entirely above the existing roof structure. The building process is quite easy by building pony walls on the exterior walls and interior beams etc. raising the second floor structure above the first floor roof.

 

The question is, "How would you proceed with Chief to create that dead space between the first floor roof and the second floor floor?"

 

In the past I've used an air gap under the second floor framing and/or a dummy second floor (which is where I'm leaning) to create the space between structures and was wondering if there's another technique out there I might try? The roof will be tricky because of what Chief does with roof but a ceiling plane may work there. 

 

Any ideas? Thanks

SECOND_FLOOR_FRAMING_QUESTION.plan

[Renerabbitt]

What’s the structural plan of attack?

i would think a dummy second floor...can you get a floor truss to conform?

[HumbleChief]

4 minutes ago, Renerabbitt said:

What’s the structural plan of attack?

i would think a dummy second floor...can you get a floor truss to conform?

We have a 21 ft. span and it looks like we can get a 14" TJI to play at that distance, then about 12 ft from the outside wall we'll change joist direction so we can cantilever out for a 6 ft. deep deck. There's a stairway as well so a series of beams will most likely be employed as well, determined by the structural engineer. Hope that answers?

[Renerabbitt]

12 minutes ago, HumbleChief said:

We have a 21 ft. span and it looks like we can get a 14" TJI to play at that distance, then about 12 ft from the outside wall we'll change joist direction so we can cantilever out for a 6 ft. deep deck. There's a stairway as well so a series of beams will most likely be employed as well, determined by the structural engineer. Hope that answers?

Okay so either a dummy floor or raise the existing floor and set a ceiling plan and manually frame some stuff to represent the existing roof...sounds like a decent amount of manual framing.

Assuming you've got some kind of strapping or hold down between floors, shear transfer etc. I feel like the ceiling plan may be more agreeable, never tried anything like that before, maybe someone else is more equipped to answer

[HumbleChief]

8 minutes ago, Renerabbitt said:

Okay so either a dummy floor or raise the existing floor and set a ceiling plan and manually frame some stuff to represent the existing roof...sounds like a decent amount of manual framing.

Assuming you've got some kind of strapping or hold down between floors, shear transfer etc. I feel like the ceiling plan may be more agreeable, never tried anything like that before, maybe someone else is more equipped to answer

Thanks Rene, I think that if we raise the existing floor (ceiling height I'm assuming) that will create a floor for the second floor above and the small pony wall can be detailed in. The dummy second floor, which in reality isn't really a dummy at all the more I think about it. It's not living space but it could be considered a genuine second floor.

 

The roof has to go because nothing will build/frame on top of a 'Chief roof' so a ceiling plane with manual framing may be in order no matter the decision. It's a small second floor so no big to manually frame. Still thinking but leaning again towards the dummy second floor.

 

Done this (air space between floors) numerous times over older structures and it saves a TON of work if you want to preserve electrical plumbing HVAC in an an older ceiling cavity but never tried it with a sloped roof that we want to keep.

[HumbleChief]

All right - so far so good 

[Kbird1]

On 4/18/2019 at 11:47 AM, HumbleChief said:

All right - so far so good 

 

You do have some "crazy" going on in this Plan Larry I saw those too   but it's a nicely done model I'd say , nice work with the terrain and all the little "details", I also see alot of Manual work in there to make it look like the "real thing".

 

Tried a couple of different ideas but adding a 24" high 2nd floor, cutting a hole in the roof, and then adding standard 8' 3rd floor worked the best.... not sure what else I "broke" but here is the Plan file and a few Pics. I didn't do it, but wonder if you couldn't now add a roofplane back on the second floor inside the walls, if needed, to show framing. Below I pulled the backclipped view through the Roof line still there behind the Addition.

 

     

 

         SECOND_FLOOR_FRAMING_MHD_PLAY.plan

 

 

[HumbleChief]

51 minutes ago, Kbird1 said:

 

You do have some "crazy" going on in this Plan Larry I saw those too   but it's a nicely done model I'd say , nice work with the terrain and all the little "details", I also see alot of Manual work in there to make it look like the "real thing".

 

Tried a couple of different ideas but adding a 24" high 2nd floor, cutting a hole in the roof, and then adding standard 8' 3rd floor worked the best.... not sure what else I "broke" but here is the Plan file and a few Pics. I didn't do it, but wonder if you couldn't now add a roofplane back on the second floor inside the walls, if needed, to show framing. Below I pulled the backclipped view through the Roof line still there behind the Addition.

 

     

 

         SECOND_FLOOR_FRAMING_MHD_PLAY.plan

 

 

Wow, thanks Mick. Didn't think of a hole in the second floor roof so I removed it and replaced it with an interior ceiling plane, and in this case there is no original framing other that the 2 x T&G roofing over 4 x 8 beams so when cut back to the framing the ceiling plane allows that ceiling material to remain.

 

The top floor was trickier because it does need framing but the framing needs to sit below the roof plane so it can match the existing eave overhang. I created a ceiling plane, framed it, placed it just under the roof plane which has the same 2 x T&G roofing so I get new framing for insulation and the slim line eave look as the existing.

 

There were some really weird stray attic walls that gave the plan fits and if you can believe this the original plan had no 'windows'. Everything was a p-solid to create windows but no actual windows. That was a piece of work.

 

Lots of other tricky areas around the stairs etc. and I'll present the current progress to the builder tomorrow and we'll wrap up the design.

 

Thanks so much again for taking the time to play around. Check the current plan out and see what I came up with. Still details missing at least it represent the current design intent.

SECOND_FLOOR_FRAMING_2.plan

[Kbird1]

3 hours ago, HumbleChief said:

Wow, thanks Mick. Didn't think of a hole in the second floor roof so I removed it and replaced it with an interior ceiling plane, and in this case there is no original framing other that the 2 x T&G roofing over 4 x 8 beams so when cut back to the framing the ceiling plane allows that ceiling material to remain.

 

The top floor was trickier because it does need framing but the framing needs to sit below the roof plane so it can match the existing eave overhang. I created a ceiling plane, framed it, placed it just under the roof plane which has the same 2 x T&G roofing so I get new framing for insulation and the slim line eave look as the existing.

 

There were some really weird stray attic walls that gave the plan fits and if you can believe this the original plan had no 'windows'. Everything was a p-solid to create windows but no actual windows. That was a piece of work.

 

Lots of other tricky areas around the stairs etc. and I'll present the current progress to the builder tomorrow and we'll wrap up the design.

 

Thanks so much again for taking the time to play around. Check the current plan out and see what I came up with. Still details missing at least it represent the current design intent.

SECOND_FLOOR_FRAMING_2.plan

 

Looking good Larry , if you are presenting this tomorrow , there are some Floaters out on the left side and what looks like a 4x4 in the window on the 3rd Floor but by now you may have gotten to cleaning up anyway. The 3rd floor Roof I think I'd have tried tried making the Room Taller and then lowering the Roof plane into the house to get your Rafters and 1 1/2 thick soffit/fascia

 

 

My idea of adding the roof plane back inside the 2nd storey walls does work too....

 

[HumbleChief]

1 hour ago, Kbird1 said:

The 3rd floor Roof I think I'd have tried tried making the Room Taller and then lowering the Roof plane into the house to get your Rafters and 1 1/2 thick soffit/fascia....

 

That was my first instinct but didn't see how I could have 2 x 10 rafter/joists and only a 1 1/2" fascia with starter board and the look I was after. It would end up like the section above. Did I miss a trick there? For some reason I can't think of now I didn't simply use a 1 1/2" sub fascia/fascia combo but may have over thunk it.

 

So I made the room taller, dropped the framing in a ceiling plane, then placed the roof over that with only that 2 x T&G and a roof surface to create the 1 1/2" fascia. We'll see if the builder wants to go that route or plan 'B' which we don't have at this moment.

 

I am presenting tomorrow but only for further refinement as the builder and I make a lot of design and structural decisions together so we'll begin that process tomorrow. The floaters are OK for that process but I could not for the life of me figure out where that 4 x came from that shows up in that window. Just wasn't any wall that it related to so will turn off framing, wall for that 3D views. ALWAYS stumped by something...

 

 

[Kbird1]

26 minutes ago, HumbleChief said:

simply use a 1 1/2" sub fascia/fascia combo but may have over thunk it.

 

That was what I was thinking of trying.....

 

Framing in the Window apprears to be coming from a  Wall 1/2 way down the stairs.... I deleted them and rebuilt framing for that wall and it was back...I think it is cos you have some Balloon framed in that area and some overlapped walls there too

 

 

[HumbleChief]

Yeah will probably just use a simpler fascia/sub fascia combo to get that structure and look.

[HumbleChief]

Thanks Mick, yeah that interior wall was in 3 sections which was producing that framing in the window and that siding was from the dummy 2nd floor. I remember now that I just ran out of brain steam and quit after I got the general look I wanted but thanks for getting me back on track and looking through different eyes.

[Kbird1]

23 minutes ago, HumbleChief said:

Thanks Mick, yeah that interior wall was in 3 sections which was producing that framing in the window and that siding was from the dummy 2nd floor. I remember now that I just ran out of brain steam and quit after I got the general look I wanted but thanks for getting me back on track and looking through different eyes.

 

I know how you feel , the CA Rabbit Hole beats us all  sometimes I just have to walk away and comeback hours later or the next day and look to see what I was missing.....

 

M.

[HumbleChief]

Just now, Kbird1 said:

 

I know how you feel , the CA Rabbit Hole beats us all  sometimes I just have to walk away and comeback hours later or the next day and look to see what I was missing.....

 

M.

Exactly...