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Quantum
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Posts:262
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| 12/24/2007 9:54 AM |
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Wow, nice job having all that foam on the outside! You know the value of the thermal mass of concrete. I suggest you use waterproof concrete for that deck, so no membrane is needed. Might even have the surface stamped and stained to look like terrazzo or stone.
You can't put a fiberglass or EPS layer between the roof and wall though, because when you remove shoring the whole roof will drop! Anyway, the insulation would be compressed so much as to have no effect, and also may allow water to migrate in!
I think thermal bridging is not really a problem in this case because when you insulate below the roof deck that means 16" of wall is insulated as well. Thermal inertia of concrete again works to your favor here by forcing heat to go through 16" of wall before it connects with cold. Thermal isolation. I highly suggest you spray closed-cell foam, preferably soy-based, as your insulation. If you use batt or other air-permeable insulation you will have condensation on the underside of the concrete when it is cold! Closed-cell foam will not allow humid air near it to condense. 16" of foam should give you around R-80.
As to the deck, it's not clear whether it is supported by columns or cantelievered. If supported by columns I'd make an 'expansion joint' of EPS between the floor and deck, with #5 rebar running continuously through both for strength, bent at the ends. If cantelievered with beams, the stresses are different. Maybe EPS and extra rebar in the top half, with concrete in the bottom for compressive strength. Foam the beams as well.
IANASE (I am not a Structural Engineer), and you definitely need to consult one. It will be well worth the money if you find an enlightened one.
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PatrickT
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Posts:138
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| 12/24/2007 11:42 PM |
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Quantum,
Happy Holidays.
I am working with a structural engineer but my concerns are thermal :( As far as the roof deck, load is on the joists. The slab spans between them. For example, one room is 30' by 30'. All 4 walls are ICF. The floor is supported by 7 joists. The loading is concentraited on the point of contact for these 7 joists. Perimeter of the slab carries nothing along the walls where the joist rests and just 2' by 30', half the distance between the first joist and parallel wall. This can be comparred to a wood framed floor. So in my proposal, the 1/4" fiberglass sheet would go under the joist foot. HD foam would go between the joists.
The outside mid level deck is on steel posts, no cantilever.
Patrick T
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Quantum
Registered Users
Posts:262
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| 12/25/2007 11:04 AM |
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Not following. Still sounds like the joists would sink, the fiberglass sheet would be compressed to uselessness, and the deck is still connected to the walls?
Also fiberglass rebar is useless, AFAIC. |
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