vdubbin
New Member
Posts:13
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| 28 Dec 2010 02:34 PM |
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Hello all,
Working on the design of a house my wife and I are building this coming summer. We are incorporating some passive solar elements and other fun stuff (maybe other posts will cover these).
We are doing a timber frame with SIP walls, full basement (walkout south), and two full floors above. Everything is south-oriented. My main question here: is there any reason I cannot ask for a few inches of poured concrete for my first floor deck and maybe even the second floor? I understand this will probably crack some over time but with pre-cut and grouted break-lines I'm not too concerned about that. What I want is the thermal mass.
So, I would like to do this with regular (not light-weight) concrete and I'm not sure how the floor-system needs to be designed to support this. The weight of the concrete is fairly easy to calculate but once cured I would think it is part of the structure of any given span and thus not necessary simple "dead weight".
Of course, I may be completely wrong. Any ideas?
-Jeff
Also, please checkout my project website "87oaks.com" (I just started it so it's still coming together). This site also has my SolarCalc program which maps the sun's location for anywhere on the globe and corrects for angle, airmass, and the shadow cast by designed overhangs. This gives a potential solar energy picture for windows (any direction or orientation). This program was a pet-project so it is not commercialized - it is, however, fully free so please try it if you would like... |
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jmagill
Basic Member
Posts:374
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| 28 Dec 2010 03:53 PM |
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Our floor is 2" of concrete on a plywood deck. We beefed up the joists and the amount of them. We acid stained and we use ours for radiant floors but wood due the same for solar.
We have some cracking but mainly in door ways and where hallways meet larger sections of floors. We could have controlled the placement of the cracks with scoring.
We used regular concrete and are very happy with the results. |
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jmagill
Basic Member
Posts:374
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| 28 Dec 2010 03:58 PM |
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Our floor is 2" of concrete on a plywood deck. We beefed up the joists and the amount of them. We acid stained and we use ours for radiant floors but wood due the same for solar.
We have some cracking but mainly in door ways and where hallways meet larger sections of floors. We could have controlled the placement of the cracks with scoring.
We used regular concrete and are very happy with the results. |
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jonr
Senior Member
Posts:5341
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| 28 Dec 2010 04:04 PM |
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Evidently the new PVA fibers are providing some amazing crack control for concrete. But personally, I'd much prefer a water tank for solar (or any off peak) storage.
http://www.nycon.com/RECS15.htm
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lzerarc
Basic Member
Posts:423
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| 28 Dec 2010 04:19 PM |
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I am not sure how structural thin poured concrete can be made on a wood floor structure. One thing I might look into is, if you want it structural, why not actually make it that way? Maybe explore actually using a structual steel deck (say 2" deep) with 4" of poured concrete and reinforcing. We span this sort of deck system on beams for floors anywhere from 4-8' on center, depending on what your loading is. Remember your mass only needs to be within the glass ratio distance away, (typically around 10'-ish), so you are not talking a lot of structure like this most likely. I do not know your glass surface area, but just make sure your concrete thickness is enough for the surface area of the glass. My guess is 2" really would not be thick enough.
Maybe also look into stamping the concrete and staining as well. Stamping will help reduce some of the cracking. We did an interior project where we used saw joints at 2' squares then grouted and sealed them. It looks just like nice tiling with the stain, and 5 years later, yet to crack anywhere. |
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FBBP
Veteran Member
Posts:1215
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| 29 Dec 2010 12:59 AM |
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Posted By vdubbin on 28 Dec 2010 02:34 PM
So, I would like to do this with regular (not light-weight) concrete and I'm not sure how the floor-system needs to be designed to support this. The weight of the concrete is fairly easy to calculate but once cured I would think it is part of the structure of any given span and thus not necessary simple "dead weight".
Of course, I may be completely wrong.
Assuming you are using some sort of engineered floor joist, just as you designer to run it again with 1.5" concrete overlay. It is a simple dead weight however the original calc's for the floor would have upped the stiffness of the floor system to avoid vibration. This extra stiffness is not need with the concrete because it will dampen the vibration on its own. The extra engineering can than be used to carry the weight of the concrete. Just be sure to tell the designer you want to use real concrete (12 lbs / sq. ft. " I think) as opposed to gypcrete or light weight. Be sure to use fibres and possible mix water conditioner. I poured my hydronic floors last Tuesday (1.5") and am starting to get some light shrink cracking at doorways etc. but they will be covered with a stamped overlay which will be the finished floor. |
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Bruce Frey
Basic Member
Posts:429
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| 29 Dec 2010 04:20 AM |
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Jeff,
Are you planning to use concrete as your floor finish? If not, you can probably achieve the same effect using thickset tile or stone (using a ±1.5" to 2" setting bed).
As others have pointed out, the concrete has no structural value in your proposed scheme. Your designer should consider the extra weight of your floor AND consider the deflection requirements of the floor finishes you plan to use.
Bruce |
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jonr
Senior Member
Posts:5341
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| 29 Dec 2010 08:30 AM |
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Is it recommended to put down two layers of plastic sheet to decouple the concrete from the wood? |
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cmkavala
Veteran Member
Posts:4327
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| 29 Dec 2010 08:39 AM |
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Posted By Bruce Frey on 29 Dec 2010 04:20 AM
Jeff,
Are you planning to use concrete as your floor finish? If not, you can probably achieve the same effect using thickset tile or stone (using a ±1.5" to 2" setting bed).
As others have pointed out, the concrete has no structural value in your proposed scheme. Your designer should consider the extra weight of your floor AND consider the deflection requirements of the floor finishes you plan to use.
Bruce Bruce; ditto your comments and stamped concrete on the inside of a home is a dirty nasty job that could very well have a negative effect on the resale value, thickset tile/stone is the way to go. |
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| Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
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vdubbin
New Member
Posts:13
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| 29 Dec 2010 09:24 AM |
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Hello all,
Thanks for the notes! I was actually planning on about 3-4" with some rebar reinforcement and radiant tubing – BTW: the tubing is not really for primary heat but more to add a level of thermal management to the system. Someone mentioned the masonry element only needs to be in the “glass ratio distance” (~10’) however, from as a thermodynamics standpoint it would seem that more mass, anywhere in the conditioned space, helps with thermal buffering even if it does not get the direct heating from solar radiation.
On this point I guess I figured it would be easier and probably not change the overall contract price too much just to pour the whole floor (both floors). All the concrete people are already there and it’s not a big house anyway. Further, I have NOT run the numbers but my intuition tells me thick-set tiles or stone will probably end up costing more. Stained, saw-cut, and grouted seems like a fairly nice look.
OK, so there is no “structural” element to the concrete portion of the floor system. I’m sure my designer has some of these answers but as somebody that really likes to do the research/planning does anybody have a good source for span/joists calculations? What I have found only use live and dead load numbers which I assume does not give the correct picture for the concrete system.
Very Best,
-Jeff
Project website: “87oaks.com” with “SolarCalc,” a free passive solar design tool…
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jbaron
Basic Member
Posts:122
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| 29 Dec 2010 10:20 AM |
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Do you not have a structural engineer doing this engineering work for you? |
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jonr
Senior Member
Posts:5341
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| 29 Dec 2010 11:01 AM |
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http://www.awc.org/calculators/span/calc/timbercalcstyle.asp |
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FBBP
Veteran Member
Posts:1215
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| 29 Dec 2010 11:18 AM |
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Posted By cmkavala on 29 Dec 2010 08:39 AM
Posted By Bruce Frey on 29 Dec 2010 04:20 AM
Jeff,
Are you planning to use concrete as your floor finish? If not, you can probably achieve the same effect using thickset tile or stone (using a ±1.5" to 2" setting bed).
As others have pointed out, the concrete has no structural value in your proposed scheme. Your designer should consider the extra weight of your floor AND consider the deflection requirements of the floor finishes you plan to use.
Bruce Bruce;
ditto your comments and stamped concrete on the inside of a home is a dirty nasty job that could very well have a negative effect on the resale value, thickset tile/stone is the way to go.
The stamped work used inside houses is not the same product as used outside! It is only 1/4 to 3/8" thick and the stamp mats have a much finer detailing than the mats one would use for outside. When properly done the floor looks just like a wood plank floor but the thermal dynamics are much better for both radiant and passive. |
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vdubbin
New Member
Posts:13
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| 29 Dec 2010 11:33 AM |
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Hi Jon,
Thanks for the link! (http://www.awc.org/calculators/span/calc/timbercalcstyle.asp) I think I had found that at one point in my research but I didn't/don't know if it fits given the live/dead load choices.
If the concrete is ~140lb/cubic-foot and we plan on ~3" of the stuff - that results in about ~35lb/sq-foot. The max choice on the calculator is 20psf. Further there are several choices for deflection limits and since I’m not a structural engineer and don’t have a copy of the IBC I’m not sure what is acceptable.
I guess this comes back to how the concrete is incorporated into the floor structure and if there are different rules-of-thumb when designing such a system.
Thanks again for all your input (that goes for everyone in this community)!
Cheers,
-Jeff |
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vdubbin
New Member
Posts:13
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| 29 Dec 2010 11:44 AM |
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Posted By FBBP on 29 Dec 2010 11:18 AM
The stamped work used inside houses is not the same product as used outside! It is only 1/4 to 3/8" thick and the stamp mats have a much finer detailing than the mats one would use for outside. When properly done the floor looks just like a wood plank floor but the thermal dynamics are much better for both radiant and passive. This is an interesting technique (fine-detail interior stamping) that I don't have much knowledge of. Does anyone have example links and the like. This is a little off-topic and maybe deserves a new thread – I’ll go looking for an existing “interior concrete floor: polished v stamped” and start one if not found. |
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rvalue
New Member
Posts:66
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| 30 Dec 2010 02:17 PM |
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Have you considered a Hambro or Lite-Deck floor? Hambro is pretty close in price to a wood floor with concrete overlay. Jake Vierzen R-Value Concrete Structures www.rvaluehomes.com |
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Details matter!
Jake Vierzen
R-Value Homes
Grand Rapids, MI
616.299.3654 |
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