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发表于 2010-2-16 20:07
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草稿是拿英文写的，有些词的中文翻译可能不太对。这时可以参考一下这个英文稿。
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Introduced advanced framing
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The future is not plastics, the present is plastics, and the future is wood.
8 i) y* y" y& c* L6 U-Joseph Lstiburek
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I known advanced framing for many years and very interested for that. Actually its not new to home building. This technology also known as Optimum Value Engineering (OVE) can back its history as early as 1960s (NAHB Research Center developed OVE in thirty years ago). There are meanly two benefits to use advanced framing system save lumber cost and save the energy. I was been told it will save about10%- 25% wood for framing and save 5%-10% energy. For save the energy, the mean idea is about increasing the R value. Wood is NOT a good insulator. Of course comparing metal, wood is far good. But it is not good enough compare insulation material. Most framers think structurally, not thermally. Thermal bridging across framing members reduces overall R-value because a 2×4 or 2×6 is a poor insulator compared to fiberglass or cellulose. Thats why eliminating unnecessary framing in exterior walls is so important. Todays best enclosures are use foam sheathings, housewraps, and spray insulation. As an environmentalist, it is very attractive for me. Advance framing systems major points as bellow.
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1.Increasing rafter spacing from 16 to 24
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( a- e# I( l# P2 a' }2 s- bAnd we also need consider roof pitch. As the roof pitch go steeper, it will cost more lumber to build it. Alberta Building Code 2006(Chapter 9, Table 9.26.3.1 Roofing types and slope limits) allow minimum 4/12 roof pitch for Asphalt shingle or 3/12 for wood shingle roof. I once design a small house with 6/12 roof pitch and the roof truss manufacture told me that since their standard pitch is 4/12, increase to 6/12 will cost me $10 per square feet more. Of course if the house span is big, sometimes you have to go steeper roof to reduce the snow load and prevent the ice dam. I should explain that $10 per square feet price increasing is not normal, the roof truss guy want to give me a sky high price to force me change the pitch to their standard, but the idea is steeper roof do cost more money. (On average, a 12/12 roof can cost up to 50% more than a roof with a 4/12 slope. Many find that it is worth it though because the roofing material is estimated to last up to 50% longer and will require less maintenance in the long run.) My UofA supervisor is a big fan of flat roof, his argue is since the City of Edmonton has a height limitation for single house which is 8.6 meter. Flat roof can save more height from roofing. The other thing that I noticed is that according Alberta Building Code 2006, if the roof pitches more than 4/12, the roof height is just count half.
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2.Change the wall stud spacing from 16 to 24 center to center.* k# @8 N: N. }( p- a* Z
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Use 2×6 studs with 24 spacing is quite enough for take the loading. Some people might say it will become a flimsy wall. But half-inch drywall over studs 24 in on center isnt that flimsy (especially over dense pack cellulose), but if you dont believe it, then use 5/8-in drywall.
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5 B; Q: e# N8 h2 `- f+ N$ K4 S# oThe other complaint is drywall blocking. Using drywall clips and floating the corners (leaving them unattached to the framing) are excellent ways to reduce drywall cracks.8 ^+ G4 G3 m' g: s: m1 G* p
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3.Change the floor joist spacing from 16 to 24 center to center.9 o( y& F. \ `7 @0 Q$ F$ E6 J
9 B4 a8 d, W) B4 H8 M0 GRemoving every third joist could make floors more bouncy, but using thicker subfloor (1 ½ in panels) with proper glued and screwed, it will stiffen it back up.6 s' [5 [ R' C; F1 z3 T
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4.Single top plate instead of double top plate
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! j9 E* T, ?8 Z# D' FCode requires stack framing (structural support members are all aligned vertically) and metal splice plates to be used with single top plates.
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3 C Q( y* |, H2 s6 a& \5 D5.Eliminate non-bearing opening door header and window header.
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6.Places doors and windows on stud layout
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X0 [) s1 G. ~. B% u3 i7 IBecause many materials come in 8-ft. sheets, we should account for that fact in our basic dimensions. We also should slide doors and windows to the nearest stud. I used to design a 9 feet ceiling house and the framing manufacture told me since the lumber came with 8 feet or 10 feet, every single stud need to be cut and the cost will increase roughly $5 per square feet.4 b p' `: f! f) Y3 v
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7.Demands that framing members be lined up (or staked) for direct load transfer
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Lining up framing members directly on top of each other shouldnt be big deal, but apparently it is because many builders dont do it. Stack framing makes everything simpler. Fewer pieces go together faster, make less work for everyone, and leave more room for insulation.
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, w8 P6 ~3 [- h3 ?2 t+ x+ n8.Details to do the better insulation
/ _5 G, M8 |' T( C: iEspecially for high-wind, seismic, and high snow-load areas, connections detail should be developed for advanced framing system.1 E# l! l# W) t: ^& i3 j A
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- }; N* Q+ ~: e' u7 e8 wSome thoughts for the advanced framing design5 t" `7 {% I7 v5 o$ k) Z0 t+ b
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1. Design it for real, dont fly and keep your foot on the ground.
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A dimension of 23 ft. 6 in. makes no sense to anyone except town planners, architects, and designers.
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) D6 ]7 \8 `; [2 v) w# A2 f& ^. F' WOne of my architect friend use to told me he setup his minimum units to 1/256 in (1mm). Even no body build the house that way. Sometimes architects or designers seams like work for their own interest not for the owner or public. They can really enjoy their own idea even nobody could notice that.. n" V5 T3 L4 G! O2 [) D' d
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2. The more you think, the more you get8 A2 Q! A0 e6 [7 s
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The design is not just about safety, its about comfortable as well. As a civil engineer, I design platform. The deflection of the platform can go 5% and still keep structurally safety, but when people walk on that, they will fell uncomfortable, it will make them fell the platform will be crashed. u( c& L! L `% X/ i) a. s
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3. Imperial system vs. Metric system4 M+ O1 B- ? A1 R6 d
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5 D( E }6 G- E( ?: _$ l- s: I4. Keep some margin for your design/ t, c9 }+ r3 ?- C5 v. \
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Actually some people do not recommend this advanced framing system for seismic or high wind area, because its a high risk to do that. I used to attend a lecture which is host by a famous professor from University of TanJing. He said he and his colleague used to design two similar buildings at the same time. His colleague use finite element analysis cut a lot of margin to save the cost which he didnt do. During the Tang Shan earthquake in 1976, his colleagues building claps but his not. So, as an engineer, youd better be conservative rather than progressive. I used to work in Landmark, and saw one 2×6 stud break ,due to a MuLv in the lumber, during the framing period. Even this lumber go though several QC already (sawmill, lumber manufacture, distributor, building etc.). Keep in mind, wood is not like concrete or steel, its a homogeneous material. 6 J/ z1 B1 N% l. b; h; V
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If you cannot remember too much after reading this article, please remember the following: Next time you build your house, please make the roof truss, floor joist and wall studs with 24 spacing and replacing plywood or OSB wall with at least 1 in. of rigid-foam sheathing. |
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发表于 2010-2-16 19:59
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刚刚跟builder签的合同，因为是24” stud间距，所以觉得他们是在偷工减料了。再就是R20的insulation，觉得总是不满足，但是现在跟旧房子比比看看，好像还不错哈。
发表于 2010-2-16 23:54
发表于 2010-2-17 00:40
恭喜发财
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