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NHSIP&ICF
Registered Users
Posts:3
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| 02/20/2008 5:57 PM |
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I've been lurking on this site for the last month or so, and there seems to be some pretty experienced builders here. I've been working with SIPs and ICFs for the past two years.I've done six ICF foundations, and just finished my first ICF shell(28x44 1 story,full basement,and attached garage).I have put up three SIP shells (28x32,28x44,and 36x60 with 8x20 bump out) all with truss roofs.I am starting my first spec house in the spring which is 28x36 1 1/2 story on an ICF foundation with a SIP roof. The panels for the roof are 4'x20' only bearing on the ridge beam and the walls. I was planning on using insulated splines for the roof, as I will for the walls,unfortunately the manufacturer/engineer are saying that I must use 2x lumber as splines based on the snow load and roof pitch, 80lb snow load and an 8-12 pitch. Do any of you guys use insulated splines for roofs? Are there any other options besides 2x lumber for this application.This is a small house,I wouldn't think that I would be limlited to 2x lumber on such a small roof.Thanks for your input,
Matt |
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PanelCrafters
Registered Users
Posts:1323
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| 02/20/2008 7:02 PM |
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Posted By NHSIP&ICF on 02/20/2008 5:57 PM
The panels for the roof are 4'x20' only bearing on the ridge beam and the walls. I was planning on using insulated splines for the roof, as I will for the walls,unfortunately the manufacturer/engineer are saying that I must use 2x lumber as splines based on the snow load and roof pitch, 80lb snow load and an 8-12 pitch. Do any of you guys use insulated splines for roofs? Are there any other options besides 2x lumber for this application.This is a small house,I wouldn't think that I would be limlited to 2x lumber on such a small roof.Thanks for your input,
Matt
Matt,
Other than adding a couple of purlins, you'll need to follow the engineer's request. However, you could probably substitute insulated TJI's for the 2x material. Stronger, and your thermal break will probably drop to about 1/2" per joint. Enercept is one manufacturer that uses them.
Good Luck! |
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....jc
If you're not building with OSB SIPS(or ICF's), why are you building? |
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NHSIP&ICF
Registered Users
Posts:3
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| 02/20/2008 7:55 PM |
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| Thanks for the quick reply.I'll check out Enercept. Although thermal breaks were a major concern of mine, the stability (expansion/contraction)of the dimensional lumber over a 20' span.After seeing all the documentation of the failed SIP roofs in Alaska,I want to be sure that I use the right components to create a long lasting structure.This is my first SIP roof, and I plan on using another layer of sheathing(cold roof) and standing seam metal roof.Would insulated TJIs be your preference in this type of application? |
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Alton
Registered Users
Posts:308
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| 02/20/2008 8:03 PM |
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I have had reports that dimensional lumber with crown bow was difficult to install as splines in the field for long spans. Some installers I know switched to engineered lumber to avoid the crown bow.
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Alton C. Keown
Residential Designer and Construction Technology Consultant
Auburn, Alabama
334 329-0957 AT&T Cellular |
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PanelCrafters
Registered Users
Posts:1323
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| 02/20/2008 8:26 PM |
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Posted By NHSIP&ICF on 02/20/2008 7:55 PM
This is my first SIP roof, and I plan on using another layer of sheathing(cold roof) and standing seam metal roof.Would insulated TJIs be your preference in this type of application?
The span and load dictate your options. In your case the engineer has specified a structural spline. As a builder, I'm sure that you know why TJI's have replaced standard dimensional lumber: Stronger, Straighter and longer spans.
My preference? It's between adding purlins or structural splines. I can not offer an opinion. I haven't seen the design. But as far as a structural spline goes, I'm not sure where you could do better than an insulated TJI. |
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....jc
If you're not building with OSB SIPS(or ICF's), why are you building? |
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NHSIP&ICF
Registered Users
Posts:3
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| 02/20/2008 8:57 PM |
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Thanks alot for your input guys,I had been thinking about using engineered 2xs earlier today and forgot to mention that. I'm going to push for the use of insulated TJIs to the engineer, I don't think he is aware of all the possible options. Do you guys prefer using a cold roof over SIPs?
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panelwright
Registered Users
Posts:19
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| 02/20/2008 10:25 PM |
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Matt,
I encourage a panel design that lets the panel do the work. If we force too thin a panel to span too great a distance, we are forced to use a spline detail that adds structural support. Unfortunately, this detail will result in a slower install, an increase in expense, and a thermal bridge. When confronted with your quandary, I first look to an analysis of the total required roof load. (Remember to include the let-off for a metal roof and an increased pitch) With that number in hand, I search the load design charts for a panel thickness that will make the grade using a surface spline detail. (or insulated spline, block spline, super-spline. they're all the same basic configuration) This detail solves the three problems mentioned above. If we still can't get to an acceptable design load, then look to the possibility of shortening your span. Your structure may be a prime candidate for purlins as JC suggested or, my favorite, the offset ridge. Either of these support options may allow a decreased span and get you back to the joint detail that you should find most favorable.
Your question about a cold roof can only be answered if we call it by its correct name which is a "Dry roof". It's not a matter of hot & cold, but dry & wet. The only real advantage to ventilating a roof is improving the roofs capacity to dry!!!! So when do we use a dry roof? When we build in wet and/or cold climates. (with the emphasis on "period")
Finally, your reference to Alaska inferred it was a product or component problem. In fact, it was an installation defect. Our industry is plagued with too many people trying to do what they haven’t been taught how to do. The key to a successful SIP installation depends more on good installation technique then it does on good panel design. As you move towards your first SIP roof project, I encourage you to seal it, seal it, and seal it again. Make it tight and ventilate it right!
Good luck,
AL
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ReadyToRetire
Registered Users
Posts:195
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| 02/21/2008 3:55 PM |
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Al,
Stupid question time: Wouldn't offsetting the ridge make the critical span longer?
Very respectfully,
Larry
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NWP
Registered Users
Posts:53
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| 02/21/2008 7:58 PM |
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Hello Matt,
We are a manufacturer located in the northeast and have been using regular spline in areas where the snow loads range anywhere in the 80-110#. When we have any questions we pass it by our engineer to spec out, we have yet to use 2x materials. We also use thermal spline which the engineer will give the ok to like he has in the past.
We just completed a shell erection on a home in Freemont NH that used osb splines on a 12 pitch with the panels spanning 22'. Not sure where you are located but would if you would like to talk feel free to get in touch through personal contact.
Ralph |
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racer1
Registered Users
Posts:7
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| 02/21/2008 10:09 PM |
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I built a sip House 3 yrs ago just like you talking about.. I used enercept for the whole thing..I used their sip foundation panels, walls and roof. 34x36, with a loft. I used a main beam in the center. No purlins. 4x 24 roof panel with a I joist for the splines..8/12 pitch.... The whole system works...The roof panels slide together very easy. 3yrs, lots of snow, and my roof is straight and strong. The whole interior of roof is lined with 1x8 tongue and groove knotty pine......See attached pic....
....Jim....
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Father of the Paw
Registered Users
Posts:8
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| 03/04/2008 8:40 PM |
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Hey Ralph,
Am facing the same quandary as Matt, which splines to use on with 8" 4'x20 roof panels, 19' span' 10x12 pitch. Would like to avoid any thermal breaks; part of the reason for going with sips in the first place. Of all the tech/assembly manuals I've downloaded all seem to recommend dimensional lumber or TJIs for roof splines. Surface splines would certainly help cut our costs and would avoid thermal bridging. Would the type of spline used be dictated by the manfacturer or local code official.
Any Input?
Mark in Kansas |
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Dick Mills
Registered Users
Posts:124
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| 03/04/2008 9:24 PM |
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Mark,
Not to be too nitpicky, but I think your usage of the term "thermal breaks" isn't truly what you are trying to say. You want thermal breaks (places where thermal conductivity is minimized), you don't want thermal bridges (those places where thermal conductivity is higher).
So, you want to avoid thermal bridging.
Dick Mills |
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Gsfrey
Registered Users
Posts:60
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| 03/05/2008 4:08 PM |
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Question:
We use a tongue and groove for all of our roof panels. Now given the span is merely 4' given this is a traditional truss layout for the roofs we construct, but why couldn't you just tongue and groove the entire roof regardless of span given the structural nature of the SIPS?
If it's a code thing, I get it. But it seems the structural integrity of the panel is such, and we drive cars over 20' panels all the time to demonstrate their strength, it would withstand the stress.
Thanks, |
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Greg Freyermuth
915-256-7563, Phone
GregFreyermuth@elp.rr.com, E-Mail |
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cmkavala
Registered Users
Posts:807
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| 03/05/2008 4:19 PM |
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Posted By Gsfrey on 03/05/2008 4:08 PM
Question:
We use a tongue and groove for all of our roof panels. Now given the span is merely 4' given this is a traditional truss layout for the roofs we construct, but why couldn't you just tongue and groove the entire roof regardless of span given the structural nature of the SIPS?
If it's a code thing, I get it. But it seems the structural integrity of the panel is such, and we drive cars over 20' panels all the time to demonstrate their strength, it would withstand the stress.
Thanks, You need to control the edge somehow with fasteners, otherwise you have 4 ft. of uncontrolled OSB able to do what ever it wants
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Chris Kavala
chris@southernsips.com
1-877-321-SIPS |
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Gsfrey
Registered Users
Posts:60
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| 03/05/2008 4:24 PM |
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| But if you tongue and groove the panels, with SIP's EPS glued into the accompanying panel, where is your edge to control? You could have as much as 6'' of mated EPS glued into the panels. Put a board into the ends of the roofs. Not being a contrarian, but it seems this is a viable alternative. |
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Greg Freyermuth
915-256-7563, Phone
GregFreyermuth@elp.rr.com, E-Mail |
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ReadyToRetire
Registered Users
Posts:195
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| 03/06/2008 4:59 PM |
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Greg,
As I understand it, the foam's function is to prevent the skins from coming closer together. The issue that I see is how much of the load you can transfer across the joint. All of the ones that I've seen do something to physically connect the surface on one SIP to the surface on the next: splines with tight fastener schedules, 2x material with fasteners (the 2x is stiff, but the fasteners are concentrated at the very edge of the surfaces), or I-beams. But each has a fastener that transfers the load from the skin to the joint, the joint material transfers it to the other fastener, which transfers it to the other skin. If the fasteners are reasonably close to each other they can transfer a reasonable % of the load. But all are dependent on the strength of the connector material.
Your idea would be easier, but it would replace OSB or 2x or I-beam with a block of foam. Stick a block of foam between two supports and stand on it -- what happens? The foam isn't strong enough to carry the load. It's not strong enough to carry (transfer) the load between panels, when the panels are under load the foam would rip out.
Very respectfully,
Larry
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cmkavala
Registered Users
Posts:807
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| 03/06/2008 5:36 PM |
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Posted By Gsfrey on 03/05/2008 4:24 PM
But if you tongue and groove the panels, with SIP's EPS glued into the accompanying panel, where is your edge to control? You could have as much as 6'' of mated EPS glued into the panels. Put a board into the ends of the roofs. Not being a contrarian, but it seems this is a viable alternative.
Intstead of reinventing the wheel, just use steel SIPs
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Chris Kavala
chris@southernsips.com
1-877-321-SIPS |
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Gsfrey
Registered Users
Posts:60
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| 03/06/2008 5:52 PM |
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Respectfully, The foam, which is part of the SIP panel, is glued into the adjoining panel, much like it is glued into the panel normally. Except of course for the fact the glued tongue and groove, if you will, are not glued under pressure. The 2x dimensional lumber is not the load bearing portion of the SIP's. If it were you could only platform frame with the trusses sitting firmly atop the 2x dimensional lumber joining the panels together. Instead you can rest the trusses along the top of the panel anywhere because of the incredible job of weight transference that occurs whenever a load is placed on top of a SIP wall and the weight of the load in passed along into the foundation of the home.
Secondly, only a portion of the SIP would be void of the chemical bond that occurs when the panels are joined under pressure. For example only the portion of the panel that is glued on site would not enjoy that same bond. I am not sure, maybe I need to put my money where my mouth is and put some of these site glued, tongue and groove panels under a controlled weight and stress test and see. If it could be shown that the tongue and groove is strong enough, well now we are on our way to world shaking stuff. Imagine the speed and convenience. Why it would be world shaking indeed...
Thanks, guys. |
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Greg Freyermuth
915-256-7563, Phone
GregFreyermuth@elp.rr.com, E-Mail |
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ReadyToRetire
Registered Users
Posts:195
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| 03/06/2008 6:36 PM |
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Greg,
From what I've seen on his site and postings, the steel SIPs that Chris have an elegant way to solve the problem of joining the skins.
Try a mental experiment before you buy hardware. Take two shallow foam slabs 1 or 2 inches thick, 6 wide, and several feet long. Contact cement a piece of OSB onto each of the long edges. Take one and locate the center of the long edges and carefully saw through the OSB without cutting the foam. You now have two models to play with. Support the ends with panels a foot or so off the ground. Place a brick in the middle of each. Keep doing that until each breaks or fails. What would you expect to happen? If you think there will be no difference, build the models and see.
My guess is that the cut surface will concentrate the load into the foam at the cut joint and fail pretty quickly.
Very respectfully,
Larry
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Gsfrey
Registered Users
Posts:60
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| 03/06/2008 7:11 PM |
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I guess I am just not painting the picture well enough. Well get some testing done and I will get back to you folks, hopefully not looking like an idiot, but I will report back.
Thanks, |
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Greg Freyermuth
915-256-7563, Phone
GregFreyermuth@elp.rr.com, E-Mail |
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