CathyK
New Member
Posts:39
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| 01 Sep 2008 01:28 PM |
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We're about to use an OSB SIP roof (fairly simple design....a "T" shape so 2 peaks, 2 valleys) but are still concerned about the long term integrity of the product. We live in the Adirondack Mountains of NY. I just read the long article about the horror stories associated with SIP roofs in Juneau, AK. Granted it appears to a great extent that many of the issues has to do with poor installation techniques rather than SIP itself. I'm looking for feed back on 1)longevity and 2)recommendation for vapor barrier/felt/grace ice shield and the like for use under a standing seam metal roof. In addition, has anyone used Cedar Breather or Stoguard spray on vapor barrier? Thanks in advance. Cathy
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rnortman
Basic Member
Posts:112
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| 01 Sep 2008 05:53 PM |
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The most fool-proof design uses a ventilated drainage space between the cladding and the SIP. This can be accomplished by putting 1-2" furring strips over the SIP roof (running vertically), and then attaching your metal roof to those strips. (You may need another layer of OSB on top of the furring strips, depending on the metal roofing manufacturer's recommendations.) The space between the metal roof and the SIPs should then be open at the top and bottom (with a ridge vent at the top to keep the rain out, and possibly a Cor-A-Vent type product at the bottom to keep the bugs out). Underneath the furring strips you should have a vapor permeable membrane, to allow the OSB SIPs to breathe into the ventilated space, while draining away any actual water that makes it through your cladding through space. In this way whatever water or water vapor makes it through the metal cladding will not be trapped, and will rapidly drain or evaporate away. Exterior-grade OSB can handle being wet briefly; it just doesn't like being wet continuously.
Of course, this can be an expensive solution. You will probably need the second layer of OSB for most types of standing seam roofing, though I gather there are some types that will install directly over the furring strips. It also adds height to the roof which may cause design problems. But you are pretty safe from moisture problems this way.
(Note that the furring strips may instead be called purlins by roofing guys. When you do it to a wall, it's furring. For roofs, they'd use purlins. Same basic idea.)
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Alton
Veteran Member
Posts:2164
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| 01 Sep 2008 09:47 PM |
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There is a new synthetic material on the market that is used for furring strips under a roof. It is grooved so that it can be installed horizontally. I mention this because some metal roofing (shingles) requires a horizontal purlin for attachment purposes. |
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Residential Designer &
Construction Technology Consultant -- E-mail: Alton at Auburn dot Edu Use email format with @ and period .
334 826-3979 |
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CathyK
New Member
Posts:39
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| 02 Sep 2008 06:45 AM |
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You wouldn't use a self-adhesive water and ice shield? Just something like Tyvek under the strips? Thanks. Cathy
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rnortman
Basic Member
Posts:112
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| 02 Sep 2008 09:17 AM |
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Posted By CathyK on 09/02/2008 6:45 AM
You wouldn't use a self-adhesive water and ice shield? Just something like Tyvek under the strips? Thanks. Cathy
You want a breathable (vapor permeable) barrier under the furring/purlin strips, to shed water but still allow moisture to escape from the OSB. Tyvek works. Building felt works (better?). Many (most?) self-adhered membranes are not very breathable -- they stop water and also water vapor, which will prevent the OSB from drying when it inevitably gets wet somehow (leaks, condensation, initial construction, etc.).
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k_radanovich
New Member
Posts:13
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| 15 Sep 2008 08:17 PM |
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There is a new underlayment for metal clad roofs that I found at a trade show recently that looks like a great solution to haveing a cold roof over your sips roof. It is a breather membrane that has what amounts to plastic piles on it that the manufacturer says gives you the airspace and the breathable membrane in one material. It is manufactured by Delta and is called Delta-Trela. The web address is DELTATRELA.com I don't remember the cost but I thought he said around $1.00-$1.50 a square foot. I will be using it on my next cold roof application.
KR |
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| President/CEO<br>Green Walls-US, INc.<br>SIPs, ICF's & Antique Timber Frame |
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vb
New Member
Posts:88
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| 01 Jul 2010 12:32 AM |
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Not to hijack this post but.. I am planning a cold roof for my project and will be putting it on next week. I am using furring strips with osb and 50 year comp roofing. Does anyone have a suggestion for how far to space the furring strips ( 16" centers)? Also I am thinking I should screw the furring to the panel, is this overkill? |
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wes
Advanced Member
Posts:810
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| 01 Jul 2010 07:59 AM |
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vb
The thickness of your OSB will determine the spacing of your furring strips.
7/16" (the most commonly used thickness) requires 16" oc support.
Thicker material (5/8 or 3/4) can span 24".
Screws are actually a good idea, greater pullout resistance in the SIPS' osb skin.
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| Wes Shelby<br>Design Systems Group<br>Murray KY<br>[email protected] |
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cmkavala
Veteran Member
Posts:4327
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| 06 Jul 2010 01:26 PM |
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Mortman;
purlins are structural members, furring is not, roofs can be furred as well as walls |
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| Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
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cmkavala
Veteran Member
Posts:4327
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| 12 Jul 2010 05:20 PM |
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tanveer;
what do your links have to do with the topic? |
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| Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
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BabyBldr
Basic Member
Posts:123
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| 11 Aug 2010 10:37 PM |
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Posted By cmkavala on 06 Jul 2010 01:26 PM
Mortman;
purlins are structural members, furring is not, roofs can be furred as well as walls Cmkavala, that is an interesting note on terminology/function. Do you know where the term "girts" would fall? Not a big issue, I was just curious if you happen to know. Thanks! |
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cmkavala
Veteran Member
Posts:4327
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| 12 Aug 2010 06:17 AM |
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Posted By BabyBldr on 11 Aug 2010 10:37 PM
Posted By cmkavala on 06 Jul 2010 01:26 PM
Mortman;
purlins are structural members, furring is not, roofs can be furred as well as walls
Cmkavala, that is an interesting note on terminology/function. Do you know where the term "girts" would fall? Not a big issue, I was just curious if you happen to know.
Thanks!
Yes I do, they are side wall supports commonly used in pole buildings and metal buildings, similar to purlins. ..............is this a test? |
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| Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
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wes
Advanced Member
Posts:810
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| 12 Aug 2010 05:02 PM |
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Hey Chris,
I have a better question for you.
Where did the terms 'purlins' and 'girts' come from?
I have always thought these two terms were unusual, to say the least.
No, this isn't a test, because I don't know the answers.
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| Wes Shelby<br>Design Systems Group<br>Murray KY<br>[email protected] |
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trigem1
Basic Member
Posts:123
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| 12 Aug 2010 07:13 PM |
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Just had to add my two cents worth.
With SIPs for walls and roof, you never get an ice dam because the insulation is all the way out to the end of the roof and cannot thaw and freeze at the eave; so you do not need Ice & Water, although many local building codes call for it.
Regarding the internal SIP roof (not walls) seams – it is critical to either 100% seal the interior seam or use seam tape which I supply with roof panels. Interior moisture rising up can get into the seam and then in very cold environments can freeze. The only example of this happening was in northern Alaska, but it did damage the panels.
Tyvek is cheap and tears easily so is a mediocre water barrier. I recommend Perma-R, which private labels for a lot of building material suppliers. It is tough and cheaper than Tyvek. To find a local suppler, call them. http://www.permarproducts.com
Steve
GrandCountySIPs.com
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| Steve Etten |
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Bruce
Basic Member
Posts:142
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| 12 Aug 2010 08:19 PM |
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Your ice dam comment kind of assumes the only way they form is from heat from the inside. I thought they could also form by the warm sun warming the snow at the peak and it melts and flows down. Once it gets near the bottom of the roof it refreezes because the roof is colder there. Wouldin't that also cause an ice dam? This would happen regardless of the roof being SIPs or not; wouldn't it? |
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Como
Basic Member
Posts:128
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| 13 Aug 2010 12:09 AM |
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Posted By trigem1 on 12 Aug 2010 07:13 PM
Just had to add my two cents worth.
With SIPs for walls and roof, you never get an ice dam because the insulation is all the way out to the end of the roof and cannot thaw and freeze at the eave; so you do not need Ice & Water, although many local building codes call for it.
Regarding the internal SIP roof (not walls) seams – it is critical to either 100% seal the interior seam or use seam tape which I supply with roof panels. Interior moisture rising up can get into the seam and then in very cold environments can freeze. The only example of this happening was in northern Alaska, but it did damage the panels.
Tyvek is cheap and tears easily so is a mediocre water barrier. I recommend Perma-R, which private labels for a lot of building material suppliers. It is tough and cheaper than Tyvek. To find a local suppler, call them. http://www.permarproducts.com
Steve
GrandCountySIPs.com
Steve,
I was interested because I have a small project to build a Garn Barn, www.garn.com, so I will have two wood boilers producing a lot of heat hopefully.
I was thinking of SIPS, essentially the size of a 2 car garage, I need a door large enough to move a lot of wood through. Would SIPS not be a good choice for roofing in this case?
David
www.comodepot.com |
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cmkavala
Veteran Member
Posts:4327
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| 13 Aug 2010 07:54 AM |
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Posted By wes on 12 Aug 2010 05:02 PM
Hey Chris,
I have a better question for you.
Where did the terms 'purlins' and 'girts' come from?
I have always thought these two terms were unusual, to say the least.
No, this isn't a test, because I don't know the answers.
Wes; don't know where it originated , it how I have always refered to them that way back from when I sold pole barns enough about purlins and girts , lets talk about sleepers |
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| Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
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Como
Basic Member
Posts:128
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| 13 Aug 2010 11:34 AM |
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Sleepers is English for Railroad ties... |
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trigem1
Basic Member
Posts:123
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| 13 Aug 2010 09:09 PM |
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New Member with question about ice dams on SIP roof,
I live just outside of the Rocky Mountain National Park. During the winter, most days, we experience strong sunshine during the day and cold nights. It's not unusual to see water dripping off my SIP roof during the afternoon, and I'm sure it freezes at night. As a last minute decision, I added a heated entrance to the main entry. I conventionaly framed it, added R-30 insulation with a vapor barrior. That's the only place I ever get an ice dam. None of the rest of the roof gets any ice daming. You know how ice will develope on a bridge at that critical freezing point? I think on my framed overhang, with no insulation, it cools faster and the ice will form some time before the rest of the roof freezes, builds up, and forms a dam. If the whole roof is the same temperature, it all freezes and thaws at pretty much the same time, and not make ice dams. That's my theory anyway.
Thanks for asking.
Steve
GrandCountySIPs.com |
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| Steve Etten |
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thebigindian
New Member
Posts:5
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| 13 Aug 2010 11:38 PM |
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Cathy, in both NY and NJ We have frameguard coated sips that inhibit rot , mold, midew and insects. greenroomsystems.com Or use a MGO sip roof and never worry about rot insects and one better FIRE - it does not burn... http://www.tristatesips.com/index.html email R. Patel at [email protected] Ema |
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