SIPs - Seam Taping
Last Post 29 May 2015 03:43 PM by Lbear. 23 Replies.
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bru15User is Offline
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25 May 2015 01:15 AM
Building, utilizing SIPs roof and walls. Climate Zone 6 in Idaho. 1) I know we tape the inside seams, but should the exterior seams be taped? 2) For the bottom sill plate..What is the opinion on using (in order) rubber gasket, treated plywood, poly-sealant, then a normal 2x6 as the sill buildup? The Panel would sit on the treated plywood, not the slab. 3) Is a 2x4 on it's 3.5" side adequate for the vented roof or should it be stood on its 1.5" side? Would a 2x3 be enough?
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25 May 2015 02:36 AM
Posted By bru15 on 25 May 2015 01:15 AM
Building, utilizing SIPs roof and walls. Climate Zone 6 in Idaho. 1) I know we tape the inside seams, but should the exterior seams be taped? 2) For the bottom sill plate..What is the opinion on using (in order) rubber gasket, treated plywood, poly-sealant, then a normal 2x6 as the sill buildup? The Panel would sit on the treated plywood, not the slab. 3) Is a 2x4 on it's 3.5" side adequate for the vented roof or should it be stood on its 1.5" side? Would a 2x3 be enough?

Taping the inside seams is a must. The outside is not as important but if you are a belt a suspender person, then I would invest the time and few bucks to tape the outside. SIGA WigLuv is excellent for exterior SIP seams and Rissan is great for interior seams.

A 2x4 laid flat (1.5" in height) is more than adequate for a venting roof channel. Laying it on the 3.5" side is not necessary and would make for a difficult attachment. Just lay it flat and the 1.5" of air space will be more than enough to dry. I would just use a 2x4 since they are plentiful and inexpensive.

Are you putting 1/2" or 5/8" OSB over the 2x4 furring strips?


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25 May 2015 07:02 AM
Why treated plywood rather than PT 2x6 etc?

What about alum termite shield or poly guard?

As to the roof there are many opinions on weather or not that air space is needed rather than a good vapor barrier.

I decided against the air space on my build and using a barrier.

Seams on the interior are a must, but I wonder if using a good caulking on corner joints like were wall & roof meet would stay in place better than bending tape into the joint.

ON the outside the important thing is to get the foam in the joints by drilling holes every 12-18 " and injecting same.

Then again a vapor barrier under siding like drainable wrap  watch their video on the water gap
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25 May 2015 12:03 PM
Thanks all.

Probably will tape outside, it seemed a good idea, but rarely see it mentioned.

I have seen a few houses (non SIPs) that built a cold roof and put the 2x4s on the 1.5" end.... supposedly for more air flow. I thought on the flat would be adequate (and easier). What is being used for the screening on the eave portion of this vent (to keep bugs out)?

Thinking 5/8" sheathing over, since there are not joists in the SIPs every 2 feet. SIPs roof is 12 1/2". Still out on that one.....

Treated Plywood saves a bunch. I have 365 feet of sill plate. My SIPs wall are 6 1/2" thick....I would have to rip 2x8s for the first layer on the sill. The first layer is just to keep the SIPs (OSB) off of the concrete. A EPDM gasket under it. Poly sealant on top, then the 2x6 that the SIPs attaches too. The SIPs manufacturer thought the 3/4" plywood would be fine.

I am in Zone 6. Temps can drop to -20, up to 85. We get a lot of summer rain, winter can have 5 feet snow on the ground....leading to a lot of ice dams around. Seems like people get leaks in regular roofs then put up a cold roof and they stop. I want to address this from the beginning.

No termites.....too cold all year. No real shield, but I will have a flashing covering about 2" of the SIPs extending down, covering 6" of the foam slab insulation (under the soil fill). Borate spraying the SIPs for the lower 2'.

My wall to roof are angle cut so SIPs meet SIPs, no wedges to install.

Intended to fur out the wall (3/4") over Tyvek (unless something better), then Cedar T&G 1 1/2" siding. Leaving space on the bottom and top for flow. What is used to screen these areas?

As far as the slab....It's a mono pour, R-18 insulated sides and under.
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25 May 2015 12:39 PM
You only need 1mm of space for water to run out, and air to flow, 2by's are over kill, but it's your house.


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25 May 2015 12:51 PM
Posted By bru15 on 25 May 2015 12:03 PM


Treated Plywood saves a bunch. I have 365 feet of sill plate. My SIPs wall are 6 1/2" thick....I would have to rip 2x8s for the first layer on the sill. The first layer is just to keep the SIPs (OSB) off of the concrete. A EPDM gasket under it. Poly sealant on top, then the 2x6 that the SIPs attaches too.

a 4x8 is about $40 so about $7 and change each 8', but you will have more butt joints.

A 2x8x16' is $16, it is thicker obviously and you just cut 3/4" off, I think It's easier to cut a 2by than sheet goods into strips
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25 May 2015 09:24 PM
Posted By bru15 on 25 May 2015 12:03 PM


Thinking 5/8" sheathing over, since there are not joists in the SIPs every 2 feet. SIPs roof is 12 1/2". Still out on that one.....


I am in Zone 6. Temps can drop to -20, up to 85. We get a lot of summer rain, winter can have 5 feet snow on the ground....leading to a lot of ice dams around. Seems like people get leaks in regular roofs then put up a cold roof and they stop. I want to address this from the beginning.


Check out 5/8" AdvanTech OSB. It outperforms plywood on many levels.

Cold roofs on OSB SIPs is not a bad thing and recommended by the Building Science Corporation and all the top-name building scientists. The cold roof will also act as a "sacrificial layer" to any roof damage. If a roof SIP gets damaged, you are in a world of hurt and expensive fixes. A standard truss roof with OSB sheathing can be replaced and repaired all day long. The same cannot be done with a SIP if it gets water/moisture damage.

The 2x4 furring channels will work great in keeping the SIP OSB nice and dry when it gets wet. The 2x4s will also provide a strong and wide area to put down the plywood or OSB and screw it down to.

OSB SIPs come in 7/16" thick skins. Typically metal roofs need at least 1/2" or preferably 5/8" thick OSB to provide proper screw retention. Some roof manufacturers will not warranty a roof if it is installed on a 7/16" thick OSB sheathing. It's about the screw pullout in that thickness. If water gets into that area the OSB can swell and the OSB even loses more strength.




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25 May 2015 10:32 PM
Posted By Lbear on 25 May 2015 09:24 PM
Posted By bru15 on 25 May 2015 12:03 PM


Thinking 5/8" sheathing over, since there are not joists in the SIPs every 2 feet. SIPs roof is 12 1/2". Still out on that one.....


I am in Zone 6. Temps can drop to -20, up to 85. We get a lot of summer rain, winter can have 5 feet snow on the ground....leading to a lot of ice dams around. Seems like people get leaks in regular roofs then put up a cold roof and they stop. I want to address this from the beginning.



OSB SIPs come in 7/16" thick skins. Typically metal roofs need at least 1/2" or preferably 5/8" thick OSB to provide proper screw retention. Some roof manufacturers will not warranty a roof if it is installed on a 7/16" thick OSB sheathing. It's about the screw pullout in that thickness. If water gets into that area the OSB can swell and the OSB even loses more strength.


I think the pull thru was an issue many years ago when the manufacturers used a different method.

can you please name the manufactures that will not warranty the roof?
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25 May 2015 11:37 PM
Posted By gosolar on 25 May 2015 10:32 PM

I think the pull thru was an issue many years ago when the manufacturers used a different method.

can you please name the manufactures that will not warranty the roof?

First point is that code minimum in most areas is 1/2" minimum on the roof sheathing. In my area it states that the roof sheathing must be "1/2" minimum roof sheathing" and areas with higher snow loads it states, "5/8" minimum roof sheathing".

I would advise one to check with their local code and see what the minimum sheathing thickness is for the roof. Can an inspector tell the difference between 7/16" and 1/2"? Most likely not but the code is what the code states. If it's 5/8" minimum sheathing then they surely will tell the difference between 5/8" and 7/16" OSB.

As far as roofing manufacturers go. I would contact whichever roof manufacturer you are using and ask them if 7/16" OSB is sufficient for their attachment. If they are OK with it and will warranty it, then have them put it in writing. Metal roofing companies prefer 5/8" sheathing to attach their screws & clips into but will tolerate 1/2". With 7/16" you will get sketchy answers regarding the warranty.

Can you find a metal roof manufacturer that will warranty the roof being installed and attached using 7/16" OSB?
If so, get it in writing because all the ones I talked to will not warranty it. The problem is that 7/16" OSB does not have much holding strength in it. The metal roof screws and clips rely on the holding strength to prevent the panels from sliding off in snow events or lifting off in high winds. A good 12" of snow or a 60mph wind will pull a metal panel off of a roof if it is not secured properly.

Best read this from the JLC:

Metal Roofing and 7/16" OSB
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26 May 2015 07:42 AM
As far as the code goes and sheathing thickness, sips are approved nationwide with 7/16", including S Fl  hurricane zones.

Besides the argument can be made that the roof is not 7/16" but double that with two layers.

I think you're mixing up the facts of sheathing thickness over rafter support spacing and metal attachment.

https://www.disastersafety.org/hail/metal-roofs/   states 7/16"

Firestone 7/16" 

Texas Dept of insurance 7/16

Now unless you can show otherwise can we agree sips 7/16 is good to go, to say nothing of thousands of installs out there.
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26 May 2015 03:19 PM
GoSolar,


Every building code dept is different and every roof manufacturer has different requirements. Once again, 7/16" OSB is a sub-standard attachment area for a metal roof. There is not much grip in 7/16" OSB to hold down a metal roof that might experience heavy snow loads and high winds.

There is no one-size fits all application here. One will have to call the roof manufacturer that they plan on using and find out if they will OK and warranty their metal roof being attached to 7/16" OSB. If they say, "yes", then you are good to go. If they say, "no", then you will have to find another manufacturer or just install a cold roof with 5/8" sheathing and kill two birds with one stone (venting of SIP and proper sheathing thickness for metal roof attachment).


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26 May 2015 06:05 PM
Good info. A couple items... Roof will be asphalt not metal. 3/4" furring on walls...can't find anything to use that is smaller thickness or would consider.
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26 May 2015 10:37 PM
Posted By Lbear on 26 May 2015 03:19 PM
GoSolar,


Every building code dept is different and every roof manufacturer has different requirements. Once again, 7/16" OSB is a sub-standard attachment area for a metal roof. There is not much grip in 7/16" OSB to hold down a metal roof that might experience heavy snow loads and high winds.

There is no one-size fits all application here. One will have to call the roof manufacturer that they plan on using and find out if they will OK and warranty their metal roof being attached to 7/16" OSB. If they say, "yes", then you are good to go. If they say, "no", then you will have to find another manufacturer or just install a cold roof with 5/8" sheathing and kill two birds with one stone (venting of SIP and proper sheathing thickness for metal roof attachment).



Just came across this engineering test report on 7/16" OSB

LBear still think it doesn't work?
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27 May 2015 03:01 AM
Posted By gosolar on 26 May 2015 10:37 PM


LBear still think it doesn't work?

I think you are missing the point. As I stated before, as long as your local code inspector approves it and the roofing manufacturer approves it, you are good to go. So if the two agencies OK the 7/16" then you are good.

Judging from the report you referenced it appears to be a Florida application. There are no snow loads in Florida. That is why the 7/16" is passable for that manufacturer.

With that being said, any roofer knows that 7/16" is NOT a good screwing base for metal roofs. Can it be used? Apparently so but it is not ideal. 1/2" roof sheathing is the bare minimum but 5/8" is ideal


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27 May 2015 06:38 AM
Posted By gosolar on 26 May 2015 10:37 PM
Posted By Lbear on 26 May 2015 03:19 PM
GoSolar,


Every building code dept is different and every roof manufacturer has different requirements. Once again, 7/16" OSB is a sub-standard attachment area for a metal roof. There is not much grip in 7/16" OSB to hold down a metal roof that might experience heavy snow loads and high winds.

There is no one-size fits all application here. One will have to call the roof manufacturer that they plan on using and find out if they will OK and warranty their metal roof being attached to 7/16" OSB. If they say, "yes", then you are good to go. If they say, "no", then you will have to find another manufacturer or just install a cold roof with 5/8" sheathing and kill two birds with one stone (venting of SIP and proper sheathing thickness for metal roof attachment).



Just came across this engineering test report on 7/16" OSB

LBear still think it doesn't work?



gosolar,
the ultrarib roofing in the test report is not a typical home installation, the exposed fastener roofing is more typical in agricultural or commercial installation
Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br />
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27 May 2015 06:48 AM
Posted By Lbear on 27 May 2015 03:01 AM
Posted By gosolar on 26 May 2015 10:37 PM


LBear still think it doesn't work?

I think you are missing the point. As I stated before, as long as your local code inspector approves it and the roofing manufacturer approves it, you are good to go. So if the two agencies OK the 7/16" then you are good.

Judging from the report you referenced it appears to be a Florida application. There are no snow loads in Florida. That is why the 7/16" is passable for that manufacturer.

With that being said, any roofer knows that 7/16" is NOT a good screwing base for metal roofs. Can it be used? Apparently so but it is not ideal. 1/2" roof sheathing is the bare minimum but 5/8" is ideal





Lbear,
there a are no snow loads in Florida , but there are hurricane codes and wind design criteria that affect screw pull out values much more than snow load,
Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br />
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27 May 2015 06:55 AM
Posted By bru15 on 25 May 2015 01:15 AM
Building, utilizing SIPs roof and walls. Climate Zone 6 in Idaho. 1) I know we tape the inside seams, but should the exterior seams be taped? 2) For the bottom sill plate..What is the opinion on using (in order) rubber gasket, treated plywood, poly-sealant, then a normal 2x6 as the sill buildup? The Panel would sit on the treated plywood, not the slab. 3) Is a 2x4 on it's 3.5" side adequate for the vented roof or should it be stood on its 1.5" side? Would a 2x3 be enough?



bru15,
sorry to see your thread get hijacked , but as you will find out on this forum if you hang around it long enough is: the opinions by some are by those that have no real life experience in construction, but have strong opinions based on their research, sometimes based on faulty information, just like a computer ----- garbage in / garbage out
Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br />
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27 May 2015 10:36 AM
Speaking of garbage in-garbage out: The recommendation to put a vapor barrier on the outside (cold side) of a SIP structure in climate zone 6 is ludicrous. Don't do it!
As a SIP professional with 25+ years of experience I can assure you that is bad advice. The consulting work I do nationwide often involves forensic investigation of SIP projects gone bad. It is not uncommon to find an exterior VB installed in cold climates which leads to trapped moisture.
You are better served by installing back ventilation in both walls and roofs then wasting money on taping your exterior joints.
I'd be happy to walk you through the process and other details if you contact me via private message.

good luck
Al Cobb
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27 May 2015 11:02 AM
www.premiersips.com disagrees, they recommend for example

http://www.cosella-dorken.com/bvf-ca-en/products/roof/underlayments_metal/products/trela.php

Vapor permeable underlayment with structured separation and drainage layer for ventilated and non-ventilated pitched roofs and facades with metal cladding.


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27 May 2015 05:15 PM
Gosolar, Please explain how they disagree. If, in fact, they recommend the underlayment suggested, it is in complete agreement with my recommendation. The Delta underlayment is not a vapor barrier and, it does aid in back-ventilation. Look at the perm rating and you will see that it, much like the Benjemin Obdyke material you suggested earlier are not vapor barriers.

I stand by my recommendation as one that is endorsed by Premier, BSC, SIPA, the IRC, and basic building science 101.

Regards,
Al Cobb
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