Fasteners for AdvanTech Roof Sheathing
I’m trying to cut through code requirements vs manufacturer installation requirements.
Quick summary:
*Zone 6A
*Low slope unvented roof assembly for a small addition
*3/4″ TG Advantech roof sheathing
*Local code is 2015 IRC / 2015 IBC
Huber states that it is acceptable to screw the Advantech sheathing with #8 wood screws with a minimum embedment of 1″. I haven’t been able to find any screw approved option within the code, though frequently there is a statement within the code to the effect of “…and manufacturer installation instructions”. Perhaps I missed something within the code? What takes precedence: manufacturer’s installation instructions or code?
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Replies
Why would you want to screw it? Nails are the way to go (and the way any framer is going to install it).
steve41,
Building codes offer prescriptive requirements which have to be met unless you can get an appropriately qualified engineer to offer an approved alternative. Manufacturer's installation instructions are additional requirements, they don't supersede or replace those in codes.
As an aside: The idea that you have to follow manufacture's requirements typically comes from one sentence in most codes. It's increasingly less clear what it means, as the requirements often contradict both codes and other information by the same manufacturers. So for instance the fastener schedules given for many types of sheathing don't meet our code here in coastal BC, and installation requirements by many manufacturers that show the use of related products (say Tyvek only showing using their own flashing for window sill-pans) stand on pretty shaky legal ground.
Simpson makes screws for diaphragms - intended and approved for use on floors. So you would need to make sure there is no objection to use on the roof. They also offer a collated screw gun to install them.. Screws will be more expensive than nails.
Steve41. Screw it down. Read FEMA recommendation. I specified in my building contract to have screws. I ended up with nails - aaarrrr.
FEAM quote
https://flash.org/resources/files/HGCC_Fact18.pdf
"Fastener Selection
An 8d nail (2.5 inches long) is the minimum size nail to use for fastening sheathing panels. Full round heads are recommended to avoid head pull-through. Deformed-shank (i.e., ring- or screw-shank) nails are required near ridges, gables, and eaves in areas with design wind speeds over 110 mph (3-second gust), but it is recommended that deformed shank nails be used throughout the entire roof. If 8d “common” nails are specified, the nail diameter must be at least 0.131 inch (wider than typical 8d pneumatic nails). Screws can be used for even greater withdrawal strength, but should be sized by the building designer. Staples are not recommended for roof sheathing attachment in high-wind areas."
The manufacturers will often have their assemblies specifically tested and will obtain approval. You could call or email Advantech customer service. These large companies quite often answer questions from individual. I have had manufacturer engineers asking me if I wanted them to send me the assembly drawings - there are some really good people out there wanting to help.
Thanks everyone, really appreciate the feedback.
Malcolm: Yes, this is exactly what I have bumped into on several occasions: contradictions between code and manufacturers instructions. It's challenging to sort through.
user-6184358: Thanks, I'll take a look at Simpson options.
mr reference: Great link and recommendation to contact Huber. I have emailed them and a few other screw manufacturers. I'll likely reach out to my code guy as well. I believe that he would be fine with screwing the sheathing given that it is Huber's recommended practice, though not supported within the code. I have also yet to find an approved screw (with ICC-ES report) for this application.
It's obviously not a show-stopper if I nail the panels. I like the potential for reuse that using screws provide in the event of future remodeling / deconstruction. I also like the greater pull-out resistance for a roof application. I'm not looking to start a nail vs. screw battle. Both have their place.
If you want to do the future a solid don't use screws or ring shank nails.
I have taken apart stuff built with screws and it is horrid. Normal demo blade will quickly dull when you hit a screw shank and nocking studs out with a sledge causes the screws to either break or damage the wood. Of course one can unscrew but this takes too long and simply not worth your time. I would say a quarter of screw heads are rounded when someone was careless driving them in, no way to get them out.
It might feel like screws are easy to remove but this is generally not the case even with paneling. Screw heads in OSB are impossible to see and tend to fill with gunk over time. When you think you have fully unscrewed a full sheet of OSB, go to lift it up to find out that there is still 2 or 3 missed, can't use a prybar as the screws pulling through will break the sheet.
Generally I find anything that is nailed down with cheap straight shank nails is the best. Nails are cheap, satisfy most codes and very quick to dismantle. If you really want to do the future a favor use galvanized nails as these won't rust into place.
Hello Steve, I agree that it is not a show-stopper. I provided an additional link in my response to Akos below. The link provides a roof assembly approved by Miami Dade County with screwed down roof sheeting for maximum resistance to hurricane winds. The assembly calls for #8 screws, like Huber does for Advantech sheeting. Here is the link with all the details...
http://www.idealroofing.ca/english_canada/pdf/products/hf/NAO_16-0105.04.pdf
Another thing to think about is taping the joints between the sheets of Advantech. This is much more important when using non-T&C sheeting. I was listening to an insurance expert who explained that a great % of water damage in high wind storms occurs after the roofing shingles (or other products) are blown off by the wind. With most typical construction using H clips, the water from the rain will pour into the house through the gap created by the H clips. If you are using a T&C Hub Advantech board, maybe taping is not required but for myself I would be doing it anyway. On my own roof, we have a synthetic (non a tar product) ice and watersheild over the entire roof deck.
Thanks Akos. Definitely some valid points you've made.
My deconstruction experience is limited to my 120 year old house. The old square nails held things together amazingly well. Well enough to cause a fair amount of swearing- particularly when the nails spontaneously broke while prying. In my case, the few old screws that were found were easily removed.
I'm not a builder so if something takes a little more time it's not an issue. My general mindset has always been to use screws for anything (in the shop) I may want to easily disassemble at some point without wrecking the materials. As you have pointed out there may be other factors to consider. I've certainly done a hands-and-knees screw hunt on a sheet of OSB before.
I think screws in construction were popularized by a certain bald HGTV figure to push cordless tools from a yellow company. Any contractor that is using screws to build anything structural for you is wasting their time and your money.
Even if you have a small job to do, buying a framing nailer is well worth the money. The cordless ones are not cheap but are incredebly convenient even for small jobs. I find that I'm always grabbing it. Even for jobs like laminating LVL beams, you don't want to use screws. Screws are expensive and take a long time to install. Nailing out an LVL beam with a framing nailer is under a minute.
As for screws, watch the stuff from box stores. I find those construction screws are way to brittle and prone to cracking. The unthreaded shank on them is also very short so if you need to pull 2x lumber flat you end up driving the screw way too deep into the wood. This is hard to find, hard to remove and damages the wood. I would check what your local lumber yard or fastener place has instead.
Akos, I don't agree at all with you comment "screws in construction were popularized by a certain bald HGTV". This is simply a gross over generalization. Nails win hands down in most applications. If we focus on roof decking, FEMA and Miami Dade County know what they are talking about (see below).
I did find the statement "Nails are cheap, satisfy most codes and very quick to dismantle" very important in this context, because of the last part of the sentence. It is easy for a person to dismantle... which also means that it is easy for very strong winds to dismantle (i.e. tear off). I fully agree that we need to plan for future remodels, but securing the sheeting to withstand extreme winds is much more important - IMO. I also wonder how often is a person remodeling a house going to tear of the off large sections of roof sheeting?
I recently changed my screen name to "mr_reference" because I like to provide - where possible - references to back up what I say. I did that in my response with a FEMA document that is extremely detailed (https://flash.org/resources/files/HGCC_Fact18.pdf).
Here is a second reference from a producer of steel roofing. The company has approval to install some of their metal roofing products in a hurricane zone, Miami Dade County FL. This link shows what Miami Dade County - requires - for their roof sheeting. You can skip to page 3, section titled "Deck Attachment".
http://www.idealroofing.ca/english_canada/pdf/products/hf/NAO_16-0105.04.pdf
"In accordance with applicable Building Code, but in no case shall it be less than the
following: Sheathing shall mechanically fastened to the joists with #8 x 1-3/4” wood
screws spaced 4” o.c. around the perimeter of the plywood sheet, and 6” o.c. in the field of
the plywood sheet."
I do fully agree that nails have a lateral shear strength that the vast majority of screws do not. With roof decking, Miami Dade County specifies the size of screw required, that being a #8 and they also recommend 1-3/4" length for "New Construction 19/32” or greater plywood or wood plank...".".
I agree that nailing is faster. But nail guns use "common nails" and will never even use "spiral shank nails".
Green Building Advisor covers a wide range of topics and does it better than anyone around. This said, I would really like to see more about building structures that are wind resistant, earthquake resistant and designed to perform better in situations of heavy rain and overland flooding. Screwing down the roof sheeting is the tip of the iceberg.