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Author Topic: Wrap and Strap Question: Fasteners  (Read 4122 times)

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Offline Brian_Weekley

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Wrap and Strap Question: Fasteners
« on: March 28, 2012, 09:06:42 am »
My frame is coming along nicely.  I’m starting to think about the siding aspects for my barn/cabin.  I’ve read many of the threads and studied Rooster’s excellent pictorial showing the “wrap and strap” method for insulating the siding and roofing.  However, I’m having a hard time understanding how the fasteners (pole barn nails) can hold the weight of the external siding with the insulation sandwiched in between.  In my example below, I have 1x sheathing (inner) followed by two layers of rigid foam (4”), 2x4 straps, and 1x siding (exterior).  Therefore, the pole barn nails must penetrate 6 ˝” before any of it reaches the meat of the interior 4x4 girt.  10 inch long nails through the strap would penetrate the girt 3 ˝ “.  Depending on the weight of the exterior siding, it just seems like those nails would have to withstand a lot of force trying to bend them over.  Would the walls eventually sag?  I know this depends on factors like the insulation thickness, weight of the siding, etc...  I have questions:  Is this typically a problem?  What is the maximum insulation thickness that works well for walls using this technique?  How far apart (spacing) should the girts be to attach strapping?  What nail spacing do you need for adequate holding power?

Thanks again for entertaining my rookie questions.  You guys are awesome!

 
e aho laula

Offline Rooster

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Re: Wrap and Strap Question: Fasteners
« Reply #1 on: March 28, 2012, 10:44:50 am »

BW,

Welcome to the world of wrap and strap.  Here are some things that I did, and also learned from.

I used 3" of foam on my exterior walls and full 1" straps...this thickness worked well with the 80d ringshank polebarn nails.  I staggered nailed with 16" spacing.  One 4ft section of strapping on the endwall, (left of one of the OH garage doors), had only 3 nails securing it to the interior girt, and I could do pull-ups on it until I got tired, (22 for those of you that are counting).  Also the siding weight is normally transfered to the most rigid part of the wall...on mine it was the sill and the top-plate. I normally nail my siding from the bottom up, so all the initial weight of the siding is on the sill. For your thicker wall, you could go to a long timber screw.

Will Leverett
Log & Timber Connections
478-474-9745
www.logandtimberconnections.com

Tell him, "Rooster sent yah!"

He has good pricing, excellent fasteners, and quick turn-around on orders.

I used 1/4"x10" counter-sunk head screw for my roof strapping.

My girt spacing was a combination of the original spacing for the barn (40-48in)that I used to build the carriage house, and where the seams for the outer most layer of insulation would end up. I tried to have the seams line up with the girt elevations so that my straps would cover the horizontal seams.

I hope this helps.

Roooster
"We talk about creating millions of "shovel ready" jobs, for a society that doesn't really encourage anybody to pick up a shovel." 
Mike Rowe

"Old barns are a reminder of when I was young,
       and new barns are a reminder that I am not so young."
                          Rooster

Offline bigshow

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Re: Wrap and Strap Question: Fasteners
« Reply #2 on: March 28, 2012, 01:26:10 pm »
Rooster, thats incredible! (the pullups)
I never try anything, I just do it.

Offline Brian_Weekley

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Re: Wrap and Strap Question: Fasteners
« Reply #3 on: March 28, 2012, 07:00:35 pm »

But isn’t it cheating when your feet are touching the ground?   ;D

Thanks, Rooster.  When I think of SIPS, I picture them seated in a spline resting on the sill.  Therefore, much of the weight is transferred directly to the sill and the screws basically just hold the SIP panels against the frame.  Based on your description for wrap and strap, I envision the use of spacer blocks mounted at the top plate and bottom sill (width of the foam) so the exterior siding can be nailed directly to solid wood and be well supported at those locations.  Does this make sense?

 

In reality, I was only planning 2-3 inches of insulation on the walls.  In this figure, I show 3 inches of insulation with a 3 inch spacer attached below the insulation with 1x3 straps.  The bottom spacer would also act as a rodent stop.

Thanks, Brian
e aho laula

Offline Jim_Rogers

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Re: Wrap and Strap Question: Fasteners
« Reply #4 on: March 28, 2012, 07:56:49 pm »
In this picture:



You can see two 2x4's nailed to the sill for the wall panels to sit on. If I am correct these would support the panels until they are screwed onto the frame.

Jim Rogers

PS. I am also working on a wrap and strap cross section detail drawing to post when I have all the facts straight.
I have email a copy to Rooster to review and advise if I have it right before I post it and make it available to others to see and use.
I hopefully will have it done tomorrow.
Whatever you do, have fun doing it!
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Offline mmhailey

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Re: Wrap and Strap Question: Fasteners
« Reply #5 on: March 28, 2012, 10:06:19 pm »
Question?

Have you settled on the type of foundation? There are several options for extending the foundation to carry the weight of the insulation, strapping, and siding.

 

 

If the insulation. If you already have a foundation, or you have an existing one "Nevermind"  :D

Here is a pic of mine. I think you can see the extended mudsill
Give a man a fish, feed him for a day. Teach a man to fish, and turn him into a liar.

Offline Brian_Weekley

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Re: Wrap and Strap Question: Fasteners
« Reply #6 on: March 28, 2012, 11:16:29 pm »
mmhailey,  My sill timbers will sit directly on a dry-fit stone foundation.  Therefore, anything exterior to the frame must be attached to it.

Jim, I think a wrap and strap drawing would be very helpful to many here.

--BW
e aho laula

Offline frwinks

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Re: Wrap and Strap Question: Fasteners
« Reply #7 on: March 29, 2012, 12:38:58 pm »
Brian, check out the REMOTE wall manual, it has a ton of info on the exterior insulation apporach ;)
http://cchrc.org/docs/best_practices/REMOTE_Manual.pdf
for fasteners I used Deckfast roofing screws, much cheaper than timberlocks and our PEng was happy with them.

http://www.sfsintecusa.com/products/dekfast/

many lengths to choose from:
http://www.bestmaterials.com/SearchResult.aspx?CategoryID=750

I have 5.5" of polyiso and 1" roughsawn strapping on walls.  8" of foam and two layers of 2x4 strapping on the roof. For the roof I used 14" screws, it worked out great...

g/l

Offline Brian_Weekley

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Re: Wrap and Strap Question: Fasteners
« Reply #8 on: March 29, 2012, 11:01:25 pm »
Thanks, frwinks.  Good info.  One interesting tidbit was the angle to drive the fasteners.  Unfortunately, many guides like this address conventional framing where the strapping can easily be attached on standard 16 or 24 inch centers instead of timber frames! 

OK, let me throw one more monkey wrench in the mix.  One additional siding option I’m considering is to put shakes on the exterior.  Don’t cringe, but I was considering polymer shake shingles instead of wood (modern outside/traditional inside).  However, this would require a solid substrate to nail the shingles to instead of the straps/furring strips used to hold the insulation on.  Therefore, I was thinking about sandwiching the insulation with something like CDX plywood (covered with a housewrap, maybe some polymer matrix for air space (e.g., Home Slicker) and finally the shingles).  However, this brings up another concern about fastening—are girts spaced 3-4 feet apart enough to prevent the plywood from bowing in between?  Anyone have experience with this one?  Too many decisions!

 
e aho laula

Offline D L Bahler

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Re: Wrap and Strap Question: Fasteners
« Reply #9 on: March 29, 2012, 11:22:54 pm »
I am not familiar with polymer shakes, but wood shakes I am familiar with. With wood you do not need a solid substrate to nail to, you need furring spaced to where the nails go on your shakes. The rest can be open. Look at the roof of an old barn from underneath some time, you can see the shingles. These will have roof lath every foot or so depending on the size of shingle used, but the rest is wide open.  Really old buildings you can some times see the lath is 2 foot apart or so, and is just half-round poles nailed across the rafters.

Offline addicted

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Re: Wrap and Strap Question: Fasteners
« Reply #10 on: March 30, 2012, 10:56:07 am »
Brian
 Last month or maybe two months ago fhb magazine had a good article about a barn that was converted to an office/workshop with a wrap/strap format 16 yrs ago. He recently ripped off the exterior and re-applied a new wrap/strap and reported on the products that failed and the ones that worked.  I remember him saying that the epoxy coated screws worked as long as they were kept in a well managed area.  The places that water was not managed well, the screws corroded. Much cheaper than stainless.

Rusty

Offline witterbound

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Re: Wrap and Strap Question: Fasteners
« Reply #11 on: March 30, 2012, 11:24:08 am »
I'd bet those polimer shingles are intended to be nailed through the sheathing into the studs to hold them up....

Offline Brian_Weekley

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Re: Wrap and Strap Question: Fasteners
« Reply #12 on: March 30, 2012, 12:02:23 pm »

Addicted, I located some videos on the Fine Homebuilding website.  Looks like it might be related to what you saw.  I'll check it out when I get home.

witterbond,  I did check on what substrate is necessary.  The polymer shingles may be attached to structural sheathing (minimum ˝” thick) attached to the outside of the foam (as long as the sheathing is properly tied to the inner frame).
e aho laula

Offline witterbound

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Re: Wrap and Strap Question: Fasteners
« Reply #13 on: March 30, 2012, 04:22:27 pm »
cool.

Offline addicted

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Re: Wrap and Strap Question: Fasteners
« Reply #14 on: March 31, 2012, 11:37:43 am »
The fhb issue I spoke of was march. no. 225
He points out some great ideas and reviews of products.  The title of the article is foam shrinks.  In the article he refers to eps as the product used in the beginning and now he is switching to polyiso. The downside of the article is that it is only five pages long. I would have preferred an entire volume on the subject. If anyone is considering wrap and strap I highly recommend this issue.
I have no affiliation with fhb
Rusty

Offline timberwrestler

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Re: Wrap and Strap Question: Fasteners
« Reply #15 on: March 31, 2012, 02:51:08 pm »
I don't think it's necessary to angle the screws, especially for a lightweight cladding like shingles.  Here's an article on wrap and strap screwing:
http://www.greenbuildingadvisor.com/blogs/dept/musings/fastening-furring-strips-foam-sheathed-wall
The latest issue of JLC also has an article, but I haven't had time to read it yet.

I'd stick with wood shingles, but I'd vertically strap through the foam, and then skip sheath with 1x3 or 4 horizontally.  That way, you'll get a rainscreen assembly.  If you want to use the composite shingles, you have to consider the little details that the manufacturers never point out.  With real shingles you can vary the layout so that windows or corners don't have 1/2" exposures.  You're stuck with panelized products.  Pre-dipped cedar or even fiber cement shingles will last a mighty long time, and have minimal maintentance and are repairable.  If you want to use the composites, I'd still vertically strap 24" OC, and then sheath with 1/2" CDX.

Offline Brian_Weekley

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Re: Wrap and Strap Question: Fasteners
« Reply #16 on: April 03, 2012, 09:15:45 pm »

Thanks to everyone's feedback, I've attached my modified siding scheme:  1x pine, felt, 2x 1.5" polyiso foam (staggered and taped), 1x4 strapping, 24 OC (attached top, bottom, and 2 girts with 8" fasteners), sheathing, typar with house slicker (for air gap), and fiber-cement shakes.

 

Does this look reasonable?  See any concerns with this proposal?

Thanks, Brian
e aho laula

Offline Jim_Rogers

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Re: Wrap and Strap Question: Fasteners
« Reply #17 on: April 04, 2012, 08:28:44 am »
Looks good to me, except you may want to but some flashing under the shingles behind the rain slicker and other sheathing out and over the 2x bottom piece just in case some water gets in. It would have a place or way to run out and not sink into your bottom 2x's.
I think they call it Z flashing, maybe.

Jim Rogers
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Offline sailorman

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Re: Wrap and Strap Question: Fasteners
« Reply #18 on: April 04, 2012, 09:05:17 am »
On your last siding scheme, could the strapping be dropped and place sheathing against foam,  screw directly to frame members, maybe use adhesive to foam as well? What benift does strapping do if sheathing is to be applied? Would this not be a simirial to a SIPS? I would think not using strapping would save time and money if your purchasing the strapping.

Offline timberwrestler

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Re: Wrap and Strap Question: Fasteners
« Reply #19 on: April 04, 2012, 09:51:08 am »
That looks good Brian.  You could skip the 2x on the bottom of the foam if you want, but they won't hurt.  You don't need flashing there because they're under the drainage plane on the plywood.  And you can skip the interior tar paper if you're using ship lapped or T&G boards.  I'd cut some window screening up, and wrap it around the bottom of the vertical straps to keep bugs and bees out.  And I'd spray foam and tape the foam seams.

The Homeslicker is nice, but quite expensive.  You can buy homeslicker bonded to tyvek, but it's easier and cheaper to do them separately.  I assume your FC shingles are panelized, but if they're not, with regular shingles you want to put 1/4 ply or wood strips ~6" wide at the corners, because you can't weave shingle corners with homeslicker very well.  Check out Nichiha, they have some FC shingles that look remarkably good.

Sailorman, you can't really skip the strapping, because there's likely no support for the plywood at the panel edges.