Exterior sheathing required under steel siding?

Ajping3830 · Sep 19, 2017

Just joined the forum, I have next to nothing for construction experience or knowledge...

So I am getting quotes to have a full foundation framed wall 24x40x12 garage built with steel siding and roof. I will be insulating the walls and will be running radiant floor heat year round.

So one contactor is adamant that I need sheathing under the siding, and the other one is just as sure that I do not.
I have found a lot of information stating sheathing under a metal roof is unnecessary, but I have not been able to find any info about walls.

Can I get some advice on this please? Also I live pretty high on a hill and I see some nasty winds from time to time if that factors in...

brownbagg · Sep 19, 2017

Yes and no. the plywood reinforces the wall in shear, so if its just a garage then no, but if its a resident bldg then yes. and it the same wall with roofs, residential require plywood under metal roofs, but a shop no, but it is a good idea to have it.

rburke65 · Sep 19, 2017

I don't know if there is a requirement for the X heating, BUT.......do ya need it....no. Do you want it.....YES. This is like adking do I need shoe laces....nope. Do you want em.....Yep. Do it once. Do it right. You will never be sorry. Listen to your gut. Good like.

BillK · Sep 19, 2017

If I was having it done I would find out who the siding manufacturer is and ask them. They probably have a web site with all of the installation requirements. That way you wont be guessing.

That being said, my gut feeling would be that sheathing would give an extra level of strength and insulation. You dont say where you are located but if you are going to be running infloor heat year round I would want the structure as air tight and strong as possible.

Ajping3830 · Sep 19, 2017

Pretty much what my feeling was.... But... specifically... what are the differences going to be, other than a large chunk of $$$? Is there going to be a big impact on insulation quality? I have a friend that does professional spray foam so will be going that route. Also where I live there is no zoning so I don't have to worry about that. I will eventually be turning this into a small machine shop, or hope to anyway lol.

Ajping3830 · Sep 19, 2017

BillK said:
If I was having it done I would find out who the siding manufacturer is and ask them. They probably have a web site with all of the installation requirements. That way you wont be guessing.

That being said, my gut feeling would be that sheathing would give an extra level of strength and insulation. You dont say where you are located but if you are going to be running infloor heat year round I would want the structure as air tight and strong as possible.

Not a bad idea, I will see if I can find the requirements from the MFG'r. Also I'm in western NY.

850xpeps · Sep 19, 2017

My advice would be do it. And put a membrane under the tin on the roof. It can be set right on the shearing and eliminate the rattle in the rain or hail because the tin can't bounce. It will also keep your insulation in your walls and tyvek or house wrap so any moisture behind tin runs down and out.

Firebrick43 · Sep 20, 2017

You are getting some very bad advice here.

First you say "full foundation framed wall"

This is vague and open to some misunderstanding. I am going to assume you mean platform framed or standard stick framed? Or do you mean ballon framed?

Pole buildings are the most common wood framed metal panel sided building. Most pole buildings use the poles/post to take shear stress. Even they need the ends sheathed sometimes when the door openings are large or the are uncommonly tall.

A platform frame building uses OSB/ply(minimum in the corners) or diagonal steel or wood bracing that is inlet into the studs. Also most use the roof decking as a shear panel.

If you live in a high wind area then not at least diagnal bracing is damn right stupid IMHO if you are not doing a pole barn. If it was my building I would do a pole barn but if I did platform framing it would be fully sheathed, 7/16 walls and 5/8 roof with 8D ringshank nails.

Now from a code stand point. You don't have a location listed so how is anyone going to give you a correct answer. Even then you need to check locally and I would pay an engineer to sign off on any platform or ballon framed building without sheathing on the roof and at least corners.

readhead · Sep 20, 2017

I would agree with Firebrick. Some kind of shear value has to come into play. Unless the metal has been specifically designed to provide shear value it will not stiffen the structure. The metal is only a cover to keep the weather out. As an example pole buildings gain shear by having the poles buried in the ground. Pre-engineered metal buildings use cable or rod bracing. Your home has sheeting or diagonal bracing applied to the framing. In all these buildings the exterior cover serves to weather proof the building.

That being said, a metal cover can be designed to provide shear value and the finish but may get pretty involved and expensive.

You also mentioned spray foam. If you go that route I would definitely install sheeting to separate the metal from the foam. Problems are starting to show up with spray foam applied directly to the metal. Rust through is a problem and replacement of sheets for repair or remodeling is a nightmare once the sheets are essentially glued to the building.

Just last month I was approached to disassemble a metal building to make way for an expansion of a auto dealership. They hoped to sell the building and make a little money. When I got there I saw that the building had been spray foamed. I gave the owner the number for a demolition company. The building was taken down with an excavator and had to be hauled several hundred miles to a location that would remove the foam so the metal could be recycled. In the end it cost him 68K to have the building removed. It was a 30x40x12.

n20junkie · Sep 20, 2017

Firebrick hit it on the head.

A stick build is weak and fragile without its sheathing. Just one sheet of plywood will pretty much lock a wall into plumb (or out of it).

So the sheathing is your ONLY shear strength in a stick build, and your relying on just the steel to do this job. At a minimum, a lot more screws than standard would need to be used than standard cladding purposes.

I see nothing wrong with just the steel, if there is valid literature that can approve the steel for this. Secondly, the steel siding is actually installed in accordance with those written approvals or literature.

Ajping3830 · Sep 20, 2017

Ok I'm starting to get the idea. I asked the contractor about it again and he said once the structure is all together, the metal will be stronger than any sheathing.
The metal he is planning to use is Tuff Rib 29ga panel. He claims he builds them this way all the time, but I have yet to talk to anyone that thinks it's a good idea.

Terrible time to build a garage, sheathing prices are way up due to demand from the hurricane fiasco.

BoostedOne · Sep 20, 2017

Ajping3830 said:
But... specifically... what are the differences going to be, other than a large chunk of $$$?

24x40=128' perimeter=16 sheets of plywood laid horizontal.
12' tall= 3 sheets of plywood.
48 sheets of plywood to sheath. 7/16 OSB is what, $10 a sheet? Were talking 500 bucks. Its not a large chunk of money.

Ajping3830 said:
The metal he is planning to use is Tuff Rib 29ga panel. He claims he builds them this way all the time, but I have yet to talk to anyone that thinks it's a good idea.

29 gauge is thin... Yes people use it, but for marginal extra cost I would get 26. And even 26 can be punctured by things if you are not careful. My shop has sliding style doors and I have holes/tears in 26 gauge from opening the doors and a gust of wind comes and blows the door into the walls.

Firebrick43 · Sep 20, 2017

Ajping3830 said:
Ok I'm starting to get the idea. I asked the contractor about it again and he said once the structure is all together, the metal will be stronger than any sheathing.
The metal he is planning to use is Tuff Rib 29ga panel. He claims he builds them this way all the time, but I have yet to talk to anyone that thinks it's a good idea.

Terrible time to build a garage, sheathing prices are way up due to demand from the hurricane fiasco.

I could find no diaphragm data about tuff rib. I did find some on 26 ga classic rib. 296 lbs per foot. Very adamant about being on 2x4 purlins 24" on center(were you going to use purlins on the wall?). Also the amount of screws required at the edges of the panel was about double of what is common.

7/16 OSB applied horizontal with 6" spacing on 8D nails along the edge is 280. So comparable "if" the metal is applied correctly.
If you use 4" spacing on the OSB edges its 430 lbs per foot, significantly better with just a few more nails. Can't see the advantage of not sheathing as the purlin cost eats up probably half of what the OSB cost and you can still change panels out if damaged (if you use spray foam).

Do NOT use the classic rib data. Please ask for the diaphragm data for the 29ga tuff panel as I could not find any. Somehow I doubt you will either.

Ajping3830 · Sep 21, 2017

Ok so I talked with the contractors again about not running any sheathing. First off these guys were recommended to me by several people and from my perspective really seem to know what they are doing. I'm basing this off of many details that other contractors never even pointed out or asked questions about while giving me a quote. They told me how they understood my concern and that if it wasn't done correctly it would absolutely be an issue...

So I got them to give me pictures of all the framing on another garage they just built very similar to what I am looking at, using no sheathing under the metal. Its a 32x30x12. Same square footage, other than the dimensions all of the frame work and exterior work will be identical right down to the overhangs and seamless gutters that they build on site. Main difference being that I will have a couple courses of block above the slab.

Here are the pics, sort of in random order, let me know what you guys think. I don't have much of an idea what I am looking at, but it looks good to me...

<a href="https://ibb.co/eoQZTk"><img src="https://preview.ibb.co/jpM8ok/1.jpg" alt="1" border="0"></a>
<a href="https://ibb.co/d0puTk"><img src="https://preview.ibb.co/bKVOM5/2.jpg" alt="2" border="0"></a>
<a href="https://ibb.co/c3o4Tk"><img src="https://preview.ibb.co/g20vZQ/3.jpg" alt="3" border="0"></a>
<a href="https://ibb.co/jtJhEQ"><img src="https://preview.ibb.co/fHFjTk/4.jpg" alt="4" border="0"></a>
<a href="https://ibb.co/eQnaZQ"><img src="https://preview.ibb.co/gxN9uQ/5.jpg" alt="5" border="0"></a>
<a href="https://ibb.co/crEdok"><img src="https://preview.ibb.co/hFJ4Tk/6.jpg" alt="6" border="0"></a>
<a href="https://ibb.co/krAvZQ"><img src="https://preview.ibb.co/jLJ4Tk/7.jpg" alt="7" border="0"></a>
<a href="https://ibb.co/kPe015"><img src="https://preview.ibb.co/hJTtM5/8.jpg" alt="8" border="0"></a>
<a href="https://ibb.co/iOHng5"><img src="https://preview.ibb.co/hMY4Tk/9.jpg" alt="9" border="0"></a>
<a href="https://ibb.co/cWeNEQ"><img src="https://preview.ibb.co/gbqUuQ/10.jpg" alt="10" border="0"></a>
<a href="https://ibb.co/mPq7g5"><img src="https://preview.ibb.co/bzq7g5/11.jpg" alt="11" border="0"></a>
<a href="https://ibb.co/m35jTk"><img src="https://preview.ibb.co/iDKYM5/12.jpg" alt="12" border="0"></a>

readhead · Sep 21, 2017

Everything looks good until it fails. This guy has been lucky so far.

slip knot · Sep 21, 2017

I wouldn't have an issue with that building. I've built several building using a similar framing style and they survived a cat 4 hurricane.

lakeroadster · Sep 21, 2017

If it's an engineered building with a PE stamp I wouldn't be concerned building it without sheathing under the steel.

If there's no PE stamp, then have them use sheathing under the steel.

If you are going to insulate the building, then, stamp or no stamp, have them use sheathing under the steel.

NUTTSGT · Sep 22, 2017

Looking at those pictures, I believe that garage will be a storage garage and not worked in. Nice looking building, but I wouldn't be happy with it and would consider not using those guys if they are leading you towards building like that.

If I was stick building, there is no way I would not sheath the exterior of the structure with OSB or plywood. There's also no way you're going to convince me that the metal siding is going to be stronger than sheathing.

Personally, I would call :bs:

on that contractor and not use him.

readhead · Sep 22, 2017

John just reinforced my previous comment. If the metal sheeting is designed to provide shear value then there is no problem. I erect lots of metal sheathed buildings and have never had one that used the metal for shear value. Never is a strong word and I know from reading trade publications that buildings are designed using the metal for shear value, but it is a very small percentage with very specific requirements. My guess is this is a seat-of-the-pants system that has been successful but has no real design behind it.

Clearly a lot of things work out fine in real life but I think there are two camps on this forum. As I was thinking this through I can only offer my own opinion. Being a trade professional and business owner for the last forty five years my thought process is influenced by concern for a quality installation, warranty issues and liability. I probably lean toward conservative design requirements in order to provide the best quality product for my customers.

Across the lake at the other camp there are things being built with alternative ideas and materials. I'm okay with that. Of course safety is a concern. Most of the time money drives decisions about material and systems to assemble the material. There is no mystery that I am not a fan of pole buildings but I know that there is a place for them in the choices of building systems.

Back to the question at hand after my little rant. Both options are viable if executed properly. I would lean toward sheeting for the reasons stated but if the builder can make a qualified argument for no sheeting then go for it.

n20junkie · Sep 22, 2017

I have questions/concerns about the shear loading of a corrugated steel panel as well.

They pictures they sent lead to more unanswered questions IMHO.

The horizontal mounting strips, eliminates the direct tie in of the steel to the studs, so what is providing the shear strength? The transfer from studs - to nailed furring strips - to corrugated steel siding? Seems barnyard at best.

n20junkie · Sep 22, 2017

slip knot said:
I wouldn't have an issue with that building. I've built several building using a similar framing style and they survived a cat 4 hurricane.

Wind forces and a 3 foot load of snow are two totally different loads.

OP sure where the OP is, but it seems like a good storm up here would smash that building flat when the walls give way.

Ajping3830 · Sep 22, 2017

I'm in rural western NY, about 1.5hrs south of Buffalo. There is zero risk of hurricanes or anything of that nature in this area, but being higher up on a hill I do get some wind, though I would not say it's enough to be destructive. I have several rickety old wooden out buildings on the property and have never had problems in the 7 years I have lived here.

Another thought, I would be having some people I know do the spray foam and electric, then have the buildersame come back and put up metal on the inside of the building. Would this do anything for strength or no?

Ajping3830 · Sep 22, 2017

lakeroadster said:
If it's an engineered building with a PE stamp I wouldn't be concerned building it without sheathing under the steel.

If there's no PE stamp, then have them use sheathing under the steel.

If you are going to insulate the building, then, stamp or no stamp, have them use sheathing under the steel.

And a "PE stamp" is what exactly?

Firebrick43 · Sep 22, 2017

Professional engineer.

Black Oak · Sep 22, 2017

I had a pole barn estimate given to me that stated the mastic putty material that one can put in on the ridge seams "makes it as rigid and strong as stick built with OSB sheathing" . He truly believed that, based on his years of experience . I eventually went conv. stick built.

NUTTSGT · Sep 22, 2017

Ajping3830 said:
I'm in rural western NY, about 1.5hrs south of Buffalo.

Just for future reference, you might want to add that location to your profile.

GJ is full of members across the US, Canada, across the pond, down under and many other parts of the world. What might work for one poster, may not work for all. This is why adding a "general" location is helpful to all giving and receiving advice/information.

lakeroadster · Sep 22, 2017

Ajping3830 said:
And a "PE stamp" is what exactly?

Firebrick43 said:
Professional engineer.

Ajping3830, The value to you is it means a Professional Engineer reviewed the drawings. The PE is licensed and his career can be in jeopardy if he approves a bad design.

If there is no PE Stamp the design could have been done by some high school kid who took a drafting class, that has no clue as to if the design is adequate for the given application.

Most jurisdictions require a PE stamp... by a PE registered in your state... becuase as NUTTSGT pointed out above, what works in one location may not work in another.

Exterior sheathing required under steel siding?

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