Hi,
We’re planning a 4 room remodel. Our 1949 ranch has 2×4 walls, with 3/4 inch redwood shiplap siding. There is no sheathing between the studs and the siding (quite common for homes of the era and in this area– San Fran Bay Area). This makes window replacement a challenge; I replaced three windows a couple years back and the side jambs stood proud 1/2 inch past the dry wall, making the moulding really tricky.
In thinking about our remodel, I was wondering if it makes sense to sheath the insides of the walls prior to sheetrocking. This would add shear strength– a good thing around here– and make is easy to attach cabinets and such. Is there a downside? Is there any code against this? I’m most concerned about the implications for vapor. If anyone has any thoughts, I’m all ears!
Replies
Under the circumstances, what you suggest is a pretty good idea although it won't make installing new windows a whole lot easier. No vapor issues that I can think of, both plywood and OSB would allow the passage of water vapor. You probably have some wiring to navigate, other than that, go for it.
Thanks. I was thinking that we'd gut the rooms, rewire/ plumbing as needed, install new windows and insulate. Then once that passes inspection, I'd sheath with ply and then sheetrock. Would you add a vapor barrier between the sheathing and sheetrock?
Interior shear walls are a great idea, especially on the walls that run across the narrow ends of your house. You should also get hold-downs and bolts in there if applicable. (Is it a slab? crawl space?)
I don't know if you are real experienced or not, Simpson has a seismic upgrade booklet for homeowners that is very understandable.
Take photos before you cover it up, they'll help with insurance or resale value.
k
It is a crawl space-- great idea on the other seismic stuff and the pictures.Thanks.
Ok, so there is a crawl space. Is the cripple wall (the short wall from the foundation to the first floor) bolted, hd'd and shearwalled? Making the first floor itself rigid with shearwalls is good, but if the load isn't carried all the way to the foundation, you could still have major damage in an earthquake. Also, use struc. 1 plywood.
Apologies if you know all this.. I'd rather say the obvious than leave valuable info out.
K
There is a crawlspace-- quite literally. Clearance in the crawl is about 2 feet and less in some spaces. There is just a foundation, sill plate and then floor joists. The sill plate is bolted to the foundation, but there are no other seismic tie downs or plywood between the floor joists. In terms of shear, the house is 1 story and has a composition shingle roof. I just assumed that it wouldn't be worth adding ply between the floor joists.
I see. you wouldn't need plywood down there then, but rather solid blocking to keep the joists from racking over, or metal connectors to firmly attach the floor joists to the rim joists.
You need to try to get the shear force (and the rotational force it generates)transferred from the bottom of the first floor ply panels down to the foundation proper. You can do this via the subfloor diaphragm, or at the wall/rim joist connection.
You would also want hold downs for sure, which should be epoxied into the foundation and go up into the first floor shear walls. Those deal with the rotational forces.
And, depending on when the mudsill was bolted, you may want to add a bunch of bolts there- older bolts were commonly not galvanized and may be in poor condition.
Yeah, crawl spaces aren't fun to work in. You could hire that part out, I suppose.
k
You could cut down the window jambs prior to installation if they are wood. A cheaper alternative than the ply would be a double layer of sheet rock. Not much help for shear strength if that is really needed.
We have a lot of windows that are casements mulled together. I really debated trimming the jamb, but I didn't want to hack the window and didn't know what to do where the windows were mulled.Thanks!
Probably not. Is there any felt between the siding and studs? What are you planning to use for insulation? By the way, your inspector will want to see your new wiring/plumbing before you insulate.
If there was felt, and I think there was originally, I bet it has deteriorated. For most of the insulation I was considering standard batts. But on the kitchen wall, which can get hit by rain and storm rain, I was considering closed cell spray insulation. Right now those walls have nothing... a little cool in the winter.
>> No vapor issues that I can think of, both plywood and OSB would allow the passage of water vapor. <<
Actually CDX and OSB have a perm rating of around 1. I'm not saying the sheathing would cause a problem in his application, but what I am saying is that it is not real good at passing water vapor. I suspect that this number 1 rated structural plywood being discussed would be the same but have no personal experience with that material.
To the OP: definitely do NOT add any vapor barrier between the drywall and the proposed sheathing.
I've done what you're talking about. I ordered extension jambs and pulled them and cut them to size. It would certainly be cheaper than what you're suggesting.
In retrospect, i'd probably order the windows without the jambs and just make them before trimming.
Why not order your windows with smaller jamb extensions?
Probably should have done that when I was replacing the 3 windows a couple years ago. I didn't realize the house didn't have sheating until I had the new windows and had ripped the old windows out.Given that we're going to go down to studs in the rooms that we're going to remodel, I thought the benefits of adding sheathing might outweigh the dollar cost. I was concerned that there might also be a vapor issue that I wasn't considering. But if I'm interpreting the responses correctly, there really isn't a vapor concern.
Good not just for hanging cabinets, but anything.
I'd be interested in hearing a persuasive argument against OSB in this application. Something other than elitism.
The argument against osb (or cdx) is seismic. op is in the bay area.
k
(edited addition: You can go to simpson's web site for a pdf of their homeowner's seismic retrofit guide. It doesn't cover everything, but explains the basics very well. http://www.strongtie.com/ftp/fliers/F-PLANS07.pdf )
Edited 4/19/2008 12:07 am ET by KFC
Que?
Why is an OSB shearwall not seismic?Rebuilding my home in Cypress, CA
Also a CRX fanatic!
If your hair looks funny, it's because God likes to scratch his nuts. You nut, you.
As KFC mentioned earlier, I should be using Structural 1 rated sheathing (ply or OSB). I found some useful stuff on the web about the differences between structural rated 1 and 2. The following slide show was also helpful because it talked about some other details (e.g., fasteners) as well.http://www.abag.ca.gov/bayarea/eqmaps/fixit/ch3/sld001.htm
It's all 'seismic'- even the lap siding has shear value if you've got two nails through each piece into a stud. But, osb<cdx<structural #1
where were you on october 17, 1989?
k
Edited 4/19/2008 9:54 am ET by KFC
I was in college in Michigan at that time. I've felt a couple small ones over the years and hence my interest in the sheathing.
Right- good for you. I was actually directing that Q. to the guy who asked if my preference for structural no.1 plywood over OSB was "elitist". Some would ask if a one story house "needs" any seismic strengthening...
No one who was in the Bay Area during Loma Prieta would say that. And that was only a moderate quake... You figured that out without even being here then. Kudos.
There is no building code for residential eq retrofits, so I can't say "you are legally required to use struc.1 ply", but as long as you've got the walls open, it's a real good idea to do it all as well as possible. Why cheap out there? The cost difference will be negligible compared to the overall expense and effort.
Which is why I also think you should put the HD's in (for overturning forces) and probably blocking or clips for the joists in the crawl space (to carry the lateral force from the shear panels above to the mudsill), and check those existing AB's for size and rust, to make sure those same forces are transferred from the mudsill to the concrete.
Unless you're just fixing it up to sell. Even then it's a good idea, but fiscally less so.
K
Ok, I'm gonna back up here, and eat a little crow (only a little, though)
Everyone who said OSB can be used for seismic is of course right. OSB struc 1 has the same ratings as struc 1 ply, at least in terms of general load. I apologize for being flip.
But, (and I know the osb vs. ply thing has been done), I haven't found comparative specs on fasteners in any of the articles or threads. lots of talk about panel stiffness and panel strength, but no talk about cyclical loading of edge nailing in osb vs. ply. Did I miss that in my searches? That is where shear panels tend to fail.
does anyone have the comparative stats on lab tests of edge nailing strength?
my own experience keeps me from backing down too much on this. Maybe under perfect lab conditions (nails not overdriven, etc.) the nails will tear out equally, but I'm certain that real world applications will prove struc 1 ply more resistant. And, I haven't found the lab stats yet either- they might back me up anyway. But I should lose the dismissive attitude either way...
k
That makes a little more sense to me.
I do understand a certain scepticism about OSB... But...
Awhile back I was having some conversations here about using screws instead of nails as a preferred fastener for just about everything, based on the merits of overall strength and durability, not efficiency or economy. I made up some tests and used two long blocks of wood to test screws and nails in everything from metal hangers to OSB.
In the OSB tests (I only did a couple, not a long series), when stress was applied in shear, the nails pulled out of the wood and rarely tore through the OSB. The screws supported much more load and eventually tore through the OSB. This was scrap OSB that had seen weather and had some swelling - it wasn't new pieces I was playing with.
Whatever you think of the whole nails vs. screws thing, one thing that surprised me was how tough OSB turned out to be.
BTW, in '89 I was living in Illinois :)Rebuilding my home in Cypress, CA
Also a CRX fanatic!
If your hair looks funny, it's because God likes to scratch his nuts. You nut, you.
You know, that's interesting. I remember reading that OSB doesn't hold fasteners as well.
I think his test involved fastening the OSB to framing, so the screw passed thru the osb and into the frame and the head tightened against the osb. It did not test the properites of anything fastened to the osb alone, say, like a screw fastening a piece of trim where the only part of the screw in the osb was the threaded shank, and no framing on the other side. Make sense? And if I'm wrong Paul, I apologize.
"I am the master of my fate, I am the captain of my soul." Invictus, by Henley.
You're right.Osb does not hold a nail as well as dimensional lumber because the osb is only 1/2" thick or so. But....if your pound a spike into a pile of osb it will be tough to withdraw. Bob's next test date: 12/10/07
Absolutely right - I have no idea!
I think that thinner nails used for trim might have less of that "punch out" that a larger fastener might have - i.e. small hole in front, big hole in back.Rebuilding my home in Cypress, CA
Also a CRX fanatic!
If your hair looks funny, it's because God likes to scratch his nuts. You nut, you.
I like those kinds of tests too. If I see it for myself, I'll lose my superstitions a lot faster. I may have to do some with nails in various panels myself.
Maybe the retrofitters and engineers I've worked with in the bay area are behind the times, but they all spec struc. 1 ply. It's also available in 4x10's at all the yards, and is consistently nice stuff (we do get really nice doug fir here).
Most of the lab testing of panels (osb vs. ply) involves putting panels in big jigs on tracks and applying racking or bending forces. I don't doubt that osb performs well under those conditions. I'm still clinging to my (apparently ignorant) beliefs about edge nail strength though.
I did find one test by Paul Choo(?) that said edge stapled osb is as strong as ply, but with perfectly applied fasteners. I'm not convinced, but, I also apparently don't know what I'm talking about!
Hey- at least it's not an elitist opinion, just stubborn and uninformed;)
k
P.S. As far as relative strength of screws v. nails, I was taught (FWTW!) that screws are too brittle to stand up to repeated cycles of force from seismic events.
I've still got to do a formal, comprehensive comparison, but in the initial test series I found that using specific screws of a similar shank thickness held up much better than nails - SPECIFICLY in shear. In one case, I tore the head off a 16d nail with 16ga. Simpson strap, and using a Square Driv Deckmate #9 screw I consistently could put enough force on it to tear the 16ga. strap.
The test bench was this: Two boards with a hinge connecting them on the end. Face connect a metal connector strap (or piece of OSB) across the two board with either nails or screws. Pull said boards appart. It is a straight shear connection, and easy to replicate if you want to try it out for yourself. Don't drink my kool aid - mix yourself up a batch! Here is a pic of one test bench, and another one with my OSB test. You can just see the 8d nail hanging out of the OSB in the second one (OSB held better then the nail). It wasn't an edge test like you are interested though.
OK, I'll have to post the pics in a minute - can't get Prospero here to cooperate.Rebuilding my home in Cypress, CA
Also a CRX fanatic!
If your hair looks funny, it's because God likes to scratch his nuts. You nut, you.
ok, here they areRebuilding my home in Cypress, CA
Also a CRX fanatic!
If your hair looks funny, it's because God likes to scratch his nuts. You nut, you.
That actually checks with what I was saying- I was taught that screws are usually stronger in shear initially than nails, but the exception is when you've got repeated cyclical loading, like the shaking of an eq.
The explanation was that the screws (while stronger) are more brittle, and will snap after a few oscillations, whereas the nails will bend back and forth quite a few times before they fail. I can't say I have stats on that, though.
And, I've seen plenty of details for screws in eq retrofits, e.g. A35's from joists to existing 3/4" subfloors- tico's to the joists, screws up into the t&g. Not to mention sds screws...
That is some good kool-aid though, looks like that osb held those fasteners pretty well. I'd like to try that with equally nailed osb on one end of a solid 4x, and 5-ply on the other, see which tore out first. Actually, from your photos it looks like the nails would fail at the dimensional piece before they pulled out of either...
thanks for keeping up the discussion, most would have written me off (justifiably) after my first osb v. ply rant)...
k
No...........not the screw thing again. Flame war is immenent!!!!!
As far as I'm concerned, I've made some incredible claims and have a little incredible evidence to support it. I don't have near enough of a full picture of the whole of the SvN concept. This is kind of a pet project for me that I play with when time and interest allow.
I don't think I even posted in that last SvN thread that came up!
Besides, Piffin knows he's wrong. I don't have to rub it in.
;) hee heeRebuilding my home in Cypress, CA
Also a CRX fanatic!
If your hair looks funny, it's because God likes to scratch his nuts. You nut, you.
You can't win against a guy that has a scew named after him. I was thinking after that thread that for the average homeowner assembling using screws might be more cost effective in the area of framing but I'm not so sure about shingling with screws yah know?
As my guidence councelor used to say...
"Not with THAT kind of attitude you wont!"Rebuilding my home in Cypress, CA
Also a CRX fanatic!
If your hair looks funny, it's because God likes to scratch his nuts. You nut, you.
At least you're diverting the thread from my osb issues... I think I must have been PWI.
I wonder if the OP is even following this at this point. If you are, alwaysthinking, one other thing to do while you have the wall open is make sure the bottom plate of the 1st floor wall is well nailed through the subfloor to the rim joist/rim blocking. Then you can use A35's from the rim joist/blocking to the mudsill in the crawl space to get that lateral load transferred on down.
k
A little amazed at the discussion. I was focused on my day job for the past few days and just checked the messages. KFC, by A35s, you mean the Simpson connectors, right?We're actually getting a structural engineer out here in the next week or so. Because we're shuffling interior walls, we are required to have a SE plan. For those of you who have experience dealing with structural engineers, would you review this plan with him?
A.T.,
Yes, A35's are one of the many simpson connectors. They're angle brackets used to carry lateral force from one member to another that is in line, 90 deg. to it, i.e. connecting a rim joist to a mudsill to keep them from sliding past each other (in the same plane, lengthwise). They're attached with short fat nails (joist hanger, or "tico" nails).
If you can nail the two members with 16d nails that will work too, and is what is often spec'd for the plate of the wall above to the rim joist below. Since the rim joist is already sitting on the mudsill, you can't nail up into th RJ there, so you generally use A35's or their equivalent.
Most of this comes down to transferring loads in plane, or in line like that. The plywood catches the force at the top plate of the wall, and transfers it to the bottom plate of the wall. Then you try to carry it from that bottom plate into the rim joist, then from the RJ into the mudsill, then sill into foundation. The holddowns keep the whole shebang from rotating over.
I'm sure folks would take a look at the engineer's plans. There's some pretty knowledgable folks here. I will keep an eye out myself, although my experience is pretty limited compared to a lot of guys here.
I bet you will get a pretty good understanding yourself, the basics are real simple 2-d vector physics. You model the loads along each axis of the house, and try to catch them in the walls and transfer them on down. Where necessary, the floor and ceiling diapraghms can gather lateral loads and throw them out to shear walls, basically acting as shear panels in the horizontal plane.
The only tricky part is in walls with large or many openings, like garages. These often require manufactured shear panels (Simpson and Hardi Frame are two).
Mostly it's attention to detail, and grunt work in crawl spaces. Have fun!
k
Thats a perfect solution with no downsides other than the cost. If you are poor, you'd furr the wall out with 1/2 strips or rip down the window jambs. But if you were that poor, you wouldn't be remodeling.
Happy OSBing!
Bob's next test date: 12/10/07