Replies

1. 
   DanH | Sep 10, 2010 08:48pm | #1

   Can I tape and topcoat plywood or OSB the same as drywall?

   You can try.  But all attempts I've seen at doing that end up looking like sith.

   It has occurred to me in the past, though, that you could use 3/8" OSB overalaid with 1/4" drywall and get a nice wall that was a lot tougher than standard drywall.

2. 
   Clewless1 | Sep 11, 2010 11:16am | #2

   'Easier' depends on what you are doing. If replacing the siding, obviously easier to do from the outside.

   Doesn't your existing structure have shear bracing already? I'd find it odd that it wouldn't. So maybe you need to or want to add additional bracing (wood or Simpson product). YES, you should be able to do it on the inside. Options: plywood, OSB or let-in diagnonal bracing.

   Finish the plywood/OSB? I'm guessing not. May as well drywall and finish.

   I met some sheer wall code requirements in my house w/ drywall. Not the same as seismic, I suppose ... that is the end of my limited knowledge of this topic. Drywall does have some structural properties, not sure of the limitation, though.

   Best to discuss w/ your BO, though since local codes may dictate what you should or can do.

1. 
   Claremontcat | Sep 11, 2010 02:04pm | #3

   no shear walls

   House build in 1973, with many defects.  Exterior walls have tar paper and wire mesh stapled to framing under stucco - and poorly installed insulation where I've opened up walls from inside.  Makes me want to open up all exterior walls & redo insulation along with strapping 1st & 2nd floor framing together. 

   Thanks for input.  No free lunch is right.

    

     

    

1. 
   Clewless1 | Sep 11, 2010 04:15pm | #4

   1973 construction w/ stucco ... likely has sheer elements in it. Sometimes w/ stucco only the corners are done in plywood ... still a common approach even in California. Code only requires [prescriptively] sheer panels of 2-4ft at corners. In between you don't need anything if you choose.

   If you had no sheer elements, you may likely have a lot of cracks in walls. Good wind would stress the structure enough to produce cracks in drywall.

   I wouldn't panic about the sheer thing yet before you really know the situation. You might be fretting about nothing.

2. 
   sisyphus | Sep 12, 2010 02:49am | #5

   I had a couple of clients who had some plywood that was taped and finished like drywall in their houses and they seemed happy with the result (It was done by previous builders, not me.) but to my, probably more critical, eye it didn't look so great. IIRC the texture of the surface varied too much between the plastered and plywood portions. I can't recall if it was an issue for them but I would also be concerned about the longterm stability of the plaster/wood interface depending, of course, on your local climate.

   As Dan suggested, why not just put drywall on top of some sort sheathing. You can use any sheathing material that meets your structural requirements and be less fussy about fit and fastening because appearance is irrelevant as a bonus your drywall should go up faster with less wastage. 

3. 
   sisyphus | Sep 12, 2010 02:56am | #6

   I had a couple of clients who

   I suppose another option would be to use some sort of veneer plywood inside but you would have to fasten it in a way which meets both your structural and aesthetic requirements.

3. 
   Amish Electrician | Sep 12, 2010 01:20pm | #7

   A seismic retrofit should be done under the supervision of an engineer or architect; there's more to it than a few sheets of OSB.

   Can you place the sheathing on the inside face of the walls? Maybe. A lot depends on how many penetrations there are, how often the sheathing is interrupted by interior walls, etc. Then there's still the matter of the rafter clips and such. You'll likely also need to have some of the interior 'cross walls' similarly sheathed.

   You will probably not be allowed to simply put a skim coat of mud on the OSB; it's more likely that you'll be required to have a fire-rateed wall, and that means 5/8" of drywall atop the OSB.

1. 
   Clewless1 | Sep 13, 2010 08:37am | #9

   I thought in residential construction, your wall finish can be 'just about anything' and would think that plywood or OSB would be OK ... doesn't really need a fire rating ... certainly not 5/8" GWB. Commercial const is a different matter.

   Not sure if he is truely intending to bring the structure up to current codes or simply add som sheer resistance to the walls. You're making a leap of assumptions with your statement. But you and the guy that replied bring up some potential good points. So, it all depends on what the OP wants for a result. I got the feeling he's simply wanting to add some stiffness. He never mentioned having to meet current codes and such. I met interior wall structure requirements with drywall ... reviewed and approved by the BO.

4. 
   Yersmay1 | Sep 13, 2010 08:04am | #8

   I agree with Amish Electrician.  It's my understanding that simply applying sheathing is only part of the equation.  Seismic hold downs must be strategically placed in order for the sheathing to really do its job.  An engineer will look at the structure and determine how and where these hold downs will work hand in hand with the sheathing. 

5. 
   xxPaulCPxx | Sep 13, 2010 12:40pm | #10

   I am doing the same as you as I go through the house, opening up walls.  Here is what I did:

   House is 1960 ranch, built on slab, shear is handled by diagonal let in bracing.  Slab floor.

   Around the perimeter, I drilled 12" deep 5/8" holes into the foundation (about every 4 feet).  I blasted them out with compressed air and cleaned them with a brush.  Into that I placed epoxy and 1/2" threaded rod.  This rod attached to a Simpson hold down that attached to a 2x4 in the wall.

   All of my electrical was placed flush with the wall, then deep mudrings were used to reach out to new wall depth.  I sheathed the walls with 7/16 OSB with a standard 6" edge 12" field screw spacing.

   Over this, I put on 5/8" drywall, glued on the back.  I have small rooms so I don't have the vertical seems to worry about.

   So far so good, just waiting for the big one to hit!

1. 
   Claremontcat | Sep 13, 2010 02:34pm | #11

   doing the same

   I'm using FHB article as guide to add strength - it recommends shear walls 8ft from each outside corner on 2 story house and mudsill bolted every 4ft o.c. and 12in from ends.  I've got some bolts but never opened up walls to see how many.  Don't see a downside to adding metal connectors - hurricane ties and hold-downs between 1st & 2nd floor. Sounds like a second layer of drywall is the easiest way to go - thanks for ideas!

1. 
   DanH | Sep 13, 2010 08:49pm | #12

   Of course, the place to add the hurricane ties is between the upper studs and the roof rafters, but that's damn hard to do without having a lot of finish out of the way.