|Written by Steve Schwettman|
First, we need to make sure we are speaking the same language. Let's start with some definitions of common framing terms and what they mean for our project.
Common Framing Definitions:
Sill Plate - This is the lumber that forms the bottom of your wall. It will need to be pressure treated since it is sitting on concrete. It will also need to have holes drilled for the anchors. This is the part of your wall that is physically bolted to the foundation, so it needs to be strong. Hopefully you placed your anchors in positions where they won't overlap with a stud location, otherwise you'll have to place some of your studs off of your On Center pattern, which can be quite bothersome when you go to attach your OSB and siding. You don't want your sill plates to consist of lots of short pieces of lumber because then it will be weak. Use the longest lumber that you can carry in your truck or have it delivered. I used 12 foot sections and that seemed to work fine, but longer is better. You'll want to double up some extra studs wherever 2 pieces of sill plate meet to preserve the strength of the wall.
Top Plate - This is similar to the sill plate but forms the top of your wall instead of the bottom. The best way to engineer a top plate is to DOUBLE it. Double top plates are a type of top where you use two top plates nailed together, and you stagger all of the joints and all of the edges. This creates an incredibly stiff wall and a very strong corner where the top plates overlap at the ends. The top plate normally does not need to be treated, but again you should use the longest lumber that you can. Unlike the sill plate, you don't need to double up studs at the joints in your top plate because the two layers of top plate should already have staggered joints.
Stud - This is the vertical (upright) piece of lumber in your wall. The spacing on these is important and will be discussed shortly. You're going to be buying a lot of vertical studs, it's a good idea to get the length of them correct, because the length helps determine the height of your walls. The standard way to build walls allows you to use a 92-5/8" long stud. This is slightly less than 8 feet. You will also see 8 foot (96") studs for sale, but typically you don't need them. By the time you add up the length of the 92-5/8" stud, the sill plate, and both top plates, you will be just over 8 feet anyway. Using a 92-5/8" stud means you don't have to cut them to length, which saves a huge amount of work. They are also cheaper than other stud lengths because they're the most common stud produced.
OSB Sheathing - OSB is Oriented Strand Board. It's similar to plywood but is less flexible and appears to have strands of thinly sliced wood in it, cemented together. The sheathing represents the real strength of your wall. Why then are many homes these days built without sheathing? They claim that omitting the sheathing makes the wall more efficient but it sounds like CHEAP to me. Build your wall first without sheathing and shake it around and see how flimsy it is, then attach the sheating and try to shake it. You'll see what I mean. Your blueprints should specify the MINIMUM thickness of the OSB, if not, assume it's the standard for your area. As it turns out, most OSB that is sold these days is sold 1/32" under size. So, for instance, you typically won't find true 1/2" OSB in stores, it will be 15/32" instead. This works fine and is accepted even though it's 1/32" under size. Your sheathing will begin level with the bottom of your sill plate. It will not rest on the foundation because that would cause it to absorb water and disintegrate. Instead, it should be hanging past the edge of the foundation where water can't get to it. If you anticipate snow laying against your wall for any length of time, you might also want to treat your sheathing with a wood sealer. Also, make sure to buy OSB that has the nailing pattern already printed on it. It will be either an 8x8 or 16x16 grid painted on one side of the OSB. That side is considered the outside of the OSB, and the pattern on it allows you to place your nails by sight without the need to strike a chalk line.
Tyvek or Vapor Barrier or House Wrap - This is a membrane that is attached to the outside of the OSB that allows water vapor to escape to the exterior, while resisting the entry of air. It's like GoreTex for your walls. Tyvek is usually required these days and it does protect your walls from the elements quite well. Home improvement stores usually carry their own brand of house wrap and it's often a better deal than the name brand. For some projects, you might be able to get away with using roofing tar paper instead of Tyvek. Roofing tar paper is also a good water barrier and is much less expensive than Tyvek. It is sold as either 15 pound or 30 pound. When using it in place of Tyvek, you'll want to use the 30 pound.