Bottom plate attachment

[NorthernMich]

Two questions...

one-my joists sit on cantilevered beams so I have no J-bolts coming through vertically to attach the plate to...should I lag screw the (2x6) through the floor and into a joist and if so, how many across a 14 foot span...to help fasten the walls.

two-do you put down the flooring (in my case 1/2" OSB and T&G pine) BEFORE and underneath the wall plate?  Does this strengthen the construction?

thanks...snow melting soon to open construction on cabin here soon I hope

Earl

[n74tg]

Yes, I would run the subfloor under the exterior walls.  I asked that same question several months ago.

I don't think I would run the T&G pine "finish" flooring under the wall plate as your finish flooring would be exposed to the weather until you get the building dried in.  Now, if you're going to be dried in a week or two and no rain comes maybe you could get away with it. 

On another point, unless you have your floor joists tightly spaced (like 12" spacing) I think I would avoid 1/2" thick subfloor and go with 3/4". 

As for putting in lag screws, I really can't see any other alternative.  As for spacing, how about every 2 feet (using 1/4" x 5 or 6 length screws); but I will be interested in what others say too.   Anything larger (diameter) and I think you could easily split your rim joist.

One other point to think about here is how are your floor joists connected to the cantilevered beams.  It would be a shame to make the wall to joist connection real strong, but the joist to beam connection weak.  Likewise, follow the same philosophy down the load path to the ground.  How well are the cantilevered beams connected to the columns. 

   

[MountainDon]

2 - the subfloor is always applied full width over the joists and then the walls are built on top of that. I've never heard of using 1/2" for subflooring, no matter what is going on top. Subflooring starts at 3/4" and goes up and has T&G edges to reduce flexing/squeaking where it is unsupported. Once the walls are up then the finish floor is installed.

1 - You nail the subfloor to the joists and rim-joists using 8D nails. Assemble the wall framing on the deck, then raise it and get it into position. Nail through the plate into the joists and rim-joists using 16D nails, 16" OC. If you are in a high wind or a seismic zone you may need to add strapping to connect the wall to the rim-joists; maybe also joists to the beams.

[tc-vt]

There is probably something made by Simpson for your situation.  Sometimes their products are necessary, sometimes not, sometimes they just make the job easier.

http://www.strongtie.com/

Tom

[MountainDon]

Further note: IF you decide to use lag screws you must drill the proper sized pilot hole for each screw. If you don't there is the danger of splitting the wood you are screwing into and then that's pretty much useless.


You really don't need to worry about strapping the walls to floor and the joists to beams if you are in a "normal" area. Disclaimer: If you are in a tornado/hurricane/earthquake zone then by all means go by what your state recommends.

[MountainDon]

Simpson Strongtie

[firefox]

How about using long carriage bolts? You would need to drill long straight holes all the way down, but I think it would be a lot stronger. I am just guessing, don't take this as a way to do it.

Please feel free to comment/critcize.

Bruce

[John Raabe]

See if this detail helps. It shows joists cantilevering over a beam or foundation wall. If your beams are cantilevered and the joists go opposite on top then this detail is not exactly right, but you could still strap the rim joist to the beam, and up into the studs. This ties the parts together for uplift and racking resistance.

[Don_P]

John posted while I was rambling, some of this is redundant  ,

For typical construction the wall sheathing begins at the bottom of the floor system, is nailed to the rim joists, then is nailed to the wall studs, this is the connection. The sole plate to floor nailing is specced at one 16d nail per 16". We usually shoot 2 into each joist as we align the plate. Block the sheathing where it breaks up on the wall and go again with the next sheet again tying the studs and top plate of that wall across the next floor level and onto its studs.

Rafter ties from joists to girder are a good idea. A girder needs bracing to keep it from rolling over. If not pocketed into something on its ends there needs to be something in the span.

Plywood and osb have a span rating stamped on each sheet. It appears as a fraction but it isn't. For instance a 1/2" panel can be stamped 32/16. on a roof the rafters could be spaced as much as 32" apart (for the plywood specs) and that sheet could be used across floor joists spaced no more than 16" apart. That doesn't make it good but those are the limiting specs on the sheet. Actually floor sheathing is not required at all, I've had 2 houses built with just T&G strip flooring and if done per spec it is still the code minimum.

[Jens]

In our house, and a lot that are of similar vintage, the finished floor is the subfloor of t&g pine boards.  The exterior walls were framed, then the flooring run, then the interior walls framed.  This is the first time I had heard of, let alone witnessed this type of construction.  There is a lot of flex in the flooring, being as though it is only 3/4 on 24" centers. 

The biggest reason to not have the finished flooring underneath the walls, is that the wood will move.  If it is pinned down it can buckle when humidity is high, and split when it is low.