Load bearing walls supporting 2 floors above.

[RobBase]

On my house plans I'm deleting the microllams ($!) whereever the correspond to framing I plan to do in the future.

My question regards sizing for the load bearing walls. They will support the TJI floor joists of the 1st floor and also carry loads from the second floor TJI's. Should the load bearing basement walls be 2x4 or 2x6?

Since I'll be using TJI's with squash blocks to transfer the loads through the floor, should I also double up the top plate even if the floor joists line up with the studs below?

[Rich]

It's not necessary... I've been meaning to pull out the study done by NAHB on OVE framing methods. It has some great material saving methods... I did many of the methods depicted on a 1200 sf cabin I built for a friend of mine.. 2x4 walls and it's been standing for 3 years now.. they get over 6' of snow a year :) I figured it saved about 2500 on a 30000 job. Not huge savings (7-8%) but over the long term... it will definately show up in bid differences.

[mjpliv]

If you want to use 2x4 for your primary bearing walls I would suggest adding at least one row of blocking at mid height. This may already be part of your building codes. 2x4's (and 2x6's for that matter) can only support floor and roof loads in they stay straight.

[RobBase]

Thanks, Rich and mjpliv for the replies.

Rich, is that NAHB study available online?

mjpliv, one other thing I didn't mention is that some of the walls will be almost 10' in height. Adding blocking to a 2x4 wall is ok by me, but at that height would it be better to go with 2x6's?

[mjpliv]

I would recommend 2x6 walls for the 10' walls in conjection with the mid-height blocking.

[Rich]

Yep -
http://www.toolbase.org/secondaryT.asp?TrackID=&CategoryID=917
There are a few articles in there regarding material savings - the methodologies are contained within the book called Cost Effective Home Building: A Design and Construction handbook.. it can be purchased here
http://www.toolbase.org/tertiaryT.asp?TrackID=&CategoryID=917&DocumentID=2584