I have a question about accountability in these such matters...
(although I think I know the answer) What degrees of responsibility should fall on the engineers/designers/planners versus on the construction companies/crews when the construction is not done according to design/specification...
Supposedly, the steel straps offer even greater strength/stiffness potential.
And, one big reason to using the steel is due to height concerns...
Adding the 2x4's (flat, I assume you mean) requires 1.5"; adding the steel would require like 1/4 to 3/8" absolute max...
Not just for the clamping...
Visually grading wood sometimes seems wierd....
It doesn't seem to match the stamp grade (?)
For instance, just recently looking at SPF 2x6's, I found some really attractive ones (straight grain, few knots, appearing 'strong') that were STUD grade STAMPED...
In contrast the STAMPED #2's...
"...Somehow I think that by getting such an intimate connection between the sisters, the combo would be stronger than the some (any defects in one joist, would be compensated for by the sister, and vice versa -- much like in any other 'lamination')..."
There is a typo in the above paragraph...
"...Green softwood conforms to nails okay, but the seasoned lumber you'll find in a house that's dried out a bit may just split from having a row of nails driven into it..."
I don't think it would be advisable to nail the steel strap to the joist, so it would be drilled and screwed (and glued?)...
I think the only places that this type of retrofit might even apply is:
if there is no room beneath to put a midspan beam in, or if the ceiling height below is too low to use deeper sister joists or flat 2x's added to the bottom flange...
OR, if standard sistering (with the same dimension...
In this particular instance, the ability to nail to the bottom flange of the joist is not important, and as AsianEngineer said, a 2x4 could still be attached to the side of the joist for the purpose of any attachments, if needed...
The big question here is whether the structural claims of steel...
I was reading some posts on some other forum, and I noticed the following discussion, arguing for the use of strips of steel to be afixed to the bottom flange of wooden joists, in order to increase capacity or decrease deflection.
From what I gather, this seems theoretically okay, although...