Downside to "attic trusses"

[Redoverfarm]

With the onset of winter I turned my energy into finishing the garage and garage apartment.  The addition was dried in 2004=2005.  I did finish the family room. exercise room and breezeway/pantry.  Shortly afterward the cabin was started and consumed all my time since.  Now the cabin for all intent and purpose is finished.

Well on to the project at hand.  The garage is 26'x44' which incorporates a shop 18'X26 and two car garage.  Over the garage is a 12'X44' room which I plan on making into a 1 bedroom garage apartment.  The garage has attic trusses which give me 12' from knee wall to knee wall.  They are somewhat different than deck foundation in that there is no rim joist for the subfloor to attach on the two outside walls.  Aside from getting caught with the less than nominal width of tounge and groove subfloor from 48" to 47=1/2" ( I believe).  That means a narrow strip (1-1/2") after 3 pieces to finish out the total width.   I was given the option by the truss manufacturer for a 15' room instead of a 12' room.  That would have certainly solved the narrow strip to make up what was lost on the subfloor but I would have lost valuable storage space.


Aside from the with defecit I have to install nailers between each truss to attach the subfloor to.  It seems sometimes I make things more difficult by " add on's".  In the space directly behind the kneewall which is a 7' I  intend to make 4 feet of storage.  Somewhat the same as the upstairs in the house.  That will mean that I will also have to attach nailers for the storage space flooring both behind the kneewall and the outer edge.  I do not plan on using the standard 3/4" subfloor in the storage area but 1/2" OSB since their will be no traffic and light weight load.   OK now I have to add nailers between 32 trusses at six locations.  If I rough counted them correctly that is 186 pieces approximately 14-1/2"     

I think I have a way to eliminate 1/2 of them.  At the intersection of the kneewall (2X4 to 2X8) I plan on installing alternate 2X6 & 2X8 blocks on the flat to the top portion of the truss cord.  I have been trying to figure a simple way to attach them one right after another of the same demensions (2X6 or 2X8) with addequate fastners.  So I figure I could nail all the 2X6 blocks alternately in every other bay.  Then come back with 2X8 in the open bays on either side.  That would give me 3/4" space to angle nail the 2X8 blocks from each end totaling 4-16d nails.  This would put more fastner into the blocks than just angle nailing from the outside corner/  Although there should be no weight on the outer edges do you think this is enough fasters for the small blocks.   I may be able to add an additional 3-1/2" deck screw to each end for added strength but because of he metal plates they will not be dead center.

Of course that still leaves me with the storage area out wall blocks which can be of lesser demension because I am not having to catch flooring on either side of the kneewall.  Maybe 2X4 & 2X6.  It is at thsi location that a second short kneewall will be made and insulated.  That will make the storage area insulated. 

Today I finished framing out the stairway top to except the subfloor, added nailers to the stair cavity, nailers on the gable ends and wall partitions to except drywall on the main floor.   The majority would not be accessible once the subfloor is laid. 

[Don_P]

Yup detailing most engineered products seems to be the downside. Screws from ply to blocking will hold it in place till you can nail through the framing into the blocks. The blocks can normally all be one width, if they are in a straight line you can nail from the end into one and back at an angle into the next, by the time a nail goes through the truss at an angle it's over an inch or more into the block. (if that word picture worked).
A palm nailer comes in really handy and they aren't too bad $ wise.