replacing pocketed joists-old structure

huangyhg

replacing pocketed joists-old structure
i have an old building that is being renovated. the first floor framing is essentailly all destroyed by termites and the entire first floor must be rebuilt under the existing structure. the existing floor joists are pocketed into the fieldstone foundation wall. we are going to put new joists in and they will not fit in the pockets or be able to bear on the sill plate. typically i would put a ledger board into the foundation in this situation but the wall is fieldstone and the surface is very irregular, so there is no way to bolt a ledger flush. options are 1. parge the entire wall out 6" to get a flush surface 2. parge only behind the ledger 3. instal girders on columns in front of the wall 4. any better ideas? any ideas/tips on forming and parging a portion of the wall behind a ledger and drilling through the parging and into the wall for a ledger? any better ideas?
how about building a wood stud bearing wall in front of the rubble wall?
if the fieldstone wall is in good condition, you can insert anchors in the mortar joints... consider long and oversize, the mortar may not be overly strong.  avoid patching using portland cement mortar.  the mortar can be built out for a length of 2 or 3 inches on each side of the anchor flush with your new ledger.  use a joist hanger that will develop some moment to minimize the pull-out on the anchor.  wall should be in good condition and able to take any additional forces applied to it.
this approach does not obscure the natural fieldstone...
dik
bearing wall is potential option....thw wall is in fair to poor condition. we are going to rake and repoint all the loose joints first though
the stud wall sounds like a good idea unless there could be the possiblity of the wall buckling in the future.  if you cover up the field stone with a dry wall partion you could not observe what is going on behind the wall.  if you do add a stud wall be sure to use treated wood or steel studs.
you also indicated that new joists will not fit in the pockets  which are present in the existing wall.  you might consider lvl or steel studs which should allow you to use a   
the issue is that the existing joists are of varying sizes and spacings so any new floor with regular sized and spaced joists will not work. the architect got in touch with a historical renovation contractor who has people who make him custom joist hangers for all kinds of applications like this so i may have him design the actual connectors and review them.
even if the old floor were sound, you might be called upon to reduce a persistent squeak.  in which case you might put double sisters on the middle half of each joist.  the same sisters would allow you to install a new joist in an existing pair of pockets, by cutting the joist in half and splicing it in situ.
sneaky folk might scarf the sisters and the joist (tapering both in width), disguising the splice.
mike halloran
pembroke pines, fl, usa