I am involved in a project where I am adding an additon to a ranch house. House is about 25 feet wide about about 40 deep. Most of the projects I work on are total gut jobs so I dont worry about saving existing structure. However this house has a really good first with new kitchens and baths so I want to keep from demoing the ceiling and ceiling joists.
Joists go across house as expected. The top plate on the rght side of house is about 1 inch lower then the left with a slight(1/2") pitch toward the back.
I was wondering what methods others use to level the top plate before adding a new floor in cases where the existing ceiling and ceiling joists are to remain. In cases where I am am demoing the existing celing joists and the slope isnt bad I sometimes shim under each joist.
However for cases where I am leaving the existing ceiling joists (to support exisiting drywall ceiling) and installing new joists I have been doing is scribing and cutting the rim joist to follow the contor. I like to install a rim joist because otherwise otherwise I end up with a bunch of point loads which dont line up with the stud wall(since the existing joists line up with the stud wall).
What I did in the past was a buy a engineered wood rim joist one size over(assuming slope is less then 2 inches). I placed the enginnered joist on the top plate temporally, shiming the low side until level. I then ran a scribe down the outside of the building along the top plate. This left me a line on the rim joist that followed the slope of the top plate. I then trimmed it down with a circular saw so now the contour of the rim joists makes the contor of the top plate.
This was time consuming but seems to work well. One thing that makes it even mroe time consuming is the fact that the existing ceiling joists in most cases extend flush to the edge of the top plate. This causes me to have to cut these back 1 1/2 ". I then connect them to the new rim joist with simpson angle brackets.
I was wondering how others do it when framing new floor joists in parallel to existing when top plate isnt level.