Having completed plans for a small bath addition in Philadelphia, I'm a little worried that the floors won't meet properly. Do I have to cut down to the subfloor on the existing part of the home to find the height for the connection? I need help finding the right level for the foundation.
Earle A. ~ Philadelphia, Pennsylvania
Earle, although there are transition strips available which are designed to bridge floors of uneven heights, I do think that you should try to build your bathroom addition in such away that the new finished floor is at the same height as the existing one. In my opinion, uneven floors look odd, and they never feel quite right underfoot.
One way to determine the correct height of the foundation which you will pour is to work backwards from the new finished floor. By this I mean that you should add up the thicknesses of the finished floor, the sub-floor, the floor joists, and the sill plate to determine what level the finished concrete should sit at. (Obviously, this assumes that you are pouring a foundation with a crawl space, and not a slab foundation). Once you know that calculation, you can compare those measurements with the measurements from your existing floor system, again working backwards from the finished floor.
To take these measurements you will have to find a location in your house where you can get a good look at the existing floor system, and your crawl-space is probably the place to start. When measuring your existing finished flooring, pull up a piece of base board trim and try to use a ruler in the space between the floor and the wall. If by chance the measurements of the existing flooring and framing are the same as the the measurements from the to-be-built bathroom addition, then you're in luck, because you can pour your new foundation at the same level as the existing foundation. If the new addition will have different sized floor framing, a slab foundation, or a finished floor of a different thickness than the existing one, then you will have to make some adjustments to your calculations in order for the both floors to come out level.