Expert: Mark H. Miller - 1/18/2008

Question
I have a beautiful old sofa with nice show wood from the 40's.  I want to install
no-sag springs in place of the coils.  They are gone and made too soft a seat.  
Can you give me specks on this retro-fit.  I need to know the correct height to
build the frame up   from the floor.  Is there information somewhere in the form
of line drawings with dimensions for sofa frames.

Answer
Hi,  great question.  You are doing a smart thing, it is a trade secret that once you sit on a sofa there is no way of knowing if it has coil springs or no-sag springs.

The perimeter around the frame where you nail the no-sag springs should be 10 to 11 inches from the floor.  That way with the cushions in place the total seat height should be between 16 and 18 inches.

If you need to raise the height just glue a strip of any hard-wood with Gorilla glue and drive some screws into it.

A word of caution, no-sag springs place a tremendous amount of tension on the frame from front to back, therefore you should make certain that there is a strong wood brace, level with the bottom of the frame and with a very large corner block on top of that brace both in front and in back, the corner block should reach as high as the perimeter of the seat rail - as an extra brace to prevent the frame from collapsing inward.  Space the braces about every 24 inches apart.

The springs should be spaced 4 to 5 inches apart and make certain that you use the heavy gauge for seats and not backs.

The website for Frank Chervan frames has some excellent drawings of sofa and chair frames that may be of help.

I hope this information is what your were looking for.  Please do not hesitate to contact me if you are unclear about anything.

Mark Miller.