Expert: Bruce E. Johnson - 7/27/2009

Question
Read an old post you answered about adding a foundation to foundation-less residential house.  I'm investigating adding foundation to crumbing stone and mortar foundation. You mentioned a similar project.  My question is if you remember (on your project) if the new cast in place concrete extended all the way to the old mud sill/joists/header. OR did you add a wood framing in between new foundation wall and joist assembly?  I realize each job and site conditions are different.  I'm in the early stages however of figuring out what can be done.  Thanks for any help!

Answer
Hi David, it is easier to keep the new wall down enough to form and pump concrete into it and then fill the gap with framing or multiple layers of mudsill forced into place.  For this reason you can allow a definite distance to work with.  In other words if you keep the concrete wall down 4 3/4" you can put three layers of 2x pressure treated mudsill into the gap.  It is possible to form and pour a foundation up tight to an existing mudsill by pumping the concrete into holes made at the top of the formwork.  The concrete is pumped until the form is completely filled and oozing out at the top.  Then the pump hose is moved further down the wall and the concrete is pummped into another hole until the form is filled and oozing out at the top.  By slapping the forms with a hammer as you go you can assure that the concrete is pressed up tight to the existing structure.   I hope this information helps feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com