Expert: Bruce E. Johnson - 5/29/2009

Question
the back addition of my house about 18 feet by 18 feet was build on poured concrete into those approximately 12 inch diameter "sonatubes" i think they are called. these cement supports are sitting on a poured cement slab.  This addition was here when i bought the house 9 years ago and the area where the slab is was used for storing outdor furniture as it was never closed in with proper walls.  i am wanting to put more permanent walls up as there is just ply wood that was put up on two sides that has not rotted .  I was wanting to put concrete block up about three feet and then put wood frame and siding to meet up with the siding on the 18x 18 addition above.  How do i start the concrete block on the exsisting cement slab

Answer
HI Dianne, if you have a reasonable footing along the edge of the concrete slab then you can drill into the concrete and epoxy some rebar dowels (epoxy and dowels can be bought at Home Depot or Lowes)..when laying up the block the dowels are placed so that they come up inside the hollow cells of the block then these reinforced cells are filled with mortar or grout to tie it all to the slab.  Have your block on site and lay out a temporary course to see where you want to put the dowels then mark and drill them using a concrete drill bit sized to fit the rebar..1/2" rebar will require a 5/8" bit..Then clean out the hole, dump in the epoxy and then stick the dowel in the epoxied hole.  Let it stand for several hours, preferably a day and then lay up your masonry. I attached a drawing for you to look at..I hope this information helps feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com