Expert: Dan Griffin - 5/20/2008

Question
I am building a 24' X 8' sunroom and I need to pour an 8" wide by 4" high concrete wall as a base over an exisitng concrete slab that has no cracks.  How do I properly make sure that the two bond and do I need steel in the new wall.  What type of concrete is best?

Thank you

Loris

Answer
Loris,  I'm sure trying to figure out why you want to create this "curb".  There is virtually no way to create this thing in a good structural manner.  Why are you attempting it?

Steel, bonding agent, acrylic modifiers, etc could all help, but you will not end up with a watertight, structural product.  If this is to be inspected, the room will require a footing.  YOu could dig down under the slab to frost depth and create a footing/curb detail.  Your 8" dimension sounds like you may be planning to lay some cement blocks for a wall, again, you need a footing to take the load.  A typical patio slab is 4" thick with no footing which moves up and down through the seasons and would not normally work well with anything rigid.  There are some screened in porch materials and hot tub enclosures which are flexible enough to work ok, but the glass enclosures much prefer a footing.

I'm not sure I've answered your question, but hope I've given you some good information.