Expert: Dan Griffin - 3/19/2008

Question
My wife & I are considering adding on to our house, and I though it would be nice to add onto the existing basement also. our current basement is fixed up, but the ceiling is not very high. My thought was to add onto the existing basement and make it deeper with a step down into it making for a nice living area then we could leave the existing part as a game room. My concerns are how water tight would it be, and how can you tie into the existing structure?

Answer
It is wise to be concerned about water, water tables, water tight issues.  They can all be overcome and dealt with as long as everyone is on the same page.  I assume your present basement does not have water issues.  Do you have and need a sump pump?  One other issue is sanitary sewer depth if you were planning new bar or bathroom usage, you may not be able to make sewer grade.  This can be handled by the use of a lift station.  Make sure you have adequate drainage, piping, pumps, etc to deal with water issues.  Pay attention to waterproofing, as opposed to dampproofing,  the footing, slab, and side walls.

Removing an existing load bearing wall will require some planning and engineering to say nothing about the weather jeopardy.

Your plan is doable, but you might also consider keeping the same floor line in the basement, taller basement walls, and a raised situation on the addition upstairs.  Make sure you realize what happens to window lines, roof lines, etc.