Expert: Bruce E. Johnson - 6/3/2010

Question
Hi Bruce,  We have begun excavating for a new patio at our existing basement walkout. The door opening (which begins close to the corner of the house) is about 70-71 inches wide.  On the inside wall side of the door, and 5 inches from the door is a two story fireplace chimney. So this is what it looks like, we have the house corner, a 70 -71" wide door, 5 inches of wall, two story fireplace chimney.  Our question is: we are concerned about digging all the way up to the chimney; we are afraid it may disrupt the foundation of the chimney.  There is a slight hill coming down toward the walkout and approximately 3 feet of earth at the highest point of ground covering the chimney.  Also we have found a run of 3 1/2" clay tile that was layed in front of the chimney but it abruptly ends at a small slab of cement that lays in front of what was an single width entrance door many years ago.  Do you think there is the possibility of disturbing the chimney foundation??  We are planning on laying small tumbled patio blocks.     Thanks You, Dave

Answer
Hi David, It all depends.  If the chimney foundation is done properly it should be at or below the basement foundation.  If this is not the case then you need to be careful not to undermine the footing of the chimney.  The tile you are talking about is possibly the footing drain tiles that keep the water from building up around the chimney and undermining the foundation.  If the existing grade is or has already been established over the years and all you are doing is grading out for a patio you should be okay..If you are changing the elevation radically and the chimney foundation is above the basement foundation then you may need to build a retaining wall alongside the chimney to keep the soil under the chimney foundation from washing out.  This retaining wall will need a footing drain also to divert water around it similar to the chimney footing drain.  I can't comment much further without knowing exactly what the foundation elevations of the elements in question are and what other conditions may exist..I hope this information helps, please feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com