Expert: Jeff Davis - 8/30/2004

Question
Hi, I am building a room addition 16'x30'.  I had the basement dug out to the same level of the house. I need to dig the footing and I am getting a difference of opionion on the footing depth.  The city inspector said 6"deep x 16" wide was ok.  My cement contractor said it should be 3 foot deep x 16".  I am framing the room with 2 Perka steel frames 10'x30' with total weight of about 600pounds each. I am using 8" wide cement blocks and backfilling about 5 foot of dirt. How deep should we make the footing?  

Answer
I apologize for the delay in answering I have been quite busy and have neglected checking my email.  To answer your question, footers are typically formed up with 2x4's BUT to answer your question about depth, I am not sure of your climate area, but you need to be below the frost line with your footer.  Since you already have a structure on your sight, I see no reason why you should't use the existing elevations, unless your building code advises something else.  If you were digging a crawl space type addition, then I would recommend at least a 3' depth (depends on frost line) if you do not get the footer below the frost line, walls could heave when exposed to cold weather.  

Good Luck!  I hope this answers your question.  If not let me know..