Expert: Stephen Major (Owner--Major Design Group) - 8/7/2007

Question
Hi. I have built and designed several houses from the ground up, doing most of the work myself but, I am now wanting to build a room addition onto my existing home and need some advice.  I have a 2000 sq. ft. slab home in Kentucky and want to build a room addition, approx. 16' wide by 23' long but also have a basement under it.  Since it will attach to an existing slab house, I'm not sure how close I can dig to the slab house and not damage the soil under the footer of it.  Have you done something like this before?
Thanks for any advice on the matter.
JDSurge

Answer
John,

I think you would be surprised at what some engineers (or architects) know.  You simply need to find one who has experience in residential construction.  But more importantly you need someone who will expertly evaluate the soil at your site and also to suggest a method that will allow you to proceed with this work, safely.

If you are serious about doing this project, you will most likely need a stamped building plan from a design professional anyhow, in order to obtain a building permit.  

--Steve Major


John,

Many slab foundations have thickened edges or even frost walls with footings at their perimeter.

I recommend doing an exploratory dig to see how deep the foundation is, and if the soil is of a type that will stay in place when exposed.  For instance, sandy soil will readily fall away and undermine the foundation.

Once opened, you should consult with a local structural engineer to do a site visit and make recommendations as to the best way to proceed.  These types of decisions are very site-specific, and they have the potential to be disastrous if done incorrectly.

Best of luck and let me know if you have additional questions.

--Steve Major