Building Homes or Extensions/Extending slab foundation

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Expert: - 10/19/2010


Question

Kitchen Extension
Mr. Johnson,
I am wanting to expand the kitchen in a home I am purchasing and need some advise. I want to expand a portion of the kitchen out onto the patio area 6'x10'. I am told that I can not just wall in that area and float enough concrete on top of the patio  to level out with the kitchen floor. Do I need to dug that portion of the patio out and repour? Do I connect it into the existing slab or put an expansion joint between them?

I appreciate any advise you can give me.

Thanks
Frank

Answer
Hi Frank, if you have an existing roof structure over the area in question then yes, you probably can just level up the floor and build your walls without major structural work required.  However, if you need to add a roof structure which will be supported by the new walls then you will need to add a concrete footing capable of supporting the roof load.  This would require the slab to be removed, new footings dug and reinforced and a monolithic slab repoured in its place.  Another option may be to undermine the outside edge of the exisiting slab and underpour a new reinforced footing under the outside edge to support the additional weight.  If a building permit is required for this project then you will be bound by local building codes which may require reinforcement of the outside perimeter of the existing slab.  Many times patio slabs have thickened edges of eight inches deep and eight inches wide which may suffice for moderate loading.  If you can dig down alongside the existing slab and under it in one spot you can determine the thickness and width of the perimeter concrete.  I hope this information helps, please feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com

Bruce E. Johnson

Expertise

I can answer any construction related question in regards to carpentry, concrete, drywall, masonry, structural elements of any type of building, residential or commercial. Interior or exterior.

Experience

Custom Commercial and residential buildings. Churches, theaters, schools and auditoriums. Most recently I am working with the Catholic Church on several design build committees. I have a website related to scheduling and project supervision. Although my expertise is more related to multimillion dollar commercial, educational and theatrical projects my generous credentials in residential and remodelling construction make me a viable source of information regarding all forms of building questions.

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