Expert: Dan Griffin - 6/25/2009

Question
QUESTION: Hi Dan
I WANT TO EXTEND MY EXISTING CAR PORCH SLAB BUT DO NOT WANT TO USE CONCRETE INSTEAD WANT TO GO FOR PERGOLA'S OF SIZE 9"X6" WIDTH 4'-3". I WOULD LIKE TO KNOW IF
1) I HAVE TO BREAK THE EXISTING SLAB TO FASTEN THE PERGOLA'S
OR
2) I CAN PREFAB THE PERGOLA'S AND FIX THEM BY BOLTS OR SOMETHING LIKE THAT.
3) ALSO LET ME KNOW WHAT MATERIAL I CAN USE FOR THE PERGOLA'S.

ANSWER: Neychelle, I'm sorry but I think we have a problem with terminology.  this is an example of what I know to be a pergola:
http://www.popularmechanics.com/home_journal/woodworking/3352816.html

I can't envision using this type pergola in the size you indicate.

If you are asking about fastening a vertical structure to an existing slab, yes, there would be a way to create base plates that can be attached to concrete with  appropriate concrete anchors.

I'm sure we are not talking about the same thing so please write back with a drawing or alternate description.

---------- FOLLOW-UP ----------

QUESTION: Hi Dan

Thanks a lot for the response. Below is th elink of a site showing pergloa above a car park.
http://www.ggproperties.com/07/index.jsp?project=county
This is what i'm looking for.
Can i send an autocad drawing of the plan and elevation of my house for your reference.

Thanks Neychelle

Answer
Neychelle, if you are talking about the "awnings" that jut straight out from the building, I think you will need some serious engineering.  These would be difficult if designed into the original structure.  The only material I could envision working would be a carefully designed steel framework that could be attached to steel or concrete that was designed for the loads created.

If attaching to concrete, I would think the anchor bolts would have to have been buried deep in the concrete extending out of the finished surface.  The tensile strength of the fasteners will be extreme.  I don't see a way to add this feature to an existing building.