I’m building a deck over an existing slab, ledger on house to support one side and posts with girders to support the other. It will be about 8′ high (above the slab), and approx 8′ x 16′. The slab is probably only 4″ thick, maybe 5″ at the most. Can I anchor the posts (probably 6x6s) by drilling into the concrete, epoxying a threaded rod in the hole, and then bolting a post base to the rod? If so, any suggestions on what type of epoxy to use? Thanks.
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Replies
Simpson makes an epoxy for setting bolts into existing concrete.
I think Quickrete also makes a similar product. Both available at you local home center.
PS. I wouldn't anchor the posts to the slab. Depending on your climate you need piers with an appropriate footing.
In the time of chimpanzees I was a monkey.
Edited 7/22/2006 9:15 am ET by dustinf
As for climate, I am in South Carolina. Footings would be nice, but I am trying to avoid the hassle of cutting/breaking the concrete (and the unsightly patches that would result). I would think if I can drive my car over this slab (and I have), it could handle a deck of this size. I was more concerned about uplift and what the inspector might say.
Why not call the inspector and ask his opinion of your plan? The worst that can happen is that he tells you that you need to dig proper footings/piers. You would need a permit in these parts (NE) anyway, which means a final inspection at the least, so better to know the requirements before you build, rather than retrofitting afterwards.
"I am the master of my fate, I am the captain of my soul." Invictus, by Henley.
Yeah, I reckon this is one instance where it might be better to ask permission rather than forgiveness.
To bolt down your metal post bases you could also use a wedge type of anchor like this one:
http://www.smithfast.com/trubolt.htm
Around here they sell them at home centers, etc. I've tried to get them out before and it was not possible. I ended up cutting them off, beating them down below the concrete surface, and then patching the concrete.
Something to think about though is that when you put posts on your concrete slab you will be creating points loads on the slab and this will very possibly crack the slab. This will be more or less of a problem depending on how stable the subgrade is below the slab and how thick the slab is.
Also, if the deck/porch is to be inspected the BI likely won't accept this method of support since it is a total unknown (to him), as for all he knows the slab is 2" think at one or more of the support points. If you live in an area with building codes, the minimum footing thickness is at least 6" or maybe 8, and if there is a frost line where you live, the slab probably doesn't go that deep.