Queston can Deck posts be attached to existing concrete slab?


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Old 04-14-10, 07:38 AM
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Queston can Deck posts be attached to existing concrete slab?

In building our 22' W X 10' D X 8' H free standing deck, one end of the deck will be over an existing concrete slab on ground which serves as an entrance-walkway to basement/garage. This means that 2 of the 6 support posts will need to be placed on a portion of the existing slab and the other 4 posts will be placed on sonoform concrete piers.

My question is: Can these two end-support 6"X6" posts be mounted directly on the existing concrete slabe via a galv Simpson post bracket fastened to the concrete OR, will the concrete slab have to be drilled out to accept the same sonoform-poured concrete piers as the other 4 support posts that will be at below-frostlevel depth?
The concrete slab basement walkway has shown no frost-movement in the 15 years I've lived there.
Thanks,
Greynold99
 
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Old 04-15-10, 06:03 AM
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The correct way to do it is to install the footings to the frost line, if there is any. Even if there is no permit involved, at this time, it could be a problem if you want to sell the house.
 
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Old 04-15-10, 02:35 PM
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You could install the posts on the slab but most likely the slab isn't designed to hold the weight of the deck and you could end up with problems later. Can you cantilever the deck so the posts are not on the concrete? If not, I would rent a concrete saw and cut holes where the post will be, dig it out and pour a footer then finish around the post when done.
 
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Old 04-16-10, 06:51 AM
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Thanks for both of your replies

Pulpo & Dan0661,
Appreciate each of your replies. I suppose as Dan0661 suggests if the slab is a thin 3"-4" thickness, then the thing to do is bite-the-bullet and drill/excavate the necessary below-frost pier footings for end-deck posts.

On the other hand, and believe me I suspect I could find a 6"-8" or greater thickness slab under there... One thing I didn't point out is that the existing overhead entrance concrete slab that is to be removed (the one that is cracking and moving on the far end side - not on the end where I want to place the posts) was constructed using concrete block construction on the existing ground-slab, on at least this end and front-side. So, there is NO movement by the existing overhead slab on this end since built 25 years ago and existing ground-slab is supporting a whole lot more weight than my wooden frame deck replacement will be by far.

We'll know more when the current overhead slab is removed and will be able to make a better decision then.
Thanks again,
Greynold99
 
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Old 04-16-10, 07:43 AM
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Even if we are 100% sure that the slab is strong enough to hold the weight, it violates building codes in most places.

It's not hard to install those footings. Rent a jack hammer, get a post hold digger, sono tubes & 3 bags of quickcrete per hole. You'll be done in less than a day.
 
 

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