Deck Posts on Existing Concrete Patio Slab

Reply

  #1  
Old 07-12-17, 10:52 AM
R
Member
Thread Starter
Join Date: Nov 2013
Location: United States
Posts: 6
Received 0 Votes on 0 Posts
Deck Posts on Existing Concrete Patio Slab

Installing a 13' l x 12' w x 2' h deck. 6 deck posts will be installed on concrete footings and piers, while the remaining 4 posts would be anchored to an existing 4" think concrete patio slab. Only 3' of the deck will hang over this slab. First, is this allowable or must the slab be removed so footings and piers can be installed? Also, can an expanding foam alternative such as Sika or other backfill brands be used in place of concrete for the posts installed in soil?
 
Sponsored Links
  #2  
Old 07-12-17, 11:09 AM
M
Forum Topic Moderator
Join Date: Mar 2005
Location: USA - N.E.Tn
Posts: 47,640
Received 316 Votes on 280 Posts
Does the slab have a footer that goes down to the frost line? if not, that section of the deck would be subject to movement with the freeze/thaw cycles.
 
  #3  
Old 07-12-17, 11:31 AM
R
Member
Thread Starter
Join Date: Nov 2013
Location: United States
Posts: 6
Received 0 Votes on 0 Posts
It does not appear to have a footer from what I can tell. The slab is at least 6 years old and in great condition. Is there a way I might be able to determine whether it has footings or not?
 
  #4  
Old 07-12-17, 11:42 AM
S
Banned. Rule And/Or Policy Violation
Join Date: Jun 2017
Location: USA
Posts: 785
Received 0 Votes on 0 Posts
You should be able to see if the post go below the slab. Post some pics, if you can't tell. If there are no footings, put some temporary posts on the slab & dig under the original posts. Pour new footings. That will keep the deck up to code.
 
  #5  
Old 07-12-17, 12:07 PM
R
Member
Thread Starter
Join Date: Nov 2013
Location: United States
Posts: 6
Received 0 Votes on 0 Posts
There are no posts currently above the slab, so I am assuming there is nothing below. When I removed the preexisting deck (which butted right up against the patio slab) I was able to see the side of the 4" slab, which I was able to measure, but I do not see anything underneath the slab from the one side I can currently see.
 
  #6  
Old 07-12-17, 12:16 PM
S
Banned. Rule And/Or Policy Violation
Join Date: Jun 2017
Location: USA
Posts: 785
Received 0 Votes on 0 Posts
I read your first post again. Anchoring posts to a slab is no longer code. All posts must have footings. The slab doesn't have to be removed to install footings. You can install footings through the slab.
 
  #7  
Old 07-12-17, 12:18 PM
R
Member
Thread Starter
Join Date: Nov 2013
Location: United States
Posts: 6
Received 0 Votes on 0 Posts
Thank you ShortyLong! In regards to using an expanding foam product for backfill as opposed to concrete when setting posts, do you know if this is allowed?
 
  #8  
Old 07-12-17, 12:50 PM
S
Banned. Rule And/Or Policy Violation
Join Date: Jun 2017
Location: USA
Posts: 785
Received 0 Votes on 0 Posts
I'm not sure how an expanding foam product would be used in that scenario. In all the decks that I've built as part of a crew or alone, we never did that. Dig a hole to the frost line, insert a sonotube & fill it with concrete, concave on top to stop the collection of water. While the concrete is wet, set the bracket for the post or for the beams depending on your design. Let the bracket set with the concrete. Maybe a bracket isn't needed at all, again depending on the design. The following day you can continue the build. If that isn't clear, let me know.
 
  #9  
Old 07-12-17, 12:53 PM
Handyone's Avatar
Member
Join Date: Aug 2000
Location: U.S.
Posts: 5,451
Received 0 Votes on 0 Posts
Here are the requirements in my area. Be advised this is for a lightweight patio cover, not a deck, but you still have live and dead loads.

D. Patio cover posts and/or columns may be supported on slabs (minimum 3 1/2” thickness) of not less than 2,500 psi compressive strength, anchored with standard approved post base, installed per manufacturer’s installation instructions.
Pad footings are not required when the total load (live plus dead) does not exceed 750 pounds.
I would consult an architect, they could figure this quickly and it shouldn't cost much.
There also might be a member here that already knows what the live and dead loads are on a 13x12 deck.
 
Reply
Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description: