Deck Posts: Using existing foundation wall?
A bit of background:
Harry homeowner here so I appologize if I’m not using trade terms correctly!
I’m replacing an existing moderate sized deck (aged and outdated) with a much smaller deck that will simply serve as access to a large patio. The existing deck is about 4 to 5 feet above grade but overhangs an “English Basement” style walkout/stairwell. The below grade portion of the walk-out is 8″ thick reinforced concrete (poured) and tied to the basement foundation.
The desired dimensions of the new deck are about 5ft deep by 9ft wide. Our basement access foundation is 4ft from the house and it just so happens that our county allows cantilevering of deck joists up to 20% beyond the supported span. This is where it becomes either an “Woo-Hoo!” or “Doh!” moment:
1) Is using the top existing 8″ thick walkout foundation as the “footer” for my deck posts (6″x6″)feasible?
1a) If so, what’s the best connection method to the existing foundation? (I’ve used case in place ties but not had experience adding ties to cured concrete)
1b) Any precident or literature here that could help appease the county inspectors/building department? Google searches turn up as dead ends on this one.
1c) Any other pointers/gotchas’s?
2) If the answer to 1) is “Doh!”, any other options besides digging new footers to the existing walkout foundation depth?
This is Fairfax County, VA in case any of you are local.
Regards,
Brian
Replies
Brian
Yes,
Simpson among others, have a 6x6 post base that you retrofit to existing concrete. Your stair well would be the same application as a top of pier mount (for your inspector). All that's left is you presenting your wall as an adequate "pier" with proper footing and the inspector approving.
Look to Simpson post bases.
All you should need is the same type of post base you'd put on top of a poured concrete pier.
If one side of the deck is attached to the house (be sure the ledger is secure!) and there is some sort of diagonal brace (eg, a plank fastened diagonally on the bottom of the deck) then you do not need any further bracing on the posts. The posts do need to be anchored DOWN, to guard against wind uplift, but the post base should do that, if properly installed.
Deck Connections
Brian,
Your inspector may want to verify the size of the footing under the supporting wall. The deck ledger connection code, if followed, can be challenging, here are a couple of examples. Your situation may vary, so interpretation is in order.
Thanks for all the replies. I will proceed with the plan and follow up when I hear back from the county permits/inspectors!
Assuming you are talking about two columns supporting the deck (plus the ledger at the house) the design load on the columns is about 700 pounds. The added load to the soil through the foundation wall is minimal. It will not be a problem (assuming the wall is not settling). A reasinable inspector should realize that the load for that size deck is small.