Building Floating Deck over ground and Concrete slab

jagnew

I have an ugly as heck concret slab out the back of the house. It's 15 years old and just too small to BBQ + guests.

I'm planning on building a floating deck that spans the width of our house foundation. So the deck will go over the ground + the slab. Approximate deck dimensions are 20' X 10'. I'll be laying some fabric and gravel to kill off any vegitation under the deck area.

I'm really not sure how to proceed with getting the deck foundation set up, or how to properly estimate the height of the deck and the materials I'll need. Or even if I can build over the slab without making the deck too high to open the back down and step out on. I would really appreciate some expertise.

I've seen some posts about using deck blocks for floating decks but I'm really stumped how to go over an existing slab and transition onto ground and keep the deck reasonably level (with enough slope for water runoff).

The slab is 120" X 93" X 8" (3" of the slab is above ground).

The land slopes down towards the right of the house so the clearance to the bottom of the siding of the house changes as you move left to right.

- furthest left there is 6" of clearance from the ground to the bottom of the siding of the house.
- on the slab there is 5" of clearance
- on the farthest right there is 8" of clearance

attached are a couple of screenshots of the planned area where the deck should be. Of note is a gate on the right side of the house that opens inside so the total width of the deck shouldn't interfere with opening the gate.

Again would really appreciate some expertise on this. The deck itself is simple it's just getting this foundation setup right, and level over the slab and ground that's really got me hesitant to tackle it.

Attached Images

  

jaydevries

not much height.
the best way bison deck system.
http://www.bisonip.com/index.php
another way is to notch 2x6 and make sleepers for on pad then when hit dirt use floating deck pads buried in ground to get correct height. i would use 10' 2"x6" with deck pads set in 1' from end on each side

__________________
be careful my advice only comes from general knowledge i know about the 4 rules it takes to plumb and they are
1 poop needs to flow down hill. 2 hot on left cold on right
3 i get a pay check on Mondays 4 do not chew finger nails at or after work.

hand drive

looks like you have enough distance between top of concrete and the bottom of your door to just frame over that slab with notched joists. if the slab is 8" thick it may even hold some of the weight of the deck though you want to add footings and not rely to much on the slab. to determine your deck height keep the top of the decking about 2" down from the bottom of the door.

also, determine which way your decking will go and that determines which way your deck joists will go.

Being that close to the ground you will want plenty of space between the decking boards for ventilation also.