I want to build an 12x16 deck on top of an 8x10 slab. Slab is in good condition. I want to lay the floor boards across the slab. I was going to build a frame ( with2x6's) that would be on top of the ground and in some areas partially underground to attach the floor boards too where the wood deck would overhang the slab. Is this real for me to do? Would the whole deck be able to withstand freezing? Should the support beams in and on the ground be cemented in or supported with stone?
That sounds ideal to me, up to the point where the boards touch the ground. There surely has to be a way to do it where all the support is anchored to the slab without resorting to putting posts in or, having boards touch the ground.
this would not be a recommended approach. besides what frost action and differential settling would do to this setup, how are you going to fasten the decking to the concrete? you will need sleepers (don't fasten deck boards directly to the concrete). also, dirt and crap will get trapped under the decking on the portion that is over the slab--a few years and you will have plants growing between the deck boards.
an 8x10 slab is not a huge deal to pull up. why not pull it up and do the job right?
Don't lay the deck boards directly on the slab. There's no good way to attach them, and there wouldn't be any drainage for the water that flows between the deck boards.
As a start, imagine the slab isn't even there, and build the deck as you would anywhere else.
Set concrete deck blocks on your slab, and out in the yard beyond the slab. Install short posts as needed to make things level, and build a frame with beams and floor joists. You can use joist hangers to keep the joists at the same level as the beams. Then attach your deck boards to the joists.
If you don't have the space between the deck and your entry door to use the deck blocks, you could support the floor joists with bricks or concrete pavers instead. Adhere the brick to the slab with masonry adhesive to keep it from moving.
If you don't even have room for the floor joists, you'll need to get creative. You could lay pressure treated 2x4 "sleepers" on the slab, using adhesive to keep them from moving. Then attach your deck boards to the sleepers. Be sure to provide for drainage though, such as using short boards for the sleepers and leaving gaps between the ends where water can drain away. Out beyond the slab, switch to standard joists, posts, deck blocks.
As other's posted, it may just be easier to rent a jack hammer and tear out the old slab.
It also sounds like you might be building into a slope? If so, I'd dig the hill back away from the deck, either increasing the angle of the slope, or installing retaining blocks or something. You don't want the wood to be in contact with the ground.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.