So let's talk about the concrete for a minute. There are plenty of cliches about the value of a good foundation. For cause. This foundation has some good points and some faults.
Pros
already in place
strong
waterproof
cheap
Cons
not level
difficult to remove
not level
quite high relative to the threshold of the door to the house
not level
not expandable
not level
I'm sure the balance of these attributes is obvious. This is a poor foundation. Poor maybe unfair. It is a foundation that will be difficult to work with and build on. Y'know, the important parts of a foundation.
I thought of tearing it up, moving it out, digging downward and laying a bed of gravel which could offer good drainage and a compacted solid level foundation. Upon which I could place pier blocks. Upon which I could place and level strong beams. Upon which I could easily place the frame. Upon which the deck boards could be laid. Ah, such a beautiful dream.
But the prospect of breaking up all that concrete and hauling it away, or using it as rubble... suffice to say we did not choose that way. It was easier (at that moment) to just build on it, after all the old deck was built on it. I have come to regret this decision.
The keen observer probably has noticed in some of the pictures pieces of wood underneath the frame. These are shims and blocks and spacers to support the 2x4s that comprise the frame joists.
A word here--the distance between the threshold of the doors to the house down to the surface of the concrete patio is about four inches. I don't have much height/depth to work with. This deck will basically be a floor--very thin.
The concrete is strong, and there's no way I'm going to crush a 2x4 on edge, but it will sway and bow if I have it suspended between two (short) posts. And if I don't raise the bottom of the joist, I won't have a flat level surface to attach the deck boards to. Do you see my dilema?
This deck will be very thin, and variably so. *sigh* This part of the job will take a very long time, solidly supporting the joists in each part of each frame. I went through a few different versions of how best to accomplish this. I tried fitting the proper thickness of wood (well, really, everywhere this is the ultimate goal) but with different attempts to secure these little posts. Nails. Shims. Construction adhesive. Other blocks of wood.
I have finally settled on friction. The early efforts of this method involved me eyeballing the distance between the bottom of the joist and the concrete, cutting a section of 2x4 the right height/thickness, test fitting it, and if it was perfect, *WONDERFUL*. If it was really loose, maybe find another spot nearby to fit it into. If it was too tight by a lot, I'd have to stand up again and walk to the saw, grip the fragment and trim it a little. Walk back, kneel down, fit it in again.
I eventually learned the hard way that I could not rest on the frame while I did this, screwing up the distance and the level. I could not tap the block into place with a hammer, screwing up the level. I could not shim it firmly with wedges or shims, screwing up the level. It really just had to be finger snug. Scores of times. I started to say thousands, there aren't thousands of these blocks. It felt like it, and I made many more trips back and forth than there are actual blocks. Tedious as fuck. Regret.
What will keep those little blocks in place, you ask? You ask good questions. You will get your answers, stay tuned.
Back to the goddamn frames and blocks and knee pads and ibuprophen and sawdust and colorful language.