Raising/Levelling a floor on cement

I am planning on raising a floor a floor on a current cement floor in a small room (100 sq.ft). This was a porch at some point and the cement floor has a pitch away from the house, so I plan on leveling the floor at the same time.
Assuming my plan makes sense, I would run the furring strips away from the house, one end would be about 1/2" thick and the other end, thick enought to achieve a level floor (I predict no more than about 1" 1/2. Each strip would be gun nailed in the cement every 16" or so and plywood (1/2" thick) would be screwed on top to receive whatever finish is decided (carpet or laminate).
My plan is to start by snapping a line around the room showing the height of the level floor and measuring the thickness of each strip from there.
I'm looking for general opinions on the project and tips to get it done right? How wide a piece of wood should be used to support the plywood floor? What's the best way to cut each piece on a angle on the full length of the piece (about 8')?
Any other gotchas or specifics I should be worried/concerned/carfull with?
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1/2" ply isn't good enough for 16" OC, and probably not good enough for 12". Think 5/8" or better still, 3/4".

This is a good time to rent a laser level.

You'd need to make a taper jig for a table saw to come close to getting reasonable tapers. Tapering jigs 8' long are a PITA to handle. Besides, assuming the floor isn't uniformly sloped, it'll "telegraph" the unevenness.
Scribing, then jig or bandsawing each sleeper to make dead certain it was level would be a serious PITA.
You should consider a self-levelling flooring compound. At 1 1/2" at one end, that could mean a heck of a lot of it. But, if it's feasible, it's by far the easiest.

You're going to have to assess the need for vapor barrier.
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Chris Lewis, Una confibula non set est
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Chris Lewis wrote:

Or tongue & groove OSB subfloor?
Charlesg wrote:

Use a string level to mark your corners, then snap the line (or use a laser level as suggested by Chris Lewis)

You could cut the pieces straight and use shims to make it level, however you'll need a lot of shim material and it'll have to be placed under every nail/fastener.
Ditto the comment about a possible need for vapor barrier. In addition, depending on climate, what about insulating?
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snipped-for-privacy@unixrealm.com says...

I trim pieces like this fairly often using just a circular saw. Cut the pieces from 2x4's or even 2x3's. Lay the boards across two saw horses and measure each end, snap a chalk line. It helps to C clamp one end of the board to the saw horse to keep it steady, move the clamp when you get to it. Use a nice coarse blade for the saw, I recommend an 18 or even 16 tooth Dewalt framing blade, it's what I use.
Now, if you plan your cut line well, you may be able to cut each board into two equal pieces that fit, especially if you use 2x3's.
If you aren't comfortable sawing straight in a narrow 2x4, start out with a 2x10 or something. Layout the first taper and cut it, then swap ends to layout the next one, this will keep the remaining board fairly even in width as you go.
Dennis
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I believe you will experience difficulty in "shooting" than many nails in something that is not much more than a furring strip.
I just removed a floor that was 3/4 ply with 16" OC structure. It was way to springy for the tile I am installing.
Why does an exterior floor have to be level?
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I would guess that this slab was once open to the weather, but is now enclosed.
bill

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Why not run the furring strips parallel to the house wall on 16" centers. Then you would not have to taper anything. If you felt the slope were too much for square furring strips, it would be easier to cut a bevel along the length on a table saw than a taper that long. The flooring would obvoiusly run perpendicular to the furring strips. 2x4 material cut to size would probably be most economical
If the slope is less than 1" for 10' then concrete leveling compound might be easier. For 100sf and 1" slope you would need only about 4-5 bags and something to build a form on the low end. Might even cost less than lumber and fastners, never mind less labor.
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I'd consider using a levelling compound. Otherwise, I'd probably bandsaw them into the taper. Cheers, cc
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