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A vinyl sunroom was built onto my home over an existing backyard cement slab. The slab had a slope, and so the sunroom has a slope to it. I am trying to figure out a way to level it out now. Furniture l. It is 10x10, and it looks like it goes down about 4" over the 10' run. I was thinking of:

a) Self-leveling cement, but that seems like it is only used for smaller leveling and would require a lot of it.

b) Building a floor over it with 2x6s angle cut and spaced every 18" with plywood over it. But then I would have to anchor the 2x6s to the cement somehow.

c) Level it with regular concrete.

I am thinking about B or C as my answer. I want to lay porcelain tile over the new floor.

EDIT: Thanks for the feedback. I want to clarify...

  1. I need to level the floor inside the sunroom.
  2. This sunroom is made of vinyl panels, and I want it level inside so furniture isn't tilted and pens don't roll off the desk inside it. The roof is flat, 4" thick, and also vinyl I suppose. I want to leave the sunroom in-place and not take it apart and reassemble.
  3. My fault - I meant every 16" joists. And yes, I suppose I don't have to anchor them.
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    Level the slab or the sunroom? Aside from that ambiguity, your question is a bit vague. It's not really for us to decide what's best for you in your situation. Also, joists would be at 16, 19.2, or 24" intervals. 18" is nonstandard.
    – isherwood
    Feb 19 at 21:30
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    Please see How to Ask and take the tour.
    – isherwood
    Feb 19 at 21:31
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    2x6s have some weight to them, so why anchor. They will stay in place quite well.
    – crip659
    Feb 19 at 21:32
  • What is a "vinyl sunroom"? Is it vinyl wall segments attached to each other? What's the roof made of? Why do you want it to be level? What's that going to buy you? It's entirely possible that if you level the slab now, that the panels won't match back up. Are you planning on disassembling, leveling the slab & reassembling? Loads of additional detail would help us help you.
    – FreeMan
    Feb 19 at 22:02
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    if the slope in the floor was not and issue before, it does not have to be for porcelain tile. Concrete is a great substrate to put tile on.
    – RMDman
    Feb 20 at 0:03

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I do believe your patio slope is pretty extreme. Normally, an outdoor surface is sloped at 1/8" or 1/4" per foot for drainage. For a 10' run, that would give you a drop of 1-1/4" to 2-1/2". If you actually have a 4" drop, someone got carried away. I can understand why you do want this to be more level.

As an out-of-the-box suggestion, you might consider leveling each individual piece of furniture. This would be significantly easier and much less costly, even if you had to buy/modify leveling feet for each piece.

If you're set on leveling the whole floor instead, I'd suggest that option B - (install tapered sleepers so the tops are level) would be the easiest and (most likely) lowest cost solution.

You'll want to use pressure treated lumber for these sleepers since concrete will wick water from the ground and will, eventually rot wood that's in direct contact with it. You might have a vapor barrier under the slab, but you might not. Even if you do, the foundation walls around the edge won't have a barrier and they'll wick water to the main part of the floor.

You'll want to do some very careful measurements to see if the floor is flat (not level). If it is, you're in luck! You can very carefully measure and cut one sleeper, then lay it down and ensure the top surface is level. Once you've got that first one, you can use it as a template to build a jig to make cutting the rest of them quick, easy and accurate.

Once they're cut, you can install them with a few concrete appropriate anchors. You can use a Tapcon™ style screw, designed to be installed in a pre-drilled hole in the wood/concrete. You can use a powder actuated nailer that drives a nail directly through the wood and into the concrete using what is, essentially, a bullet cartridge where the "bullet" is a nail. You could probably even install them using an appropriate construction adhesive.

You don't really need a lot of fasteners, just enough to keep the sleepers from moving until you've got your flooring installed on top of them. You could, in theory, just lay the sleepers down and attach the flooring to them, but then you have to deal with the fact that the sleepers will move every time you bump them until you've got a couple of pieces of flooring attached, holding them in position. Attaching them to the concrete simplifies the process of installing the flooring on top.

Make sure you follow the instructions for subflooring for your tiles. You don't want to go to all this effort and not have a stiff enough base for your tiles and have them crack after a year or two.

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  • Thank you VERY much for that very good response. I heard from someone else that I can run the sleepers (they called them shims) parallel to the outside wall. It doesn't need to be ripped at an angle then. Each successive sleeper is cut is slightly narrower until the narrowest is closest to the inside wall. I hope that makes sense. Thoughts?
    – HAL9000
    Feb 20 at 21:49
  • You can do that, too. You have to cut a bevel on the long edge and you have to measure each one individually. I'd think that there would be far more room for error running them across the slope than down. As mentioned, if you run them down the slope, you can create a jig to cut them all exactly the same (if the floor will allow it). Which you do is up to you.
    – FreeMan
    Feb 20 at 22:21

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