How can I level a sloped floor?

Question

I have a 10x13 first-floor room which used to be a porch but at some point was closed in by the previous owners, and sheet linoleum was glued down to the plywood subfloor. Unfortunately they didn't correct for the built in slope of the original porch when the closed it in, so the room has a consistent 1-inch slope towards the outside of the house (e.g. it's not an intermittent 'sag,' 'warp,' or 'dip,' the whole floor slopes out relatively consistently). I need to level the floor in order to put down hardwood as I will be using the space for my business. I have been advised (by 3 different people) to solve the problem in 3 different ways:

1. Screw down wire mesh straight to the existing linoleum and pour Self Leveling Compound to bring the slope level.
2. Pull up the subfloor and sister new 2x8s to the joists but leveled instead of at an angle
3. Pull up the subfloor and then attach custom-cut wedges to lay on top of the joists correcting them to level.

Now, option 1 has a certain amount of appeal simply because I don't have to pull up the linoleum, rip up the subfloor, or engage in any cutting, nailing, bolting, screwing, gluing, or replacing of subfloor to accomplish the leveling task. On the other hand, the notion of a large quantity of self leveling compound drying on me as I'm desperately attempting to mix it, pour it, feather it, etc. makes me nervous (a 10x13 room with a constant slope- thus the entire 130 sq. ft. floor will end up with at least some SLC on it- 1 inch deep on one side of the room, and feathered to nearly nothing on the other). So my questions are as follows:

• Am I missing any major options for leveling my floor?
• Are any of the options above not realistically viable (e.g. I have a friend who doesn't know what they're talking about in recommending one or more of the above options)
• Is SLC really 'a breeze' to use (as I have been told it is), or are my fears of not being able to get the entire 10x13 room poured and feathered inside of the ~20 minute setting window well founded? I will have volunteer help, but there will be no 'pros,' so if it's not actually a 'breeze' this could be an issue...
• Which option would you choose, and why?

Answer 1

I'm really fascinated by your question and suggested solutions. I am glad to hear that you question the wisdom of some of the suggestions. There are a few factors that are important to consider before picking a solution.

What type of hardwood flooring are you thinking of using? Nail down, staple down, glue down or floating? With any type but a floating floor, SLC is definately the wrong product to use underneath, as it will shatter when nailed, and the thinner areas will probably separate from the underlayment when glued to. I also expect SLC will not adhear well to the old vinyl flooring or even the plywood subfloor. Any flex of the plywood subfloor will result in cracks and broken chunks of concrete.

I would explore the possibility of jacking the lower end up one inch. This would of course depend on what type of foundation it is resting on, the roof structure, if the existing ceiling is now level, or does it also slope the same one inch, and finally, if there are any windows in the side walls, as it would effect the level of those as well if jacked.

Assuming jacking is not an option, the next easiest way would be to install "purlins" or surface shim boards every 12 to 16 inches on center across the floor in decreasing thickness and install a new 3/4 inch subfloor over these, screwing it down all the way into the old floor.

The most work, but successful method would be to remove the old floor completely and sister the original floor joists. Using full size sister joists would not be necessary. 2X4s or 2X6's would be fine as long as a good bond was maintained to the existing 2X8's. The custom wedge idea would work fine, but potentially difficult to rip long lengths for each joist and have them all consistent without a good ripping template, but could be done with a little forethought and clever rip guide.