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Raising a sunken room.

ripmeister | Posted in Construction Techniques on February 10, 2003 11:04am

My folks  just bought a house with a sunken family room that they want to raise so it is contiguous with the rest of the house.  The floor is concrete slab.  It needs to be raised about 5 inches.  Looking for input on my idea to rip 2 x 6s and hang them from ledger boards attached to opposite walls.  I think sleepers may be too difficult to get level, in addition to any necessary wiggle room in order to get the new and existing floors in the same plane.  Any experience or ideas on this would be greatly appreciated.  Thanks

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  1. User avater
    GoldenWreckedAngle | Feb 11, 2003 12:53am | #1

    What size is the room?

    1. ripmeister | Feb 11, 2003 05:21pm | #4

      The room is 12 x 15.  I plan on running a doubled up "beam" essentially down the center of the long dimension and hanging joists perperpendicular to that out to each of the long  walls to ledgers.  The more I've thought about it another potential approach came to mind, that being using 2x4s as the joists and doing a double  layer of sheet material to achieve my 5"s.  I'm  not sure how this would compare to 2x6s ripped to 4.25" with a single layer of .75 T&G ply.  The concern here is with such a minimum depth, building something that isn't going to be springy.  With either approach I would use the same basic layout with a built up center beam and joists of approx. 7 feet on either side.

      1. FastEddie1 | Feb 11, 2003 05:37pm | #5

        First impression is that 7 ft 2x4's will be a little light.  I have not read the other thread.  What if you framed it in 2x4 and after getting everything level and even, filled under them with some type of grout or mortar.  Use pt lumber. 

        Do it right, or do it twice.

        1. ripmeister | Feb 11, 2003 06:30pm | #6

          That seems reasonable.  As a matter of fact with my 5" requirement the 2 x 4s should essentially contact  the concrete pad.  What do you think about simply shimming and using a vapor barrier rather than treated lumber?  I would think this would take care of any compressive forces, leaving my only to worry about the lateral forces which I think two layer of ply would more than compensate for.  Thanks again for your input.

          1. User avater
            NannyGee | Feb 11, 2003 06:57pm | #7

            Why not use non-treated 2x4 & conventional sub floor, but make up differences in height by using treated shims every few feet under the 2x4's? This would make the height match up exactly even if the original is not perfectly flat, use conventional material, & the 2x4's with support shims every 3-4' will be plenty stiff, and only the shims need to be treated (yes, you must have treated touching concrete, even with a vapor barrier between - just to be safe). I would rip the shims from the edge of a piece of treated 2x material so it's large enough to bear weight without crunching - put the uncut side down on the concrete & obviously, don't bevel-cut the shims - cut them flat so they don't slide and then toenail them.

          2. ripmeister | Feb 11, 2003 08:52pm | #9

            Thank-you all for your input.  I think I like the idea of using 2 x 4 joists with short sleepers underneath and perpendicular to make contact with the slab along with a single layer of .75" ply for the floor.  This seems like it would give me the most wiggle room to get the planes to line up and be as level as possible.  A couple of final questions and then  I'll stop beating this horse.  I figure 6" lengths of treated 1 X 6's laid on their faces would suffice as the sleepers.  With this approach do you think I could go to 16" OC with the joists or should I stay at 12".  Also, with the  treated sleepers do you think I need a vapor barrier.  The slab, originally had carpet on it, so I assume any moisture transition problems were taken care of when the slab was originally poured.  Again, thank-you all for your input.

          3. User avater
            GoldenWreckedAngle | Feb 11, 2003 09:12pm | #10

            Your sleepers don't need to be that wide but if you keep them spaced between 4 and 5 feet on center you can easily go with the 16" joist spacing. Never bank on assumptions- vapor barrier is cheap, cheap insurance. Maybe you don't HAVE to have it but IMHO it's worth the minimal time and expense. If for no other reason- it gets the wood off of the concrete all together and minimizes the chance of moisture damage to your sleepers down the line. Good luck!

            Kevin Halliburton

            "Moderation is a fatal thing: Nothing succeeds like excess." -Oscar Wilde-

            Edited 2/11/2003 1:16:34 PM ET by wrecked angle

          4. bd342 | Feb 11, 2003 09:17pm | #11

            I wouldn't put treated material inside the building envelope like that.

            If you need treated material for protection against moisture or insect problems then you have got big problems allready and should worry about that first.

          5. ripmeister | Feb 11, 2003 09:31pm | #12

            You make a good point.  What is your opinion then on shimming if I were to go that route.  Would you put down a vapor barrier or just lay the lumber directly on the slab.  As I said in my last post I'm not sure about the moisture situation and would assume it was already addressed as this floor had carpet laid on it with no apparent moisture problems.

          6. FastEddie1 | Feb 11, 2003 09:40pm | #13

            Use treated lumber.  That space will be non-venmtilated, and you need all the protection you can get.  If yoiu have the time, buy the pt lumber a couple of weeks early and let it sit in the sun...it will dry out quite a bit, which will reduce the shrinkage that will occur after installation. 

            Do it right, or do it twice.

          7. User avater
            Lunicy | Feb 11, 2003 10:08pm | #15

            gypcrete

            Can't I go 1 day without spilling my coffee?

          8. User avater
            GoldenWreckedAngle | Feb 11, 2003 10:43pm | #16

            Lunicy,

            That was going to be my first response but I think Gypcrete is about 100 lbs. per cubic foot dry. (?) That's putting 750 lbs. or so on the existing slab without even counting the weigh of water in the mix. I would be concerned about putting that much weight on an old foundation that wasn't designed for the load. Especially not knowing what is under that existing slab. Sure would be a lot easier though.

            Kevin Halliburton

          9. JohnSprung | Feb 12, 2003 03:28am | #20

            Ordinary concrete is 137 lbs per cubic foot per Machinery's Handbook.  At 5" thick, that would be 57 pounds per square foot, very evenly distributed.  Adjusting from your figure of 750 lbs total, it's a tad over half a ton.  It may sound like a lot when you think about lifting it by hand, but that's in the piano and waterbed range.  The dump it fulla mud option perhaps deserves further consideration.  But a cyberguess is no substitute for on-site expertise.

            -- J.S.

          10. busta_duke | Feb 12, 2003 05:03am | #21

            I'm new here but have raised a lot of rooms in my area using concrete. If you are filling in 5" thick slab and don't want all the weight.  Install sheets of 2" thick foam board over the existing concrete slab using liquid nails. Make sure you have a 6" area down the center and around the edges left open so that new concrete rest on existing floor.  Install 1/0 highway mesh 1 1/2" above foam board then fill and finish with 3000 PSI concrete. I've never had a problem with weight on any of the slabs I've done this way.  Hope this helps out.

            busta :0)

          11. User avater
            GoldenWreckedAngle | Feb 12, 2003 09:12pm | #25

            Busta,

            Not a bad idea! This addresses the weight issue and would give the raised floor the same "concrete feel" as the rest of the room. I like it!

            Kevin Halliburton

            "Nothing astonishes men so much as common sense and plain dealing" -Ralph Waldo Emmerson-

          12. User avater
            GoldenWreckedAngle | Feb 12, 2003 08:50pm | #24

            You make an arguable case but my real concern was not only the dead load weight of the new slab but the weight of the live/dead load that may end up on top of that slab. It's one thing to set the weight of a grand piano on a concrete slab over this square footage- quite another to stack a Grand piano on top of that already max-weighted slab. If you max out the bearing capacity of the slab with a permanent dead load, subsequent live/dead loads could be more than the slab will safely carry.

            Kevin Halliburton

            "A man can fail many times, but he isn't a failure until he begins to blame someone else." -John Burroughs-

          13. JohnSprung | Feb 13, 2003 10:50pm | #28

            Right, that's why I say you need an expert opinion to set your mind at ease before going ahead.  If this isn't on a hillside and the ground isn't wet, chances are a local soils engineer will tell you that the ground is good for something like 2000 to 7000 pounds per square foot.  But that's just chances.  Still it could pencil out that the engineer's fee plus mud and labor would cost less than the materials and labor to go the wood floor route. 

            The mud over foam idea would cut the weight from about 1000 lbs to about 600 lbs.  Again, do the arithmetic for every option and compare the answers....

            -- J.S.

          14. bd342 | Feb 12, 2003 12:24am | #17

            To see if you do have moisture issues try laying a piece of visqueen down on the slab and duct taping the edges .(4' sq. would probably be big enough) let it sit for a day or two see if there is any condensate present.

            If not then there is no moisture present and there is no reason for the visqueen.

            when you start shimming it is much easier to shim and apply dabs of glue to keep the shims in place and attach it to the slab so as to prevent the sleepers from working loose over time. when you dont have to work with visqueen as a vapor barrier.

            as far as cutting pieces of treated material for shimming there are 2 reasons I would not do so .

            1. high initail moisture content will let the shims shrink more so than say dry shim shingles.

            2. I dont like cutting into that arsenic laden stuff and then imediately putting it in an area that will be closed in where whatever out-gassing occurs will be inside the building envelope.( every time you cut the stuff material gets released)

            p.s. Can't you talk them into leaving the step?

          15. ripmeister | Feb 12, 2003 12:45am | #18

            Thanks for your input.  No, can't talk them into leaving the step.  I like your idea about the visqueen test.  I can't imagine that with carpet having been on this spot that moisture is a problem, however better safe than sorry.  I guess I'll need to mull over these various options.  Another thought I had was that if my shim height is consistent perhaps I could go with some of the plastic decking material for sleepers. or even strips of cementitious backer board.  Those two would seem to address, the shrinkage and CCA toxicity issues the only issue being the inability to custom fit varying shim heights.  Thank-you all again for your input.  I'm a newby to this site but have been a longtime FHB subscriber.  This is awesome!

          16. User avater
            JeffBuck | Feb 12, 2003 01:36am | #19

            stick a board in the hole.....

            hold a chalk line across.....

            snap.....

            there's your "level line"....even it it ain't level.

            setting the sub floor on top.....there ya go.

            wanting the sub to flush up with what's there....

            measure down from your chalk line 3/4"...there ya go.

            You're filling a hole...why's this so difficult?

            Not U personally...but this Q's come up a few times before.

            Just frame it flush and get on with life...I think the last one had a nice solid concrete pad to work on top of too.....people pay good money for nice concrete pads to build up from.

            JeffBuck Construction   Pittsburgh,PA

             Fine Carpentery.....While U Waite                  

          17. ripmeister | Feb 12, 2003 08:03pm | #23

            This isn't difficult, as you say.  The question is whats the best way to go about it without building a trampoline?  The actual framing of the floor isn't the issue.  In fact I'll frame the suspended floor with my eyes shut.  How it is supported however with the issues of moisture, shrinkage etc. in my mind deserves examining the various possibilties, especially those that I havn't thought of, not only in terms of final product but also in terms of time and cost.  Like they say, you can change anything about a structure.  There is a way to do it as long as you are willing to pay for it.

          18. FastEddie1 | Feb 12, 2003 05:08am | #22

            Don't understand why you keep trying to use constant-thickness shims.  Using trex decking (or similar) might work...why not set your miter saw to 5 or 10 degrees and cut a bunch of taperd shims?

            Having carpet on the floor has nothing to do with moisture in the slab.  The carpet is porous (ever notice how fast dog pee soaks through?) so any moisture in the slab just passes through.  The reason for taping down the visqueen is to see if there is moisture there, because it will be trapped under the plastic.  Could be a verrrry slooowly leaking in-slab pipe that won't harm carpet, but might give problems with something else.

             

            Do it right, or do it twice.

          19. ripmeister | Feb 12, 2003 11:02pm | #26

            I figured I use opposing wedges originally, but then someone on this thread raised the concern of them moving which seemed to make sense, arguing for more of a true sleeper.  Flat sleepers could at least be more effectively toenailed to the bottom of the joists rather than trying to keep the thin tapered edge of a shingle in place, especially by nailing it.  I suppose you could use adhesive.  Certainly a wedge would be much easier to place for each point application and the variations that would exist.

          20. User avater
            GoldenWreckedAngle | Feb 13, 2003 02:03am | #27

            http://forums.taunton.com/tp-breaktime/messages?msg=27381.3

          21. User avater
            NannyGee | Feb 11, 2003 10:07pm | #14

            little slabs of treated 1x would be fine if what you need is a very consistant 3/4" (or 11/16) but any variation away from that would suggest custom cutting from 2x material as I suggested earlier.

            good luck.

          22. User avater
            GoldenWreckedAngle | Feb 11, 2003 07:02pm | #8

            That was pretty close to what I was fixin' to suggest. anything suspended over that distance at that depth is going to bounce a little. Best bet is to take advantage of the rigid slab you have at your disposal. Good luck!

            Kevin Halliburton

            "It is only persons of firmness who can have real gentleness." -Rochefoucauld-

  2. User avater
    CloudHidden | Feb 11, 2003 01:28am | #2

    Look around for a thread about this same thing about a month ago.

    Edit: found it http://forums.prospero.com/tp-breaktime/messages?msg=26162.1



    Edited 2/10/2003 5:30:35 PM ET by Cloud Hidden

    1. ripmeister | Feb 11, 2003 05:10pm | #3

      Thanks for the link.

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