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Best way to raise a sunken floor?

Calhoun's picture

We have a ranch type house that has a sunken living room that we would like to raise to the level of  our other floors.   We intend to have hard wood flooring installed over it and the other rooms around it.  Ceiling height is not a problem.  The floor needs to come up about  5 3/4 inches.  I figure that some ripped 2x6 's and some 3/4 inch tongue and groove OSB would do the trick.  The big question is what way should the 2x6's be oriented and should construction adhesive or anything else be used between the old subfloor and the 2x6's that will be put down?  The current floor joists run East/West and the new Hardwood flooring will be put down North/South.  A contractor told me to just put the 2x6's down North/South to make hitting the current floor joists with nails easier.  Will this pose problems with the hard wood flooring?  Is there a better/proper way to do this?


Thank-you, thank-you very much.


Calhoun Brown

(post #91353, reply #1 of 9)

The big question is what way should the 2x6's be oriented and should construction adhesive or anything else be used between the old subfloor and the 2x6's that will be put down? 


What is underneath the sunken subfloor? I guess I'd land the new ripped 2x6's on top of the old. Then I'd use construction adhesive and blocking to hold them in place. Get rid of any carpeting or mushy material between the current floor and the supports.


 


 The current floor joists run East/West and the new Hardwood flooring will be put down North/South. 


I'd keep them going the same direction as the original. It is hard to rethink someone else's design without looking at the complete plan.


 


 A contractor told me to just put the 2x6's down North/South to make hitting the current floor joists with nails easier.


Yes it would be easier to hit the intersections but I'm iffy on the support issue.


Come back with the Centers of the joists under the sunken floor, The dimensions of the sunken area, and what supports the whole room. Hardwood will telegraph a bad intersection of the old surface with the new. Thick subfloor is a cheap insurance policy.


"Jack of all trades and master of none...You got a problem with that?"


Edited 1/2/2003 9:25:24 AM ET by Booch

Jack of all trades and master of none - you got a problem with that?

(post #91353, reply #2 of 9)

we did this a few months back in our existing home.... We ran new floor joists the same direction as the originals ones. Our depth was more like 8 inches though, so we used 2x6's and we used joist hangars....  i talked to a carpenter uncle of mine, and he recommended that I have the floor boards be 1-1/2" thick(e.g.-two layers of 4x8 sheets of plywood/particle board). The bottom lair could be particle, but the top lair be good quality plywood with adhesive caulk between the lairs and screws about ever 4-6 inches around the perimeter of each sheet...  he also recomended that we lay the 4x8 sheets in opposing directions (e.g.-bottom lair run north south, and top lair run east west).....  It may be overkill but you definitely cant tell the difference between the floors....


Hope it helps,


 


 

(post #91353, reply #3 of 9)

I can't say for sure without seeing the actual building, but you may be going to a lot more work and expense than necessary, and producing a rather non-standard result.  It might be possible to cut the existing floor -- joists and subfloor together -- loose, and jack the whole shebang up to where you want.  The issues would be possible kick-out of a wall with the horizontal restrant of the floor removed, and re-attaching it to the building, probably using joist hangers and some sort of new ledger boards. 


I've jacked my two story house up, a mere floor by itself weighs a lot less than you might think.  My old floor is 2x6 on 16" centers with plank subfloor and t&g oak.  It comes to 6 pounds per square foot.  So for a 10' x 20' room that's only 1200 pounds, about half the weight of a typical car.  One end would be only 600 pounds, so tweaking individual joists into their final positions would be something in the low hundreds of pounds, easily doable with a crowbar.


You should pay for some expert on-site advice before doing any of this, and you'll need lots of cribbing and wedges to do the lift safely.


 


-- J.S.


 

 

 

-- J.S.

 

(post #91353, reply #4 of 9)

I put tar paper down to stop the joist from squeeking on the old floor kinda of a buffer use 30 lbs not 15 it's worth the extra 2 bucks.

(post #91353, reply #5 of 9)

Thanks for some creative input on this subject.  I still have to sort through some issues with this project, but I have more to go on now, ....... well, the idea about raising the existing floor left me exhausted. 


Thanks again,


Calhoun Brown


 

(post #91353, reply #6 of 9)

I would cut around the floor and LOWER the rest of the house.

 

 

(post #91353, reply #7 of 9)

I just did this for a client...raised a 16x22 floor about 3 1/2" total.  We laid ripped down 2x4's perpendicular to the existing joists, using a bead of construction adhesive under each new joist/sleeper and toe-nailed each at opposing sides at every new/old joist intersection.  End-nailed "rim joists" at each end of the room where the joist ends butted against the walls, and in turn nailed the rims to the wall studs. 


Absolutely no rolling, no need for blocking, and a new glued and screwed 3/4" TIG subfloor  completed the job.  It was solid as a rock, level and beautiful.  Transistion to the existing floor level was invisible.  Took two guys about a day and a quarter.


Caveat: I'd expect for anything over a 2x6, you'd want to include blocking in the center of the room.  Also, the cavity between the floors is a great place to lay sound-deadening insulation (this was a masterbed above a garage).

(post #91353, reply #9 of 9)

> ....... well, the idea about raising the existing floor left me exhausted. 


But consider the amount of material you'd have to buy, haul home, and cut and nail together.  Jacking up what you already have might be the *easy* way to do this.  The question is what it would take to make it work structurally.


 


-- J.S.


 

 

 

-- J.S.

 

(post #91353, reply #8 of 9)

Dont forget the moisture barrier over the concrete slab to preclude rotting joists and warped hardwood floors!


On top of this, I would recc. that you run the sleeper joists in the same direction as the others if you want to match up your finished flooring directions.