I’m looking for some advice on adding a second layer of OSB to a 3/4″ T&G subfloor. This is new construction. 3/4″ T&G was rained on several times. Some flaking. I-joists are 16″ oc. I’m thinking of adding a layer of 1/2′ or 5/8″ OSB on top of the 3/4″ T&G after the roof is on, which should be mid-next week. 3/4″ T&G is glued and nailed. Question I have is “If I add a second layer of OSB should it run the same direction as the first layer and overlap the seams or should it run perpendicular to the first layer?” Glue and nai lto the joists as the first layer or maybe screw it thru the first layer? Thanks for any advice. Larry.
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A little rain shouldn't hurt OSB but another layer would make your floor stiffer so why not. I'd lap all the joints in both directions and screw it down to the joists.
I thought - to prevent squeeks - you were supposed to attach the 2nd layer to the subfloor below, not the floor joists.
I'm trying to think how that would prevent squeeks. Certainly one should screw BETWEEN joists as well.
Thanks for the reply, Florida.
Larry
How's the adding going to affect your door openings and stair rise?
I think I can adjust the stairs. More of a concern is the entry doorways. Ledger board is already attached forthe outside deck so that there's no step up/step down. Adding new layer of OSB will mean the deck will be 5/8" or 1/2" lower than planned. No too much of a height difference but just enough to trip and be a real nuisance. I guess I could add some quarter round treated molding at the doorways/deck . Any suggestions? Thanks
Suggestion?
At the deck, cut a trim that will "ramp up" to the threshold of the door. Feet will sweep up and over with little chance of trippage because there won't be a sharp or severe lippage.
not to count every door in the house that swings over carpet and its padding or hardwwod or tile will all have to be modified or you headers in every door should go up...also some code say if your windows are below 32" then and are more than 4.5 sq.ft. then they should be shatter resistant to prevent fall threw accidents...which adds to the cost of the window as well.
Ace
Are you referring to the newer version of the IRC re. glass?
I ask because here in NW Ohio, it has always (since in the 70's at least) been glass within 18" of floor, tall glass (6') was always made up tempered and anything within 30/36" of a door (and the door glass itself). Add to that glass in or within 32" of a tub or shower..............
But 32"? Never heard of that.? I'd question the 4.5 s.f. also-that'd only be less than a 2 x 2'-6" sash.
Just trying to clear up the question and/or learn about the newer codes that haven't really hit Ohio yet.
thanks.
OSB Flooring
If you go to the trouble of the second layer, glue and screw. Overlap the seams in both directions, use screws long enough to reach the joists, should be a nice stiff installation.
second layer of subfloor
i do not understand totally your answer here===I'd lap all the joints in both directions ==does that mean you would alternate the direction that you apply the osb or continue in the same direction but alternate the joints
ericpaul.
Lap'd both directions means that the long edge would be staggered as well as the end of the sheets----from the first layer. No edge would line up one layer to the other.
I think.
Here I was thinking it meant you poured cream along the joints and let the cat in.
If the first layer is only nailed I'd definitely screw through both layers into the floor joists. Stagger the joints as suggested and use plenty of construction adhesive and screws. I see no benefit to using 1/2" osb - it's so flimsy it won't add much unless it's completely bonded to the lower layer, which it won't be.
Having said that, what seems like a minor issue isn't. If your stairs are cut correctly you'll spend two or three times as much shimming everything so your rises work out correctly - EACH riser and tread will need to be shimed and no two risers will be shimmed the same amount. Havng to screw with every door opening in the house will double the door install times. In the end you've made more work for yourself.
However, a double layer of 3/4" osb glued and screwed is super stiff - ideal really.
Larry
Most new construction is rained on and most problems with OSB are at the joints/seams.
Get a floor sander and hit those expanded edges to even it out and be done. Adding to the top will only "cover" whats there. Minor flaking shouldn't be a problem with carpet pad or thin underlays. Then there's no complications with stairs and entries.