I just found this site, and this is my first posting. I searched for an answer on this, but couldn't find it. I'm hoping some of you guys can give me some insight.

I have a hardwood floor (narrow ash strips) that covers several rooms (LR, DR, Foyer, Kit, GR, halls). Its over a crawl space. The subfloor is OSB. The floor joints are 2" x 10"s. Most are on 16" centers. The great room is on 12" centers, since it spans ~16'. These joints are also cross braced in the center of the span. The OSB is laid perpendicular to the floor joints. The flooring strips are laid length-wise with the OSB. The house is about 1 1/2 years old.

This past winter, a number of separations between the hardwood strips opened up. The worst were about the width of 2 quarters. These cracks occured only in door openings between rooms. There were no significant separations anywhere else in the floor. As the weather has turned to summer, the separations have closed somewhat: now they are maybe a dime wide.

After crawling under the house, I found that the separations only occur where there is a seam between two sheets of OSB, and when one sheet is nailed mainly to one set of joints, and the other sheet is nailed mainly to another set of joints. By set, I mean that they are separated by double 2" x 12's, and the ends of the floor joints rest on 2" x 2"s nailed to both sides of the 2" x 12"s. Where two sheets of OSB are nailed to the same set of floor joints, no separation occurred.

So, it looks to me like the different sets of floor joints move, with respect to each other, with changing weather. The builder says he can have new, wider boards put in, to fill the gaps, but I'm concerned that this won't fix the root problem, and they will open up again next winter, or worse buckle up.

Has anyone seen a situation like this? Is there anyway keep the different sets of floor joints from moving with respect to each other?

Sorry this posting is so long, but I wanted to try and give all the conditions.

Any comments, advice or suggestions would be greatly appreciated.

Oops... I typed joints everywhere, but meant joists.

I believe I understand. IMO, that is shoddy framing practice. A structural panel ties framing members together and those members support the panels. They work together. To separate a system by nailing panels to different joists on a seam is to invite problems. Now understand, had that room had carpet or vinyl, you would not be posting here. But as it is, you have an ash strip floor (nice wood, BTW). The only thing I can think of to try is to join those two joists together better with lag bolts or structural straping. It is either that or tear out flooring, tear out subflooring, and redo, which I don't think anyone wants to do. You may also wish to try to monitor and maintain constant interior temperatures and humidity levels, though I think it is mostly a subfloor/framing issue and not environmental. I'd try bolting the two offending joists together with carriage bolts or lag screws. Use lots and go the whole length of those joists. The idea is to prevent independant movement. Then wait till next year to see what happens.

Yep, that's a big problem waiting to happen. No strength built into the system.

Don't even want to think what is going to happen, as the foundation settles more.

I agree with Gary except I would not use lags. I would bore holes and insert big machine bolts with washers on either side. It will bite better than lags. It will cost acouple more dollars, but it doesent really take any longer to do.

I'm not sure I understand where Gary is talking about put the bolts. I've made a rough sketch of the situation to help talk from (I hope this works...). The sketch is not to scale.

[/img]

The 2" x 12"s sit on concrete block piers.

Note that the separation occurs to the left of the 2" x 12"s, where there is just a little on the OSB sheet nailed to the 2" x 10"s on the left. In some cases, the separated seam is up to 6" away from the 2" x 12"s. In one case, the seam is about right on top of the 2" x 12"s. Where the whole OSB sheet doesn't cross over the 2" x 12"s, there is no separation.

Are you saying to bolt the ends of the 2" x 10"s to the 2" x 12"s, or to bolt the 2" x 12"s together, or both?

Thanks

That is one hokey way of framing a subfloor. How close to the ground are the framing members? Here in CA, bulked up beams are not allowed; only solid lumber. In other words, one cannot nail two 2x12's together for a beam (girder). One must use a 4x12. Another weak link is the use of those 2x2 ledgers to support the joists. The joists should either sit on top of the beam (my preference) . Or if that is not possible, those joists should be hung with joist hangers. Ledgers are not allowed here either. Another possibility that may be causing flooring separation is that the joists are over spanned or at their maximum span. When this happens, the joists deflect too much which can cause the subfloor panels to open up. I think all you can do is bolt the 2x12's that form the center load carrying beam together better using bolts and washers. Use 1/2" bolts and place two at every joists bay, one on top at left side and one at the bottom on the right side. Do not drill the bolt holes too large; just large enough to allow the bolts to slip in. Then after that, install joist hangers on every joist end that attaches to the bean (2x12). You may also need additional load carrying beams installed midway under your joists to reduce flexing. That's about all I can think off outside of ripping everything out and redoing it.

Gary, thanks for the suggestions. To answer your question, the 2 x 12s are about 2 1/2 feet off the ground, at the lowest point. I guess the doubled-up 2 x 12s and the ledgers are common here (Northern Alabama). It was like that on our previous house, and I've seen it on other new houses. Seems like lots of opportunity for things to move around, though.

If that bulked up girder (beam) is over two ft. off the ground, why in the world didn't they set it lower and place the joists on top of the beam instead of using that flimsy ledger. Then the joists could be sistered together and blocked, creating a much stronger, stouter system. The architect/engineer needs to go back to school or come here out west to see how proper framing is done. Look here for proper connections.
Joist to girder to post connection done properly:
http://www.worldofstock.com/closeups/BIN1279.php
http://www.worldofstock.com/closeups/BIN1277.php
http://www.worldofstock.com/closeups/BIN1295.php
http://www.worldofstock.com/closeups/BIN1284.php
http://www.worldofstock.com/closeups/AAB1415.php
Notice all the connections are either resting on top of each other or use hangers. None using ledgers!

I agree: those pictures look like a much better way. I heard a designer say once that all wood has to be at least two feet from the ground, in a crawlspace... maybe for moisture or termite control, I'm not sure.

I'm going to talk to the builder to see what he can do about this.

Thanks

That varies by locale. Here, it was 18" for framing members. Subterranean termites can find ways to build tunnels up foundation walls so height off the ground isn't for termites. It is considered for air flow to allow the wood not to get too close to the ground and become damp. But that is irrelevant in a wood flooring install as the earth needs to be covered with a poly vapor barrier/retarder anyway. But even so, hangers should have been used instead of a ledger.