Floor Joist Bridging

mike boufford · 02-10-2008, 09:56 PM

My wife is driving me nuts with this one. The floor of our 2,000 ft2 ranch is made from a 2x10 joist construction with the steel beam running down the center of the house. The builder did not use cross bracing on this house, and from what I've read this is only required for floors with a factor of 6 or greater (10/2=5 in this case). The floor does have some banging sounds emanating from the HVAC ducting in certain places, which can sometimes be annoying.

Should the builder have cross braced, and if so can I go back and nail cross braces in myself? I've done mostly trim work including door replacement, decorative shelves, etc... but rough carpentry is a bit new for me.

mark942 · 02-11-2008, 07:19 AM

Cross bracing is to keep the joists in rack.I always cross brace whether it be wood or metal bracing.Metal braces are a bit expensive but are adjustable ( no cutting )repetitive redundant nailing but well worth the effort..........

My .02 cents.

mike boufford · 02-11-2008, 07:43 AM

It doesn't sound as if bracing will correct squeak and rattles nor the banging sound coming from the cold air return (?), correct? I don't want to do needless work, but what can I do to correct a situation where the builder may not have used screw and glue to put the sub floor down?

mark942 · 02-12-2008, 05:53 AM

Take a look @ your ducting.Make sure that all joints are taped and screwed.Also make sure there is strapping where needed.As to the squeaking in the floor.Hopefully you have access to your basement/crawl space,you can see if the floor is moving in a certain place.Might be located on a joist or a seam.If it is on a joist you can toenail screw through the joist to tighten it up.If it is on a seam you will need to nail a block from joist to joist under the seam for a nailing backer.Then screw in a few screws on either side of the seam to tighten it all up.The nailing will be done from the underside of the floor.I am sure the upper is finished.Hope this helps you out.

**AtlanticWBConst.** · 02-12-2008, 07:39 AM

Try posting this "noise issue", regarding the duct work in the HVAC Forum. I have a feeling that the lack of cross bridging and the noises may not be related.

m tessier · 01-27-2010, 04:42 PM

Most of the country uses the International Code Council codes (ICC) . Section R502.7.1 of the 2006 International Residential Code says:

R502.7.1 Bridging.

Joists exceeding a nominal 2 inches by 12 inches (51 mm by 305 mm) shall be supported laterally by solid blocking, diagonal bridging (wood or metal), or a continuous 1-inch-by-3-inch (25.4 mm by 76 mm) strip nailed across the bottom of joists perpendicular to joists at

intervals not exceeding 8 feet (2438 mm).

The 2009 code is the same except for the following exceptions:
Trusses, structural composit lumber, structural glued laminate members and I-joists shall be supported laterally as required by the manufacturer's recommendation.

So basically, bridging is not required for dimensional lumber 2x12 or less. End bracing, i.e., rim/ band joist and floor sheathing is considered sufficient. That being said I still prefer to see it.