Floor Joists

Solid Blocking

Blocking Requirements: Blocking keeps taller joists from tending to twist onto their sides when heavily loaded. By 2003 International Building Code (IBC), in addition to having to install blocking where joists overlap over a center beam, blocking is also required every 8 feet for 2x10 and taller joists. In other words, the distance between any two rows of blocking, or any one row of blocking and the end of the deck, cannot be more than 8 feet. As long as blocking meets this requirement, it does not necessarily have to be centered over the length of the floor joists.

Check Point - Cantilevering floor joists and beams simplifies construction because framing members don't need to line up perfectly and yet you can end up with a perfectly square deck. In addition, tucking the posts and beams underneath looks neat. Unfortunately, the general rules of thumb for correctly sizing the lumber for cantilevers are often overly conservative or don't take into consideration the uplifting forces at the opposite end of the cantilever. For less than the cost of a 12-foot treated 2x6 board, get a password and have immediate access to on-line calculators that will show you how to get the most out of your lumber while meeting building codes. 

For decks, solid blocking cut from the same size boards as the joists works best. Technically, X-bracing cut from 1x4's and fit in-between the joists in an "X" pattern, or even metal "X-ties", could be used - you may have seen this type of bracing used in homes. BestDeckSite doesn't recommend 1x4 X-bracing because the nailed ends are weak and often split. Metal ties are out of the question as they aren't readily available with a double hot dipped galvanized coating.

As a matter of course for any joist size, we recommend using blocking every 8 feet. The blocking goes a long way toward firming up the framing before the decking goes down. It'll also make installing the decking easier since all the joists will be in nice straight lines.

Check Point - There are building codes for the minimum allowable contact between floor joists and wood beams, as well as, wood beams and concrete. There are also codes regulating the size and location of holes and notches that can be cut into framing members. When you get a password, you'll get immediate access to the pertinent building codes related to deck and gazebo building. Why learn the hard way that your deck is not code compliant when for a small password fee, you can read for yourself how to build your deck or gazebo right.

Watch The Joist Layout: Make sure to stretch a tape across the joists as you're nailing in the blocking. It's real easy to throw off the joist spacing over a distance by nailing in blocks that are off a bit in length. After several blocks, the joist layout can easily be thrown out by an inch or more if you're not watching and making minor corrections as you go.

Important: ACQ treated lumber is very corrosive of hardware, connectors, and flashing. This is due to the high amount of copper in the ACQ preservative used to treat the wood. For brackets, strapping, hangers, bolts, screws and all other metal hardware and connectors, the minimum recommendation has been upgraded from G185 hot-dipped galvanized steel to stainless steel or specialty fasteners with coatings specially designed to be ACQ corrosion resistant. Regardless of the thickness of the coating, galvanized steel and coated aluminum should not be used when in contact with ACQ treated lumber.

The content under the "How-To" menu is a small sampling of all the material covered on BestDeckSite. For immediate access to in-depth information on proper nailing, the use of metal connectors, an on-line Joist Calculator, lapping joists, sizing framing for hot tubs, and multi-level decks, as well as, comprehensive coverage of all aspects of gazebo and deck building, get a password and log-in now.

     Floor Joists

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