SPACING LEDGERS FROM THE HOUSE
Another option is to minimize the surface contact area with the house by using standoffs between the ledger and the house. However, changes to the 2007 IRC are likely to limit standoffs to being made from steel washers stacked no more than 1/2 inch deep, unless you have an engineering or ICC-recognized code report. Closer ledger bolt spacing is required when standoffs are used (see Decking News, Jan/Feb 07). For years I’ve made standoffs from scraps of composite decking. I used to run lag bolts right through these, but now I use 5-inch LedgerLoks (www.fastenmaster.com).
FastenMaster had this connection tested by Washington State University. This testing showed that with 1-inch spacers as shown below, 5-inch LedgerLok screws performed as in the chart. Your engineer can design similar connections for the decks you build. The test data for LedgerLoks can be obtained by contacting FastenMaster at 800/518-3569.
Composite decking doesn’t hold moisture, and leaves a gap of about 1 inch between the house and the ledger, allowing a generous space for airflow, and for leaf litter and rain to drop straight through. To assist with water runoff, I slant the top of the blocking 15 degrees from the center in both directions. I seal the top of the blocking by caulking it with Dap Sidewinder Polymer Sealant.
