You need to layout your joist, by marking layout marks on the ledger and girders that show which joist will be located. Joists are located “on-center” distance, where their centers occur exactly every 16”, 24”, or 32”. The distance between joists depends on several important factors:
1. Size of the joists
2. Spacing of the joists
3. Length of span from ledger to girder
4. Type of wood used for joists
5. Any heavy loading, such as snow
You must ensure that the spacing between the joist are correct, as wrong measurements can cause the deck to collapse. A building inspector can stop your project. Talk to a local retailer or building code office about the proper spacing of your joist.
To make the layout:
With a nail nailed at the center of one of the two outer joists already installed, measure along the ledger, making a clear mark every 24” (or 16”). These marks indicate the center of each joist.
Make a second mark 3/4” to either the left or right side of each of these first marks which indicates one side of each joist rather than the middle. This will make it easier for you to locate the joist hangers on the ledger. Make a good straight mark for this, since you will be nailing your joist hanger to this mark. Nail the hangers on flush with the edge of these new marks.
Do a similar layout on the girder as you did on the ledger for each joist that crosses the girder.
Begin nailing the metal joist hangers on the ledger using the special stubby joist hanger nails provided with the hangers.
Installing the Remaining Joist
Install all your joist before you cut them to length.
Simply insert the joists into the joist hangers. Be sure to crown each joist, pointing the bow skyward (as per explained in previous chapter on installing outer joist).
Insert it in the hanger, and nail hanger nails through the hanger into the joist. Then toenail the joist (using two 10d HDG nails) through the joist into the girder. Use special HDG L-shaped fasteners which are recommended in earthquake areas.
Note: Place galvanized metal flashing on top of each joist before the deck boards are applied as this helps keep water from getting trapped between the decking and the joists, causing rot.