# deck training

***what does this mean ? On-center spacing of ledger fasteners in inches = 100 ÷ joist length in feet. *********

Take the joist length and divide it by 100 and get the recommend number of fasteners or lag screws needed.

The ledger attached to the house needs to be bolted to the house. I guess this equation prefers the distance between bolts to be decided by length of the floor joists. I thought every 12 " was standard.
5ft long joists need bolts spaced every 20" since its a small deck
10ft long joists need bolts every 10"
Thats my understanding if it

It’s really just a rule of thumb and the above posts are correct. Every deck should be engineered if above 30" in height which will dictate the ledger attachment detail.

It’s from http://www.nachi.org/deck-inspections.htm It’s a quick way for inspectors to notice and note (report) if there seems to be too few deck ledger fasteners (the most common cause of deck collapses).

So for example, if you are inspecting a deck that has joists that are 10 feet long, 100/10=10, so you should see ledger board fasteners at least every 10 inches.

Another example: If you are inspecting a deck that has joists that are 12 foot long, 100/12=8.5, you should see ledger board fasteners at least every 8.5 inches.

Remember, as a home inspector, you have to be able to point to some reference to report that you suspect there may be too few ledger board fasteners. InterNACHI’s formula is that reference you can cite.