5/4 Decking?

Five quarters. 1 and 1/4 inches, rough cut.

djb

Rough wood, at one stage of its trip to your shop, is reckoned in 1/4" increments in nominal thickness ... or thereabouts.

IOW, a 5/4 (five quarter) board would measure 1 1/4" in nominal thickness, a

A 4/4 board, sold as "dimensioned lumber", or after you have joined and planed it, would have an actual finished thickness of 3/4".

In figuring board feet, lumber retailers sell you 3/4" thick "dimensioned lumber", but calcuate the board feet using the 4/4 "nominal" thickness.

For sheet goods, like decking, all bets are off and it is not necessarily the same. 5/4 decking is usually about 1 1/16" in finished thickness, IME.

There's more to it, but that should get you started in tlaking the lingo at a hardwood lumber yard.

Actually meant to differentiate between sheet goods and lumber sold specifically for decking ... sorry!

Lumber is mill run (cut at the saw mill) by 1/4" incriments. This is 1 1/4" stock, rough sawn.