In this post we will look at the fabrication and leveling of the cross braces in the sub floor assembly. With the long beams in place and held square to the ends by heavy supports, the warp in these long boards became pronounced in the middle. By carefully trimming the cross braces to exact length and levering them into position, then gently driving them into place with a rubber mallet. we were able to true up most of the more exaggerated warping and bring the joists mostly level.
Codes call for various spacing maximums for different situations and woods dimensions. We started out following the standard “16” top dead center” on the 20 foot joists, though we fudged the final placement before gluing to allow better access to the foundation beams below . On the cross bracing we Double-Blocked where the deck plates would later join above, every 47.5″ to be exact, with the blocks set on either side, giving maximum support under each edge of the deck plates instead of trying to balance both edges with a gap over a 1.5 inch span. Additional supports not directly supporting a deck plate edge were staggered to help prevent sagging at 24″ and 18″ respectively. All well within code. We had to use the pipe wrench and rubber mallet to set more then half the blocks, though the glue made them slide in nicely.
Setting these blocks wasn’t easy. As I mentioned before the 20′ long Joist beams were actually on 5.25 inches tall. The pieces I cut my braces from ranged from 5.25 to 5.6 inches tall. Why? depends on the cut and the cure of the wood, the temperament and the skills of the sawyer or miller who produces it. Anyhow I had to trim most of the cross braces on the table saw.
Even after a trim a few problem spots had to be leveled with block plane and power sander. After a preliminary round of leveling by eye, I set string guides and pulled them tight. WOW less then 1/8 of discrepancy diagonally at over 22 feet !!!! That’s amazing (read lucky) After adjusting one last problem spot near the port wheel well, We were ready to do a quick clean up, and begin adding insulation. We used a single sheet of our intended deck plating as a measurement and as a plat form to work from.