Double blocking is stronger than single blocking, and screws hold better than nails. The author attached two blocks to the rim, joists, and vertical block (not yet installed) using four screws per block per side. Blocking installed parallel to the rim joist, as shown, tended to split along the bolt line unless a heavy steel reinforcing plate was used.

The strongest blocking runs perpendicular to the rim joist. It’s best to align the blocks with a nearby joist for extra stiffness and add a solid block between the rim and first inboard joist at the ends of the deck.

TimberTech/Azek’s reinforcing plate is predrilled with eight holes (two pairs of four holes) positioned near one corner of the plate, to match the pattern in the base plate. This arrangement enables the plate—and the post above—to be located close to the rim joist and a deck joist. The same plate design is used to reinforce the blocking on the Vinylast and UltiMount posts. The post must be oriented such that the bolt holes clear the rim joist and deck joist by at least 1/4 inch so the base plate will fit.

When post kits were installed with bolts and washers rather than with a reinforcing base plate, the washers and nuts began to pull through the blocking long before test loads on the post reached 500 lb.

Join the Discussion

Please read our Content Guidelines before posting

Close X