After some recent inspections I thought we should talk a little bit about properly capping concrete block piers.
The function of the pier cap is to evenly distribute the weight of the manufactured home, its contents and the added weight of any potential snow on the roof into the concrete block pier. Ultimately, taking approximately 5,000 to 6,000 pounds from the chassis beam and spreading it out over the top of each concrete block pier in a manner so that the pier will not crack, break, or otherwise fail under the weight.
The first thing to remember is that the cap MUST be the same size as the pier. A pier constructed of single stacked (8” x 16”) concrete blocks, must have a cap that measures 8” x 16”. If the cap does not fully cover the block, the weight will not be applied evenly over the top surface of the block, and the result will likely be a failure of the pier blocks.
The biggest problem I see with cap blocks are that installers often use improper materials to cap concrete block piers. DO NOT USE plywood, OSB, 1” thick lumber, or decking boards! Decking boards would include 5/4” x 6” pressure treated lumber or any composite type of decking.
I checked nine different manufacturers installation manuals, and found that six of the nine specify the same materials for pier caps:
Solid precast masonry 4” thick-8” x 16”, pressure treated lumber 2” x 8” x 16” or ½” thick x 8” x 16” painted steel. I must admit, I never saw anyone use ½” steel, so if you do, please send me a picture!
Two manufacturers don’t mention pressure treated lumber, and only specify 2” thick hardwood as an option to 4” masonry or steel. One manufacturer simply says solid masonry or hardwood with no mention of thickness!
Now is a great time to double check that you are using proper materials as pier caps. As installation manuals are prone to change, make certain that you are using the current manuals for the homes you are receiving. I know that some folks are using ABS (plastic) pier caps. If that is you, be sure to get a DAPIA approved design from the manufacturer for your installer file.