How To Repair a Load-Bearing Post (page 3 of 3)

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How To Repair a Load-Bearing Post: Safely Lift the Beam

I have never lifted a house beam without having the hairs stand up on my neck as I pumped the jack and heard the beam, floors and walls above groaning in response. Before lifting, double-check your equipment, visualize your plan and think safety. Follow these rules:

Only use shoring posts rated to carry your beam load. Rent whatever type exceeds the load specified by the structural engineer.
As the hydraulic jack lifts the beam, turn the handle of the shoring post to keep the post head tight to the beam.
Only use shoring posts to support a beam while work is under way. Never use hydraulic jacks as shoring devices. Jacks may have defective internal seals that could leak hydraulic fluid and cause the jack to slip and drop the load.
Raise the beam only until the post is released.

Once the load is released from the old post, have an assistant remove the post. Then label both its top end and its location along the beam for exact repositioning later.

Concrete Footings and Plinths
If you have to replace undersized footings, it’s time to excavate, place steel reinforcing rods and pour concrete for them. With the post removed, break out an undersized footing with a sledge and shovel (wear goggles and gloves) and pour the new one. Follow these tips for building solid footings and plinths:

During excavation, make a depth gauge to ensure a footing with uniform thickness and a level bottom.
Suspend the reinforcing rod two-thirds down inside the footing for maximum strength. Buy 2-ft. lengths of 1/2-in. rebar (about $1) at home centers.
Select concrete with a minimum compressive strength of 4,000 psi (check the packaging, or order it that way).

For maximum strength, add only the amount of water specified by the manufacturer.
Mix and pour all the concrete for each footing in less than one hour so that the batches bond well.
Save time by setting the plinth block on a still-wet footing once the concrete can support the weight of the block. To accommodate our 6x8 wood post, we used a standard 8x8 half-corner block. Make sure your plinth is at least as large as your post.

Reinstalling the Posts
Install the post on a new plinth and footing only after the concrete has cured for seven days.

Wood posts are easier to work with, so stick with wood rather than metal. Home centers and lumberyards carry steel “mono-posts” and steel posts with telescoping sections, but you need special skills and techniques to properly support wood beams with steel posts. Consult with engineers and/or local building officials before using them.

Your local building officials may insist you install only new, pressure treated 6x6 posts set on plinths. We had no such restrictions and reused our old wood posts because they were still tall enough after sawing off the rot. Most old posts don’t have a square, level top. Don’t change that. For the best contact and load transfer, reinstall the posts exactly in their original position under the house beam, with all those old irregularities fitting like a hand in glove. To prevent any moisture from wicking into the post from the plinth, lay sill sealer or galvanized sheet metal between the two.

In your excitement to reset the posts and finish the job, don’t take risks. Use an assistant and lower the jack very slowly, leaving the shoring in place while putting weight onto the posts.

Complete the job by installing the specified metal strapsand T-braces to connect the plinth block, post and house beam all together—especially in earthquake-prone areas. Once that’s done and the support strapping is reinstalled on all gas, electric, plumbing and heating lines, you’ll have the satisfaction of completing a job that will last for the life of the house.