Moment Post Base: Key Features and Proper Application

If you’re building a free-standing structure such as a pergola or carport, or even a free-standing deck or fence, there is a new moment post base that just might be the ideal post base for the job.

The Simpson MPBZ Moment Post Base is patent-pending but has already proven to be an effective provider of moment resistance for columns or posts.

Read on to learn all about moment post bases and the benefit they bring.

What is a Moment Post Base?

Moment post bases are designed to fully encapsulate a post or column beam to provide “moment” resistance (aka rotation around the base of the posts), in addition to lateral, uplift and downward forces.

Simpson’s new moment post base is the first moment post base to receive ICC-ES code listing for moment resistance.

What are the Features of a Moment Post Base?

Moment post bases provide code-required 1” standoff. This allows moisture to drain and prevents rot and decay of the post or column. Plus, Simpson’s ZMAX® finish provides excellent corrosion resistance.

There are internal tabs and holes to help with placement and installation, as well as screw placement. This moment post base also features additional holes that allow you to attach trim material.

When to use a Moment Post Base

Moment post bases are ideal for building just about any free-standing structure with post columns. Because they are corrosion-resistant, moment post bases are a smart choice for any outdoor application. They are also great on structures where an open frame is needed, without access to vertical or knee-bracing.

Simpson moment post bases are available for nominal 4×4, 6×6, and 8×8 posts.

Installing a Moment Post Base

You will need to install each moment resisting post base (using embedment level indicators and form board attachment holes) before wet-set concrete is poured around them.

Make sure to place each post on tabs 1” above the top on your concrete.

Simpson SDS connector screws are included with each post base. Make sure you use these heavy-duty screws for installation – not lag screws or other connectors.

Moment Post Base vs Regular Post Base

Regular post bases (i.e. Simpson ABU) are just fine for standard posts that need to be anchored, but don’t need moment resistance and/or are anchored to an existing structure.

Moment post bases are not necessary for structures anchored to existing structures, but can definitely still be used in any post base application.

What do you think about these new moment post bases? Let us know in the comments below.