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MPBZ Moment Post Base


The new patent-pending Simpson Strong-Tie® MPBZ is the first post base specifically designed to provide moment resistance for columns or posts. An innovative overlapping sleeve design encapsulates the post, helping to resist rotation around its base. It is available for 4x4 and 6x6 posts. The MPBZ is ideal for outdoor structures, such as carports, fences and decks. Built-in standoff tabs provide the required 1" standoff to resist decay of the post while eliminating multiple parts and assembly. Additionally, the MPBZ is available in ZMAX® as the standard finish to meet exposure conditions in many environments.

Key Features

  • Internal top-of-concrete tabs
  • 1" standoff tabs
  • Additional holes provided to attach trim material
  • Weep hole provided for water drainage


  • 12 gauge


  • ZMAX® coating


  • Use all specified fasteners; see General Notes.
  • Install MPBZ before concrete is placed using embedment level indicators and form board attachment holes.
  • Place post on tabs 1" above top of concrete.
  • Install Simpson Strong-Tie Strong-Drive 1/4" x 2 1/2" SDS Heavy-Duty Connector screws, which are supplied with the MPBZ. (Lag screws will not achieve the same load.)
  • Concrete level inside the part must remain 1/4" or less above embedment line for water drainage.
  • Annual inspection of connectors used in outdoor application is advised. If significant corrosion is apparent or suspected, then the wood, fasteners and connectors should be evaluated by a qualified engineer or inspector.
  • For seismic design in accordance with ASCE7, the following seismic design coefficients are recommended unless justified otherwise by analysis: R = 1 1/2, Ω = 1 1/2, Cd = 1 1/2.

Related Literature

Load Tables

    These products are available with additional corrosion protection. Additional products on this page may also be available with this option, check with Simpson Strong-Tie for details.

  1. Loads may not be increased for short-term loading.
  2. Higher download can be achieved by solidly packing grout in the 1"-standoff area before installation of the post. Allowable download shall be based on either the wood post design or concrete design calculated per code.
  3. Concrete shall have a minimum compressive strength,, f'c = 2500 psi.
  4. Tabulated rotational stiffness accounts for the rotation of the base assembly due to deflection of the connector, fastener slip and post deformation. Designer must account for additional deflection due to bending of the post.
  5. Multiply tabulated Seismic and Wind loads by 1.4 or 1.6 (1.67 for 2015 IBC) respectively to obtain LRFD capacities.
  6. In accordance with IBC Section 1613.1, detached one- and two- family dwellings in Seismic Design Category (SDC) C may use “Wind and SDC A&B” allowable loads.
  7. Download shall be limited by the design capacity of the post.
  8. Foundation dimensions are for MPB anchorage only. Foundation design (size and reinforcement) by Designer.
  9. Allowable load shall be the lesser of the wood assembly or concrete allowable load. To achieve full wood assembly allowable moment loads, additional concrete design and reinforcement by Designer is required.
  10. For loading simultaneously in more than one direction, the allowable load must be evaluated using the following equation: (Design Uplift/Allowable Uplift or Design Download/Allowable Download) + Design Moment/Allowable Moment + Design Lateral/Allowable Lateral ≤ 1.0.

Code Reports

Part IAPMO UES ER ICC-ES ESR City of Los Angeles State of Florida
MPB44ZSubmitted for listing: Please contact us for status and test data.
MPB66ZSubmitted for listing: Please contact us for status and test data.


Part Orthographic Perspective
MPB44ZNone None
MPB66Z front view
MPB66Z left view
MPB66Z right view
MPB66Z top view
Typical MPB66Z Installation