Starting from the Bottom | #AIABLTI509.20


2 HSW Credits | Online Narrated Class | Instructor: Paul Spite
Problems occur when poor choices are made selecting materials for the foundation and floor assembly, in conjunction with the type of foundation chosen. This course takes a systematic look at decisions made in choosing specific components of construction, from the ground to the top of the first finished floor.

SKU: 6824 Category:


Starting from the Bottom

Course Description

When a floor collapses or when mold appears on it, we can be sure of one thing. Such problems likely began when poor choices were made selecting materials, from the level of the grade to the level of the finished floor. Like the problems they spawn, choices made in proper or improper floor design, begin at the bottom and work their way upward.

This course takes a systematic look at decisions made in choosing specific components of construction, from the ground to the top of the first finished floor. Those choices need to be sound and dependable, since the top of that floor is the base upon which the rest of the enclosure will rest.

This design process includes an analysis of water attacking the structure, why specific foundation options are selected, what framing members will support the floor, how vapor drive will be controlled, what insulation will be installed to isolate climates, the subflooring that will be the primary barrier between the inside atmosphere and any space below, and the underlayment and finish flooring that will be placed above.

If we do our job well as designers, that last component will be the only part of everything chosen, to ever need further attention or consideration from our clients.

By the end of this course, the design professional will:

  • Understand building science principles relevant to floor system design and moisture intrusion issues that affect indoor air quality, as well as structural integrity
  • Readily identify system components in a high-performance floor assembly, such as grade, crawl space, vapor retarder, framing systems, insulation, sub-floor, underlayment and finish flooring.
  • Be able to explain how the changing codes and evolving building materials are impacting and influencing sub-flooring system design
  • Realize the principles behind the vapor drive in operation below floors, and how to anticipate and prevent the movement of moisture into flooring components.
  • Develop a solid rationale for fastener types chosen and implemented to combine flooring assembly components.
  • Have a grasp of recommended design methodology incorporating building science principles and code requirements, to ensure a designed floor assembly provides durability and increases occupant well-being

Course Outline

Starting Points


Designing in Entirety

Terminology and Concepts

Exterior Parameters Affecting Performance

Wrong Place, Wrong Time

Unskilled Labor

Evolving Codes

Climate in Project Location

Air and Water Movement

Interior Parameters Affecting Performance – Our Choices

Managing Incoming Moisture

Foundation Considerations

  • Flooring Placement on Slabs
  • Placement Over Crawl Spaces
  • Placement Over Basements

Moisture and Vapor Control Measures

  • Vapor Retarders
  • Water Vapor Retarder Classifications
  • Tips for Using Water Vapor Retarders

Framing System Choices

  • Sizing Framing Members
  • Limitations of Dimensional Wood Framing

Climate Separation via Insulation

  • Insulation Types
  • Recommendations for Combining Insulation and Floor Covering Types

Fastener Selection

  • Adhesives
  • Mechanical Fasteners
  • Combined Adhesives and Fasteners

Choosing Subflooring

  • Getting It Flat
  • Deflection Concerns
  • Inherent Moisture Resistance
  • Anything Else?
  • Subflooring Material Choices
  • Installing Subfloors


Finish Floor Coverings

  • General Preparation
  • Basic Types of Finish Flooring
  • When Permeability Matters
  • Specific Flooring Installation Tips
  • General Thoughts on Finish Flooring

Applying Design from the Ground Up

Problematic Design Scenario

Floor Assemblies in Hot Humid Climates

Experimental Study

General Design Recommendations

  • Spaces Below Buildings
  • Choosing Floor Components in Hot, Humid Climates
  • HVAC Systems to Control Indoor Humidity
  • General Building Recommendations
  • Occupant Use

Summarizing How to Start From the Bottom

  • Credit(s) earned on completion of this course will be reported to AIA CES for AIA members.  Certificates of Completion for both AIA members and non-AIA members are available to print upon completion of the course. 
  • This course is registered with AIA CES for continuing professional education.  As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA or any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product.
  • Course instructors will be available by email at, or telephone (800-727-7104) between 8am and 6pm Eastern Standard Time. They will assist you with questions regarding course content. 
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