Connections & installation
Screw Pullout vs. Pullover in Steel Connections
Learn the difference between screw pullout and pullover, identify the steel layers involved, and compare connection data without misreading load tables.
Locate the two different interfaces
Pullout describes loss of the screw's engagement in the supporting material. Pullover describes the attached sheet moving over the fastener head or washer. Both involve a screw connection, but they concern different parts of the assembly.
A useful sketch labels the material under the head separately from the material receiving the threads. Without that distinction, someone can read a thickness from the wrong layer and compare the wrong table. Keep the connection's orientation and load direction with the sketch so the responsible designer can identify the checks that actually apply.
References: BLAZER screw properties and connection data (PDF)
Do not confuse fastener strength with connection strength
A data sheet may present fastener tensile or shear properties alongside values for particular connected materials. Those headings describe different information. A number describing the screw itself is not automatically a load rating for the complete installed connection.
Before comparing values, write down what each table says it represents, including the units and basis. Identify whether values are ultimate, nominal, allowable, or another stated form. Retain notes and limitations with the table rather than copying one attractive number into an estimate. The design professional must apply the appropriate checks and factors for the project.
References: BLAZER screw properties and connection data (PDF) · Fastening Systems Technical Guide
Use the failure mode to ask the right question
This comparison is a reading aid for technical conversations. It does not establish allowable loads or a repair method.
| Term | Area of the assembly | Information to confirm |
|---|---|---|
| Pullout | Screw engagement in supporting material | Support thickness, material, and exact screw |
| Pullover | Attached material beneath head or washer | Sheet properties and specified head or washer |
| Fastener tension | Screw body | Product-specific mechanical properties |
| Connection design | Complete assembly and load path | Applicable checks in the approved design |
Avoid shortcuts when a product changes
A supplier may suggest a larger head, longer screw, or different diameter. Each suggestion changes a different attribute; none establishes that the complete connection remains acceptable. Ask for the exact alternative designation and the relevant documentation, then send the comparison through the project's required review.
Do the same when the steel changes. A fastener substitution and a support-thickness revision should not be evaluated as unrelated events. Put both changes in the same package so that the reviewer sees the actual proposed assembly. Retain the disposition with the revised material schedule and withdraw superseded descriptions from active purchasing.
Example: reading a panel attachment submittal
Suppose a submittal includes a screw property sheet and a panel attachment detail. The property sheet contains a prominent tensile value, while the detail uses a thin attached panel and a separate steel support. A careful review first matches the exact screw, panel, support, and washer arrangement, then identifies which connection data apply.
The purchasing record should cite the accepted submittal and detail, not turn the screw's tensile value into a marketing description such as holds a certain weight. That avoids a false promise and makes later replacements easier to review against the same assembly.
- Label the attached sheet and receiving steel separately.
- Keep units, table headings, and limitations attached to values.
- Confirm that the product and assembly match the approved design.
- Refer unresolved design checks to the responsible professional.
Common questions
Will a longer screw always improve pullout resistance?
Not necessarily. The governing behavior depends on the actual steel and fastener arrangement. Length is not a general substitute for the connection design checks. Record which assembly dimension changed and request a review that addresses that specific change, rather than seeking a general stronger-screw recommendation.
Can a larger washer solve pullover?
A washer change needs review as part of the whole connection. Use only the accepted arrangement and applicable product data; do not assign a new capacity from appearance.
Sources & further reading
Use the current documentation for the exact product and project. Source links do not imply a partnership or endorsement.
- BLAZER screw properties and connection data (PDF) Triangle Fastener Corporation
- Fastening Systems Technical Guide Simpson Strong-Tie
Prepared with AI assistance. Linked references require current project-specific review. How these guides are prepared.
Prepare a supply inquiry
- Record the project drawing or detail and the specified product, profile, or system.
- List the complete configuration, physical units, quantities, and cuts per piece.
- Request current manufacturer documents; confirm compatibility, price, and availability before ordering.
- Obtain the responsible professional's review for loads, code requirements, or installation.